Coherent pion photoproduction from deuterium at intermediate energies

International Nuclear Information System (INIS)

Osland, P.; Rej, A.K.

1975-12-01

The coherent photoproduction of neutral pions on deuterons is studied at energies around the (3,3) resonance and discuss the effects of the Fermi motion, rescattering and kinematical approximations. The results are very dependent upon what kinematical approximations one adopts for the impulse approximation term, which dominates up to very large angles. Allowing for this uncertainty in the kinematics, our results are in good agreement with the most recent experimental data

psi and excess leptons in photoproduction

International Nuclear Information System (INIS)

Ritson, D.M.

1976-03-01

The A-dependence of psi photoproduction was measured on beryllium and tantalum. From this it is found sigma/sub psi N/ = 2.75 +- 0.90 mb. A study was made of excess leptons relative to pion production in photoproduction. A μ/π ratio of 1.40 +- 0.25 x 10 -4 was found at 20 GeV incident photon energy. The energy dependence of psi photoproduction was determined and appeared to have a ''pseudo-threshold'' at 12 GeV

Photoproduction of pions on low-energy protons

International Nuclear Information System (INIS)

Grushin, V.F.

1989-01-01

This paper reports that a study is made of the complete experiment problem and photoproduction of pions on protons. The problem of the volume and content of a complete experiment is solved in the area of photon energies up to 500 MeV for the channels γp-π + n and γp-π → π 0 p. Experimental data assuring a complete experiment are used for multipole analysis of the channels γp → π + n, π 0 p and the real and imaginary parts of s- and p-wave multipole amplitudes are obtained. Estimates are produced for the pole parameters (mass and width) of the Δ + 33 isobar. An electrical quadrupole amplitude of the transition γp → Δ + 33 was found which is significantly different form zero, indicating the existence of a tensor interaction between quarks in hadrons. Data on photoproduction on mesons are used to extract quantitative estimates of the vector and tensor constants of interaction of an ω meson with nucleons

Data compilation of single pion photoproduction below 2 GeV

International Nuclear Information System (INIS)

Ukai, K.; Nakamura, T.

1984-09-01

An updated data compilation on single pion photoproduction experiment below 2 GeV is presented. This data bank includes not only the data of single pion photoproduction processes but also those of the proton Compton scattering (γp → γp) and the inverse process of the γn → π - p (π - p → γn). The number of total data points are 6240 for γp → π + n, 5715 for γp → π 0 p, 2835 for γn → π - p, 177 for γn → π 0 n, 669 for γp → γp, and 112 for π - p → γn processes. The compiled data are stored in the central computer (FACOM M-380R) of the Institute of Nuclear Study, University of Tokyo, for direct use of this data bank and on magnetic tapes with the standard label for other laboratories. The FACOM computer is compatible with an IBM 370 series or IBM 303X or 308X series machines. The data on the magnetic tapes are available on request. (Kato, T.)

Pion inelastic scattering, pion photoproduction and inelastic electron scattering on light nuclei

International Nuclear Information System (INIS)

Ehramzhyan, R.A.

1985-01-01

Partial transitions in pion photoproduction reaction on 6 Li, 10 B, 12 C nuclei are considered. Particular stress is paied to simultaneous analysis both of (γ, π) ad (e, e'), (π, π') reactions. Such analysis is concretely ixemplified with the use of both phenomenological and microscopic approaches. Microscopic analysis is shown to give correct representation of reaction mechanism (γ, π), (e, e') and (π, π') at intermediate energies. Spin-isospin dipole resonances in 1p-shell nuclei are considered. It is shown that nuclear system excitation spectrum gross-structure is a result of resonance configuration splitting

Isotensor electromagnetic current in low energy pion photoproduction

International Nuclear Information System (INIS)

Aznauryan, I.G.; Nagorskaya, I.A.; Zaslavskij, A.N.

1974-01-01

Recent experimental data on single pion photoproduction in the Δ (1236) resonance region are discussed. The role of the high energy contributions into the dispersion integrals are analyzed. Estimates for the magnitude of the isotensor contributions are obtained in the dispersion approach using the experimental data of various groups. In spite of the great number of the experiments the estimate is ambiguous yet since there are direct discrepancies between the data of various groups, besides, certain available data are incomplete. The data of some groups are compatible with 10% isotensor contribution

Study of the Two Pion Photoproduction on Deuterium

Science.gov (United States)

Gauss, Lewis P. Graham, Jr.

Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the primary challenges in strong inter-action physics. This interaction is governed by Quantum Chromodynamics (QCD), which is a theory for understanding the dynamics of strong. QCD displays the asymptotic freedom of hadrons at very short distances and also the confinement of quarks and gluons inside hadrons. However, solutions of this QCD theory in the non-perturbative domain of the interaction are extremely difficult to achieve, mainly because confinement happens on the hadronic scale on which the coupling constant is large and prevents any perturbative approach. Thus leaving us with strategies such as lattice QCD or formulating QCD sum rules to get around this problem. In exclusive hadron production the γN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be investigated through the transition amplitudes to the N and Δ resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through meson photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of the nucleon and the photo-excited resonance decays through photon scattering off a deuteron producing two pions in the final state. This photoproduction process off the deuteron will be used to investigate known baryon resonances in the two pion channel. The two pion final state will be investigated for unraveling new information into the photo-coupling strengths. We want to explore final state interactions, search for properties of known resonances, and to explore the possibility of seeing missing states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large Acceptance

Measurement of the G double-polarisation observable in pion photoproduction

International Nuclear Information System (INIS)

McAndrew, J.; Watts, D.; Pasyuk, E.

2012-01-01

The g9a experiment using the CLAS detector in Hall B of Jefferson Lab will measure double-polarization observables using a polarized energy-tagged photon beam in conjunction with the frozen spin target, FROST. This contribution describes the extraction of the G double polarization observable in the single pion photoproduction using a linearly polarized photon beam in the energy range 730-2300 MeV and the longitudinally polarized frozen spin target, FROST.

Double-polarization observable G in neutral-pion photoproduction off the proton

Energy Technology Data Exchange (ETDEWEB)

Thiel, A.; Lang, M.; Afzal, F.; Beck, R.; Boese, S.; Funke, C.; Gottschall, M.; Gruener, M.; Hammann, C.; Hannappel, J.; Hartmann, J.; Hoffmeister, P.; Honisch, C.; Kaiser, D.; Kalinowsky, H.; Kalischewski, F.; Klassen, P.; Klempt, E.; Koop, K.; Kube, M.; Mahlberg, P.; Mueller, J.; Muellers, J.; Piontek, D.; Schmidt, C.; Seifen, T.; Sokhoyan, V.; Spieker, K.; Thoma, U.; Urban, M.; Pee, H. van; Walther, D.; Wendel, C.; Winnebeck, A. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Eberhardt, H.; Bantes, B.; Dutz, H.; Elsner, D.; Ewald, R.; Fornet-Ponse, K.; Frommberger, F.; Goertz, S.; Hammann, D.; Hillert, W.; Jude, T.; Kammer, S.; Kleber, V.; Klein, F.; Reeve, S.; Runkel, S.; Schmieden, H. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Anisovich, A.V.; Bayadilov, D.; Nikonov, V.; Sarantsev, A. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Bichow, M.; Meyer, W.; Reicherz, G. [Ruhr-Universitaet Bochum, Institut fuer Experimentalphysik I, Bochum (Germany); Brinkmann, K.T.; Gutz, E. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen und Kernphysik, Bonn (Germany); Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Crede, V. [Florida State University, Department of Physics, Tallahassee, FL (United States); Dieterle, M.; Keshelashvili, I.; Krusche, B.; Witthauer, L. [Universitaet Basel, Institut fuer Physik, Basel (Switzerland); Friedrich, S.; Makonyi, K.; Metag, V.; Nanova, M. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Gridnev, A.; Lopatin, I. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Wilson, A. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Florida State University, Department of Physics, Tallahassee, FL (United States); Collaboration: The CBELSA/TAPS Collaboration

2017-01-15

This paper reports on a measurement of the double-polarization observable G in π{sup 0} photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable G is determined from reactions of linearly polarized photons with longitudinally polarized protons. The polarized photons are produced by bremsstrahlung off a diamond radiator of well-defined orientation. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for G are compared to predictions by the Bonn-Gatchina (BnGa), Juelich-Bonn (JueBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed. (orig.)

Measurement of the helium-3 Panofsky ratio and of π+ photoproduction near the threshold for deuterium and helium-3

International Nuclear Information System (INIS)

Botton, Nico de.

1979-01-01

Photoproduction measurements near the threshold are described for two and three-nucleon systems. The experimental techniques used gave the photoproduction cross section value with a precision of a few percent. This accuracy is essential when observing the contribution of multi-nucleon effects which represents a correction to the dominant contribution foreseen by the operator of one-body photoproduction. The method of relative measurement with respect to the elementary process of photoproduction on the proton gives a direct comparison of the experimental result with the momentum approximation at the +-1.5% precision level. No coherent description of multi-nucleon contributions, the overall effect of which should be relatively small in view of the above observation, exists at present. Only the part of these contributions corresponding to the rescattering of the pion has been estimated using a simple model of multiple scattering by fixed nucleons, but more detailed calculations would be needed to confirm these results. The other exchange current terms would also have to be evaluated in order to situate the interpretation of photoproduction results at the same level as that of electron scattering data [fr

Neutral pion photoproduction off nucleons and nuclei near threshold

International Nuclear Information System (INIS)

Kamalov, S.S.; Chumbalov, A.A.

1989-01-01

The modern experimental data on the coherent photoproduction off 4 He, 6 Li, 12 C, 16 O, 40 Ca and 208 Pb are analyzed in terms of the DWIA in the momentum space. It is shown that the elaborated elementary amplitudes do not give a possibility of the simultaneous self-consistent description of the process on free nucleons and nuclei. 36 refs.; 11 figs.; 2 tabs

Study of the Two-pion Photoproduction on the Deuteron

Energy Technology Data Exchange (ETDEWEB)

Graham, Lewis P. [Univ. of South Carolina, Columbia, SC (United States)

2012-12-01

Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the primary challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD), which is a theory for understanding the dynamics of strong. QCD displays the asymptotic freedom of hadrons at very short distances and also the confinement of quarks and gluons inside hadrons. However, solutions of this QCD theory in the non-perturbative domain of the interaction are extremely difficult to achieve, mainly because confinement happens on the hadronic scale on which the coupling constant is large and prevents any perturbative approach. Thus leaving us with strategies such as lattice QCD or formulating QCD sum rules to get around this problem. In exclusive hadron production the yN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be investigated through the transition amplitudes to the N and Delta resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through meson photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of the nucleon and the photo-excited resonance decays through photon scattering off a deuteron producing two pions in the final state. This photoproduction process off the deuteron will be used to investigate known baryon resonances in the two pion channel. The two pion final state will be investigated for unraveling new information into the photo-coupling strengths. We want to explore final state interactions, search for properties of known resonances, and to explore the possibility of seeing missing states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large

Watson's theorem and resonant pion photoproduction amplitude in the delta channel

International Nuclear Information System (INIS)

Wittman, R.; Davidson, R.; Mukhopadhyay, N.C.

1984-01-01

The CGLN and BL theories of the pion photoproduction on nucleons, used in nuclear calculations, are examined regarding their predictions of the resonant M 1 + and E 1 + multipoles. The nonunitary BL approach violates Watson's theorem, and predicts these multipoles porly. In the static limit, the CGLN multipoles satisfy Watson's theorem and are in fine agreement with data. The unitarized BL multipoles agree with those from the Olsson theory and data. (orig.)

Photoproduction of pions on nuclear in chiral bag model with account of motion effects of recoil nucleon

International Nuclear Information System (INIS)

Dorokhov, A.E.; Kanokov, Z.; Musakhanov, M.M.; Rakhimov, A.M.

1989-01-01

Pion production on a nucleon is studied in the chiral bag model (CBM). A CBM version is investigated in which the pions get into the bag and interact with quarks in a pseudovector way in the entire volume. Charged pion photoproduction amplitudes are found taking into account the recoil nucleon motion effects. Angular and energy distributions of charged pions, polarization of the recoil nucleon, multipoles are calculated. The recoil effects are shon to give an additional contribution to the static approximation of order of 10-20%. At bag radius value R=1 in the calculations are consistent with the experimental data

Near-threshold photoproduction of {phi} mesons from deuterium

Energy Technology Data Exchange (ETDEWEB)

Qian, X., E-mail: xqian@caltech.ed [Duke University, Durham, NC 27708 (United States); Kellogg Radiation Laboratory, California Institute of Technology, CA 91125 (United States); Chen, W.; Gao, H. [Duke University, Durham, NC 27708 (United States); Hicks, K. [Ohio University, Athens, OH 45701 (United States); Kramer, K. [Duke University, Durham, NC 27708 (United States); Laget, J.M. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Mibe, T. [Ohio University, Athens, OH 45701 (United States); Qiang, Y. [Duke University, Durham, NC 27708 (United States); Stepanyan, S. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Tedeschi, D.J. [University of South Carolina, Columbia, SC 29208 (United States); Xu, W. [Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States); Adhikari, K.P.; Amaryan, M. [Old Dominion University, Norfolk, VA 23529 (United States); Anghinolfi, M. [INFN, Sezione di Genova, 16146 Genova (Italy); Ball, J. [CEA, Centre de Saclay, Irfu/Service de Physique Nucleaire, 91191 Gif-sur-Yvette (France); Battaglieri, M. [INFN, Sezione di Genova, 16146 Genova (Italy); Batourine, V. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Bedlinskiy, I. [Institute of Theoretical and Experimental Physics, Moscow 117259 (Russian Federation); Bellis, M. [Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Biselli, A.S. [Fairfield University, Fairfield, CT 06824 (United States); Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

2011-02-07

We report the first, kinematically-complete measurement of the differential cross section of {phi}-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, K{sup +} and K{sup -} near the theoretical production threshold of 1.57 GeV. The extracted differential cross sections (d{sigma})/(dt) for the initial photon energy range of 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Our finding is different from recent LEPS results on {phi}-meson photoproduction from deuterium in a similar incident photon energy range, but in a different momentum transfer region.

Phi photoproduction near threshold with Okubo-Zweig-Iizuka evading phi NN interactions

CERN Document Server

William, R A

1998-01-01

Existing intermediate and high energy phi-photoproduction data is consistent with purely diffractive production (i.e., Pomeron exchange). However, near threshold (1.574 GeV K sup + K sup - decay angular distribution. We stress the importance of measurements with linearly polarized photons near the phi threshold to separate natural and unnatural parity exchange mechanisms. Approved and planned phi photoproduction and electroproduction experiments at Jefferson Lab will help establish the relative dynamical contributions near threshold and clarify outstanding theoretical issues related to apparent Okubo-Zweig-Iizuka violations.

Total disintegration of three-nucleon nuclei in charged-pion photo-production

International Nuclear Information System (INIS)

Dzhibuti, R.I.; Kezerashvili, R.Y.

1984-01-01

The total disintegration of three-nucleon nuclei in charged-pion photo-production is studied within the framework of the microscopic approach based on the method of hyperspherical functions. The initial and final nuclear states are described using the same NN potentials. The differential and total cross sections are calculated using various NN potentials. It is shown that the cross sections are sensitive to the form of the NN interaction and to the final-state interaction of the three nucleons. It is found that the cross section for π - meson production is systematically larger than the cross section for π + meson production. The importance of an experimental investigation of these reactions is shown

Two-pion production in photon-induced reactions

Indian Academy of Sciences (India)

A deeper understanding of the situation is anticipated from a detailed experimental study of meson photoproduction from nuclei in exclusive reactions. In the energy regime above the (1232) resonance, the dominant double pion production channels are of particular interest. Double pion photoproduction from nuclei is ...

Reaction mechanisms in coherent nuclear photoproduction

International Nuclear Information System (INIS)

Lazard, C.

Nuclear coherent pion photoproduction is studied. Pion rescattering and propagation effects inside nucleus and mesic exchange current effects are discussed. Influence of nuclear wave functions and Fermi motion is presented [fr

Elastic and inelastic pion reactions on few nucleon systems

International Nuclear Information System (INIS)

Lensky, V.

2007-01-01

In the present work, we are studying elastic and inelastic pion reactions on few-body systems within the framework of chiral effective theory. We consider two specific reactions involving pions on few-nucleon systems, namely pion production in nucleon-nucleon collisions, and incoherent pion photoproduction on the deuteron. These two reactions are closely related to the issue of dispersive and absorptive corrections to the pion-deuteron scattering length, which we also consider in our analysis. The incoherent pion photoproduction is also considered as the possible source for a high-precision determination of the neutron-neutron scattering length. (orig.)

Elastic and inelastic pion reactions on few nucleon systems

Energy Technology Data Exchange (ETDEWEB)

Lensky, V.

2007-09-29

In the present work, we are studying elastic and inelastic pion reactions on few-body systems within the framework of chiral effective theory. We consider two specific reactions involving pions on few-nucleon systems, namely pion production in nucleon-nucleon collisions, and incoherent pion photoproduction on the deuteron. These two reactions are closely related to the issue of dispersive and absorptive corrections to the pion-deuteron scattering length, which we also consider in our analysis. The incoherent pion photoproduction is also considered as the possible source for a high-precision determination of the neutron-neutron scattering length. (orig.)

The two-nucleon system above pion threshold

International Nuclear Information System (INIS)

Poepping, H.; Sauer, P.U.; Zhang Xizhen

1987-01-01

A force model is presented for the description of the two-nucleon system below and above pion threshold and its coupled inelastic channels with one pion. It uses Δ-isobar and pion degrees of freedom in addition to the nucleonic one. The force model is based on a hamiltonian approach within the framework of noncovariant quantum mechanics. It extends the traditional approach with purely nucleonic potentials in isospin-triplet partial waves. It is constructed to remain valid up to 500 MeV c.m. energy. The characteristics of the force model is its mechanism for pion production and pion absorption which is mediated by the Δ-isobar. Even without any fit of phenomenological parameters the force model is able to account for the experimental data of elastic nucleon-nucleon scattering' of the inelastic reactions pp ↔ π + d and of elastic pion-deuteron scattering with satisfactory accuracy. No need for the introduction of dibaryon degrees of freedom has been found yet. The force model is a realistic one in the two-nucleon system. In many-nucleon systems it forms the unifying basis for a microscopic description of nuclear structure and nuclear reactions at low and intermediate energies. (orig.)

DWIA in the momentum space for (γ,π0) reaction near threshold

International Nuclear Information System (INIS)

Chumbalov, A.A.; Eramzhyan, R.A.; Kamalov, S.S.

1987-01-01

Differential cross sections and total cross sections of coherent photoproduction of neutral pions on 4 He, 12 C and 40 Ca nuclei using impulse approximation and the method of distorted waves in impulse representation are calculated. Pion distortion wave effects near threshold of photon energy are shown not to exceed 25%. Good agreement with the experiment is reached due to the application of total elementary amplitude, which takes into account both nonlinear terms in a pion momentum and the terms, which depends on the pion momentum

Photoproduction of vector mesons off nucleons near threshold

International Nuclear Information System (INIS)

Friman, B.

1995-01-01

A simple meson-exchange model is proposed for the photoproduction of ρ- and ω-mesons off protons near threshold. This model provides a good description of the available data and implies a large ρ-nucleon interaction in the scalar channel (σ-exchange). This phenomenological interaction is applied to estimate the leading contribution to the self-energy of ρ-mesons in matter. The implications of our calculation for experimental studies of the ρ-meson mass in nuclei are discussed. (author)

Interaction of slow pions with atomic nuclei

International Nuclear Information System (INIS)

Troitskij, M.A.; Tsybul'nikov, A.V.; Chekunaev, N.I.

1984-01-01

Interactions of slow pions with atomic nuclei near to pion condensation are investigated. From comparison of experimental data with the theoretical calculation results on the basis of precise microscopic approach not bound with the random phase approximation (RPA) nuclear matter fundamental parameters near a critical point can be found. Optical potential of slow pions in nuclei, πN-scattering amplitudes and lengths, π-atom level isotopic shift, phenomenon of single-nucleon pion absorption by nucleus, phenomenon of nuclear critical opalescence are considered. The results of πN-scattering lengths calculation, sup(40-44)Ca, sup(24-29)Mg, sup(16-18)O π-atom level shift are presented. It is shown that the presence of π-condensate in nuclei can explain the observed suppression of p-wave potential terms. The phenomenon of single-nucleon pion absorption by nucleus is one of direct experiments which permits to reveal the π-condensate. The nuclear opalescence phenomenon is manifested in increase of pion photoproduction reaction cross section for account of nucleus proximity to π-condensation as compared with the calculated in the Fermi-gas model. The suggested method for calculating precondensate phenomena operates the better, the nearer is the system to the condensation threshold whereas the RPA method in this region is inapplicable

Inclusive Photoproduction of Neutral Pions in the Photon Hemisphere at HERA

CERN Document Server

Adloff, C.; Andrieu, B.; Arkadov, V.; Astvatsatourov, A.; Ayyaz, I.; Babaev, A.; Bahr, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Bate, P.; Beglarian, A.; Behnke, O.; Beier, C.; Belousov, A.; Benisch, T.; Berger, Christoph; Bernardi, G.; Berndt, T.; Bertrand-Coremans, G.; Bizot, J.C.; Borras, K.; Boudry, V.; Braunschweig, W.; Brisson, V.; Broker, H.B.; Brown, D.P.; Bruckner, W.; Bruel, P.; Bruncko, D.; Burger, J.; Busser, F.W.; Bunyatyan, A.; Burkhardt, H.; Burrage, A.; Buschhorn, G.; Campbell, A.J.; Cao, Jun; Carli, T.; Caron, S.; Chabert, E.; Clarke, D.; Clerbaux, B.; Collard, C.; Contreras, J.G.; Coughlan, J.A.; Cousinou, M.C.; Cox, B.E.; Cozzika, G.; Cvach, J.; Dainton, J.B.; Dau, W.D.; Daum, K.; David, M.; Davidsson, M.; Delcourt, B.; Delerue, N.; Demirchyan, R.; De Roeck, A.; De Wolf, E.A.; Diaconu, C.; Dixon, P.; Dodonov, V.; Donovan, K.T.; Dowell, J.D.; Droutskoi, A.; Duprel, C.; Ebert, J.; Eckerlin, Guenter; Eckstein, D.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellerbrock, M.; Elsen, E.; Erdmann, M.; Faulkner, P.J.W.; Favart, L.; Fedotov, A.; Felst, R.; Ferencei, J.; Ferrarotto, F.; Ferron, S.; Fleischer, M.; Flugge, G.; Fomenko, A.; Foresti, I.; Formanek, J.; Foster, J.M.; Franke, G.; Gabathuler, E.; Gabathuler, K.; Garvey, J.; Gassner, J.; Gayler, Joerg; Gerhards, R.; Ghazaryan, Samvel; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goodwin, C.; Grab, C.; Grassler, H.; Greenshaw, T.; Grindhammer, Guenter; Hadig, T.; Haidt, D.; Hajduk, L.; Haustein, V.; Haynes, W.J.; Heinemann, B.; Heinzelmann, G.; Henderson, R.C.W.; Hengstmann, S.; Henschel, H.; Heremans, R.; Herrera, G.; Herynek, I.; Hilgers, M.; Hiller, K.H.; Hilton, C.D.; Hladky, J.; Hoting, P.; Hoffmann, D.; Hoprich, W.; Horisberger, R.; Hurling, S.; Ibbotson, M.; Issever, C .; Jacquet, M.; Jaffre, M.; Janauschek, L.; Jansen, D.M.; Janssen, X.; Jemanov, V.; Jonsson, L.; Johnson, D.P.; Jones, M.A.S.; Jung, H.; Kastli, H.K.; Kant, D.; Kapichine, M.; Karlsson, M.; Karschnick, O.; Kaufmann, O.; Kausch, M.; Keil, F.; Keller, N.; Kennedy, J.; Kenyon, I.R.; Kermiche, S.; Kiesling, Christian M.; Klein, M.; Kleinwort, C.; Knies, G.; Koblitz, B.; Kolanoski, H.; Kolya, S.D.; Korbel, V.; Kostka, P.; Kotelnikov, S.K.; Krasny, M.W.; Krehbiel, H.; Kroseberg, J.; Krucker, D.; Kruger, K.; Kupper, A.; Kuhr, T.; Kurca, T.; Kutuev, R.; Lachnit, W.; Lahmann, R.; Lamb, D.; Landon, M.P.J.; Lange, W.; Lastovicka, T.; Lebedev, A.; Leissner, B.; Lemaitre, V.; Lemrani, R.; Lendermann, V.; Levonian, S.; Lindstroem, M.; Lobo, G.; Lobodzinska, E.; Lobodzinski, B.; Loktionova, N.; Lubimov, V.; Luders, S.; Luke, D.; Lytkin, L.; Magnussen, N.; Mahlke-Kruger, H.; Malden, N.; Malinovski, E.; Malinovski, I.; Maracek, R.; Marage, P.; Marks, J.; Marshall, R.; Martyn, H.U.; Martyniak, J.; Maxfield, S.J.; Mehta, A.; Meier, K.; Merkel, P.; Metlica, F.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.O.; Mikocki, S.; Milstead, D.; Mkrtchyan, T.; Mohr, R.; Mohrdieck, S.; Mondragon, M.N.; Moreau, F.; Morozov, A.; Morris, J.V.; Muller, D.; Muller, K.; Murin, P.; Nagovizin, V.; Naroska, B.; Naumann, J.; Naumann, Th.; Negri, I.; Nellen, G.; Newman, Paul R.; Nicholls, T.C.; Niebergall, F.; Niebuhr, C.; Nix, O.; Nowak, G.; Nunnemann, T.; Olsson, J.E.; Ozerov, D.; Panassik, V.; Pascaud, C.; Passaggio, S.; Patel, G.D.; Perez, E.; Phillips, J.P.; Pitzl, D.; Poschl, R.; Potachnikova, I.; Povh, B.; Rabbertz, K.; Radel, G.; Rauschenberger, J.; Reimer, P.; Reisert, B.; Reyna, D.; Riess, S.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rusakov, S.; Rybicki, K.; Sankey, D.P.C.; Scheins, J.; Schilling, F.P.; Schleif, S.; Schleper, P.; Schmidt, D.; Schoeffel, L.; Schoning, A.; Schorner, T.; Schroder, V.; Schultz-Coulon, H.C.; Sedlak, K.; Sefkow, F.; Chekelian, V.; Sheviakov, I.; Shtarkov, L.N.; Siegmon, G.; Sievers, P.; Sirois, Y.; Sloan, T.; Smirnov, P.; Smith, M.; Solochenko, V.; Solovev, Y.; Spaskov, V.; Specka, Arnd E.; Spitzer, H.; Stamen, R.; Steinhart, J.; Stella, B.; Stellberger, A.; Stiewe, J.; Straumann, U.; Struczinski, W.; Sutton, J.P.; Swart, M.; Tasevsky, M.; Tchernyshov, V.; Tchetchelnitski, S.; Thompson, Graham; Thompson, P.D.; Tobien, N.; Traynor, D.; Truoel, Peter; Tsipolitis, G.; Turnau, J.; Turney, J.E.; Tzamariudaki, E.; Udluft, S.; Usik, A.; Valkar, S.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Vazdik, Y.; von Dombrowski, S.; Wacker, K.; Wallny, R.; Walter, T.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; White, G.; Wiesand, S.; Wilksen, T.; Winde, M.; Winter, G.G.; Wissing, C.; Wobisch, M.; Wollatz, H.; Wunsch, E.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhokin, A.; Zomer, F.; Zsembery, J.; zur Nedden, M.

2001-01-01

The inclusive cross section for the photoproduction of neutral pions has been measured as a function of the transverse momentum, rapidity, and Feynman x of the pizero mesons at an average photon--proton centre-of-mass energy of 208 GeV and for photon virtualities below Q^2=0.01 GeV^2. The pizero measurement extends the range covered by previous charged particle measurements at HERA by two units of rapidity in the photon direction down to a value of -5.5 in the gamma p centre-of-mass frame. The pizero transverse momentum distribution is well described over the whole measured range by a power law ansatz, while an exponential fit falls below the data at transverse momentum values above 1.5 GeV/c. Good agreement with the predictions of the Monte Carlo models PYTHIA and PHOJET is found. In the context of the PYTHIA model the data are inconsistent with large intrinsic transverse momentum values in the photon.

Photoproduction of vector mesons off nucleons near threshold

International Nuclear Information System (INIS)

Friman, B.; Soyeur, M.

1995-11-01

We propose a simple meson-exchange model of the photoproduction of ρ-and ω-mesons off protons near threshold (E γ < or∼2 GeV). We show that this model provides a good description of the available data and implies a large ρ-nucleon interaction in the scalar channel (σ-exchange). We use this phenomenological interaction to estimate the leading contribution to the self-energy of ρ-mesons in matter. We discuss the implications of our calculation for experimental studies of the ρ-meson mass in nuclei. (orig.)

Features of πΔ photoproduction at high energies

Science.gov (United States)

Nys, J.; Mathieu, V.; Fernández-Ramírez, C.; Jackura, A.; Mikhasenko, M.; Pilloni, A.; Sherrill, N.; Ryckebusch, J.; Szczepaniak, A. P.; Fox, G.; Joint Physics Analysis Center

2018-04-01

Hybrid/exotic meson spectroscopy searches at Jefferson Lab require the accurate theoretical description of the production mechanism in peripheral photoproduction. We develop a model for πΔ photoproduction at high energies (5 ≤Elab ≤ 16 GeV) that incorporates both the absorbed pion and natural-parity cut contributions. We fit the available observables, providing a good description of the energy and angular dependencies of the experimental data. We also provide predictions for the photon beam asymmetry of charged pions at Elab = 9 GeV which is expected to be measured by GlueX and CLAS12 experiments in the near future.

Determination of amplitudes in neutral pion photoproduction and comparison with partial waves analysis in the energy range of 1.3 to 2.1 GeV

International Nuclear Information System (INIS)

Forozani, G.

2004-01-01

The magnitude of four independent amplitudes are obtained pion photoproduction in the energy range of 1300 to 2100 MeV incident photon. Different cross section and three polarization parameters are required for such amplitudes reconstruction at different pion scattering angles. Results of the direct amplitudes reconstruction have been compared with the solution of partial wave analysis SM95 and SM00K at all energies. This analysis indicates that we have a fair agreement between the present work and the results of partial wave analysis at many angles

Determination of amplitudes in neutral pion photoproduction and comparison with partial waves analysis in the energy range of 1.3 to 2.1 GeV

International Nuclear Information System (INIS)

Forozani, G.

2004-01-01

The magnitude of four independent amplitudes are obtained in neutral pion photoproduction in the energy range of 1300 to 2100 MeV incident photon. Differential gross section and three polarization parameters are required for such amplitudes reconstruction at different pion scattering angles. Results of the direct amplitudes reconstruction have been compared with the solution of partial wave analysis SM95 and SM00K at all energies. This analysis indicates that we have a fair agreement between the present work and the results of partial wave analysis at meny angles (Author)

Data compilation of single pion photoproduction below 2 GeV

International Nuclear Information System (INIS)

Inagaki, Y.; Nakamura, T.; Ukai, K.

1976-01-01

The compilation of data of single pion photoproduction experiment below 2 GeV is presented with the keywords which specify the experiment. These data are written on a magnetic tape. Data format and the indices for the keywords are given. Various programs of using this tape are also presented. The results of the compilation are divided into two types. The one is the reference card on which the information of the experiment is given. The other is the data card. These reference and data cards are written using all A-type format on an original tape. The copy tapes are available, which are written by various types on request. There are two kinds of the copy tapes. The one is same as the original tape, and the other is the one different in the data card. Namely, this card is written by F-type following the data type. One experiment on this tape is represented by 3 kinds of the cards. One reference card with A-type format, many data cards with F-type format and one identifying card. Various programs which are written by FORTRAN are ready for these original and copy tapes. (Kato, T.)

Photoproduction of the φ(1020) near threshold in CLAS

International Nuclear Information System (INIS)

Tedeschi, D.J.

2002-01-01

The differential cross section for the photoproduction of the φ (1020) near threshold (E γ = 1.57GeV) is predicted to be sensitive to production mechanisms other than diffraction. However, the existing low energy data is of limited statistics and kinematical coverage. Complete measurements of φ meson production on the proton have been performed at The Thomas Jefferson National Accelerator Facility using a liquid hydrogen target and the CEBAF Large Acceptance Spectrometer (CLAS). The φ was identified by missing mass using a proton and positive kaon detected by CLAS in coincidence with an electron in the photon tagger. The energy of the tagged, bremsstrahlung photons ranged from φ-threshold to 2.4 GeV. A description of the data set and the differential cross section for (E γ = 2.0 GeV) will be presented and compared with present theoretical calculations. (author)

Photoproduction of {omega} mesons on nuclei near the production threshold

Energy Technology Data Exchange (ETDEWEB)

Nanova, M.; Friedrich, S.; Metag, V.; Thiel, M.; Gregor, R.; Kotulla, M.; Lugert, S.; Novotny, R.; Pant, L.M.; Pfeiffer, M.; Roy, A.; Schadmand, S.; Trnka, D.; Varma, R. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Weil, J.; Mosel, U. [Universitaet Giessen, Institut fuer Theoretische Physik I, Giessen (Germany); Anton, G.; Bogendoerfer, R.; Hoessl, J.; Suft, G. [Universitaet Erlangen, Physikalisches Institut, Erlangen (Germany); Bacelar, J.C.S.; Castelijns, R.; Loehner, H.; Messchendorp, J.G.; Shende, S. [Kernfysisch Versneller Institut, Groningen (Netherlands); Bartholomy, O.; Crede, V.; Ehmanns, A.; Essig, K.; Fabry, I.; Fuchs, M.; Funke, C.; Gutz, E.; Hoeffgen, S.; Hoffmeister, P.; Horn, I.; Junkersfeld, J.; Kalinowsky, H.; Klempt, E.; Lotz, J.; Pee, H. van; Schmidt, C.; Szczepanek, T.; Thoma, U.; Walther, D.; Weinheimer, C.; Wendel, C. [Helmholtz-Institut fuer Strahlen- und Kernphysik Universitaet Bonn, Bonn (Germany); Bayadilov, D. [Helmholtz-Institut fuer Strahlen- und Kernphysik Universitaet Bonn, Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Beloglazov, Y.A.; Gridnev, A.B.; Lopatin, I.V.; Radkov, A.; Sumachev, V.V. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Dutz, H.; Elsner, D.; Ewald, R.; Gothe, R.; Klein, Frank; Klein, Friedrich; Konrad, M.; Menze, D.; Morales, C.; Ostrick, M.; Schmieden, H.; Schoch, B.; Suele, A. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Jaegle, I.; Krusche, B.; Mertens, T. [Universitaet Basel, Physikalisches Institut, Basel (Switzerland); Kopf, B. [Institut fuer Kern- und Teilchenphysik, TU Dresden, Dresden (Germany); Universitaet Bochum, Physikalisches Institut, Bochum (Germany); Langheinrich, J. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Universitaet Bochum, Physikalisches Institut, Bochum (Germany)

2011-02-15

The photoproduction of {omega} mesons on LH{sub 2}, C and Nb has been measured for incident photon energies from 900 to 1300MeV using the CB/TAPS detector at ELSA. The {omega} lineshape does not show any significant difference between the LH{sub 2} and the Nb targets. The experiment was motivated by transport calculations that predicted a sensitivity of the {omega} lineshape to in-medium modifications near the production threshold on a free nucleon of E{sub {gamma}}{sup lab}=1109 MeV. A comparison with recent calculations is given. (orig.)

Inelastic photoproduction of ω and rho+-mesons

International Nuclear Information System (INIS)

Nelson, C.A. Jr.; May, E.N.; Abramson, J.; Andrews, D.E.; Harvey, J.; Lobkowicz, F.; Singer, M.N.; Thorndike, E.H.; Nordberg, M.E. Jr.

1978-01-01

We report measurements of inelastic photoproduction of ω and rho +- mesons from hydrogen and deuterium at incident photon energies in the range 7.5-10.5 GeV. For ωΔ and rho - Δ ++ production differential cross sections dsigma/dt' and spin density matrices are presented. For higher missing masses the cross sections dsigma/dM/sub X/ 2 and invariant structure functions F(x) are also given. The data are compared to a one-pion-exchange model. We conclude that pion exchange is dominant for inelastic ω photoproduction, but unimportant for rho +- during annealing, even though the resistively determined transport scattering time increased by a factor of 7.8 during annealing. Orbital depairing was found to follow a relation zeta = zeta 0 + αH 2 and to increase with annealing in a manner expected from the change in mean free path determined from measurements of H/sub cnu/

Inclusive charged and neutral pion photoproduction at 20 GeV

International Nuclear Information System (INIS)

Rickman O'Dell, V.

1987-05-01

The inclusive charged and neutral pion distributions from the interactions of 20 GeV photons on protons have been measured. The assumptions and analysis done to obtain these distributions are described, and the pion distributions are found to agree with general predictions of the quark-parton model. The quark-quark fusion model and the recombination model were compared to the inclusive pion distributions assuming the photon could be approximated by a superposition of rho and omega vector meson states - an assumption prompted by the Vector Meson Dominance Model of photon structure. Quark models applied to the difference in the charged pion cross sections are examined. The inclusive charge structure of the photoproduced charged pions and that of electroproduced and hadroproduced charged pions were compared

Pion photoproduction cross section at large momentum transfer

Energy Technology Data Exchange (ETDEWEB)

Sjoegren, Johan [Univ. of Glasgow, Scotland, United Kingdom

2015-02-27

The Real Compton Scattering experiment was performed in Hall A at the Thomas Jefferson National Accelerator Facility. It was designed to measure, for Compton scattering and π⁰-photoproduction, the differential cross section over a range of kinematic points and the polarisation transfer to the proton at a single kinematic point. The full range of the experiment in Mandelstam variables t and s was 1.6-6.46 GeV² and 4.82-10.92 GeV² respectively with beam energies of 2-6 GeV. The motivation for the experiment is to test the cross section and polarisation transfer predictions of perturbative QCD versus that of predictions from Generalised Parton Distribution models. This thesis will give an overview of the pertinent theory, experimental setup in Hall A and the extracting of the π⁰-photoproduction cross section.

Strange Twists in Neutral Pion Photo/Electro-Production

OpenAIRE

Meißner, Ulf-G.

1995-01-01

I review the interesting tale of the electric dipole amplitude in neutral pion photoproduction and the resulting consequences. I also discuss why there is new life related to P--wave multipoles. Electroproduction is briefly touched upon.

Study of the Production of Single Pions in Pion-proton Collisions near Threshold

CERN Multimedia

2002-01-01

This experiment aims at a complete-kinematics measurement of the processes @p|-p @A @p|-@p|+n and @p|+p @A @p|+@p|+n in the region of incident momenta between 300 MeV/c and 460 MeV/c. It uses the Omicron Spectrometer with detectors placed in the magnetic field close to a 12 atm. hydrogen gas target. The apparatus has an acceptance of 4\\% for the processes to be studied. \\\\ \\\\ Their threshold is at 279 MeV/c and pion production in this region is interesting from the point of view of the determination of transformation properties of the chiral-symmetry-breaking part of the Lagrangian.

Pion electroproduction at threshold on the nucleon. Contribution to the measurement of the nucleon form factor

International Nuclear Information System (INIS)

Duval, M.A.

1989-11-01

A pion electroproduction experiment is discussed. The experiment is carried out at threshold on the proton, at the Saclay Linear Accelerator. The scattered electron and the produced pion are detected in coincidence. The aim of the investigation is to measure the nucleon axial form factor. Theoretical concepts and previous experiments are reviewed. The experimental set-up is described, in particular the new pion arm and the trigger simulation. The preliminary analysis of six kinematical points at the momentum transfer of two inverse fermis squared shows the feasibility of the experiment. The pions detection and their identification are satisfactory and allow measurements to be performed [fr

Photoproduction of eta mesons from threshold to 1.2 GeV

International Nuclear Information System (INIS)

Rigney, A.; Breuer, M.; Hoffman-Rothe, P.; Anton, G.; Arends, J.; Berrier-Ronsin, G.; Beulertz, W.; Blanpied, G.; Bock, A.; Bruns, M.; Didelez, J.; Djaladi, C.; Edel, G.; Frascaria, R.; Maass, R.; Helbing, K.; Hey, J.; Noeldeke, G.; Hourani, E.; Mayers, M.; Preedom, B.; Ritchie, B.; Rosier, L.; Saghai, B.; Schumacher, M.; Smend, F.; Whisnant, S.

1995-01-01

We have measured total and differential cross sections for η-meson photo-production on 7 cm thick 1 H, 2 D, and 14 N liquid targets from threshold to 1.2 GeV, using the tagged Bremsstrahlung photon beam produced by the electrons extracted from the ELSA storage ring at Bonn. The photoreaction was identified by detecting the η decay products in the neutral meson spectrometer SPES0-2π, while the recoil baryons (proton, neutron, or deuteron) were detected by a variety of large angle scintillator detectors. Some of our recent preliminary results, both theoretical and experimental, will be discussed. copyright 1995 American Institute of Physics

Photoproduction of neutral kaons in the threshold region

International Nuclear Information System (INIS)

Takahashi, Toshiyuki

2004-01-01

It is expected that γ + n → K 0 + Λ reaction provides important information to the study of strangeness creation mechanism. Neutral Kaon Spectrometer (NKS) has been constructed at Laboratory of Nuclear Science, Tohoku University, which was designed to measure pions with magnetic spectrometer after the K s 0 → π + π - decay to identify K 0 by reconstructing the reaction. Principle of the design of the spectrometer and experimental set up are described. Up to the present quasi-free reaction from carbon target has been successfully observed in the threshold energy region. K s 0 was clearly separated in the preliminary data analysis indicating that performance of NKS is high enough to the objective. Information of γ + n → K 0 + Λ reaction is expected to be obtained by further analysis. (S. Funahashi)

Exclusive $\\rho^0$ Meson Photoproduction with a Leading Neutron at HERA

CERN Document Server

Andreev, V.; Begzsuren, K.; Belousov, A.; Bolz, A.; Boudry, V.; Brandt, G.; Brisson, V.; Britzger, D.; Buniatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A.J.; Cantun Avila, K.B.; Cerny, K.; Chekelian, V.; Contreras, J.G.; Cvach, J.; Dainton, J.B.; Daum, K.; Diaconu, C.; Dobre, M.; Dodonov, V.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Ferencei, J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Haidt, D.; Henderson, R.C.W.; Hladký, J.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jung, H.; Kapichine, M.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kretzschmar, J.; Krüger, K.; Landon, M.P.J.; Lange, W.; Laycock, P.; Lebedev, A.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Malinovski, E.; Martyn, H.-U.; Maxfield, S.J.; Mehta, A.; Meyer, A.B.; Meyer, H.; Meyer, J.; Mikocki, S.; Morozov, A.; Müller, K.; Naumann, Th.; Newman, P.R.; Niebuhr, C.; Nowak, G.; Olsson, J.E.; Ozerov, D.; Pascaud, C.; Patel, G.D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Plačakytė, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Rusakov, S.; Šálek, D.; Sankey, D.P.C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schöning, A.; Sefkow, F.; Shushkevich, S.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Straumann, U.; Sykora, T.; Thompson, P.D.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wünsch, E.; Žáček, J.; Zhang, Z.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

2016-01-23

A first measurement is presented of exclusive photoproduction of $\\rho^0$ mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years $2006$ and $2007$ at a centre-of-mass energy of $\\sqrt{s}=319$ GeV and correspond to an integrated luminosity of $1.16$ pb$^{-1}$. The $\\rho^0$ mesons with transverse momenta $p_T0.35$, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality $Q^2 < 2$ GeV$^2$, the total energy of the photon-proton system $20 < W_{\\gamma p} < 100$ GeV and the polar angle of the leading neutron $\\theta_n < 0.75$ mrad. The cross section of the reaction $\\gamma p \\to \\rho^0 n \\pi^+$ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a $\\rho^0$ meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross se...

Photoproduction experiments

International Nuclear Information System (INIS)

Wattenberg, A.

1977-01-01

Results of some experimental collaborations to search for new particles through photoproduction are briefly surveyed. The J/psi photoproduction on protons has been observed to rise slowly till above 12 GeV and then very steeply up to 55 GeV, exhibiting a pseudo-threshold behaviour. The psi production on Be and Ta is obtained to be sigmasub(psiN)=3.5+-0.8 mb at 20 GeV, which is somewhat higher than the vector dominance photoproduction value. A mass spectrum is shown for the γ+Be → μμ reaction at 90-200 GeV exhibiting a psi-like peak. Another mass spectrum for the γ+p → e + e - +p reaction shows very prominent rho/ω and phi peaks on top of Bethe-Heitler background. More data is needed to determine whether these events are due to very improbable statistical fluctuations or due to new narrow resonances

Low-energy photoproduction of PHI-mesons

CERN Document Server

Barth, J; Glander, K H; Hannappel, J; Jöpen, N; Klein, F J; Klein, F; Lawall, R; Menze, D; Neuerburg, W; Ostrick, M; Paul, E; Schulday, I; Schwille, W J; Wiegers, B; Ernst, J; Kalinowsky, H; Klempt, E; Link, J; Pee, H V; Wieland, F W; Wisskirchen, J; Wu, C

2003-01-01

Photoproduction of PHI-vector-mesons has been studied from reaction threshold up to W=2.4 GeV with the SAPHIR spectrometer at the Bonn electron stretcher ring ELSA. Total cross-sections, differential cross-sections and decay angular distributions were measured. We find evidence for strong non-diffractive contributions to PHI photoproduction. (orig.)

Photoproduction of the vector mesons ω(782) and φ(1020) on the proton from the production threshold up to a photon energy of 2. 6 GeV

International Nuclear Information System (INIS)

Barth, J.

2002-05-01

This paper reports on a measurement of the photoproduction of ω(782) and Φ(1020) vector mesons with the SAPHIR detector at the electron accelerator facility ELSA. The incident photons were tagged in an energy range from reaction threshold up to 2.6 GeV. ω and Φ events were selected by separating their signal in the invariant mass spectrum of their decay products, i.e. in the π + π - π 0 and the K + K - system, respectively. As a cross check for normalization the inclusive two and three pion production was evaluated. The results agree with earlier experiments. From the experimental data total cross sections σ tot , differential cross sections dσ/dt as well as decay angular distributions in both, Gottfried Jackson and helicity frames, were extracted. For the ω production they show that diffractive processes play an important role as expected from higher energy data. However, at threshold s-channel resonances significantly contribute. In the region of large four-momentum transfers (vertical stroke t vertical stroke > 1 GeV 2 ) significant deviations from t-channel exchange mechanisms are observed. The Φ production can be described mainly by diffraction, but also other t-channel exchange processes seem to contribute. (orig.)

Photoproduction in the Energy Range 70-200 GeV

CERN Multimedia

2002-01-01

This experiment continues the photoproduction studies of WA4 and WA57 up to the higher energies made available by the upgrading of the West Hall. An electron beam of energy 200 GeV is used to produce tagged photons in the range 65-180 GeV; The photon beam is incident on a 60 cm liquid hydrogen target in the Omega Spectrometer. A Ring Image Cherenkov detector provides pion/kaon separation up to 150 GeV/c. The Transition Radiation Detector extends the charged pion identification to the momentum range from about 80 GeV/c upwards. The large lead/liquid scintillator calorimeter built by the WA70 collaboration and the new lead/scintillating fibre det (Plug) are used for the detection of the $\\gamma$ rays produced by the interactions of the primary photons in the hydrogen target. \\\\ \\\\ The aim is to make a survey of photoproduction reactions up to photon energies of 200 GeV. The large aperture of the Omega Spectrometer will particularly enable study of fragmentation of the photon to states of high mass, up to @C 9 G...

ϕ-meson photoproduction on hydrogen in the neutral decay mode

Science.gov (United States)

Seraydaryan, H.; Amaryan, M. J.; Gavalian, G.; Baghdasaryan, H.; Weinstein, L.; Adhikari, K. P.; Adikaram, D.; Aghasyan, M.; Anderson, M. D.; Pereira, S. Anefalos; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bennett, R. P.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Collins, P.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Fassi, L. El; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Gevorgyan, N.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lewis, S.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Martinez, D.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munevar, E.; Camacho, C. Munoz; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Tang, W.; Taylor, C. E.; Tian, Ye; Tkachenko, S.; Ungaro, M.; Vineyard, M. F.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; CLAS Collaboration

2014-05-01

We report the first measurement of the photoproduction cross section of the ϕ meson in its neutral decay mode in the reaction γp →pϕ(KSKL). The experiment was performed with a tagged photon beam of energy 1.6≤Eγ≤3.6 GeV incident on a liquid hydrogen target of the CLAS spectrometer at the Thomas Jefferson National Accelerator Facility. The pϕ final state is identified via reconstruction of KS in the invariant mass of two oppositely charged pions and by requiring the missing particle in the reaction γp →pKSX to be KL. The presented results significantly enlarge the existing data on ϕ photoproduction. These data, combined with the data from the charged decay mode, will help to constrain different mechanisms of ϕ photoproduction.

Reconciling threshold and subthreshold expansions for pion-nucleon scattering

Science.gov (United States)

Siemens, D.; Ruiz de Elvira, J.; Epelbaum, E.; Hoferichter, M.; Krebs, H.; Kubis, B.; Meißner, U.-G.

2017-07-01

Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion-nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the Δ (1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the Δ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the Δ-less theory the resummation of 1 /mN corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.

πN scattering and γN → Nπ photoproduction within the unitary improved Born approximation

Science.gov (United States)

Mariano, A.

2007-07-01

Following the programme of describing consistently several processes where the isobar Δ(1232 MeV) nucleon resonance appears as an intermediate state, in this work we propose to unitarize our old improved Born approximation already used to describe successfully π+p elastic and radiative scattering, to treat pion photoproduction. First we add the effect of final state interactions and make a new determination of the mass, width and the coupling constant to the pion-nucleon state of the Δ resonance. Then extending the model for pion photoproduction and using the resonance parameters determined previously, we are able to define effective form factors (at k2γ = 0) for the γN → Δ vertex with values GM = 2.97 ± 0.08 and GE = 0.055 ± 0.010, by fitting the data for the M3/21+ and E3/21+ multipoles. These values are fully consistent with recent chiral effective field theory calculations, and using them we can predict satisfactorily the data for other multipoles and the photoproduction cross section. Finally, we intend a model-independent determination of the bare form factors making a dynamical dressing of the vertex, getting G0M = 1.69 ± 0.02, G0E = 0.028 ± 0.008 and R0EM = -1.67 ± 0.45%, which are compared with different quark models.

Many-body effects in photoreactions of light nuclei below pion threshold

International Nuclear Information System (INIS)

Cavinato, M.; Marangoni, M.; Saruis, A.M.

1983-01-01

In the present paper it is discussed the reaction mechanism in photoabsorption of light nuclei below pion threshold in the frame of a self-consistent RPA theory with a Skyrme force. The role of both exchange currents in electromagnetic operators and two-body correlations in the nuclear wave function has been studied in the RPA formalism. Exchange currents in RPA calculations are related to the effective mass in the Hartree-Fock field. Comparison is made between the RPA formalism and the Gari and Hebach theory. The relative contribution of exchange currents and nuclear correlations to the photoreaction of 16 O is evaluated from proton threshold up to 80 MeV. E1 and E2 multipoles are included in the calculation

Exclusive ρ{sup 0} meson photoproduction with a leading neutron at HERA

Energy Technology Data Exchange (ETDEWEB)

Andreev, V.; Belousov, A.; Fomenko, A.; Gogitidze, N.; Lebedev, A.; Malinovski, E.; Rusakov, S.; Vazdik, Y. [Lebedev Physical Institute, Moscow (Russian Federation); Baghdasaryan, A.; Zohrabyan, H. [Yerevan Physics Institute, Yerevan (Armenia); Begzsuren, K.; Ravdandorj, T. [Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar (Mongolia); Bolz, A.; Huber, F.; Radescu, V.; Sauter, M.; Schoening, A. [Universitaet Heidelberg, Physikalisches Institut, Heidelberg (Germany); Boudry, V.; Specka, A. [LLR, Ecole Polytechnique, CNRS/IN2P3, Palaiseau (France); Brandt, G. [Universitaet Goettingen, II. Physikalisches Institut, Goettingen (Germany); Brisson, V.; Jacquet, M.; Pascaud, C.; Zhang, Z.; Zomer, F. [LAL, Universite Paris-Sud, CNRS/IN2P3, Orsay (France); Britzger, D.; Campbell, A.J.; Dodonov, V.; Eckerlin, G.; Elsen, E.; Fleischer, M.; Gayler, J.; Ghazaryan, S.; Haidt, D.; Kleinwort, C.; Krueger, K.; Levonian, S.; Lipka, K.; List, B.; List, J.; Meyer, A.B.; Meyer, J.; Niebuhr, C.; Olsson, J.E.; Ozerov, D.; Pirumov, H.; Pitzl, D.; Placakyte, R.; Schmitt, S.; Sefkow, F.; Shushkevich, S.; South, D.; Steder, M.; Wuensch, E. [DESY, Hamburg (Germany); Buniatyan, A.; Newman, P.R.; Thompson, P.D. [University of Birmingham, School of Physics and Astronomy, Birmingham (United Kingdom); Bylinkin, A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Moscow (Russian Federation); Bystritskaya, L.; Fedotov, A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Cantun Avila, K.B.; Contreras, J.G. [CINVESTAV, Departamento de Fisica Aplicada, Merida, Yucatan (Mexico); Cerny, K.; Pokorny, B.; Salek, D.; Valkarova, A.; Zacek, J.; Zlebcik, R. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Chekelian, V.; Grindhammer, G.; Kiesling, C.; Lobodzinski, B. [Max-Planck-Institut fuer Physik, Munich (Germany); Cvach, J.; Hladka, J.; Reimer, P. [Academy of Sciences of the Czech Republic, Institute of Physics, Prague (Czech Republic); Dainton, J.B.; Gabathuler, E.; Greenshaw, T.; Klein, M.; Kostka, P.; Kretzschmar, J.; Laycock, P.; Maxfield, S.J.; Mehta, A.; Patel, G.D. [University of Liverpool, Department of Physics, Liverpool (United Kingdom); Daum, K. [Fachbereich C, Universitaet Wuppertal, Wuppertal (Germany); Universitaet Wuppertal, Rechenzentrum, Wuppertal (Germany); Diaconu, C.; Hoffmann, D.; Vallee, C. [Aix Marseille Universite, CNRS/IN2P3, CPPM UMR 7346, Marseille (France); Dobre, M.; Rotaru, M. [Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering (IFIN-HH), Bucharest (Romania); Egli, S.; Horisberger, R. [Paul Scherrer Institut, Villigen (Switzerland); Favart, L.; Grebenyuk, A.; Hreus, T.; Janssen, X.; Roosen, R.; Van Mechelen, P. [Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerp (Belgium); Feltesse, J.; Schoeffel, L. [Irfu/SPP, CE Saclay, Gif-sur-Yvette Cedex (France); Ferencei, J. [Slovak Academy of Sciences, Institute of Experimental Physics, Kosice (Slovakia); Goerlich, L.; Mikocki, S.; Nowak, G.; Sopicki, P.; Turnau, J. [Institute of Nuclear Physics Polish Academy of Sciences, Krakow (Poland); Gouzevitch, M.; Petrukhin, A. [IPNL, Universite Claude Bernard Lyon 1, CNRS/IN2P3, Villeurbanne (France); Grab, C. [Institut fuer Teilchenphysik, ETH, Zurich (Switzerland); Henderson, R.C.W. [University of Lancaster, Department of Physics, Lancaster (United Kingdom); Jung, H. [Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerp (Belgium); DESY, Hamburg (Germany); Kapichine, M.; Morozov, A.; Spaskov, V. [Joint Institute for Nuclear Research, Dubna (RU); Kogler, R. [Universitaet Hamburg, Institut fuer Experimentalphysik, Hamburg (DE); Landon, M.P.J.; Rizvi, E.; Traynor, D. [Queen Mary, University of London, School of Physics and Astronomy, London (GB); Lange, W.; Naumann, T. [DESY, Zeuthen (DE); Martyn, H.U. [I. Physikalisches Institut der RWTH, Aachen (DE); Meyer, H. [Fachbereich C, Universitaet Wuppertal, Wuppertal (DE); Mueller, K.; Robmann, P.; Straumann, U.; Truoel, P. [Physik-Institut der Universitaet Zuerich, Zurich (CH); Perez, E. [CERN, Geneva (CH); Picuric, I.; Raicevic, N. [University of Montenegro, Faculty of Science, Podgorica (ME); Polifka, R. [Charles University, Faculty of Mathematics and Physics, Prague (CZ); University of Toronto, Department of Physics, Toronto, ON (CA); Povh, B. [Max-Planck-Institut fuer Kernphysik, Heidelberg (DE); Rostovtsev, A. [Institute for Information Transmission Problems RAS, Moscow (RU); Sankey, D.P.C. [STFC, Rutherford Appleton Laboratory, Didcot, Oxfordshire (GB); Sauvan, E. [Aix Marseille Universite, CNRS/IN2P3, CPPM UMR 7346, Marseille (FR); Universite de Savoie, CNRS/IN2P3, LAPP, Annecy-le-Vieux (FR); Soloviev, Y. [DESY, Hamburg (DE); Lebedev Physical Institute, Moscow (RU); Stella, B. [Universita di Roma Tre, Dipartimento di Fisica, Rome (IT); INFN Roma 3 (IT); Sykora, T. [Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerp (BE); Charles University, Faculty of Mathematics and Physics, Prague (CZ); Tsakov, I. [Institute for Nuclear Research and Nuclear Energy, Sofia (BG); Tseepeldorj, B. [Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar (MN); Ulaanbaatar University, Ulaanbaatar (MN); Wegener, D. [TU Dortmund, Institut fuer Physik, Dortmund (DE); Collaboration: H1 Collaboration

2016-01-15

A first measurement is presented of exclusive photoproduction of ρ{sup 0} mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energy of √(s) = 319 GeV and correspond to an integrated luminosity of 1.16 pb{sup -1}. The ρ{sup 0} mesons with transverse momenta p{sub T} < 1 GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum, x{sub L} > 0.35, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality Q{sup 2} < 2 GeV{sup 2}, the total energy of the photon.proton system 20 < W{sub γp} < 100 GeV and the polar angle of the leading neutron θ{sub n} < 0.75 mrad. The cross section of the reaction γp → ρ{sup 0}nπ{sup +} is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a ρ{sup 0} meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, σ{sup el}(γπ{sup +} → ρ{sup 0}π{sup +}), is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction γp → ρ{sup 0}nπ{sup +}. (orig.)

Photoproduction of mesons on the nucleon at intermediate energies; Photoproduction de mesons sur le nucleon aux energies intermediaires

Energy Technology Data Exchange (ETDEWEB)

Guidal, M

1997-01-01

In this work a model is proposed to simulate the photoproduction of pseudoscalar mesons ('PI' and K) on the nucleon at high energy. This model is based on the exchange of mesonic or baryonic Regge trajectories, it is gauge invariant and it uses a Feynman diagram formalism inspired from isobaric models. The measurements concerning the following reactions {gamma}p {yields} n{pi}{sup +}, {gamma}n {yields} p{pi}{sup -}, {gamma}p {yields} p{pi}{sup 0} and {gamma}n {yields} n{pi}{sup 0} are reviewed and the new model is confronted to the experimental results. The model gives a reasonable and coherent description of these 4 reactions. The model has also been applied to the photoproduction of strange mesons and of {lambda} and {sigma} baryons and has been extrapolated at low energy to the threshold of the reaction, the model matches the results even up to E{sub {gamma}} = 2 GeV for differential cross-sections and recoil polarization. An attempt has been made to associate a Regge based description, which is valid with low transfers, with perturbative quantum chromodynamics which is valid with high transfers. The model relies on the saturation of trajectories in the high transfer region and on the counting laws that give the right variation of the cross-section. It seems that a model based on linear trajectories can be reliable up to 4 GeV. The domain of high transfer has been too little investigated to provide enough experimental data to validate the model. An experiment whose purpose is to study the photoproduction of {phi} at high transfer, is proposed. This experiment requires an accelerator with high useful cycle because of the smallness of the expected cross-section. The CEBAF (continuous electron beam accelerator facility) as well as the CLAS 4{pi} detector is presented. The study of {gamma}p {yields} p{phi} and {gamma}p {yields} K{lambda}{sup *} (1520) requires the discrimination of kaons from pions so the measurement of 180 ps as time resolution allows the

Coupled-channel analysis for phi photoproduction with Lambda

NARCIS (Netherlands)

Ozaki, S.; Hosaka, A.; Nagahiro, H.; Scholten, O.

We investigate photoproduction of phi mesons off protons within a coupled-channel effective-Lagrangian method which is based on the K-matrix approach. Since the threshold energy of the K Lambda(1520) channel is close to that of phi N, the contribution of this channel to f photoproduction near the

Scale of corrections to the t-pole approximation in the quasielastic knockout of pions from nucleon by high energy electrons

CERN Document Server

Neudachin, V G; Yudin, N P

2002-01-01

Investigation of the dominant role of the simplest t-pole diagrams is completed in the processes of pion electroproduction on nucleons at quasielastic knock out kinematics and electron energies of a few GeV. Competition role of pi- and rho-meson t-pole diagrams and s-pole diagram (tree diagram) is regarded. When virtual photon mass is large enough (Q sup 2 >= 2 (GeV/c) sup 2), the latter amplitude is not essential both for longitudinal (d sigma sub L /dt) and for transverse (d sigma sub T /dt) cross sections. At Q sup 2 = 0.7 (GeV/c) sup 2 in the longitudinal cross section the interference term between pion t-pole and s-pole amplitudes is still essential. Vertex functions g subrho sub N sub N (t), obtained from the cross sections of the quasielastic knockout of rho mesons and from cross section of pion photoproduction, are compared. Their discrepancy must give impulse to the development of gauge invariant theory of pion photoproduction

Helicity Asymmetry Measurement for π⁰ Photoproduction with FROST

Energy Technology Data Exchange (ETDEWEB)

Iwamoto, Hideko [George Washington Univ., Washington, DC (United States)

2011-08-15

This thesis reports on the first helicity asymmetry measurement for single neutral pion photoproduction using the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This measurement used longitudinally polarized protons and circularly polarized photons at energies between 350 MeV and 2400 MeV. The experimental results are compared to three available model calculations.

Helicity Asymmetry Measurement for pi⁰ Photoproduction with FROST

Energy Technology Data Exchange (ETDEWEB)

Iwamoto, Hideko [George Washington Univ., Washington, DC (United States)

2011-08-15

This thesis reports on the first helicity asymmetry measurement for single neutral pion photoproduction using the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This measurement used longitudinally polarized protons and circularly polarized photons at energies between 350 MeV and 2400 MeV. The experimental results are compared to three available model calculations.

Measurement of elastic ω photoproduction at HERA

International Nuclear Information System (INIS)

Derrick, M.; Krakauer, D.; Magill, S.

1996-08-01

The reaction γp→ωp (ω→π + π - π 0 and π 0 →γγ) has been studied in ep interactions using the ZEUS detector at photon-proton centre-of-mass energies between 70 and 90 GeV and vertical stroke t vertical stroke 2 , where t is the squared four momentum transferred at the proton vertex. The elastic ω photoproduction cross section has been measured to be σ γp→ωp =1.21±0.12±0.23 μb. The differential cross section dσ γp→ωp /d vertical stroke t vertical stroke has an exponential shape e -b vertical stroke t vertical stroke with a slope b=10.0±1.2±1.3 GeV -2 . The angular distributions of the decay pions are consistent with s-channel helicity conservation. When compared to low energy data, the features of ω photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the ρ 0 and φ photoproduction cross sections at HERA show a similar behaviour. (orig.)

Measurement of coherent π0 photoproduction on 3He and 3H in the resonance region

International Nuclear Information System (INIS)

Bellinghausen, B.; Gassen, H.J.; Reese, E.; Reichelt, T.; Stipp, P.

1984-01-01

Neutral pion photoproduction has been measured on 3 He and 3 H nuclei in the Δ(1,232) resonance region. Resonance averaged cross-sections are presented as a function of momentum transfer and compared to theoretical calculations. (orig.)

Measurement of Beauty Photoproduction near Threshold using Di-electron Events with the H1 Detector at HERA

CERN Document Server

Aaron, F.D.; Andreev, V.; Backovic, S.; Baghdasaryan, A.; Baghdasaryan, S.; Barrelet, E.; Bartel, W.; Begzsuren, K.; Belousov, A.; Belov, P.; Bizot, J.C.; Boudry, V.; Bozovic-Jelisavcic, I.; Bracinik, J.; Brandt, G.; Brinkmann, M.; Brisson, V.; Britzger, D.; Bruncko, D.; Bunyatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A.J.; Cantun Avila, K.B.; Ceccopieri, F.; Cerny, K.; Cerny, V.; Chekelian, V.; Contreras, J.G.; Coughlan, J.A.; Cvach, J.; Dainton, J.B.; Daum, K.; Delcourt, B.; Delvax, J.; De Wolf, E.A.; Diaconu, C.; Dobre, M.; Dodonov, V.; Dossanov, A.; Dubak, A.; Eckerlin, G.; Egli, S.; Eliseev, A.; Elsen, E.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Fischer, D.J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Habib, S.; Haidt, D.; Henderson, R.C.W.; Hennekemper, E.; Henschel, H.; Herbst, M.; Herrera, G.; Hildebrandt, M.; Hiller, K.H.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jonsson, L.; Jung, A.W.; Jung, H.; Kapichine, M.; Kenyon, I.R.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kramer, M.; Kretzschmar, J.; Kruger, K.; Landon, M.P.J.; Lange, W.; Lastovicka-Medin, G.; Laycock, P.; Lebedev, A.; Lendermann, V.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Lopez-Fernandez, R.; Lubimov, V.; Malinovski, E.; Martyn, H.U.; Maxfield, S.J.; Mehta, A.; Meyer, A.B.; Meyer, H.; Meyer, J.; Mikocki, S.; Milcewicz-Mika, I.; Moreau, F.; Morozov, A.; Morris, J.V.; Muller, K.; Naumann, Th.; Newman, P.R.; Niebuhr, C.; Nikitin, D.; Nowak, G.; Nowak, K.; Olivier, B.; Olsson, J.E.; Ozerov, D.; Pahl, P.; Palichik, V.; Pandurovic, M.; Pascaud, C.; Patel, G.D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Placakyte, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Ruiz Tabasco, J.E.; Rusakov, S.; Salek, D.; Sankey, D.P.C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schoning, A.; Schultz-Coulon, H.C.; Sefkow, F.; Shtarkov, L.N.; Shushkevich, S.; Sloan, T.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Staykova, Z.; Steder, M.; Stella, B.; Stoicea, G.; Straumann, U.; Sykora, T.; Thompson, P.D.; Tran, T.H.; Traynor, D.; Truol, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wunsch, E.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhokin, A.; Zlebcik, R.; Zohrabyan, H.; Zomer, F.

2012-10-03

The cross section for ep -> e b\\bar{b} X in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel b\\bar{b} -> ee X' is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q^2 down to the threshold. The results are compared to next-to-leading-order QCD predictions.

Polarisation observables F and T in double π{sup 0} photoproduction

Energy Technology Data Exchange (ETDEWEB)

Garni, Stefanie [Departement of Physics, University of Basel, CH-4056 Basel (Switzerland); Collaboration: A2-Collaboration

2013-07-01

The measurement of single and double polarization observables gives information about the different resonance contributions to the cross section and hence leads to a better understanding of the nucleon and it's excited states. Double π{sup 0} photo-production is a very interesting reaction for the investigation of nuclear resonances. Photo-production of pion pairs allows to study states which decay preferentially via intermediate resonances. The double neutral channel has the additional advantage of only small non-resonant background contributions. Double π{sup 0}-photo-production off a transversally polarized H-butanol target has been measured using circularly polarized bremsstrahlung photons produced by MAMI-C with incident energies up to 1.5 GeV. The double π{sup 0} reaction was identified using a combined setup of the Crystal Ball colorimeter and a TAPS forward wall which results in an almost 4π acceptance. Preliminary results on the single polarization observable T and double polarization observable F are presented.

Meson Spectroscopy in Photo-production at CLAS

OpenAIRE

Nozar, Mina

2003-01-01

Photo-production of excited mesons in the 1-2 GeV mass range decaying via multi-pion or multi-kaon emission has been investigated at the TJNAF\\thanks{This work was supported by the U.S. Department of Energy and The U.S. National Science Foundation.} experiment E01-017 (g6c) in the $4.8-5.4$ GeV photon beam energy range. The main objective of the experiment is to extract resonance parameters of the produced states by way of a Partial Wave Analysis (PWA) technique. In this paper, we will focus ...

Exclusive ρ.sup.0./sup. meson photoproduction with a leading neutron at HERA

Czech Academy of Sciences Publication Activity Database

Andreev, V.; Baghdasaryan, A.; Begzsuren, K.; Cvach, Jaroslav; Hladký, Jan; Reimer, Petr

2016-01-01

Roč. 76, č. 1 (2016), 1-21, č. článku 41. ISSN 1434-6044 R&D Projects: GA MŠk LG14033 Institutional support: RVO:68378271 Keywords : deep-inelastic scattering * vector meson production * pion exchange model * elastic photoproduction Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 5.331, year: 2016

Optimal sum-rule inequalities for spin 1/2 Compton scattering. III

International Nuclear Information System (INIS)

Filkov, L.V.

1980-10-01

The analyticity (optimal) bounds for proton Compton scattering presented in the preceding paper are herewith considered from the point of view of experimental tests. An essential function occuring in this new dispersion framework is constructed numerically making use of existing cross-section data above the pion photoproduction threshold. To secure a safer construction new measurements in the photon laboratory energy region 150 MeV - 240 MeV and at small momentum transfers are necessary. The bounds on the scattering amplitudes in the low energy region below the pion photoproduction threshold are in general sufficiently restrictive so as to be useful in discriminating among variants of theoretical phenomenological analyses but subsequent extremizations needed in bounding only one combination of the amplitudes (the unpolarized differential cross-section) are weakening much the results. The question of strengthening the bounds by means of the combined use of analyticity and unitarity is discussed within a very crude example which nonetheless illustrates that the inclusion of the pion photoproduction data through more elaborate mathematical procedures would deserve the effort. (author)

F observable in double π{sup 0}-photoproduction

Energy Technology Data Exchange (ETDEWEB)

Garni, Stefanie [Department of Physics, University of Basel, CH-4056 Basel (Switzerland); Collaboration: A2-Collaboration

2014-07-01

The measurement of single and double polarization observables gives information about the different resonance contributions in the cross section and hence leads to a better understanding of the nucleon and its excited states. The double π{sup 0}-photoproduction is one of the most interesting reaction for the measurement of these observables. It allows to search for excited nucleon states which decay preferentially via cascades involving intermediate excited states. Furthermore, the background from non-resonant terms is small since the photon does not couple directly to neutral pions. Double π{sup 0}-photoproduction off a transversally polarized H-Butanol target has been measured using circularly polarized bremsstrahlung photons produced by MAMI-C with incident energies up to 1.5 GeV. The double π{sup 0} reaction was identified using a combined setup of the Crystal Ball colorimeter and a TAPS forward wall which results in an almost 4π acceptance. Preliminary results on the single polarization observable T and double polarization observable F are presented.

Exclusive Meson Photoproduction off Bound Nucleons

Science.gov (United States)

Strakovsky, Igor; Briscoe, William

2017-09-01

An overview of the GW SAID group effort to analyze pion photoproduction on the neutron-target will be given. The disentangling of the isoscalar and isovector EM couplings of N * and Δ * resonances does require compatible data on both proton and neutron targets. The final-state interactions play a critical role in the state-of-the-art analysis in extraction of the γn -> π N data from the deuteron target experiments. Then resonance couplings determined by the SAID PWA technique are compared to previous findings. The neutron program is an important component of the current JLab, MAMI-C, SPring-8, ELSA, and ELPH studies. DOE Research Grant DE``SC0016583.

Recent results in photoproduction with real and virtual photons

International Nuclear Information System (INIS)

Diekmann, B.

1984-10-01

An overview of recent experimental results on soft photon-hadron-interactions is given. It contains results on inclusive photoproduction of rho and ω-mesons, hyperons and the totally inclusive reaction: γp -> Xp. Results on the search for radially excited vectormesons and on the determination of the radiative width of the rho- meson are updated. An improved measurement of the pion form factor and a test of Vector-Meson-Dominance in case of virtual photons (vertical strokeq 2 vertical stroke 2 ) will be presented. (orig.)

Application of a Regge model to the photoproduction of pion pairs

Energy Technology Data Exchange (ETDEWEB)

Bolz, Arthur; Sauter, Michel; Schoening, Andre [Physikalisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 226, D-69120 Heidelberg (Germany); Ewerz, Carlo [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt (Germany); Maniatis, Markos [Departamento de Ciencias Basicas, Universidad del Bio-Bio, Avda. Andres Bello s/n, Casilla 447, Chillan 3780000 (Chile); Nachtmann, Otto [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)

2015-07-01

In a recent publication (arXiv:1409.8483) a model in the spirit of Regge theory is used to describe the reaction γp → π{sup +}π{sup -} p at high energies. Both resonant pion-pion production via the meson resonances ρ(770), ω(782), ρ(1450) and f{sub 2}(1270) as well as non-resonant amplitudes are considered. Photon and proton interact by the exchange of the photon, the pomeron and reggeons as well as by a yet unobserved but possible odderon. Cross sections calculated from this model and their dependencies on various kinematic quantities are discussed and compared to experimental data. The focus is on angular distributions which feature asymmetries that could be used for an odderon discovery.

Coupled channel theory of pion--deuteron reaction applied to threshold scattering

International Nuclear Information System (INIS)

Mizutani, T.; Koltun, D.S.

1977-01-01

Scattering and absorption of pions by a nuclear target are treated together in a coupled channel theory. The theory is developed explicitly for the problem of pion scattering and absorption by a deuteron. The equations are presented in terms of the integral equations of three-body scattering theory. The method is then applied in an approximate from to calculate the contribution of pion absorption to the scattering length for pion--deuteron scattering. The sensitivity of the calculated results to the model assumptions and approximations is investigated

Role of delta excitations in pion-, photon- and nucleon-nucleus reactions studied with microscopic models

International Nuclear Information System (INIS)

Engel, A.

1995-01-01

Delta excitation plays a prominent role in intermediate heavy reactions. In this paper, comment is made on the calculations done for pion-, photon- and nucleon-nucleus reactions using the Boltzmann-Uehling-Uhlenbeck (BUU) model and the antisymmetrized molecular dynamics (AMD) model. First, it is recalled how to include delta degrees in microscopic models in general. Then, the comparison of the microscopic calculation performed by the author with the experimental data is presented. Deltas in microscopic models are discussed. Pion-nucleus reactions have been studied since pion beams became available, especially for exploring the delta resonance in a nuclear medium. The dependence of pion absorption cross section on incident pion energy is shown. The photon-induced pion production in the resonance energy region was studied with the BUU model. The calculated results of neutral pion photo-production are shown. In both inelastic proton scattering and (p,n) charge exchange reaction, the excitation of delta resonance can be observed clearly in the experimental data. The results of the AMD calculation for 12 C(p,p') reaction are shown. (K.I.)

Pion, pion-pion, and pion-nucleus interactions

CERN Document Server

Mukhin, K N; Tikhonov, V N

2002-01-01

This survey is devoted to describing the early studies of 1.1. Gurevich on pion physics that were performed by the photoemulsion method and the studies of the pion-pion interaction that were made by his colleagues on the basis of the hydrogen-bubble-chamber and the magnetic-spectrometer method (as well-as on the basis of the photoemulsion method). Two approaches-an extrapolation of experimental data from the physical region to the pion pole and a theoretical calculation based on the Roy integral equations-are used to deduce information about the pion-pion interaction. The first results obtained for pion-pion and pion-nucleus interactions in the experiments that are being currently performed in Brookhaven and at CERN ( pi pi interaction) and at TRIUMF (Canada) and in Brookhaven (pion-nucleus interaction) are presented, along with the existing theoretical concepts in these realms of physics. (80 refs).

From meson-baryon scattering to meson photoproduction

Energy Technology Data Exchange (ETDEWEB)

Mai, Maxim

2013-09-01

In the present work we investigate the properties of the lowest baryon resonances. The starting point of our analyses is the low-energy effective theory of quantum chromodynamics, called chiral perturbation theory. As such it describes the long-range observables in terms of the low-energy effects, while the high-energy effects are subsumed in the so-called low-energy constants. In the region of the aforesaid lowest baryon resonances any strict perturbative expansion fails and some resummation scheme is required. For this we employ the Bethe-Salpeter equation (BSE) which guarantees the exact unitarity of the S-matrix and allows to generate resonances dynamically, however, abandoning some other basic principles of quantum field theory as described in chapter 2. Restricting the driving term of this equation to local terms of the second chiral order, we derive an exact solution of the BSE for meson-baryon scattering in chapter 2. Without putting the interaction kernel on shell we preserve the exact correspondence of this solution to an infinite chain of Feynman diagrams. In chapter 4 we apply this ansatz for antikaon-nucleon scattering, trying to get a new insight into the nature of the subthreshold resonance, i.e. {Lambda}(1405). The properties of this resonance have been debated for decades and in recent years it has again attracted a lot of attention by theoreticians since this resonance can be dynamically generated from the so-called chiral unitary approaches. Moreover, the recent measurement of the energy shift and width of kaonic hydrogen in the SIDDHARTA experiment at DA{Phi}NE has provided a very tight constraint on K{sup -}p scattering length. Typically, these approaches predict a two pole structure of {Lambda}(1405), but the question is how precise one can determine the position of these poles relying on data at and above the anti KN threshold. Moreover, we apply our framework for the analysis of pion-nucleon scattering in chapter 3. There we show that the

Low energy theorems in pion production

International Nuclear Information System (INIS)

Holstein, B.R.; Washington Univ., Seattle, WA

1992-01-01

Considerable activity-both theoretical and experimental-has recently taken place involving the threshold and near threshold of pion photo- and electroproduction. This activity is herein summarized and a program for future work is outlined

Off-shell effects in the coherent π0 photoproduction off nuclei

International Nuclear Information System (INIS)

Chumbalov, A.A.; Kamalov, S.S.

1987-01-01

A strong sensitivity of coherent π 0 -meson photoproduction on nuclei to different ω reaction energy change in elementary amplitude t πγ (ω) is demonstrated. Various assumptions concerning ω behaviour in the extraenergy area can change differential cross sections 1.5-2 times. The best agreement of the DWIA-results with experimental data is obtained at ω being equal to its own value of pion-nucleon system free relativistic Hamiltonian. Such a result agrees with relativistic potential theory effects

Low-energy photoproduction of omega-mesons

CERN Document Server

Barth, J; Glander, K H; Hannappel, J; Jöpen, N; Klein, F; Lawall, R; Menze, D; Neuerburg, W; Ostrick, M; Paul, E; Schulday, I; Schwille, W J; Wiegers, B; Ernst, J; Kalinowsky, H; Klempt, E; Link, J; Pee, H V; Klein, F J; Wieland, F W; Wisskirchen, J; Wu, C

2003-01-01

The photoproduction of the vector meson omega has been studied between threshold and W=2.4 GeV with the SAPHIR detector at the Bonn electron stretcher ring ELSA. Besides, the total cross-sections angular distributions in the CMS and decay angular distributions in the helicity and Gottfried-Jackson systems have been measured.

Radiation-accompanied pion photoproduction on the proton

International Nuclear Information System (INIS)

Rost, M.

2004-01-01

In the year 1997, Tatischeff et al. found resonance-like states in the invariant mass spectrum of the missing particle X at M=1004, 1044 and 1094 MeV, utilizing the reaction pp→Xpπ + . Investigating the reaction pd→ppX, resonance structures have been observed at M=966, 986 and 1003 MeV in a further experiment by Filkov et al. Such kinds of exotic states contradict various nucleon models which describe the Δ(1232) resonance as the first excited state. Instead, quark cluster models with and without color-magnetic interactions have been formulated to explain these resonance structures. Lvov et al. argued that no such structure had been reported in real Compton scattering data. As a counter argument, Kobushkin suggested that these resonances have a total anti-symmetric spin-flavour wave function and therefore only the N-2γ decay channel is allowed. In this work, the reaction γp→X 0 π + →nγγπ + is utilized for the search of these exotic resonances. Data were taken in parallel with the pion polarizability experiment at the MAMI accelerator facility in Mainz. Real photons are created by the bremsstrahlung process of the electrons in a thin radiator foil. Their energy is determined by the A2 photon tagging facility (Glasgow tagger). A 10 cm long liquid hydrogen target was used as a proton target. Charged reaction products are detected in a multi wire proportional chamber in forward direction, at theta 2 crystals containing TAPS spectrometer at polar angles of theta >60 . For neutron detection, a time of flight detector with 111 single modules was used. Additionally, the reaction channels γp→pπ 0 and γp→nπ 0 π + are analysed to test the apparatuses. For single pion production, differential cross sections are obtained and compared with theoretical models as well as experimental data. For the γp→nπ 0 π + channel, invariant mass spectra of particles in the final state are determined and compared with simulation. The data indicate that the main

Separation of minimum and higher twist in the photoproduction of mesons with large transverse momenta

International Nuclear Information System (INIS)

Hoeger, K.C.

1990-10-01

Higher-twist effects in point-like photon interactions on hydrogen have been studied in xF-distributions of charged particles for -0.2 2.0 GeV/c. Data were taken with a tagged photon beam with energies between 70 and 170 GeV and a pion/kaon beam at fixed energies of 80 and 140 GeV using the same setup of detectors at the CERN-Ω-spectrometer (WA69 experiment). The pion and kaon interactions were used to obtain an estimate of the hadron-like photon component. A first estimation of Higher-Twist cross sections in photoproduction of mesons at high pT has been obtained that is consistent with QCD-expectations. (orig.) [de

Evidence for a backward peak in the γd→π0d cross section near the η threshold

International Nuclear Information System (INIS)

Ilieva, Y.; Berman, B.L.; Strakovsky, I.I.; Benmouna, N.; Briscoe, W.J.; Feldman, G.; Munevar, E.; Nadel-Turonski, P.; Tkabladze, A.; Kudryavtsev, A.E.; Tarasov, V.E.; Bedlinskiy, I.; Kossov, M.; Kuleshov, S.V.; Mikhailov, K.; Pivnyuk, N.; Pogorelko, O.; Pozdniakov, S.; Serov, V.S.; Stavinsky, A.; Vlassov, A.V.; Amarian, M.; Bagdasaryan, H.; Bueltmann, S.; Careccia, S.L.; Dodge, G.E.; Gavalian, G.; Guler, N.; Hyde-Wright, C.E.; Juengst, H.G.; Kalantarians, N.; Klein, A.; Kuhn, S.E.; Lachniet, J.; Niroula, M.R.; Tkachenko, S.; Weinstein, L.B.; Zhang, J.; Ambrozewicz, P.; Gonenc, A.; Moteabbed, M.; Anghinolfi, M.; Battaglieri, M.; De Vita, R.; Ricco, G.; Ripani, M.; Stoler, P.; Taiuti, M.; Asryan, G.; Egiyan, K.S.; Avakian, H.; Boiarinov, S.; Brooks, W.K.; Burkert, V.D.; Carman, D.S.; Degtyarenko, P.V.; Deur, A.; Egiyan, H.; Elouadrhiri, L.; Guo, L.; Gyurjyan, V.; Ito, M.M.; Laget, J.M.; Mecking, B.A.; Mestayer, M.D.; Niczyporuk, B.B.; Niyazov, R.A.; Nozar, M.; Sapunenko, V.; Sharabian, Y.G.; Smith, E.S.; Stepanyan, S.; Thoma, U.; Weygand, D.P.; Wolin, E.; Yegneswaran, A.; Baillie, N.; Butuceanu, C.; Funsten, H.; Griffioen, K.A.; Ball, J.P.; Collins, P.; Dugger, M.; Pasyuk, E.; Ritchie, B.G.; Baltzell, N.A.; Djalali, C.; Dzyubak, O.P.; Gothe, R.W.; Langheinrich, J.; Lu, H.; Nasseripour, R.; Strauch, S.; Tedeschi, D.J.; Tur, C.; Wood, M.H.; Zhao, Z.; Batourine, V.; Kim, W.; Park, K.; Stepanyan, S.S.; Bellis, M.; Bradford, R.; Dickson, R.; Krahn, Z.; Kuhn, J.; Meyer, C.A.; Moriya, K.; Schumacher, R.A.; Williams, M.; Biselli, A.S.; Bouchigny, S.; Guidal, M.; Jo, H.S.; MacCormick, M.; Niccolai, S.; Branford, D.; Watts, D.P.; Calarco, J.R.; Hersman, F.W.; Holtrop, M.; Zana, L.; Chen, S.; Coltharp, P.; Crede, V.; Eugenio, P.; Ostrovidov, A.I.; Stokes, B.E.; Cole, P.L.; Crabb, D.; Pierce, J.; Prok, Y.; Smith, L.C.; De Masi, R.; Garcon, M.; Girod, F.X.; Sabatie, F.; De Sanctis, E.; Mirazita, M.; Ronchetti, F.; Rossi, P.; Donnelly, J.; Ireland, D.G.; Kellie, J.D.; Livingston, K.; McKinnon, B.; Paterson, C.; Protopopescu, D.; Rosner, G.; Doughty, D.; Fedotov, G.; Ishkhanov, B.S.; Isupov, E.L.; Mokeev, V.; Shvedunov, N.V.; Gilfoyle, G.P.; Giovanetti, K.L.; Niculescu, G.; Niculescu, I.; Goetz, J.T.; Hafidi, K.; Hakobyan, R.S.; Klein, F.J.; Sober, D.I.; Hicks, K.; Hleiqawi, I.; Mibe, T.; Jenkins, D.; Joo, K.; Markov, N.; Ungaro, M.; Zhao, B.; Khandaker, M.; Salgado, C.; Kramer, L.H.; Raue, B.A.; Kubarovsky, V.; Lawrence, D.; Miskimen, R.; Morrow, S.A.; Mutchler, G.S.; Osipenko, M.; Price, J.W.; Santoro, J.P.; Vineyard, M.F.

2010-01-01

High-quality cross sections for the reaction γd→π 0 d have been measured using the CLAS at Jefferson Lab over a wide energy range near and above the η-meson photoproduction threshold. At backward c.m. angles for the outgoing pions, we observe a resonance-like structure near E γ =700 MeV. Our model analysis shows that it can be explained by η excitation in the intermediate state. The effect is the result of the contribution of the N(1535)S 11 -resonance to the amplitudes of the subprocesses occurring between the two nucleons and of a two-step process in which the excitation of an intermediate η-meson dominates. (orig.)

Observation of a backward peak in the gamma d ---> pi0 d cross- section near the eta threshold

Energy Technology Data Exchange (ETDEWEB)

Yordanka Ilieva; Barry Berman; Alexander Kudryavtsev; I.I. Strakovsky; V.E. Tarasov; Moscov Amaryan; Pawel Ambrozewicz; Marco Anghinolfi; G. Asryan; Harutyun Avakian; Hovhannes Baghdasaryan; Nathan Baillie; Jacques Ball; Nathan Baltzell; V. Batourine; Marco Battaglieri; Ivan Bedlinski; Ivan Bedlinskiy; Matthew Bellis; Nawal Benmouna; Angela Biselli; Sylvain Bouchigny; Sergey Boyarinov; Robert Bradford; Derek Branford; William Briscoe; William Brooks; Stephen Bueltmann; Volker Burkert; Cornel Butuceanu; John Calarco; Sharon Careccia; Daniel Carman; Shifeng Chen; Philip Cole; Patrick Collins; Philip Coltharp; Donald Crabb; Volker Crede; R. De Masi; Enzo De Sanctis; Raffaella De Vita; Pavel Degtiarenko; Alexandre Deur; Richard Dickson; Chaden Djalali; Gail Dodge; Joseph Donnelly; David Doughty; Michael Dugger; Oleksandr Dzyubak; Hovanes Egiyan; Kim Egiyan; Latifa Elouadrhiri; Paul Eugenio; Gleb Fedotov; Gerald Feldman; Herbert Funsten; Michel Garcon; Gagik Gavalian; Gerard Gilfoyle; Kevin Giovanetti; Francois-Xavier Girod; John Goetz; Atilla Gonenc; Ralf Gothe; Keith Griffioen; Michel Guidal; Nevzat Guler; Lei Guo; Vardan Gyurjyan; Kawtar Hafidi; Rafael Hakobyan; F. Hersman; Kenneth Hicks; Ishaq Hleiqawi; Maurik Holtrop; Charles Hyde; Charles Hyde-Wright; David Ireland; Boris Ishkhanov; Eugeny Isupov; Mark Ito; David Jenkins; Hyon-Suk Jo; Kyungseon Joo; Henry Juengst; Narbe Kalantarians; James Kellie; Mahbubul Khandaker; Wooyoung Kim; Andreas Klein; Franz Klein; Mikhail Kossov; Zebulun Krahn; Laird Kramer; V. Kubarovsky; Joachim Kuhn; Sebastian Kuhn; Sergey Kuleshov; Jeff Lachniet; Jean Laget; Jorn Langheinrich; David Lawrence; Kenneth Livingston; Haiyun Lu; Marion MacCormick; Nikolai Markov; Bryan McKinnon; Bernhard Mecking; Mac Mestayer; Curtis Meyer; Tsutomu Mibe; Konstantin Mikhaylov; Marco Mirazita; Rory Miskimen; Viktor Mokeev; Kei Moriya; Steven Morrow; M. Moteabbed; E. Munevar; Gordon Mutchler; Pawel Nadel-Turonski; Rakhsha Nasseripour; Silvia Niccolai; Gabriel Niculescu; Maria-Ioana Niculescu; Bogdan Niczyporuk; Megh Niroula; Rustam Niyazov; Mina Nozar; Mikhail Osipenko; Alexander Ostrovidov; K. Park; Evgueni Pasyuk; Craig Paterson; Joshua Pierce; Nikolay Pivnyuk; Oleg Pogorelko; S. Pozdniakov; John Price; Yelena Prok; Dan Protopopescu; Brian Raue; Giovanni Ricco; Marco Ripani; Barry Ritchie; Federico Ronchetti; Guenther Rosner; Patrizia Rossi; Franck Sabatie; Carlos Salgado; Joseph Santoro; Vladimir Sapunenko; Reinhard Schumacher; Vladimir Serov; Youri Sharabian; Nikolay Shvedunov; Elton Smith; Lee Smith; Daniel Sober; Aleksey Stavinskiy; Samuel Stepanyan; Stepan Stepanyan; Burnham Stokes; Paul Stoler; Steffen Strauch; Mauro Taiuti; David Tedeschi; Ulrike Thoma; Avtandil Tkabladze; Svyatoslav Tkachenko; Clarisse Tur; Maurizio Ungaro; Michael Vineyard; Alexander Vlassov; Lawrence Weinstein; Dennis Weygand; M. Williams; Elliott Wolin; Michael Wood; Amrit Yegneswaran; Lorenzo Zana; Jixie Zhang; Bo Zhao; Zhiwen Zhao

2007-05-14

High-quality cross sections for the reaction gamma+d->pi^0+d have been measured using the CLAS at Jefferson Lab over a wide energy range near and above the eta-meson photoproduction threshold. At backward c.m. angles for the outgoing pions, we observe a resonance-like structure near E_gamma=700 MeV. Our model analysis shows that it can be explained by eta excitation in the intermediate state. The effect is the result of the contribution of the N(1535)S_11 resonance to the amplitudes of the subprocesses occurring between the two nucleons and of a two-step process in which the excitation of an intermediate eta meson dominates.

Study of the photoproduction of the vector meson Φ(1020) and the hyperon Λ(1520) from the production threshold up to a photon energy of 2.65 GeV with SAPHIR

International Nuclear Information System (INIS)

Wiegers, B.

2001-05-01

The photoproduction of the vector meson φ(1020) and the hyperon Λ(1520) have been measured in the finale state pK + K - from their thresholds up to 2.65 GeV using the high duty-factor electron accelerator ELSA and the 4π-detectorsystem SAPHIR. The t-dependence of φ(1020)-production shows an exponential behavior as expected from diffractive production. s-channel helicity conservation can be seen in the decay angular distribution in the helicity frame. The decay angular distribution in the Gottfried-Jackson frame is not conformable with the exchange of a Pomeron in the t-channel. For the first time, differential cross sections of the Λ(1520) photoproduction from the threshold are measured. The production angular distribution and the decay angular distribution in the Gottfried-Jackson frame show a K * exchange in the t-channel. (orig.)

Pseudoscalar meson photoproduction. Two {pi}{sup o} production on proton at GRAAL; Photoproduction de mesons pseudoscalaires. Production de deux {pi}{sup o} sur le proton a GRAAL

Energy Technology Data Exchange (ETDEWEB)

Guinault, Emmanuelle [Institut National de Physique Nucleaire et de Physique des Particules (India2P3), 75 - Paris (France)

1997-09-30

The GRAAL experiment is located at the ESRF synchrotron in Grenoble. It consists of a detection system with a large angle and a gamma beam obtained by Compton backscattering of a laser beam on the electrons of the ESRF`s storage ring. This experimental setup is devoted to the study of pseudoscalar meson photoproduction between 600 MeV and 1100 MeV. The optical setup used for the Compton backscattering is described. Beam polarization is an important parameter and two systems have been developed to analyse the polarization state of the laser beam. Preliminary measurements have been performed on the two neutral pions channel and beam asymmetry observable {Sigma} have been obtained. Invariant mass distributions of the systems (p, {pi}{sup o}) and ({pi}, {pi}) have also been calculated. Moreover, a simulation of strangeness photoproduction has been done. It shows that it is possible to study it with the GRAAL detector and a gamma beam of a larger energy. (author) 71 refs., 83 figs., 11 tabs.

The pseudo-scalar form factor of the nucleon, the sigma-like term, and the L0+ amplitude for charged pion electro-production near threshold

International Nuclear Information System (INIS)

Cheoun, Myung Ki; Kim, K.S.

2007-01-01

The pseudo-scalar form factor, which represents the pseudo-scalar quark density distribution due to finite quark masses on the nucleon, is shown to manifest itself with the induced pseudo-scalar form factor in the L 0 + amplitude for the charged pion electro-production. Both form factors show their own peculiar momentum dependence. Under the approximation on which the Goldberger-Treiman relation holds, a sum of both form factors' contributions accounts for the t-channel contribution in the charged pion electro-production near threshold

NNLO contributions to jet photoproduction and determination of {alpha}{sub s}

Energy Technology Data Exchange (ETDEWEB)

Klasen, Michael; Michael, Markus [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Kramer, Gustav [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

2013-10-15

We present the first calculation of inclusive jet photoproduction with next-to-next-to-leading order (NNLO) contributions, obtained from a unified threshold resummation formalism. The leading coefficients for direct photoproduction are computed analytically. Together with the coefficients pertinent to parton-parton scattering, they are shown to agree with those appearing in our full next-to-leading order calculations. For hadron-hadron scattering, numerical agreement is found with a previous calculation of jet production at the Tevatron. We show that the direct and resolved NNLO contributions considerably improve the description of final ZEUS data on jet photoproduction and that the error on the determination of the strong coupling constant is significantly reduced.

a Kinematically Complete Measurement of Positive Pion Production from Protons Near Threshold.

Science.gov (United States)

Hardie, John George

The total cross section for the reaction pp to pnpi^+ was measured at 294, 300, 307, 314, and 320 MeV. Angular distributions for the same reaction were measured at 294, 300 and 320 MeV. This is the first measurement of this reaction channel within 50 MeV of threshold. Study of pion production near threshold allows examination of the short range parts of the NN interaction, particularly the non-resonant partial waves. The data indicates that the contribution of p-waves to the pp to pnpi^+ reaction remains smaller than 20% up to 320 MeV. The total cross section data is compared to the theoretical calculations of Schillaci, Silbar and Young (1969) and Lee and Matsuyama (1987). Both reproduce some features of the data, but neither theory completely explains all the features of the data. There are no angular distribution predictions for comparison, but the data is symmetric around 90 degrees and appears to follow a 1+bcos^2theta _pi distribution, with the parameter b being consistent with zero for 294 MeV, about 0.05 at 300 MeV and about 0.18 at 320 MeV. This indicates that the higher partial waves are still weak at 320 MeV, although they are beginning to come into the reaction.

SAID analysis of meson photoproduction: Determination of neutron and proton EM couplings

Directory of Open Access Journals (Sweden)

Strakovsky Igor

2014-06-01

Full Text Available We present an overview of the GW SAID group effort to analyze on new pion photoproduction on both proton- and neutron-targets. The main database contribution came from the recent CLAS and MAMI unpolarized and polarized measurements. The differential cross section for the processes γn → π−p was extracted from new measurements accounting for Fermi motion effects in the impulse approximation (IA as well as NN- and πN effects beyond the IA. The electromagnetic coupling results are compared to other recent studies.

Measurement of dijet photoproduction for events with a leading neutron at HERA

International Nuclear Information System (INIS)

Chekanov, S.; Derrick, M.; Magill, B.

2009-09-01

Differential cross sections for dijet photoproduction and this process in association with a leading neutron, e + +p→e + +jet+jet+X(+n), have been measured with the ZEUS detector at HERA using an integrated luminosity of 40 pb -1 . The fraction of dijet events with a leading neutron was studied as a function of different jet and event variables. Single- and double-differential cross sections are presented as a function of the longitudinal fraction of the proton momentum carried by the leading neutron, x L , and of its transverse momentum squared, p T 2 . The dijet data are compared to inclusive DIS and photoproduction results; they are all consistent with a simple pion-exchange model. The neutron yield as a function of x L was found to depend only on the fraction of the proton beam energy going into the forward region, independent of the hard process. No firm conclusion can be drawn on the presence of rescattering effects. (orig)

Measurement of beauty photoproduction near threshold using di-electron events with the H1 detector at HERA

Energy Technology Data Exchange (ETDEWEB)

Aaron, F. D.; Alexa, C.; Andreev, V.; Backovic, S.; Baghdasaryan, A.; Baghdasaryan, S.; Barrelet, E.; Bartel, W.; Begzsuren, K.; Belousov, A.; Belov, P.; Bizot, J. C.; Boudry, V.; Bozovic-Jelisavcic, I.; Bracinik, J.; Brandt, G.; Brinkmann, M.; Brisson, V.; Britzger, D.; Bruncko, D.; Bunyatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A. J.; Cantun Avila, K. B.; Ceccopieri, F.; Cerny, K.; Cerny, V.; Chekelian, V.; Contreras, J. G.; Coughlan, J. A.; Cvach, J.; Dainton, J. B.; Daum, K.; Delcourt, B.; Delvax, J.; De Wolf, E. A.; Diaconu, C.; Dobre, M.; Dodonov, V.; Dossanov, A.; Dubak, A.; Eckerlin, G.; Egli, S.; Eliseev, A.; Elsen, E.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Fischer, D. -J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Habib, S.; Haidt, D.; Henderson, R. C. W.; Hennekemper, E.; Henschel, H.; Herbst, M.; Herrera, G.; Hildebrandt, M.; Hiller, K. H.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jönsson, L.; Jung, A. W.; Jung, H.; Kapichine, M.; Kenyon, I. R.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Krämer, M.; Kretzschmar, J.; Krüger, K.; Landon, M. P. J.; Lange, W.; Laštovička-Medin, G.; Laycock, P.; Lebedev, A.; Lendermann, V.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Lopez-Fernandez, R.; Lubimov, V.; Malinovski, E.; Martyn, H. -U.; Maxfield, S. J.; Mehta, A.; Meyer, A. B.; Meyer, H.; Meyer, J.; Mikocki, S.; Milcewicz-Mika, I.; Moreau, F.; Morozov, A.; Morris, J. V.; Müller, K.; Naumann, Th.; Newman, P. R.; Niebuhr, C.; Nikitin, D.; Nowak, G.; Nowak, K.; Olivier, B.; Olsson, J. E.; Ozerov, D.; Pahl, P.; Palichik, V.; Pandurovic, M.; Pascaud, C.; Patel, G. D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Plačakytė, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Ruiz Tabasco, J. E.; Rusakov, S.; Šálek, D.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schöning, A.; Schultz-Coulon, H. -C.; Sefkow, F.; Shtarkov, L. N.; Shushkevich, S.; Sloan, T.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Staykova, Z.; Steder, M.; Stella, B.; Stoicea, G.; Straumann, U.; Sykora, T.; Thompson, P. D.; Tran, T. H.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wünsch, E.; Žáček, J.; Zálešák, J.; Zhang, Z.; Zhokin, A.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

2012-10-01

The cross section for $ep \\to e b\\bar{b} X$ in photoproduction is measured with the H1 detector at the $ep$-collider HERA. The decay channel $b\\bar{b} \\to ee X^\\prime$ is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality $Q^2 \\le 1 GeV^2$, the inelasticity $0.05 \\le y \\le 0.65$ and the pseudorapidity of the $b$-quarks $|\\eta(b)|$,$|\\eta(\\bar{b})| \\le 2$. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks <$P_T$(b)> down to the threshold. The results are compared to next-to-leading-order QCD predictions.

Photoproduction of ω mesons off the proton

Directory of Open Access Journals (Sweden)

A. Wilson

2015-10-01

These data were included in the Bonn–Gatchina partial wave analysis (PWA. The dominant contribution to ω photoproduction near threshold was found to be the 3/2+ partial wave, which is primarily due to the sub-threshold N(17203/2+ resonance. At higher energies, pomeron-exchange was found to dominate whereas π-exchange remained small. These t-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the 1/2−, 3/2−, and 5/2+ partial waves were also found to contribute significantly.

The investigation of strangeness photoproduction in the threshold region at ELPH-Tohoku

Czech Academy of Sciences Publication Activity Database

Kaneta, M.; Beckford, B.; Bydžovský, Petr; Fujibayashi, T.; Fujii, T.; Fujii, Y.; Futatsukawa, K.; Gogami, T.; Han, Y. C.; Hashimoto, O.; Hirose, K.; Hosomi, K.; Honda, R.; Iguchi, A.; Ishikawa, T.; Kanda, H.; Kaneko, Y.; Kasai, Y.; Kawasaki, T.; Kimura, C.; Kiyokawa, S.; Koike, T.; Maeda, K.; Maruyama, N.; Matsubara, M.; Miwa, K.; Miyagi, Y.; Nagao, S.; Nakamura, S. N.; Okuyama, A.; Sotona, Miloslav; Tamae, T.; Tamura, H.; Tsukada, K.; Terada, N.; Wang, T. S.; Yamamoto, F.; Yamamoto, T.; Yamazaki, H.

2013-01-01

Roč. 914, SEP (2013), s. 69-73 ISSN 0375-9474 Institutional support: RVO:61389005 Keywords : strangeness * photoproduction * tagged photon beam * lambda detection Subject RIV: BE - Theoretical Physics Impact factor: 2.499, year: 2013 http://www.sciencedirect.com/science/article/pii/S0375947413005344

Leading neutron energy and pT distributions in deep inelastic scattering and photoproduction at HERA

International Nuclear Information System (INIS)

Chekanov, S.; Derrick, M.; Magill, S.

2007-02-01

The production of energetic neutrons in ep collisions has been studied with the ZEUS detector at HERA. The neutron energy and p T 2 distributions were measured with a forward neutron calorimeter and tracker in a 40 pb -1 sample of inclusive deep inelastic scattering (DIS) data and a 6 pb -1 sample of photoproduction data. The neutron yield in photoproduction is suppressed relative to DIS for the lower neutron energies and the neutrons have a steeper p T 2 distribution, consistent with the expectation from absorption models. The distributions are compared to HERA measurements of leading protons. The neutron energy and transverse-momentum distributions in DIS are compared to Monte Carlo simulations and to the predictions of particle exchange models. Models of pion exchange incorporating absorption and additional secondary meson exchanges give a good description of the data. (orig.)

Study ω and φ photoproduction in the nucleon isotopic channels

International Nuclear Information System (INIS)

Zhao, Q.

2002-01-01

We present results for the photoproduction of ω and φ meson in the nucleon isotopic channels. A recently developed quark model with an effective Lagrangian is employed to account for the non-diffractive s- and u-channel processes; the diffractive feature arising from the natural parity exchange is accounted for by the t-channel pomeron exchange, while the unnatural parity exchange is accounted for by the t-channel pion exchange. In the ω production, the isotopic effects could provide more information concerning the search of 'missing resonances', while in the φ production, the isotopic effects could highlight non-diffractive resonance excitation mechanisms at large angles. (author)

Subthreshold pion production in the reaction 139La + 139La → π+- + X

International Nuclear Information System (INIS)

Miller, J.

1988-01-01

We have measured charged pion production in the reaction 139 La + 139 La → π +- + X at three beam energies (246, 183 and 138 MeVnucleon) below the nucleon-nucleon threshold. Associated multiplicity for charged participants was obtained using a 110-element scintillator multiplicity array. Data were taken over the angular range of 21/degree/ to 67/degree/ in the laboratory (equivalent to 30/degree/ to 90/degree/ in the center of mass). Dependence of the spectra upon pion charge, energy and angle, beam energy, system mass and associated multiplicity was investigated. Based on the isotropic angular distibutions and the associated multiplicities for pion production, it appears that subthreshold pions in the range of our experiment are produced predominantly from a source at rest in the center of mass and involving a large number of nucleons. The general character of the subthreshold pion spectra is comparable to previous results above threshold. However, the scaling of the subthreshold pion yield with system mass deviates from the dependence observed in light systems, to an extent which cannot be explained by a simple nucleon-nucleon model. We also found charge dependent structure in the pion spectra, which we analysed in the framework of both Coulomb distortion and clustering models. We conclude that while we did not find clear evidence of collective effects in subthreshold pion production, it would be very worthwhile to conduct a systematic investigation of pion production for all charge states and over a range of angles, system masses and beam energies, below threshold. 170 refs., 78 figs., 10 tabs

Calculation of pion form factor

International Nuclear Information System (INIS)

Vahedi, N.; Amirarjomand, S.

1975-09-01

The pion form factor is calculated using the structure function Wsub(2), which incorporates kinematical constraints, threshold behaviour and scaling. The Bloom-Gilman sum rule is used and only the two leading Regge trajectories are taken into account

Transverse polarization of Σ+(1189) in photoproduction on a hydrogen target in CLAS

Science.gov (United States)

Nepali, C. S.; Amaryan, M.; Adhikari, K. P.; Aghasyan, M.; Anefalos Pereira, S.; Baghdasaryan, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Cole, P. L.; Collins, P.; Contalbrigo, M.; Crede, V.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; Alaoui, A. El; Fassi, L. El; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Gabrielyan, M. Y.; Gevorgyan, N.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Kvaltine, N. D.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Raue, B. A.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Tang, W.; Taylor, C. E.; Tian, Ye; Tkachenko, S.; Torayev, B.; Vernarsky, B.; Vlassov, A. V.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Weinstein, L. B.; Weygand, D. P.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2013-04-01

Experimental results on the Σ+(1189) hyperon transverse polarization in photoproduction on a hydrogen target using the CLAS detector at Jefferson Laboratory are presented. The Σ+(1189) was reconstructed in the exclusive reaction γ+p→KS0+Σ+(1189) via the Σ+→pπ0 decay mode. The KS0 was reconstructed in the invariant mass of two oppositely charged pions with the π0 identified in the missing mass of the detected pπ+π- final state. Experimental data were collected in the photon energy range Eγ=1.0-3.5 GeV (s range 1.66-2.73 GeV). We observe a large negative polarization of up to 95%. As the mechanism of transverse polarization of hyperons produced in unpolarized photoproduction experiments is still not well understood, these results will help to distinguish between different theoretical models on hyperon production and provide valuable information for the searches of missing baryon resonances.

Measurement of beauty photoproduction near threshold using Di-electron events with the H1 detector at HERA

Energy Technology Data Exchange (ETDEWEB)

Aaron, F.D. [National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest (Romania); Bucharest Univ. (Romania). Faculty of Physics; Alexa, C. [National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest (Romania); Andreev, V. [Lebedev Physical Institute, Moscow (RU)] (and others)

2012-05-15

The cross section for ep {yields} eb anti bX in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel b anti b {yields} eeX' is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q{sup 2} {<=}1 GeV{sup 2}, the inelasticity 0.05{<=} y {<=}0.65 and the pseudorapidity of the b-quarks vertical stroke {eta}(b) vertical stroke, vertical stroke {eta}(anti b) vertical stroke {<=}2. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks left angle P{sub T}(b) right angle down to the threshold. The results are compared to next-to-leading-order QCD predictions.

Measurement of beauty photoproduction near threshold using Di-electron events with the H1 detector at HERA

International Nuclear Information System (INIS)

Aaron, F.D.; Andreev, V.

2012-05-01

The cross section for ep → eb anti bX in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel b anti b → eeX' is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q 2 ≤1 GeV 2 , the inelasticity 0.05≤ y ≤0.65 and the pseudorapidity of the b-quarks vertical stroke η(b) vertical stroke, vertical stroke η(anti b) vertical stroke ≤2. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks left angle P T (b) right angle down to the threshold. The results are compared to next-to-leading-order QCD predictions.

Photoproduction of Mesons off Light Nuclei

International Nuclear Information System (INIS)

Keshelashvili, Irakli

2011-01-01

During the last few years, a series of experiments has been done at the ELSA accelerator in Bonn with the Crystal Barrel/TAPS setup and at the MAMI accelerator in Mainz with the Crystal Ball/TAPS setup. Photoproduction of light mesons off the deuteron and 3 He-nuclei has been studied in detail. We will report some of the most interesting results.A completely unexpected finding, is the pronounced structure in the excitation function of the γn → nη reaction around 1 GeV, which has no counterpart for the proton. Recent measurements at GRAAL, Sendai, ELSA [1] and MAMI estimate it's width below 50 MeV, which would be extremely narrow for a nucleon resonance at this excitation energy. In the experiment with the 3 He target, special attention was given to the threshold behavior of the γHe 3 reactions in view of possible indications for the formation of (quasi-)bound η-nucleus states, so-called η-mesic nuclei. A very strong threshold enhancement of coherent η-photoproduction off 3 He was found. In a new experiment, this reaction was measured with much better statistical accuracy compared to an earlier experiment at MAMI-B using the TAPS detector [2].

Theoretical contributions to coherent pion production in subthreshold and relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Deutchman, P.A.; Norbury, J.W.; Townsend, L.W.

1986-01-01

The analysis results from a microscopic calculation for pion production in heavy-ion collisions at intermediate to relativistic energies both above and below pion threshold are presented and the most important terms that contribute to the pion spectrum are determined. The energy dependence and the effects on the pion spectrum due to the various parameters in the theory are examined. The model is applied to coherent pion-production in 16 O + 12 C collisions. (orig.)

Strangeness photoproduction with the SAPHIR-detector

International Nuclear Information System (INIS)

Merkel, H.

1993-12-01

At the ELSA facility at Bonn a photon beam with a high duty cycle up to energies of 3.3 GeV is available. In this energy range the large solid angle detector SAPHIR enables us to investigate the strangeness photoproduction starting from threshold. SAPHIR has already achieved results for the reactions γ+p→K + +Λ and γ+p→K + +Σ 0 . This work investigates the possibilities to measure the related reactions γ+n→K 0 +Λ and γ+n→K 0 +Σ 0 at a deuteron target and to measure the reaction γ+p→K 0 +Σ + at a proton target. For the first time the Σ + polarisation has been measured. With an cross section 10 times smaller compared to the kaon hyperon reactions, the photoproduction of the Φ(1020) meson can be investigated with the SAPHIR detector too. First reconstructed events are shown. (orig.)

Photo-production of neutral kaons on C-12 in the threshold region

Czech Academy of Sciences Publication Activity Database

Watanabe, T.; Bydžovský, Petr; Dobashi, K.; Endo, S.; Fujii, Y.; Hashimoto, O.; Ishikawa, T.; Itoh, K.; Kanda, H.

2007-01-01

Roč. 651, č. 4 (2007), s. 269-274 ISSN 0370-2693 R&D Projects: GA ČR GA202/05/2142 Institutional research plan: CEZ:AV0Z10480505 Keywords : photo-production * neutral kaon * quasi-free reaction Subject RIV: BE - Theoretical Physics Impact factor: 4.189, year: 2007

The investigation of strangeness photoproduction in the threshold region at ELPH-Tohoku

Energy Technology Data Exchange (ETDEWEB)

Kaneta, M., E-mail: kaneta@lambda.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Beckford, B. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Bydžovský, P. [Nuclear Institute, 25068 Řež (Czech Republic); Fujibayashi, T.; Fujii, T.; Fujii, Y.; Futatsukawa, K.; Gogami, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Han, Y.C. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Hashimoto, O. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Hirose, K. [Research Center of Electron Photon Science, Tohoku University, Sendai 982-0826 (Japan); Hosomi, K.; Honda, R.; Iguchi, A. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Ishikawa, T. [Research Center of Electron Photon Science, Tohoku University, Sendai 982-0826 (Japan); Kanda, H.; Kaneko, Y.; Kasai, Y.; Kawasaki, T.; Kimura, C. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); and others

2013-09-20

The strangeness photoproduction processes near the threshold have been intensively studied by measuring K{sup +} in reactions such as γ+p→K{sup +}+Λ(Σ{sup 0}). There has been no reliable data on the neutron and as a consequence theoretical investigation suffered seriously from the lack of the data. We have an effort to measure the γ+d→K{sup 0}(Λ)+X reaction in the π{sup +}π{sup −} (pπ{sup −}) decay channel of K{sub S}{sup 0} (Λ) using a liquid D{sub 2} target and internally-tagged photon beams (E{sub γ}=0.80–1.08 GeV) at Research Center for Electron Photon Science (ELPH), Tohoku University. We have renewed the spectrometer (NKS2) and took data with a liquid D{sub 2} target in 2005–2007. More recently, we took data in 2010 after a detector upgrade in the vertex region to substantially increase the acceptance. The results of Λ single measurements on a deuterium target were obtained for differential cross-section as a function of momentum, as a function of angle, and integrated cross-section as a function of beam energy. The results are compared with recent theoretical studies: Isobar models (Kaon-MAID and Saclay-Lyon A) and a Regge-plus-Resonance model.

Isospin violation in pion-kaon scattering

International Nuclear Information System (INIS)

Kubis, Bastian; Meissner, Ulf-G.

2002-01-01

We consider strong and electromagnetic isospin violation in near-threshold pion-kaon scattering. At tree level, such effects are small for all physical channels. We work out the complete one-loop corrections to the process π - K + →π 0 K 0 . They come out rather small. We also show that the corresponding radiative cross section is highly suppressed at threshold

Pion-exchange contribution to the parity-violating asymmetry in pp scattering

International Nuclear Information System (INIS)

Silbar, R.R.; Kloet, W.M.; Kisslinger, L.S.; Dubach, J.

1988-01-01

Charged pion exchange, producing nΔ ++ intermediate states, contributes negatively to the weak scattering asymmetry in longitudinally-polarized pp scattering. Including this contribution moves the theoretical prediction away from the 800 MeV experimental datum. The pion-exchange contribution has both inelastic and elastic scattering components and is sizeable even below the pion production threshold. Strong distortions enhance the magnitude of the effect. 14 refs., 5 figs

Measurement of dijet photoproduction for events with a leading neutron at HERA

Energy Technology Data Exchange (ETDEWEB)

Chekanov, S.; Derrick, M.; Magill, B. [Argonne National Lab., Argonne, IL (US)] (and others)

2009-09-15

Differential cross sections for dijet photoproduction and this process in association with a leading neutron, e{sup +}+p{yields}e{sup +}+jet+jet+X(+n), have been measured with the ZEUS detector at HERA using an integrated luminosity of 40 pb{sup -1}. The fraction of dijet events with a leading neutron was studied as a function of different jet and event variables. Single- and double-differential cross sections are presented as a function of the longitudinal fraction of the proton momentum carried by the leading neutron, x{sub L}, and of its transverse momentum squared, p{sub T}{sup 2}. The dijet data are compared to inclusive DIS and photoproduction results; they are all consistent with a simple pion-exchange model. The neutron yield as a function of x{sub L} was found to depend only on the fraction of the proton beam energy going into the forward region, independent of the hard process. No firm conclusion can be drawn on the presence of rescattering effects. (orig)

Isospin breaking in pion-nucleon scattering at threshold by radiative processes

CERN Document Server

Ericson, Torleif Eric Oskar

2006-01-01

We investigate the dispersive contribution by radiative processes such as (pi- proton to neutron gamma) and (pi- proton to Delta gamma) to the pion-nucleon scattering lengths of charged pions in the heavy baryon limit. They give a large isospin violating contribution in the corresponding isoscalar scattering length, but only a small violation in the isovector one. These terms contribute 6.3(3)% to the 1s level shift of pionic hydrogen and give a chiral constant F_pi^2f_1=-25.8(8) MeV.

Isospin violation in pion-kaon scattering

Energy Technology Data Exchange (ETDEWEB)

Kubis, Bastian E-mail: b.kubis@fz-juelich.de; Meissner, Ulf-G. E-mail: ulf-g.meissner@fz-juelich.de

2002-03-11

We consider strong and electromagnetic isospin violation in near-threshold pion-kaon scattering. At tree level, such effects are small for all physical channels. We work out the complete one-loop corrections to the process {pi}{sup -}K{sup +}{yields}{pi}{sup 0}K{sup 0}. They come out rather small. We also show that the corresponding radiative cross section is highly suppressed at threshold.

To the calculation of differential and total cross sections of γπ interactions

International Nuclear Information System (INIS)

Duplij, S.A.

1980-01-01

The differential and total cross sections of different charge channels of the γπ→ππ process are calculated. At the threshold energies the vector dominance model predicts twice as large values of the total cross sections than the current algebra. In resonance the total cross section of photoproduction on a neutral pion is 10-50 μb, on a charged pion - 5-10μb, at near-threshold energies (Esub(γ)=300-600 MeV) both cross sections are of the 20-40 nb order. For the γπ→ππ process the differential cross sections according to the invariant mass of two pions are obtained for different charge channels. At the threshold energies the total cross sections of the γπ→ππ process is of the 0.1-1 nb order

Precision Measurement of Electroproduction of pi⁰ near Threshold

Energy Technology Data Exchange (ETDEWEB)

Chirapatpimol, Khem [Chiang Mai Univ. (Thailand)

2012-05-01

Electromagnetic production of neutral pions near threshold is the most basic, lowest energy reaction in which a new hadron is created. The electromagnetic interaction is well understood so measurements of this reaction can yield direct insight into the hadronic production mechanism. During the past three decades there have been many developments in both the measurement and theory of threshold pion production, starting with measurements of photo-production at Saclay in 1986 and at Mainz in 1990. These measurements indicated a surprising discrepancy with so-called Low Energy Theorems (LETs) which are based on quite fundamental symmetries and considerations. Chiral Perturbation Theory (ChPT) is an effective field theoretic description of the nuclear force which contains the underlying symmetries of the force but deals with nucleons and pions rather than quarks and gluons. It has the advantage of being applicable at low energies but requires tuning some parameters to experimental data. Once these parameters have been determined ChPT predicts how the reaction should behave as a function of the kinematic variable. When applied to the reaction, p(γ,π⁰)p, near threshold it explained the discrepancy with the LETs and made predictions for electroproduction, p(e,e'p)π ⁰. Electroproduction measurements at Mainz in the 1990's showed a clear discrepancy with these predictions of ChPT; with parameters determined from one set of kinematics the data for a second set lay far from the predicted value. However, recently completed measurements at Mainz disagreed with their previous measurements. In the experiment presented here, measurements of neutral pion electroproduction,p(e,e'p)π⁰, were made in bins of momentum transfer, Q², between Q² = 0.05 [GeV/c]² and Q² = 0.15 [GeV/c]⁰ and of center-of-mass energy, W, between 0 ≤ W ≤ 30 MeV (above threshold). The experiment was

Pion-pion interactions in particle physics

Energy Technology Data Exchange (ETDEWEB)

Martin, B R; Morgan, D; Shaw, G

1976-01-01

The aim of the book is to review the experimental and theoretical work on the processes involving pion-pion interactions. Sources of information on pion-pion scattering are examined, including pion production, dipion exchange, and weak and electromagnetic interactions. The theory and models of pion-pion scattering are discussed with reference to fixed momentum transfer, partial wave amplitudes, models and phenomenology, dynamical and field theoretic models, finite-energy sum rules, duality and the Veneziano model, resonance spectra and lastly, predictions from current algebra.

Leading neutron energy and p{sub T} distributions in deep inelastic scattering and photoproduction at HERA

Energy Technology Data Exchange (ETDEWEB)

Chekanov, S.; Derrick, M.; Magill, S. [Argonne National Laboratory, Argonne, IL (US)] (and others)

2007-02-15

The production of energetic neutrons in ep collisions has been studied with the ZEUS detector at HERA. The neutron energy and p{sub T}{sup 2} distributions were measured with a forward neutron calorimeter and tracker in a 40 pb{sup -1} sample of inclusive deep inelastic scattering (DIS) data and a 6 pb{sup -1} sample of photoproduction data. The neutron yield in photoproduction is suppressed relative to DIS for the lower neutron energies and the neutrons have a steeper p{sub T}{sup 2} distribution, consistent with the expectation from absorption models. The distributions are compared to HERA measurements of leading protons. The neutron energy and transverse-momentum distributions in DIS are compared to Monte Carlo simulations and to the predictions of particle exchange models. Models of pion exchange incorporating absorption and additional secondary meson exchanges give a good description of the data. (orig.)

Measurement of elastic ρ0 photoproduction at HERA

International Nuclear Information System (INIS)

Derrick, M.; Krakauer, D.; Magill, S.

1995-01-01

Elastic ρ 0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction γp→ρ 0 p (ρ 0 →π + π - )at photon-proton centre-of-mass energies between 60 and 80 GeV and vertical stroke t vertical stroke 2 , where t is the square of the four-momentum transferred at the proton vertex. The differential cross section dσ/dM ππ , where M ππ is the invariant mass of the two pions, and the integrated cross section, σ γp →ρ 0 p , are presented; the latter was measured to be 14.7 ±0.4(stat.)±2.4(syst.) μb. The differential cross section dσ/dt has an approximately exponential shape; a fit of the type A' t exp(-b' t vertical stroke t vertical stroke +c' t t 2 ) yields a t-slope b' t =9.9±1.2(stat.)±1.4(syst.) GeV -2 . The results, when compared to low energy data, show a weak energy dependence of both σ γp→ρ 0 p and of the t-slope. The ρ 0 is produced predominantly with transverse polarisation, demostrating that s-channel helicity conservation holds at these energies. (orig.)

Measurement of elastic ρ0 photoproduction at HERA

International Nuclear Information System (INIS)

Derrick, M.; Krakauer, D.; Magill, S.

1995-07-01

Elastic ρ 0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction γp→ρ 0 p (ρ 0 →π + π - ) at photon-proton centre-of-mass energies between 60 and 80 GeV and vertical stroke tvertical stroke 2 , where t is the square of the four-momentum transferred at the proton vertex. The differential cross section dσ/dM ππ , where M ππ is the invariant mass of the two pions, and the integrated cross section, σsub(γp→ρ 0 p), are presented; the latter was measured to be 14.7±0.4(stat.)±2.4(syst.) μb. The differential cross section dσ/dt has an approximately exponential shape; a fit of the type A' t exp(-b' t vertical stroke tvertical stroke +c' t t 2 ) yields a t-slope b' t =9.9±1.2(stat.)±1.4(syst.) μb. The results, when compared to low energy data, show a weak energy dependence of both σsub(γp→ρ 0 p) and of the t-slope. The ρ 0 is produced predominantly with transverse polarisation, demonstrating that s-channel helicity conservation holds at these energies. (orig.)

Production below the threshold and reabsorption of neutral pions in the system 129Xe+197Au at 44 MeV/u

International Nuclear Information System (INIS)

Mayer, R.S.

1992-11-01

In the framework of the TAPS collaboration at GANIL an experiment for the production of neutral pions in 129 Xe+ 197 Au collisions below the threshold for the production in the free nucleon-nucleon collision was performed. Both for π 0 and for hard photons from the data the inclusive cross sections for the production, energy and angular distributions as well as the velocity of the emitting source were derived. (orig./HSI) [de

First measurement of the π0-photoproduction on transversely polarized protons near the threshold

International Nuclear Information System (INIS)

Otte, Peter-Bernd

2015-01-01

This thesis addresses the photo induced production of neutral pions very close to the threshold energy. There are two objectives: Firstly, to test predictions made by these effective theories and models and secondly to determine all relevant partial wave amplitudes model independently from measured observables. In the future, this method shall also be applied to higher energies in the region of nucleon resonances. In the thesis, the execution and analysis of an experiment is presented which had been carried out at the Mainzer Mikrotron (MAMI) in the years 2010 to 2013. A circularly polarised, real photon beam was produced via tagged bremsstrahlung technique from the MAMI electron beam. For the first time in such experiments a transversely polarised proton target was utilised. For that purpose, butanol was dynamically polarised within a special apparatus. Because of using butanol as a target material - which resulted in less than 5 % of the pions produced on polarised protons - the background subtraction treatment is an essential task. The target was surrounded by an almost 4π-covering combined CB/TAPS detector setup. Two different background subtraction methods are being described, whereof the better had been applied in the analysis. In conclusion a detailed estimation of systematic errors are presented. For the first time transversely polarised protons provide access to previously not measured spin degrees of freedom. Using the measured data in combination with a previous experiment from the year 2008 with linearly polarised photon beam it was possible for the first time to determine model independently all complex s- and p-partial wave amplitudes. Furthermore, substantial improvements to the experimental apparatus were achieved. Examples are an electron beam polarimeter, a cellular multiplicity trigger for CB, as well as significant improvements to the data acquisition and trigger electronics. Parts of these developments are presented in this thesis.

Measurement of inverse pion photoproduction at energies spanning the N(1440) resonance

International Nuclear Information System (INIS)

Shafi, A.; Strakovsky, I.I.; Briscoe, W.J.; Arndt, R.A.; Bennhold, C.; Workman, R.L.; Prakhov, S.; Nefkens, B.M.K.; Clajus, M.; Marusic, A.; McDonald, S.; Phaisangittisakul, N.; Price, J.W.; Tippens, W.B.; Allgower, C.E.; Spinka, H.; Bekrenev, V.; Kulbardis, A.; Kozlenko, N.; Kruglov, S.

2004-01-01

Differential cross sections for the process π - p→γn have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E γ for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the γn multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations

Pion-Skyrmion scattering: collective coordinates at work

International Nuclear Information System (INIS)

Peskin, M.E.

1985-06-01

It is argued that the Skryme model, and more generally, the picture of the nucleon as a chiral soliton, can give a qualitatively correct picture of pion-nucleon scattering, considering both group-theoretic and more scheme-dependent results. The properties of the nucleon and its excited states in large-N quantum chromodynamics are discussed qualitatively. Then the pion-nucleon S-matrix is reduced. It is found that the model succeeds at the first level of calculation in producing many of the features of pion-nucleon scattering which are revealed by experiment, but that many aspects of the description need to be better understood, including the treatment of nonleading corrections near threshold and the inclusion of inelastic channels. 22 refs., 8 figs

The Fubini-Furlan-Rosetti sum rule and related aspects in light of covariant baryon chiral perturbation theory

International Nuclear Information System (INIS)

Bernard, V.; Kubis, B.; Meissner, U.G.

2005-01-01

We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E 0+ . (orig.)

The Fubini-Furlan-Rosetti sum rule and related aspects in light of covariant baryon chiral perturbation theory

Energy Technology Data Exchange (ETDEWEB)

Bernard, V. [Universite Louis Pasteur, Laboratoire de Physique Theorique, Strasbourg Cedex 2 (France); Kubis, B. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Bonn (Germany); Meissner, U.G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Bonn (Germany); Forschungszentrum Juelich, Institut fuer Kernphysik (Theorie), Juelich (Germany)

2005-09-01

We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E{sub 0+}. (orig.)

Modification of pion pairs in nuclear matter; Modifikationen von Pionenpaaren in Kernmaterie

Energy Technology Data Exchange (ETDEWEB)

Gregor, Ralf

2007-07-18

In this work the quasifree photoproduction of pion pairs on bound nucleons is analyzed for the solid targets carbon, calcium and lead. These measurements allow an isospin dependent determination of the in medium properties of pion pairs. The invariant mass distributions showed a shift in strength towards the threshold region with increasing atomic number of the targets in case of an isoscalar {pi}{pi} meson system. According to theoretical predictions this effect was interpreted as a positive signature of a partial restoration of chiral symmetry. A pioneering experiment with photon beams was performed by the TAPS collaboration at the accelerator facility MAMI-B in Mainz in 1995. This measurement observed an invariant mass shift of the isoscalar {pi}{sup 0}{pi}{sup 0} channel with increasing atomic number. In the {pi}{sup {+-}}{pi}{sup 0} channel this effect was not observed. This observation confirmed the former experiments, since final state interactions of the pions would affect in first order both isospin channels in a similar way. Due to the poor statistics, the significance of the data was however limited. The experiment described in this work reached a much higher statistical significance, allowing a review of the old data and a study of the dependence of the signal from parameters like the momenta of the {pi}{pi} system or the single pions. In this experiment, the TAPS detector was used as a forward wall in combination with the Crystal Ball detector to achieve a 4{pi} solid angle coverage for photon detection at the MAMI accelerator facility. The new readout electronics for the BaF{sub 2} crystals was used for the first time. The new data analysis confirms the previously measured and published data. However, the shift of the invariant {pi}{sup 0}{pi}{sup 0} mass to the threshold region is less pronounced than in the published data. By performing cuts on the individual pion momenta, resulting in a maximum mean free path of the pions, the shift towards lower

Pion production experiments at IUCF

Science.gov (United States)

Daehnick, W. W.

2001-12-01

Pion production in pp collisions is of special interest near threshold where very few partial waves contribute and where calculations should be manageable and results more conclusive. The first explicit calculations for pp → ppπ0 and pp → pnπ+ cross sections near threshold were made by Koltun and Reitan in 1966 and by Schillaci, Silbar and Young in 1969. They remained unchallenged and untested until cross sections very close to threshold could finally be measured1,2. The realization that the pioneering calculations missed the true cross sections by a wide margin has spurred much new theoretical research.3,4,5 ...

Bose-Einstein correlations of three charged pions in hadronic $Z^{0}$ decays

CERN Document Server

Ackerstaff, K; Allison, J; Altekamp, N; Anderson, K J; Anderson, S; Arcelli, S; Asai, S; Ashby, S F; Axen, D A; Azuelos, Georges; Ball, A H; Barberio, E; Barlow, R J; Bartoldus, R; Batley, J Richard; Baumann, S; Bechtluft, J; Behnke, T; Bell, K W; Bella, G; Bentvelsen, Stanislaus Cornelius Maria; Bethke, Siegfried; Betts, S; Biebel, O; Biguzzi, A; Bird, S D; Blobel, Volker; Bloodworth, Ian J; Bobinski, M; Bock, P; Böhme, J; Boutemeur, M; Braibant, S; Bright-Thomas, P G; Brown, R M; Burckhart, Helfried J; Burgard, C; Bürgin, R; Capiluppi, P; Carnegie, R K; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Chrisman, D; Ciocca, C; Clarke, P E L; Clay, E; Cohen, I; Conboy, J E; Cooke, O C; Couyoumtzelis, C; Coxe, R L; Cuffiani, M; Dado, S; Dallavalle, G M; Davis, R; De Jong, S; del Pozo, L A; de Roeck, A; Desch, Klaus; Dienes, B; Dixit, M S; Doucet, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Eatough, D; Estabrooks, P G; Etzion, E; Evans, H G; Fabbri, Franco Luigi; Fanfani, A; Fanti, M; Faust, A A; Fiedler, F; Fierro, M; Fischer, H M; Fleck, I; Folman, R; Fürtjes, A; Futyan, D I; Gagnon, P; Gary, J W; Gascon, J; Gascon-Shotkin, S M; Geich-Gimbel, C; Geralis, T; Giacomelli, G; Giacomelli, P; Gibson, V; Gibson, W R; Gingrich, D M; Glenzinski, D A; Goldberg, J; Gorn, W; Grandi, C; Gross, E; Grunhaus, Jacob; Gruwé, M; Hanson, G G; Hansroul, M; Hapke, M; Hargrove, C K; Hartmann, C; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Herndon, M; Herten, G; Heuer, R D; Hildreth, M D; Hill, J C; Hillier, S J; Hobson, P R; Höcker, Andreas; Homer, R James; Honma, A K; Horváth, D; Hossain, K R; Howard, R; Hüntemeyer, P; Igo-Kemenes, P; Imrie, D C; Ishii, K; Jacob, F R; Jawahery, A; Jeremie, H; Jimack, Martin Paul; Joly, A; Jones, C R; Jovanovic, P; Junk, T R; Karlen, D A; Kartvelishvili, V G; Kawagoe, K; Kawamoto, T; Kayal, P I; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Koetke, D S; Kokott, T P; Kolrep, M; Komamiya, S; Kowalewski, R V; Kress, T; Krieger, P; Von Krogh, J; Kyberd, P; Lafferty, G D; Lanske, D; Lauber, J; Lautenschlager, S R; Lawson, I; Layter, J G; Lazic, D; Lee, A M; Lefebvre, E; Lellouch, Daniel; Letts, J; Levinson, L; Liebisch, R; List, B; Littlewood, C; Lloyd, A W; Lloyd, S L; Loebinger, F K; Long, G D; Losty, Michael J; Ludwig, J; Liu, D; Macchiolo, A; MacPherson, A L; Mannelli, M; Marcellini, S; Markopoulos, C; Martin, A J; Martin, J P; Martínez, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McKigney, E A; McMahon, T J; McPherson, R A; Meijers, F; Menke, S; Merritt, F S; Mes, H; Meyer, J; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Mir, R; Mohr, W; Montanari, A; Mori, T; Nagai, K; Nakamura, I; Neal, H A; Nellen, B; Nisius, R; O'Neale, S W; Oakham, F G; Odorici, F; Ögren, H O; Oreglia, M J; Orito, S; Pálinkás, J; Pásztor, G; Pater, J R; Patrick, G N; Patt, J; Pérez-Ochoa, R; Petzold, S; Pfeifenschneider, P; Pilcher, J E; Pinfold, James L; Plane, D E; Poffenberger, P R; Poli, B; Polok, J; Przybycien, M B; Rembser, C; Rick, Hartmut; Robertson, S; Robins, S A; Rodning, N L; Roney, J M; Roscoe, K; Rossi, A M; Rozen, Y; Runge, K; Runólfsson, O; Rust, D R; Sachs, K; Saeki, T; Sahr, O; Sang, W M; Sarkisyan-Grinbaum, E; Sbarra, C; Schaile, A D; Schaile, O; Scharf, F; Scharff-Hansen, P; Schieck, J; Schmitt, B; Schmitt, S; Schöning, A; Schörner-Sadenius, T; Schröder, M; Schumacher, M; Schwick, C; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Shepherd-Themistocleous, C H; Sherwood, P; Siroli, G P; Sittler, A; Skuja, A; Smith, A M; Snow, G A; Sobie, Randall J; Söldner-Rembold, S; Sproston, M; Stahl, A; Stephens, K; Steuerer, J; Stoll, K; Strom, D; Ströhmer, R; Tafirout, R; Talbot, S D; Tanaka, S; Taras, P; Tarem, S; Teuscher, R; Thiergen, M; Thomson, M A; Von Törne, E; Torrence, E; Towers, S; Trigger, I; Trócsányi, Z L; Tsur, E; Turcot, A S; Turner-Watson, M F; Van Kooten, R; Vannerem, P; Verzocchi, M; Vikas, P; Voss, H; Wäckerle, F; Wagner, A; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wermes, N; White, J S; Wilson, G W; Wilson, J A; Wyatt, T R; Yamashita, S; Yekutieli, G; Zacek, V; Zer-Zion, D

1998-01-01

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \\lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \\lambda_3 value by 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.

Visual sensations induced by relativistic pions

International Nuclear Information System (INIS)

McNulty, P.J.; Pease, V.P.; Bond, V.P.

1976-01-01

Visual sensations were experienced when bursts of high-energy pions passed through the dark-adapted right eyes of three human subjects. The threshold for a visual sensation was typically 1 to 3 μrad at the retina. Data are presented to show that the mechanism is Cerenkov radiation generated within the vitreous humor. Threshold measurements agree with published optical data. A comparison is made between our observations and the light flashes observed in deep space by Apollo astronauts

Preliminary results for the helicity asymmetry E for eta photoproduction on the proton

International Nuclear Information System (INIS)

2012-01-01

Polarization observables are an important tool for clarifying the nucleon resonance spectrum. No previous measurements for double polarization asymmetries have been published for eta photoproduction. Double polarization measurements have been made at Jefferson Lab using a polarized photon beam and protons in a polarized frozen spin target (FROST). Data were taken during the first running period of FROST using the CLAS detector with photon energies from 0.33 to 2.35 GeV. Preliminary results for the E polarization observable for eta meson photoproduction from the proton at threshold and above, along with comparisons to several theoretical predictions are presented.

Pion Photo- and Electroproduction and the Partially Conserved Axial Current

International Nuclear Information System (INIS)

Haberzettl, Helmut

2000-01-01

The relevance of the axial current for pion production processes off the nucleon with real or virtual photons is revisited. Employing the hypothesis of a partially conserved axial current (PCAC), it is shown that, when all of the relevant contributions are taken into account, PCAC does not provide any additional constraint for threshold production processes that goes beyond the Goldberger-Treiman relation. In particular, it is shown that pion electroproduction processes at threshold cannot be used to extract any information regarding the weak axial form factor. The relationships found in previous investigations are seen to be an accident of the approximations usually made in this context

Joint resummation for pion wave function and pion transition form factor

Energy Technology Data Exchange (ETDEWEB)

Li, Hsiang-nan [Institute of Physics, Academia Sinica,Academia Rd., Taipei, Taiwan 115 (China); Department of Physics, National Cheng-Kung University,University Rd., Tainan, Taiwan 701 (China); Department of Physics, National Tsing-Hua University,Kuang-Fu Rd., Hsinchu, Taiwan 300 (China); Shen, Yue-Long [College of Information Science and Engineering, Ocean University of China,Songling Rd, Qingdao, Shandong 266100 (China); Wang, Yu-Ming [Institut für Theoretische Teilchenphysik und Kosmologie RWTH Aachen,Physikzentrum Otto-Blumenthal-Straße, D-52056 Aachen (Germany); Physik Department T31, Technische Universität München,James-Franck-Straße, D-85748 Garching (Germany)

2014-01-03

We construct an evolution equation for the pion wave function in the k{sub T} factorization formalism, whose solution sums the mixed logarithm ln xln k{sub T} to all orders, with x (k{sub T}) being a parton momentum fraction (transverse momentum). This joint resummation induces strong suppression of the pion wave function in the small x and large b regions, b being the impact parameter conjugate to k{sub T}, and improves the applicability of perturbative QCD to hard exclusive processes. The above effect is similar to those from the conventional threshold resummation for the double logarithm ln{sup 2} x and the conventional k{sub T} resummation for ln{sup 2} k{sub T}. Combining the evolution equation for the hard kernel, we are able to organize all large logarithms in the γ{sup ∗}π{sup 0}→γ scattering, and to establish a scheme-independent k{sub T} factorization formula. It will be shown that the significance of next-to-leading-order contributions and saturation behaviors of this process at high energy differ from those under the conventional resummations. It implies that QCD logarithmic corrections to a process must be handled appropriately, before its data are used to extract a hadron wave function. Our predictions for the involved pion transition form factor, derived under the joint resummation and the input of a non-asymptotic pion wave function with the second Gegenbauer moment a{sub 2}=0.05, match reasonably well the CLEO, BaBar, and Belle data.

Role of nucleon resonance excitation in φ meson photoproduction

International Nuclear Information System (INIS)

Zhao, Q.; Didelez, J.P.; Guidal, M.; Saghai, B.

2000-01-01

The resonance effects are investigated in the φ meson photoproduction near threshold through a quark model approach with an effective Lagrangian. The diffractive contribution is consistently estimated by the t-channel Pomeron exchange. Another non-diffractive process, t-channel π 0 exchange is also included. The numerical result shows that the Pomeron exchange plays dominant role in the φ meson photoproduction, while the cross sections of the non-diffractive processes, i.e., s- and u-channel excitations, and t-channel π 0 exchange, are quite small. In the polarization observables, we find that large asymmetries are produced in the backward direction by the interferences from the s- and u-channel resonances, while in the forward direction, only very small asymmetries are generated. Meanwhile, we find that the effects from the π 0 exchange are generally negligible. (author)

Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations

Science.gov (United States)

Kubis, Bastian; Hoferichter, Martin; de Elvira, Jacobo Ruiz; Meißner, Ulf-G.

2016-11-01

Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. The scattering lengths or the pion-nucleon σ-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon-nucleon potentials, and hence has a far-reaching impact on nuclear physics. We discuss the fruitful combination of dispersion-theoretical methods, in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.*

A relativistic, meson exchange model of pion-nucleon scattering

International Nuclear Information System (INIS)

Pearces, B.C.; Jennings, B.K.

1990-06-01

A relativistic meson exchange approach to the pion-nucleon interaction is developed using a three-dimensional relativistic two-body propagator, and the results using different propagators are compared. The relativistic approach is able to describe low energy scattering up to 400 MeV above threshold, while preserving the soft pion theorems. The different propagators give similar results, as the form factors necessary to get a fit suppress much of the multiple scattering. (Author) (24 refs., 4 tabs., 6 figs.)

Search for a PHI' vector meson in diffractive photoproduction of K+K-π+π-

International Nuclear Information System (INIS)

Atkinson, M.; Davenport, M.; Flower, P.; Hutton, J.S.; Kumar, B.R.; Morris, J.A.G.; Morris, J.V.; Patrick, G.N.; Sharp, P.H.; Bussey, P.J.; Dainton, J.B.; Paterson, C.; Raine, C.; Skillicorn, I.O.; Smith, K.M.; Brodbeck, T.J.; Clegg, A.B.; Flynn, P.J.; Henderson, R.C.W.; Newton, D.; Axon, T.J.; Barberis, D.; Dickinson, B.; Donnachie, A.; Ellison, R.J.; Hughes-Jones, R.E.; Ibbotson, M.; Lafferty, G.D.; Lane, J.B.; Mercer, D.; Thompson, R.J.; Waite, A.P.; Worsell, M.F.; Levy, J.M.; Laberrigue, J.; La Vaissiere, C. de; Yiou, T.P.; Brookes, G.R.; Bunn, J.J.; Galbraith, W.; McClatchey, R.H.

1986-01-01

A study of photoproduction of K + K - π + π - shows a broad threshold enhancement, about 30% of which is due to Ksup(*)Kπ production. This Ksup(*)Kπ component shows no dynamical features indicative of the existence of a PHI' vector meson in this channel. (orig.)

Pions in nuclei, from virtual-pion exchange to real-pion transfer

International Nuclear Information System (INIS)

Yamazaki, Toshimitsu.

1988-07-01

Tracing the work of Miyazawa on nuclear magnetic moments, we discuss possible experimental ways to see whether a real pion exists in nuclei or not. While virtual pions are known to play an important role in nuclei, as clarified experimentally from anomalous orbital g factors of nucleons in nuclei, nearly nothing is known for the behavior of real pions in nuclei. We have shown that deeply bound hybrid states of π - are expected to exist in heavy nuclei, which can be populated by ''pion transfer'' reactions. (author)

Photoproduction and Radiative Decay of eta' Meson in CLAS at Jlab

Energy Technology Data Exchange (ETDEWEB)

Mbianda Njencheu, Georgie [Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2017-05-01

In this work the η' meson photoproduction cross sections as well as the distribution of the di-pion invariant mass, m(π+π-), in the radiative decay mode n' -> π+π-γ have been measured using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photons in the center-of-mass energy range 1.96 GeV - 2.72 GeV. The measurements are performed on a liquid hydrogen target in the reaction γ π -> π η'(η'-> π+π-γ). The analysis is based on the highest statistics collected in this decay channel in comparison to other experiments reported so far. The n' photoproduction cross sections measured with radiative decay are in a good agreement with results of previous publication from the same data set in CLAS obtained through η' -> π+π-γ decay mode. Two free parameters, α and Β, are extracted from a model-independent fit to the m(π+π-) distribution and their values are found to agree well with recent theoretical expectations. The results of both parameters confirm the existence of the box anomaly, ρ-ω mixing and effects of the a2(1320) tensor meson in the radiative decay of η'.

Inelastic pion scattering from 3H and 3He

International Nuclear Information System (INIS)

Berman, B.L.; Anderson, G.C.; Briscoe, W.J.; Mokhtari, A.; Petrov, A.M.; Sadler, M.E.; Barlow, D.B.; Nefkens, B.M.K.; Pillai, C.

1995-01-01

Cross sections have been measured for the inelastic scattering of π + and π - mesons from 3 H and 3 He in the 10-MeV interval just above the breakup thresholds, for incident pion energies of 142, 180, and 220 MeV and scattering angles of 40 degree, 60 degree, 80 degree, 90 degree, and 110 degree. No significant departure from unity is observed for the ratios of charge-symmetric cross sections. Comparisons are made with elastic pion-scattering and inelastic electron-scattering data

Particle identification using the time-over-threshold method in the ATLAS Transition Radiation Tracker

International Nuclear Information System (INIS)

Akesson, T.; Arik, E.; Assamagan, K.; Baker, K.; Barberio, E.; Barberis, D.; Bertelsen, H.; Bytchkov, V.; Callahan, J.; Catinaccio, A.; Danielsson, H.; Dittus, F.; Dolgoshein, B.; Dressnandt, N.; Ebenstein, W.L.; Eerola, P.; Farthouat, P.; Froidevaux, D.; Grichkevitch, Y.; Hajduk, Z.; Hansen, J.R.; Keener, P.T.; Kekelidze, G.; Konovalov, S.; Kowalski, T.; Kramarenko, V.A.; Krivchitch, A.; Laritchev, A.; Lichard, P.; Lucotte, A.; Lundberg, B.; Luehring, F.; Mailov, A.; Manara, A.; McFarlane, K.; Mitsou, V.A.; Morozov, S.; Muraviev, S.; Nadtochy, A.; Newcomer, F.M.; Olszowska, J.; Ogren, H.; Oh, S.H.; Peshekhonov, V.; Rembser, C.; Romaniouk, A.; Rousseau, D.; Rust, D.R.; Schegelsky, V.; Sapinski, M.; Shmeleva, A.; Smirnov, S.; Smirnova, L.N.; Sosnovtsev, V.; Soutchkov, S.; Spiridenkov, E.; Tikhomirov, V.; Van Berg, R.; Vassilakopoulos, V.; Wang, C.; Williams, H.H.

2001-01-01

Test-beam studies of the ATLAS Transition Radiation Tracker (TRT) straw tube performance in terms of electron-pion separation using a time-over-threshold method are described. The test-beam data are compared with Monte Carlo simulations of charged particles passing through the straw tubes of the TRT. For energies below 10 GeV, the time-over-threshold method combined with the standard transition-radiation cluster-counting technique significantly improves the electron-pion separation in the TRT. The use of the time-over-threshold information also provides some kaon-pion separation, thereby significantly enhancing the B-physics capabilities of the ATLAS detector

Measurement of beauty photoproduction at threshold using di-electron events with the H1 detector at HERA

Energy Technology Data Exchange (ETDEWEB)

Sauter, Michel David

2009-12-15

The cross section of b anti b photoproduction in ep collisions has been measured with the H1 detector at HERA. Events containing b-quarks were identified through detection of two low momentum electrons in the nal state. Semileptonic decays b anti b{yields}eeX were exploited in the kinematic range of the photon virtuality Q{sup 2}<1 GeV{sup 2}, the inelasticity 0.2threshold. The results are compared to other b-quark cross section measurements, as well as to leading-order and next-to-leading-order QCD predictions. The extension to lower b-quark momenta became possible with a dedicated low momentum electron trigger in the data period 2007, which combines track (Fast Track Trigger) and calorimeter information (Jet Trigger), and by mastering the experimental challenges of low p{sub T}-electron identification. (orig.)

Photoproduction de Mesons sur le Nucleon aux Energies Intermediaire (in French) [Photoproduction of mesons on the nucleon at intermediate energies

Energy Technology Data Exchange (ETDEWEB)

Guidal, Michel [Univ. of Paris, Orsay (France)

1996-12-13

One object of this thesis is to propose a model taking account of low transfer reaction mechanisms for a series of photoproduction reactions on nucleons for photon energies ≳4 GeV. If our comprehension of processes with low transfers is correct, then extrapolating our model in the domain of large transfers and the comparison with data supplied will give us information on the domains in energy and transfers from which an interpretation of reactions in terms of the "soft" process ceases to be valid. In the domain of large transfers, only one approach in terms of "hard" process can then explain the data. We are interested in electromagnetic photoproduction reactions because the probe, firstly, interacts with the target via an exact and well known mechanism (described by the QED theory) and also eliminates the interaction phenomena in the initial state. No probe is as well known as the photon. The extraction of reaction mechanisms, amplitudes and coupling constants match is made easier than in the case of hadronic probes. The energy domain E_γ >4 GeV studied is particularly interesting because it is from this energy of incident photons that can be expected to achieve large enough pulse transfers to hope for emergence of hard processes and therefore see the cessation of validity of interpretation of hadron models. Also, resonance effects are minor and do not interfere with our interpretations. Experimentally, this area is widely unexplored and the new generation accelerators of a large duty cycle (CEBAF, MAMI, ESRF, ELF, ...) combined with 4π detectors will allow to precisely measure low cross sections reactions of a large transfer. We first study pion photoproduction reactions on nucleon because they are the most experimentally accessible reactions and many data of high energy and low transfers exist. This will require strong constraints on the model parameters of the numerous analyses performed previously. Then we'll move on to kaon photoproduction

Invariant mass dependence of two-pion inclusive correlation functions

International Nuclear Information System (INIS)

Berger, E.L.; Singer, R.; Thomas, G.H.; Kafka, T.

1976-06-01

High energy two-particle inclusive correlations are studied as a function of the invariant mass M of the pair. Using data from 205 GeV/c pp interactions, one compares the correlation functions C(M) for (+-) and (--) pairs of produced pions. Strong positive correlations are observed in both distributions in the form of a broad threshold enhancement at small M. The decrease of C(M) as M increases is interpreted in the Mueller-Regge framework. From the M dependence of C +- one extracts an effective trajectory intercept of roughly α(0) approximately equal to 0.5 +- 0.1, consistent with the (rho,f) pair. For the exotic (--) system, one finds a low intercept, α(0) approximately equal to -0.5. A rho resonance signal is observed above background in C +- (M). Near threshold, effects suggestive of Bose symmetry are seen but are not conclusive. In an exclusive picture, one relates most of the correlation in the threshold region to resonances involving three or more pions. One also examines the joint correlations in M and the azimuthal angle phi

Pion-pair formation and the pion dispersion relation in a hot pion gas

Energy Technology Data Exchange (ETDEWEB)

Chanfay, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire; Alm, T. [Rostock Univ. (Germany); Schuck, P. [Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires; Welke, G. [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy

1996-09-01

The possibility of pion-pair formation in a hot pion gas, based on the bosonic gap equation, is pointed out and discussed in detail. The critical temperature for condensation of pion pairs (Evans-Rashind transition) is determined as a function of the pion density. As for fermions, this phase transition is signaled by the appearance of a pole in the two-particle propagator. In Bose systems there exists a second, lower critical temperature, associated with the appearance of the single-particle condensate. Between the two critical temperatures the pion dispersion relation changes from the usual quasiparticle dispersion to a Bogoliubov-like dispersion relation at low momenta. This generalizes the non-relativistic results for an attractive Bose gas by Evans et al. Possible consequences for the inclusive pion spectra measured in heavy-ion collisions at ultra-relativistic energies are discussed. 21 refs.

Fermi motion versus co-operative effects in subthreshold pion and energetic gamma production

International Nuclear Information System (INIS)

Knoll, J.

1986-06-01

Various reaction mechanisms proposed to explain the production of pions at 'sub-threshold' energies and of energetic gammas are examined. They range from the nucleon-nucleon single collision mechanism to a co-operative multi-nucleon process. With a shell model prescription for the initial state energies the single collision picture cannot explain the data. The participation of many nucleons in the pion production process appears to be necessary. We present a statistical model which demands the co-operative action of several of the target and projectile nucleons in the pion production process. The formation of composite fragments alongside with the produced pion is seen to be vital to understand the experimental data within this model. (orig.)

Low energy pion-16O scattering

International Nuclear Information System (INIS)

Wafelbakker, C.K.

1981-01-01

In spite of some outward appearances, the modern microscopic theories of the pion-nucleus (πA) interaction are not fundamentally very different from each other. They can all be derived from the same source, multiple-scattering theory. They all treat the first-order optical potential in a comparatively detailed way and in all of them it is necessary to incorporate higher-order effects in general and pion-annihilation in particular phenomenologically. Basically the same physical features can be embodied in all of them. The presentation of the theoretical scheme underlying the present thesis is designed to stress this conceptual unity of current πA theory. In this thesis the methods developed by De Kam to incorporate Pauli- and binding-corrections to the impulse-approximation first-order optical potential for 4 He are extended to a more complicated nucleus, 16 O, for the first time. In concreto two situations are considered: π- 16 O scattering at energies below nucleon-knockout threshold (13.5 MeV) - 7 and 12 MeV - and at energies 40 and 49.7 MeV, above nucleon-knockout threshold but still well within the low-energy region. (Auth.)

Helicity asymmetry of the single π{sup 0} photoproduction on neutron

Energy Technology Data Exchange (ETDEWEB)

Cividini, Federico [Institut fuer Kernphysik, Universitaet Mainz (Germany); Collaboration: A2-Collaboration

2016-07-01

During the pion production reaction, the nucleon is excited to an intermediate resonant state, and a systematic analysis of the experimental data allows a determination of the main properties of the baryon resonances. A detailed knowledge of the spectrum of nucleon excited states gives essential constraints on models of nucleon structure. The data for the observables accessible using a polarised photon beam and/or polarised nucleon targets are scarce in many channels, especially in those induced on the neutron. A measurement is performed at the Mainz Microtron, using a circularly polarised photon beam and longitudinally polarised proton and deuteron targets. The detector is the large acceptance Crystal Ball/TAPS setup. The talk gives an overview of the status of the experiment and the preliminary results of the helicity asymmetry of the single π{sup 0} photoproduction reaction from the deuteron target.

Measurement of dijet cross sections for events with a leading neutron in photoproduction at HERA

International Nuclear Information System (INIS)

Breitweg, J.; Chekanov, S.; Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Pellegrino, A.; Repond, J.; Stanek, R.; Yoshida, R.; Mattingly, M.C.K.; Antonioli, P.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; De Pasquale, S.; Giusti, P.; Iacobucci, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Palmonari, F.; Pesci, A.; Sartorelli, G.; Zichichi, A.; Amelung, C.; Bornheim, A.; Brock, I.; Coboeken, K.; Crittenden, J.; Deffner, R.; Hartmann, H.; Heinloth, K.; Hilger, E.; Irrgang, P.; Jakob, H.-P.; Kappes, A.; Katz, U.F.; Kerger, R.; Paul, E.; Rautenberg, J.; Schnurbusch, H.; Stifutkin, A.; Tandler, J.; Voss, K.C.; Weber, A.; Wieber, H.; Bailey, D.S.; Barret, O.; Brook, N.H.; Foster, B.; Heath, G.P.; Heath, H.F.; Rodrigues, E.; Scott, J.; Tapper, R.J.; Capua, M.; Schioppa, M.; Susinno, G.; Jeoung, H.Y.; Kim, J.Y.; Lee, J.H.; Lim, I.T.; Ma, K.J.; Pac, M.Y.; Caldwell, A.; Liu, W.; Liu, X.; Mellado, B.; Paganis, S.; Sampson, S.; Schmidke, W.B.; Sciulli, F.; Chwastowski, J.; Eskreys, A.; Figiel, J.; Klimek, K.; Olkiewicz, K.; Piotrzkowski, K.; Przybycien, M.B.; Stopa, P.; Zawiejski, L.; Bednarek, B.; Jelen, K.; Kisielewska, D.; Kowal, A.M.; Kowalski, T.; Przybycien, M.; Rulikowska-Zarebska, E.; Suszycki, L.; Szuba, D.; Kotanski, A.; Bauerdick, L.A.T.; Behrens, U.; Bienlein, J.K.; Borras, K.; Chiochia, V.; Dannheim, D.; Desler, K.; Drews, G.; Fox-Murphy, A.; Fricke, U.; Goebel, F.; Goers, S.; Goettlicher, P.; Graciani, R.; Haas, T.; Hain, W.; Hartner, G.F.; Hebbel, K.; Hillert, S.; Koch, W.; Koetz, U.; Kowalski, H.; Labes, H.; Loehr, B.; Mankel, R.; Martens, J.; Martinez, M.; Milite, M.; Moritz, M.; Notz, D.; Petrucci, M.C.; Polini, A.; Rohde, M.; Savin, A.A.; Schneekloth, U.; Selonke, F.; Sievers, M.; Stonjek, S.; Wolf, G.; Wollmer, U.; Youngman, C.; Zeuner, W.; Coldewey, C.; Lopez-Duran Viani, A.; Meyer, A.; Schlenstedt, S.; Straub, P.B.; Barbagli, G.; Gallo, E.; Parenti, A.; Pelfer, P.G.; Bamberger, A.; Benen, A.; Coppola, N.; Eisenhardt, S.; Markun, P.; Raach, H.; Woelfle, S.; Bussey, P.J.; Bell, M.; Doyle, A.T.; Glasman, C.; Lee, S.W.; Lupi, A.; Macdonald, N.; McCance, G.J.; Saxon, D.H.; Sinclair, L.E.; Skillicorn, I.O.; Waugh, R.; Bohnet, I.; Gendner, N.; Holm, U.; Meyer-Larsen, A.; Salehi, H.; Wick, K.; Carli, T.; Garfagnini, A.; Gialas, I.; Gladilin, L.K.; Kcira, D.; Klanner, R.; Lohrmann, E.; Goncalo, R.; Long, K.R.; Miller, D.B.; Tapper, A.D.; Walker, R.; Cloth, P.; Filges, D.; Ishii, T.; Kuze, M.; Nagano, K.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Ahn, S.H.; Lee, S.B.; Park, S.K.; Lim, H.; Son, D.; Barreiro, F.; Garcia, G.; Gonzalez, O.; Labarga, L.; del Peso, J.; Redondo, I.; Terron, J.; Vazquez, M.; Barbi, M.; Corriveau, F.; Hanna, D.S.; Ochs, A.; Padhi, S.; Stairs, D.G.; Wing, M.; Tsurugai, T.; Antonov, A.; Bashkirov, V.; Danilov, M.; Dolgoshein, B.A.; Gladkov, D.; Sosnovtsev, V.; Suchkov, S.; Dementiev, R.K.; Ermolov, P.F.; Golubkov, Yu.A.; Katkov, I.I.; Khein, L.A.; Korotkova, N.A.; Korzhavina, I.A.; Kuzmin, V.A.; Lukina, O.Yu.; Proskuryakov, A.S.; Shcheglova, L.M.; Solomin, A.N.; Vlasov, N.N.; Zotkin, S.A.; Bokel, C.; Botje, M.; Bruemmer, N.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Schagen, S.; van Sighem, A.; Tassi, E.; Tiecke, H.; Tuning, N.; Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; de Wolf, E.; Bylsma, B.; Durkin, L.S.; Gilmore, J.; Ginsburg, C.M.; Kim, C.L.; Ling, T.Y.; Boogert, S.; Cooper-Sarkar, A.M.; Devenish, R.C.E.; Grosse-Knetter, J.; Matsushita, T.; Ruske, O.; Sutton, M.R.; Walczak, R.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; Dusini, S.; Limentani, S.; Longhin, A.; Posocco, M.; Stanco, L.; Turcato, M.; Adamczyk, L.; Iannotti, L.; Oh, B.Y.; Okrasinski, J.R.; Saull, P.R.B.; Toothacker, W.S.; Whitmore, J.J.; Iga, Y.; D'Agostini, G.; Marini, G.; Nigro, A.; Cormack, C.; Hart, J.C.; McCubbin, N.A.; Shah, T.P.; Epperson, D.; Heusch, C.; Sadrozinski, H.F.-W.; Seiden, A.; Wichmann, R.; Williams, D.C.; Park, I.H.; Pavel, N.; Abramowicz , H.; Dagan, S.; Kananov, S.; Kreisel, A.; Levy, A.; Abe, T.; Fusayasu, T.; Kohno, T.; Umemori, K.; Yamashita, T.; Hamatsu, R.; Hirose, T.; Inuzuka, M.; Kitamura, S.; Matsuzawa, K.; Nishimura, T.; Arneodo, M.; Cartiglia, N.; Cirio, R.; Costa, M.; Ferrero, M.I.; Maselli, S.; Monaco, V.; Peroni, C.; Ruspa, M.; Sacchi, R.; Solano, A.; Staiano, A.; Bailey, D.C.; Fagerstroem, C.-P.; Galea, R.; Koop, T.; Levman, G.M.; Martin, J.F.; Mirea, A.; Sabetfakhri, A.; Butterworth, J.M.; Hayes, M.E.; Heaphy, E.A.; Jones, T.W.; Lane, J.B.; West, B.J.; Ciborowski, J.; Ciesielski, R.; Grzelak, G.; Nowak, R.J.; Pawlak, J.M.; Pawlak, R.; Smalska, B.; Tymieniecka, T.; Wroblewski, A.K.; Zakrzewski, J.A.; Zarnecki, A.F.; Adamus, M.; Gadaj, T.; Deppe, O.; Eisenberg, Y.; Hochman, D.; Karshon, U.; Badgett, W.F.; Chapin, D.; Cross, R.; Foudas, C.; Mattingly, S.; Reeder, D.D.; Smith, W.H.; Vaiciulis, A.; Wildschek, T.; Wodarczyk, M.; Deshpande, A.; Dhawan, S.; Hughes, V.W.; Bhadra, S.; Catterall, C.; Cole, J.E.; Frisken, W.R.; Hall-Wilton, R.; Khakzad, M.; Menary, S.

2001-01-01

Differential cross sections for dijet photoproduction in association with a leading neutron using the reaction e + +p→e + +n+jet+jet+X r have been measured with the ZEUS detector at HERA using an integrated luminosity of 6.4 pb -1 . The fraction of dijet events with a leading neutron in the final state was studied as a function of the jet kinematic variables. The cross sections were measured for jet transverse energies E T jet >6 GeV, neutron energy E n >400 GeV, and neutron production angle θ n <0.8 mrad. The data are broadly consistent with factorization of the lepton and hadron vertices and with a simple one-pion-exchange model

Phase shift analysis of pion-nucleon elastic scattering from the threshold to 2.5 GeV

International Nuclear Information System (INIS)

Ayed, Rachid.

1976-10-01

An energy-independent phase-shift analysis of pion-nucleon elastic scattering is performed from threshold to 2.5 GeV/c 2 masses. It uses a coherent set of data (cross sections and polarizations for the 3 final states: π + p, π - p and π 0 n) constructed from a considerable number (approximately 30000) of experimental points. Empirical criteria of smoothness behavior with energy of the partial waves allowed to obtain a unique solution, i.e. one set of phases shifts (up to I waves) at each energy. The consistency of the solution has been checked by a dispersion relation on the B invariant amplitude. The partial amplitudes obtained have been fitted separately, as a function of energy, in order to extract resonance from background. New resonances of small elasticity have been identified. Parameters (mass, width and elasticity) of all resonant states are given. A dynamical interpretation of the resonance is discussed and their recurrence in the Chew-Frautschi plot are shown [fr

Photoproduction of positive pions from polarized protons in the region of the first resonance

Energy Technology Data Exchange (ETDEWEB)

Get' man, V.A.; Gorbenko, V.G.; Derkach, A.Y.; Zhebrovskii, Y.V.; Karnaukhov, I.M.; Kolesnikov, L.Y.; Kuz' menko, V.S.; Lukhanin, A.A.; Ranyuk, Y.N.; Rubashkin, A.L.; Sanin, V.M.; Sorokin, P.V.; Sporov, E.A.; Telegin, Y.N.; Shalatskii, S.V.; Grushin, V.F.

1980-04-01

A technique for measuring the T asymmetry for the process ..gamma..p ..-->.. n..pi../sup +/ using a polarized proton target and a quasimonochromatic beam of photons is described. The results of measuring T in the range of pion-emission angles theta(/sub ..pi../ = 3 to 150/sup 0/ at a photon energy of 340 MeV are presented and discussed. It is shown that the results obtained allow a more reliable selection of the solutions of the energy-independent multipole analysis.

The expanding pion liquid and the pion spectra

International Nuclear Information System (INIS)

Ayala, A.

1999-01-01

We compute the pion inclusive momentum distribution in heavy-ion collisions for energies at the Alternating Gradient Synchrotron (AGS), assuming thermal equilibrium and accounting for density and expansion effects at freeze out. We compare to data on mid-rapidity charged pions produced in central Au + Au collisions and find a very good agreement. The shape of the distribution at low transverse mass is explained in part as an effect arising from the high mean pion density achieved in these reactions. The difference between the positive and negative pion distributions in the same region is attributed in part to the different average yields of each kind of charged pions. (Author)

Subthreshold Production of Neutral Pions in Heavy Ion Collisions

CERN Multimedia

2002-01-01

The pion production below the threshold at 290 MeV/u (corresponding to the minimum beam velocity at which pions can be produced in nucleon-nucleon collisions) is sensitive to coherent effects in the momentum distribution of the nucleons in the internuclear collision region. Such collective or coherent effects would manifest themselves in an enhancement of the observed cross section with respect to a prediction on the basis of model momentum distributions, e.g. from the Fermi gas model. \\\\ \\\\ With neutral pions such experiments can be extended to rather low energies and rather small cross sections (in the sub-@mb range) due to the fact that the @p|0's leave the composite nuclear system undisturbed by the Coulomb forces and that their decay $\\gamma$ rays can be detected with high efficiency also at very low pion momentum. In our experiments using |1|2C~ions of 60, 74 and 84~MeV/u and |1|80 of 84~MeV/u we were able to clearly sep from background from different sources. The large efficiency of the annular lead gl...

Production of positive pions from polarized protons by linearly polarized photons in the energy region 300--420 MeV

Energy Technology Data Exchange (ETDEWEB)

Get' man, V.A.; Gorbenko, V.G.; Grushin, V.F.; Derkach, A.Y.; Zhebrovskii, Y.V.; Karnaukhov, I.M.; Kolesnikov, L.Y.; Luchanin, A.A.; Rubashkin, A.L.; Sanin, V.M.; Sorokin, P.V.; Sporov, E.A.; Telegin, Y.N.; Shalatskii, S.V.

1980-10-01

A technique for measurement of the polarization observables ..sigma.., P, and T for the reaction ..gamma..p..-->..n..pi../sup +/ in a doubly polarized experiment (polarized proton target + linearly polarized photon beam) is described. Measurements of the angular distributions of these observables in the range of pion emission angles 30--150/sup 0/ are presented for four photon energies from 300 to 420 MeV. Inclusion of the new experimental data in an energy-independent multipole analysis of photoproduction from protons permits a more reliable selection of solutions to be made.

Pion propagator in relativistic quantum field theories of the nuclear many-body problem

International Nuclear Information System (INIS)

Matsui, T.; Serot, B.D.

1982-01-01

Pion interactions in the nuclear medium are studied using renormalizable relativistic quantum field theories. Previous studies using pseudoscalar πN coupling encountered difficulties due to the large strength of the πNN vertex. We therefore formulate renormalizable field theories with pseudovector πN coupling using techniques introduced by Weinberg and Schwinger. Calculations are performed for two specific models; the scalar-vector theory of Walecka, extended to include π and rho mesons in a non-chiral fashion, and the linear sigma-model with an additional neutral vector meson. Both models qualitatively reproduce low-energy πN phenomenology and lead to nuclear matter saturation in the relativistic Hartree formalism, which includes baryon vacuum fluctuations. The pions propagator is evaluated in the one-nucleon-loop approximation, which corresponds to a relativistic random-phase approximation built on the Hartree ground state. Virtual NN-bar loops are included, and suitable renormalization techniques are illustrated. The local-density approximation is used to compare the threshold pion self-energy to the s-wave pion-nucleus optical potential. In the non-chiral model, s-wave pion-nucleus scattering is too large in both pseudoscalar and pseudovector calculations, indicating that additional constraints must be imposed on the Lagrangian. In the chiral model, the threshold self-energy vanishes automatically in the pseudovector case, but does so for pseudoscalar coupling only if the baryon effective mass is chosen self-consistently Since extrapolation from free space to nuclear density can lead to large effects, pion propagation in the medium can determine which πN coupling is more suitable for the relativistic nuclear many-body problem. Conversely, pion interactions constrain the model Lagrangian and the nuclear matter equation of state. An approximately chiral model with pseudovector coupling is favored

Diffractive pion dissociation into 5 pion final states at COMPASS

Energy Technology Data Exchange (ETDEWEB)

Neubert, Sebastian; Friedrich, Jan; Grabmueller, Stefanie; Haas, Florian; Ketzer, Bernhard; Paul, Stephan; Weitzel, Quirin [Technische Universitaet Muenchen, Physik Department E18, 85748 Garching (Germany); Chung, Suh-Urk [Technische Universitaet Muenchen, Physik Department E18, 85748 Garching (Germany); Brookhaven National Laboratory, Upton, NY 11973 (United States); Ryabchikov, Dimitry [Technische Universitaet Muenchen, Physik Department E18, 85748 Garching (Germany); Institute for High Ernergy Physics, 142284 Protvino (Russian Federation)

2009-07-01

COMPASS is a fixed-target experiment at the CERN SPS, which investigates the structure and spectroscopy of hadrons. In 2004, a first run with a 190 GeV/c {pi}{sup -} beam took place using nuclear targets. Diffractive dissociation reactions observed in this run provide clean access to meson resonances with masses up to 3 GeV/c{sup 2}. Exclusive final states with 5 charged pions have been extracted. The covered range in momentum transfer extends from threshold to a few GeV{sup 2}/c{sup 2} allowing to study resonance production in different regimes. We report on the status of the analysis of this unique data set.

Kinetics of an expanding pion gas and low-mass dilepton emission

International Nuclear Information System (INIS)

Kaempfer, B.; Technische Univ. Dresden; Koch, P.; Pavlenko, O.P.; AN Ukrainskoj SSR, Kiev

1993-03-01

We study the space-time dependence of muon pair production from dense, non-equilibrium pion matter in the framework of a Boltzmann type transport model which properly includes effects of Bose statistics. Starting from an initially supersaturated pion gas with a large positive effective chemical potential we find that this pion chemical potential stays approximately constant during the evolution. As a consequence such a scenario leads to an increased dilepton yield near the kinematical threshold for muon pair production via pion annihilation. Depending on the lifetime of the dense hadron matter formed in relativistic heavy ion collisions, this component can e observed above the background of muon pair from resonance decays and the ρ,ωbump. In such a way the measurement of the di-muon invariant mass spectrum could help to understand the initial state and the dynamical evolution of ultrarelativistic heavy ion collisions. (orig.)

Measurement of dijet cross sections for events with a leading neutron in photoproduction at HERA

Energy Technology Data Exchange (ETDEWEB)

Breitweg, J.; Chekanov, S.; Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Pellegrino, A.; Repond, J.; Stanek, R.; Yoshida, R.; Mattingly, M.C.K.; Antonioli, P.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; De Pasquale, S.; Giusti, P.; Iacobucci, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Palmonari, F.; Pesci, A.; Sartorelli, G.; Zichichi, A.; Amelung, C.; Bornheim, A.; Brock, I.; Coboeken, K.; Crittenden, J.; Deffner, R.; Hartmann, H.; Heinloth, K.; Hilger, E.; Irrgang, P.; Jakob, H.-P.; Kappes, A.; Katz, U.F.; Kerger, R.; Paul, E.; Rautenberg, J.; Schnurbusch, H.; Stifutkin, A.; Tandler, J.; Voss, K.C.; Weber, A.; Wieber, H.; Bailey, D.S.; Barret, O.; Brook, N.H.; Foster, B. E-mail: b.foster@bristol.ac.uk; Heath, G.P.; Heath, H.F.; Rodrigues, E.; Scott, J.; Tapper, R.J.; Capua, M.; Schioppa, M.; Susinno, G.; Jeoung, H.Y.; Kim, J.Y.; Lee, J.H.; Lim, I.T.; Ma, K.J.; Pac, M.Y.; Caldwell, A.; Liu, W.; Liu, X.; Mellado, B.; Paganis, S.; Sampson, S.; Schmidke, W.B.; Sciulli, F.; Chwastowski, J.; Eskreys, A.; Figiel, J.; Klimek, K.; Olkiewicz, K.; Piotrzkowski, K.; Przybycien, M.B.; Stopa, P.; Zawiejski, L.; Bednarek, B.; Jelen, K.; Kisielewska, D.; Kowal, A.M.; Kowalski, T.; Przybycien, M.; Rulikowska-Zarebska, E.; Suszycki, L.; Szuba, D.; Kotanski, A.; Bauerdick, L.A.T.; Behrens, U.; Bienlein, J.K.; Borras, K.; Chiochia, V.; Dannheim, D.; Desler, K.; Drews, G.; Fox-Murphy, A.; Fricke, U.; Goebel, F.; Goers, S.; Goettlicher, P.; Graciani, R.; Haas, T.; Hain, W.; Hartner, G.F.; Hebbel, K.; Hillert, S.; Koch, W.; Koetz, U.; Kowalski, H.; Labes, H.; Loehr, B.; Mankel, R.; Martens, J.; Martinez, M.; Milite, M.; Moritz, M.; Notz, D.; Petrucci, M.C.; Polini, A.; Rohde, M.; Savin, A.A.; Schneekloth, U.; Selonke, F.; Sievers, M.; Stonjek, S.; Wolf, G.; Wollmer, U.; Youngman, C.; Zeuner, W.; Coldewey, C.; Lopez-Duran Viani, A.; Meyer, A.; Schlenstedt, S.[and others

2001-02-26

Differential cross sections for dijet photoproduction in association with a leading neutron using the reaction e{sup +}+p{yields}e{sup +}+n+jet+jet+X{sub r} have been measured with the ZEUS detector at HERA using an integrated luminosity of 6.4 pb{sup -1}. The fraction of dijet events with a leading neutron in the final state was studied as a function of the jet kinematic variables. The cross sections were measured for jet transverse energies E{sub T}{sup jet}>6 GeV, neutron energy E{sub n}>400 GeV, and neutron production angle {theta}{sub n}<0.8 mrad. The data are broadly consistent with factorization of the lepton and hadron vertices and with a simple one-pion-exchange model.

Subthreshold pion production of 20-100 MeV energy with various projectiles (p, 3He, 12C, 16O)

International Nuclear Information System (INIS)

Sanouillet, G.; Bolore, M.; Charlot, X.

1986-05-01

The described experiments refer to pion production below and near the threshold with different projectiles (p, 3 He, 12 C, 16 O). The pion detection device was a range telescope. Experimental methods are presented and discussed. Data are compared to predictions of some models [fr

Can one distinguish T-neutrinos from antineutrinos in neutral-current pion production processes?

OpenAIRE

Hernández Gajate, Eliecer; Nieves Pamplona, Juan Miguel; Valverde Hermosilla, Manuel

2007-01-01

A potential way to distinguish tau-neutrinos from antineutrinos, below the tau-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral-current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing tau-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves,...

Dijet photoproduction

CERN Document Server

Butterworth, J M

2001-01-01

Recent jet photoproduction measurements are presented, including measurements of jet substructure which are sensitive to parton types. The implications for real and virtual photon structure are discussed. (11 refs).

Multi-pion production in deuteron-proton collisions at COSY-ANKE

Energy Technology Data Exchange (ETDEWEB)

Mielke, Malte Marius

2014-07-01

The presented work is a contribution to the research on two- and three pion production in deuteron-proton collisions. Whereas the latter has received very little attention so far, the former is attracting the interest of particle physicists since several decades. An important reason for this is the appearance of the so-called ABC effect, a striking enhancement in the two-pion invariant mass spectrum near its threshold. There is strong evidence that this is related to the presence of nucleons and in the context of recent investigations it is even linked to an excitation of dibaryon resonances. The here presented results from an exclusive measurement of the dp→{sup 3}Heπ{sup +}π{sup -} reaction with the COSY-ANKE facility at an excess energy of 265 MeV benefit from high statistics as well as a good momentum resolution. Events with coincidentally detected {sup 3}Heπ{sup ±} and {sup 3}Heπ{sup +}π{sup -} combinations were used for the analysis. Various selection steps led to a very clean data sample. The limited geometrical acceptance of the ANKE detector was studied in detail in order to successfully elaborate a reliable correction method. Based on this, it was possible to determine differential and double differential cross sections for a large fraction of the backward {sup 3}He hemisphere. The derived invariant mass distributions do allow to illuminate further details of the two-pion production processes. Besides the prominent ABC enhancement, they reveal a significant difference in the behaviour of the positively and negatively charged pions, which is interpreted to be caused by π{sup +}π{sup -} isovector contributions. The total results are successfully described in terms of a N{sup *}(1440)→Δ(1232)→N decay chain. However, the isobar model surprisingly underestimates the charge difference at low two-pion invariant masses, indicating further contribution to the isovector channel. Investigations on the simultaneously measured dp→{sup 3}Heπ{sup +}�

Electromagnetic structure of pion in the framework of adjusted VMD model with elastic cut

International Nuclear Information System (INIS)

Dubnicka, S.; Furdik, I.; Meshcheryakov, V.A.

1987-01-01

The vector dominance model (VMD) parametrization of pion form factor is transformed into the pion c.m. momentum variable. Then the corresponding VMD poles are shifted by means of the nonzero widths of vector mesons from the real axis into the complex region of the second sheet of Riemann surface generated by the square-root two-pion-threshold branchpoint. A realistic description of all existing data is achieved in the framework of this adjusted VMD model and the presence of ρ'(1250) and ρ''(1600) mesons in e + e - →π + π - is confirmed by determination of their parameters directly from the fit of data

Quasifree pion electroproduction from nuclei in the Δ region

International Nuclear Information System (INIS)

Lee, F.X.; Wright, L.E.; Bennhold, C.

1995-10-01

We present calculations of the reaction Α (e, e 1 π N)B in the distorted wave impulse approximation. The reaction allows for the study of the production process in the nuclear medium without being obscured by the details of nuclear transition densities. First, a pion electroproduction operator suitable for nuclear calculations is obtained by extending the Blomqvist-Laget photoproduction operator to the virtual photon case. The operator is gauge invariant, unitary, reference frame independent, and describes the existing data reasonably well. Then it is applied in nuclei to predict nuclear cross sections under a variety of kinematic arrangements. Issues such as the effects of gauge-fixing, the interference of the Δ resonance with the background, sensitivities to be guadrupole component of the Δ excitation and to the electromagnetic form factors, the role of final-state interactions, are studied in detail. Methods on how to experimentally separate the various pieces in the coincidence cross section are suggested. Finally, the model is compared to recent SLAC experiment. (authors)

Inelastic J/ψphotoproduction

International Nuclear Information System (INIS)

Kraemer, M.; Steegborn, J.; Zerwas, P.M.

1994-11-01

Inelastic photoproduction of J/ψ particles at high energies is one of the processes to determine the gluon distribution in the nucleon. We have calculated the QCD radiative corrections to the color-singlet model of this reaction. They are large at moderate photon energies, but decrease with increasing energies. The cross section and the J/ψ energy spectrum are compared with the available fixed-target photoproduction data and predictions are given for the HERA energy range. (orig.)

Reaction πN → ππN near threshold

International Nuclear Information System (INIS)

Frlez, E.

1993-11-01

The LAMPF E1179 experiment used the π 0 spectrometer and an array of charged particle range counters to detect and record π + π 0 , π 0 p, and π + π 0 p coincidences following the reaction π + p → π 0 π + p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring π + p elastic scattering at 260 MeV. A detailed analysis of the π 0 detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV π - beam. All published data on πN → ππN, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter ξ =-0.25±0.10. The threshold matrix element |α 0 (π 0 π + p)| determined by linear extrapolation yields the value of the s-wave isospin-2 ππ scattering length α 0 2 (ππ) = -0.041±0.003 m π -1 , within the framework of soft-pion theory

Multi-pion production

International Nuclear Information System (INIS)

Beavis, D.; Fung, S.Y.; Gorn, W.; Keane, D.; Liu, Y.M.; Poe, R.T.; VanDalen, G.; Vient, M.

1984-01-01

Preliminary analysis of pion production in 1.2 GeV/nucleon Kr-RbBr collisions is presented. The negative pion multiplicity is consistent with a convolution of Poisson distributions and a freeze-out density between 1/3 and 1/2 normal nuclear density is extracted. Global negative pion kinematic variables are used to search for possible structure in the multi-pion emission. No evidence for structured emission or conservation constraints is found. Pion interferometry analysis gives a source radius of 5.4 +- 1.2 Fermi and a freeze-out density of .3 +- .2 times normal nuclear density. 10 refs., 5 figs

Low energy pion--nucleon and pion--deuteron interactions

International Nuclear Information System (INIS)

Burman, R.L.

1975-01-01

This survey concentrates upon current experiments in the fields of pion-nucleon and pion-deuteron interactions, for low-energy incident pions--below 300 MeV. The discussion is restricted to very recent work. The topics to be covered are: π +- p → π +- p, Elastic Scattering; π +- p → π +- pγ, Bremsstrahlung; π + d → pp, Absorption; π d → π + d, Elastic Scattering; and π + d → π + pn, Breakup. (14 figures) (U.S.)

Low energy pion-pion phase shifts from chiral perturbation theory

International Nuclear Information System (INIS)

Borges, J. Sa; Barbosa, J. Soares; Oguri, V.

1997-01-01

The low energy pion-pion S- and P- experimental phase-shifts are fitted with chiral perturbation theory (Ch PT) amplitude. The low energy pion-pion S- and P- experimental phase-shifts. The parameters l 1 and l 2 of the one loop corrected amplitude are fixed and the corresponding values of the scattering lengths are calculated. We propose that the present method is the best way to fix Ch P T parameters. The unitarization program of current algebra is also discussed. (author)

Coupled channel analysis of s-wave ππ and K anti-K photoproduction

International Nuclear Information System (INIS)

Chueng-Ryong Ji; Szczepaniak, A.; Kaminski, R.; Lesniak, L.; Williams, R.

1997-10-01

We present a coupled channel partial wave analysis of non-diffractive S-wave π + π - and K + K - photoproduction focusing on the K anti-K threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both ππ and K anti-K channels. Our results indicate that these processes are experimentally measurable and valuable information on the f 0 (980) resonance structure can be obtained. (author)

Coherent π0 electroproduction on the deuteron at threshold

International Nuclear Information System (INIS)

Jeon, B.K.; Sato, T.; Ohtsubo, H.

1989-01-01

We studied the effect of the exchange current on the longitudinal form factor of neutral pion electroproduction. As a result, we obtained a large effect of the exchange current on pion production at threshold with a momentum transfer of 2-3 fm -1 . This reaction may serve as a clear test of the exchange current, which is related to the exchange axial-charge. (orig.)

Meson production near threshold: physics implications and new technical challenges

Energy Technology Data Exchange (ETDEWEB)

Meyer, H.O. [Indiana Univ., Bloomington, IN (United States). Dept. of Physics

1995-02-01

Recently, the study of pion production in few-nucleon systems has been advanced considerably, mainly due to experiments using internal targets in stored, cooled beams. Experimental progress has inspired theoretical insights: from measurements close to threshold we have learned that an enhancement of the axial charge caused by heavy-meson exchange significantly contributes to pion production. The study of the production of pions, as well as heavier mesons, with stored polarized beams and polarized internal targets is likely to heave important consequences for our understanding of the nuclear force. (author). 42 refs, 11 figs.

Photoproduction of the K= K0-(1750)

International Nuclear Information System (INIS)

Mitchell, Ryan Edward

2003-01-01

While photoproduction has often been advertised as an important environment in which to study light meson spectroscopy, solid experimental results are sparse. In fact, beyond the relatively straightforward photoproduction of the ρ, ω, and ψ mesons, the few results of exclusive photoproduction that do exist are poorly understood, and several, perhaps, have even been misinterpreted. After extensively reviewing the sometimes tenuous history of the exclusive photoproduction of the ''p'(1600),'' the ''ωπ 0 (1250),'' the ''ω(1650),'' and the ''K + K - (1750),'' new results from the E831/FOCUS photoproduction experiment at Fermilab are presented which address the interpretation of the K + K - (1750). This enhancement in low-p T K + K - pairs at a mass near 1750 MeV/c 2 has been observed by several previous photoproduction experiments, but, despite several apparent inconsistencies, it has always been interpreted as the J PC = 1 -- ψ(1680) meson. With nearly two orders of magnitude more events than any previous observation of the K + K - (1750), and based on precise measurements of its mass and width, and its absence from the K*K final state, the FOCUS data can finally render this interpretation implausible. In addition, several steps have been taken towards establishing a new interpretation. Based on limited angular analyses of its decay and the beam energy dependence of its production, they argue that, in the absence of any wild interference scenarios, the K + K - (1750) has J PC ≠ 1 -- , and, in fact, the most likely assignment appears to be 2 ++ . It is hoped that this work can help set the stage for future reevaluations and new insights in photoproduction

Direct compatibility check of the CEA and Cornell electroproduction pion form factor data with e+e- ones

International Nuclear Information System (INIS)

Dubnicka, S.; Martinovic, L.

1988-01-01

Using precise experimental information on the imaginary part of the pion form factor from e + e - → π + π - up to the inelastic threshold and QCD constraints for it in the range of momenta (m π 0 +m ω ) 2 < t < infinity, was investigated by means of a dispersion integral the reliability of individual electroproduction CEA and Cornell model-dependent pion form factor data points

Single meson photoproduction and IR renormalons

International Nuclear Information System (INIS)

Agaev, S.S.

1996-10-01

Single pseudoscalar and vector mesons inclusive photoproduction γh → MX via higher twist mechanism is calculated using the QCD running coupling constant method. It is proved that in the context of this method a higher twist contribution to the photoproduction cross section cannot be normalized in terms of the meson electromagnetic form factor. The structure of infrared renormalon singularities of the higher twist subprocess cross section and the resumed expression (the Borel sum) for it are found. Comparisons are made with earlier results, as well as with leading twist cross section. Phenomenological effects of studied contributions for π, K, ρ-meson photoproduction are discussed. (author). 21 refs, 8 figs

Connected and disconnected contractions in pion-pion scattering

Science.gov (United States)

Acharya, Neramballi Ripunjay; Guo, Feng-Kun; Meißner, Ulf-G.; Seng, Chien-Yeah

2017-09-01

We show that the interplay of chiral effective field theory and lattice QCD can be used in the evaluation of so-called disconnected diagrams, which appear in the study of the isoscalar and isovector channels of pion-pion scattering and have long been a major challenge for the lattice community. By means of partially-quenched chiral perturbation theory, we distinguish and analyze the effects from different types of contraction diagrams to the pion-pion scattering amplitude, including its scattering lengths and the energy-dependence of its imaginary part. Our results may be used to test the current degree of accuracy of lattice calculation in the handling of disconnected diagrams, as well as to set criteria for the future improvement of relevant lattice computational techniques that may play a critical role in the study of other interesting QCD matrix elements.

Workshop on hadron structure from photo-reactions at intermediate energies: Proceedings

International Nuclear Information System (INIS)

Nathan, A.M.; Sandorfi, A.M.

1992-01-01

This report contains papers on the following topics: The proton compton effect: Recent measurements of the electric and magnetic polorizabilities of the proton; experiments on the electric polarizability of the neutron; chiral symmetry and nucleon polarizabilities; chiral model predictions for electromagnetic polarizabilities of the nucleon, a consumer report; the polarizabilities of bound nucleons; nucleon polarizability in free space and in nuclear matter; mechanisms of photon scattering on nucleons at intermediate energies; pion polarizabilities in chiral perturbation theory; pion polarizabilities and the shielding of σ(700)-meson exchange in γγ→ππ processes; pion and kaon polarizabilities in the quark confinement model; radiative pion photoproduction and pion polarizabilities; pion and sigma polarizabilities and radiative transitions; the quadrupole amplitude in the γΝ-Δ transition; pion photoproduction and the γΝ-Δ amplitudes; effective- lagrangians, Watson's theorem, and the E2/M1 mixing ratio in the excitation of the delta resonance; new measurements of the p(rvec γ, π o ) reaction; multipole analyses and photo-decay couplings at intermediate energies; compton scattering off the proton; connections between compton scattering and pion photoproduction in the delta region; single-pion electroproduction and the transverse one-half and scalar helicity transition form factors; relativistic effects, QCD mixing angles, and Ν → Νγ and Δ → γΝ transition form factors; electroproduction studies of the Ν → Δ transition at bates and CEBAF

Role of square root threshold singularity in current algebra and chiral symmetry breaking calculations of Kl3, Kl4 and tau → πKν decays

International Nuclear Information System (INIS)

Truong, T.N.

1981-01-01

It is shown that discrepancies between soft pion current algebra (or chiral symmetry) calculations in Kl 4 and experiments are mostly due to the square root threshold singularity of the pion-pion interaction. For the same reason, chiral symmetry breaking calculations of the scalar Kl 3 form factor cannot be extended to the threshold of tau → Kπν decay. (orig.)

Final-state interaction in spin asymmetry and GDH sum rule for incoherent pion production on the deuteron

International Nuclear Information System (INIS)

Darwish, E.M.; Arenhoevel, H.; Schwamb, M.

2003-01-01

The contribution of incoherent single-pion photoproduction to the spin response of the deuteron, i.e., the asymmetry of the total photoabsorption cross-section with respect to parallel and antiparallel spins of photon and deuteron, is calculated over the region of the Δ-resonance with inclusion of final-state NN and πN rescattering. Sizeable effects, mainly from NN rescattering, are found leading to an appreciable reduction of the spin asymmetry. Furthermore, the contribution to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon energy of 550 MeV. Final-state interaction reduces the value of the integral to about half of the value obtained for the pure impulse approximation. (orig.)

Preequilibrium particle emissions and in-medium effects on the pion production in heavy-ion collisions

Energy Technology Data Exchange (ETDEWEB)

Feng, Zhao-Qing [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)

2017-02-15

Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, pion dynamics in heavy-ion collisions near threshold energies and the emission of preequilibrium particles (nucleons and light complex fragments) have been investigated. A density, momentum and isospin-dependent pion-nucleon potential based on the Δ-hole model is implemented in the transport approach, which slightly leads to the increase of the π{sup -}/π{sup +} ratio, but reduces the total pion yields. It is found that a bump structure of the π{sup -}/π{sup +} ratio in the kinetic energy spectra appears at the pion energy close to the Δ(1232) resonance region. The yield ratios of neutrons to protons from the squeeze-out particles perpendicular to the reaction plane are sensitive to the stiffness of nuclear symmetry energy, in particular at the high-momentum (kinetic energy) tails. (orig.)

Study of the baryon-baryon interaction in nucleon-nucleon and pion-deuteron scattering

International Nuclear Information System (INIS)

Fuchs, M.

1993-01-01

After the definition of the Hamiltonian in general form by meson production and absorption the transition to operators pursued, which connect only spaces with definite meson numbers. In this approximation first the self-energy of a single baryon was calculated in its full energy and momentum dependence. Then the formal expressions for the T matrices of nucleon-nucleon and pion-deuteron scattering were derived. The essential components of these expressions are the baryon-baryon T matrix ant transition amplitudes from pion-deuteron channels to baryon-baryon states. The central chapter dealt with the calculation of the baryon-baryon interaction for the general form of the vertices, with the solution of the binding problem and the baryon-baryon T matrix. Finally followed the results on the nucleon-nucleon and pion-deuteron scattering. For this first the transition amplitudes from pion-deuteron states to intermediate baryon-baryon states and the Born graphs of the pion-deuteron scattering had to be calculated. After some remarks to the transition from partial-wave decomposed T matrices to scattering observables an extensive representation of the total, partial, and differential cross sections and a series of spin observables (analyzing powers and spin correlations) for the elastic proton-proton, neutron-proton, and pion-deuteron scattering as well for the fusion reaction pp→πd and the breakup reaction πd→pp follows. Thereby the energies reached from the nucleon-nucleon respectively pion-deuteron threshold up to 100 MeV above the delta resonance

Photon beam asymmetry Σ for η and η′ photoproduction from the proton

Directory of Open Access Journals (Sweden)

P. Collins

2017-08-01

Full Text Available Measurements of the linearly-polarized photon beam asymmetry Σ for photoproduction from the proton of η and η′ mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF Large Acceptance Spectrometer. Results are presented for the γp→ηp reaction for incident photon energies from 1.070 to 1.876 GeV, and from 1.516 to 1.836 GeV for the γp→η′p reaction. For γp→ηp, the data reported here considerably extend the range of measurements to higher energies, and are consistent with the few previously published measurements for this observable near threshold. For γp→η′p, the results obtained are consistent with the few previously published measurements for this observable near threshold, but also greatly expand the incident photon energy coverage for that reaction. Initial analysis of the data reported here with the Bonn–Gatchina model strengthens the evidence for four nucleon resonances – the N(18951/2−, N(19003/2+, N(21001/2+ and N(21203/2− resonances – which presently lack the “four-star” status in the current Particle Data Group compilation, providing examples of how these new measurements help refine models of the photoproduction process.

Photon beam asymmetry Σ for η and η‧ photoproduction from the proton

Science.gov (United States)

Collins, P.; Ritchie, B. G.; Dugger, M.; Anisovich, A. V.; Döring, M.; Klempt, E.; Nikonov, V. A.; Rönchen, D.; Sadasivan, D.; Sarantsev, A.; Adhikari, K. P.; Akbar, Z.; Amaryan, M. J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Balossino, I.; Bashkanov, M.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Cao, Frank Thanh; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Chetry, T.; Ciullo, G.; Clark, L.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fanchini, E.; Fedotov, G.; Filippi, A.; Fleming, J. A.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Gleason, C.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Heddle, D.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jenkins, D.; Jo, H. S.; Joosten, S.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Kubarovsky, V.; Lanza, L.; Lenisa, P.; Livingston, K.; MacGregor, I. J. D.; Markov, N.; McKinnon, B.; Meyer, C. A.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Movsisyan, A.; Munoz Camacho, C.; Murdoch, G.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Paolone, M.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Prok, Y.; Protopopescu, D.; Raue, B. A.; Ripani, M.; Rizzo, A.; Rosner, G.; Roy, P.; Sabatié, F.; Salgado, C.; Schumacher, R. A.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Tian, Ye; Torayev, B.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wei, X.; Zachariou, N.; Zhang, J.

2017-08-01

Measurements of the linearly-polarized photon beam asymmetry Σ for photoproduction from the proton of η and η‧ mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF Large Acceptance Spectrometer. Results are presented for the γp → ηp reaction for incident photon energies from 1.070 to 1.876 GeV, and from 1.516 to 1.836 GeV for the γp →η‧ p reaction. For γp → ηp, the data reported here considerably extend the range of measurements to higher energies, and are consistent with the few previously published measurements for this observable near threshold. For γp →η‧ p, the results obtained are consistent with the few previously published measurements for this observable near threshold, but also greatly expand the incident photon energy coverage for that reaction. Initial analysis of the data reported here with the Bonn-Gatchina model strengthens the evidence for four nucleon resonances - the N (1895) 1 /2-, N (1900) 3 /2+, N (2100) 1 /2+ and N (2120) 3 /2- resonances - which presently lack the ;four-star; status in the current Particle Data Group compilation, providing examples of how these new measurements help refine models of the photoproduction process.

Beam Spin Asymmetry Measurements for Two Pion Photoproduction at CLAS

Energy Technology Data Exchange (ETDEWEB)

Anderson, Mark D. [Univ. of Glasgow, Scotland (United Kingdom)

2015-09-01

The overarching goal of this analysis, and many like it, is to develop our understanding of the strong force interactions within the nucleon by examining the nature of their excitation spectra. As the resonances of these spectra have very short lifetimes (tau = 1x10^-23 s) and often have very similar masses, it is often impossible to directly observe resonances in the excitation spectra of nucleons. Polarization observables allow us to study the resonances by looking at how they affect the spin state of final state particles. The beam asymmetry is a polarization observable that allows us to detect the sensitivity of these resonances, and other transition mechanisms, to the electric vector orientation of incident photons. Presented in this thesis are first measurements of the beam asymmetries in the resonant region for the reaction channel pgamma p --> p π⁺ π^-focusing on the intermediate mesonic states rho^0 and f^0, and the final state pions. The analysis used data from the g8b experiment undertaken at the Thomas Jefferson National Accelerator Facility (JLab), the first experiment at JLab to use a linearly polarized photon beam. Using the coherent Bremsstrahlung facility and the CLAS detector of Hall B at JLab allowed for many multi-channel reactions to be detected and the first measurements of many polarization observables including those presented here. A brief overview of the theoretical framework used to undertake this analysis is given, followed by a description of the experimental details of the facilities used, then a description of the calibration of the Bremsstrahlung tagging facility which the author undertook, and finally the analysis is presented and the resulting measurements.

Pion contamination in the MICE muon beam

International Nuclear Information System (INIS)

Adams, D.; Barclay, P.; Bayliss, V.; Brashaw, T.W.; Alekou, A.; Apollonio, M.; Barber, G.; Asfandiyarov, R.; Blondel, A.; De Bari, A.; Bayes, R.; Bertoni, R.; Bonesini, M.; Blackmore, V.J.; Blot, S.; Bogomilov, M.; Booth, C.N.; Bowring, D.; Boyd, S.; Bravar, U.

2016-01-01

The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240 MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than ∼1% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is f π  < 1.4% at 90% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling

Pion contamination in the MICE muon beam

CERN Document Server

Bogomilov, M.; Vankova-Kirilova, G.; Bertoni, R.; Bonesini, M.; Chignoli, F.; Mazza, R.; Palladino, V.; de Bari, A.; Cecchet, G.; Capponi, M.; Iaciofano, A.; Orestano, D.; Pastore, F.; Tortora, L.; Kuno, Y.; Sakamoto, H.; Ishimoto, S.; Japan, Ibaraki; Filthaut, F.; Hansen, O.M.; Ramberger, S.; Vretenar, M.; Asfandiyarov, R.; Blondel, A.; Drielsma, F.; Karadzhov, Y.; Charnley, G.; Collomb, N.; Gallagher, A.; Grant, A.; Griffiths, S.; Hartnett, T.; Martlew, B.; Moss, A.; Muir, A.; Mullacrane, I.; Oates, A.; Owens, P.; Stokes, G.; Warburton, P.; White, C.; Adams, D.; Barclay, P.; Bayliss, V.; Bradshaw, T.W.; Courthold, M.; Francis, V.; Fry, L.; Hayler, T.; Hills, M.; Lintern, A.; Macwaters, C.; Nichols, A.; Preece, R.; Ricciardi, S.; Rogers, C.; Stanley, T.; Tarrant, J.; Watson, S.; Wilson, A.; Bayes, R.; Nugent, J.C.; Soler, F.J.P.; Cooke, P.; Gamet, R.; Alekou, A.; Apollonio, M.; Barber, G.; Colling, D.; Dobbs, A.; Dornan, P.; Hunt, C.; Lagrange, J-B.; Long, K.; Martyniak, J.; Middleton, S.; Pasternak, J.; Santos, E.; Savidge, T.; Uchida, M.A.; Blackmore, V.J.; Carlisle, T.; Cobb, J.H.; Lau, W.; Rayner, M.A.; Tunnell, C.D.; Booth, C.N.; Hodgson, P.; Langlands, J.; Nicholson, R.; Overton, E.; Robinson, M.; Smith, P.J.; Dick, A.; Ronald, K.; Speirs, D.; Whyte, C.G.; Young, A.; Boyd, S.; Franchini, P.; Greis, J.R.; Pidcott, C.; Taylor, I.; Gardener, R.; Kyberd, P.; Littlefield, M.; Nebrensky, J.J.; Bross, A.D.; Fitzpatrick, T.; Leonova, M.; Moretti, A.; Neuffer, D.; Popovic, M.; Rubinov, P.; Rucinski, R.; Roberts, T.J.; Bowring, D.; DeMello, A.; Gourlay, S.; Li, D.; Prestemon, S.; Virostek, S.; Zisman, M.; Drews, M.; Hanlet, P.; Kafka, G.; Kaplan, D.M.; Rajaram, D.; Snopok, P.; Torun, Y.; Winter, M.; Blot, S.; Kim, Y.K.; Bravar, U.; Onel, Y.; Cremaldi, L.M.; Hart, T.L.; Luo, T.; Sanders, D.A.; Summers, D.J.; Cline, D.; Yang, X.; Coney, L.; Hanson, G.G.; Heidt, C.

2016-01-01

The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240\\,MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than $\\sim$1\\% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is $f_\\pi < 1.4\\%$ at 90\\% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.

Measurement of beauty photoproduction at threshold using di-electron events with the H1 detector at HERA

International Nuclear Information System (INIS)

Sauter, Michel David

2009-12-01

The cross section of b anti b photoproduction in ep collisions has been measured with the H1 detector at HERA. Events containing b-quarks were identified through detection of two low momentum electrons in the nal state. Semileptonic decays b anti b→eeX were exploited in the kinematic range of the photon virtuality Q 2 2 , the inelasticity 0.2 T -electron identification. (orig.)

Inelastic J/ψphotoproduction

International Nuclear Information System (INIS)

Kraemer, M.

1995-04-01

Inelastic photoproduction of J/ψ particles at high energies is one of the processes to determine the gluon distribution in the nucleon. The QCD radiative corrections to the color-singlet model of this reaction have recently been calculated. They are large at moderate photon energies, but decrease with increasing energies. I compare the cross section and the J/ψ energy spectrum with the available fixed-target photoproduction data. Predictions for the HERA energy range are given which demonstrate the sensitivity of the result to the parametrization of the gluon distribution in the small-x region. (orig.)

Ultraviolet-induced mutations in Cockayne syndrome cells are primarily caused by cyclobutane dimer photoproducts while repair of other photoproducts is normal

International Nuclear Information System (INIS)

Parris, C.N.; Kraemer, K.H.

1993-01-01

The authors compared the contribution to mutagenesis on Cockayne syndrome (CS) cells of the major class of UV photoproducts, the cyclobutane pyrimidine dimer, to that of other DNA photoproducts by using the mutagenesis shuttle vector pZ189. Lymphoblastoid cell lines from the DNA repair-deficient disorders CS and xeroderma pigmentosum (XP) and a normal line were transfected with UV-treated pZ189. Cyclobutane dimers were selectively removed before transfection by photoreactivation (PR), leaving nondimer photoproducts intact. After UV exposure and replication in CS and XP cells, plasmid survival was abnormally elevated. After PR, plasmid survival increased and mutation frequency in CS cells decreased to normal levels but remained abnormal in XP cells. Sequence analysis of >200 mutant plasmids showed that with CS cells a major mutational hot spot was caused by unrepaired cyclobutane dimers. These data indicate that with both CS and XP cyclobutane dimers are major photoproducts generating reduced plasmid survival and increased mutation frequency. However, unlike XP, CS cells are proficient in repair of nondimer photoproducts. Since XP but not CS patients have a high frequency of UV-induced skin cancers, the data suggest that prevention of UV-induced skin cancers is associated with proficient repair of nondimer photoproducts. 38 refs., 3 figs., 2 tabs

Photoneutron multiplicities of preactinide nuclei at energies above the pion threshold

International Nuclear Information System (INIS)

Arruda-Neto, J.D.T.; Simionatto, S.; Likhachev, V.P.; Garcia, F.; Mesa, J.

1998-01-01

The average photoneutron multiplicities anti ν of Au, Ta and 182 W were deduced from their previously measured excitation energies anti E x , from 160 to 250 MeV. A combined analysis of these data and those measured at Saclay up to 140 MeV allowed the extraction of information on anti E x at the ''pure evaporation'' and quasideuteron energy regions. A theoretical approach for the study of anti ν above 140 MeV, which incorporates photopion reabsorption processes by two-body, was proposed, allowing a tentative delineation of the pion mean free path in the nucleus. (orig.)

Quasifree pion electroproduction from nuclei in the {Delta} region

Energy Technology Data Exchange (ETDEWEB)

Lee, F X [TRIUMF, Vancouver, BC (Canada); Wright, L E [Ohio Univ., Inst. of Nuclear and Particle Physics, Dept. of Physics, Athens, OH (United States); Bennhold, C [George Washington Univ., Center for Nuclear Studies, Dept. of Physics, Washington, DC (United States)

1995-10-01

We present calculations of the reaction {Alpha} (e, e{sup 1}{pi} N)B in the distorted wave impulse approximation. The reaction allows for the study of the production process in the nuclear medium without being obscured by the details of nuclear transition densities. First, a pion electroproduction operator suitable for nuclear calculations is obtained by extending the Blomqvist-Laget photoproduction operator to the virtual photon case. The operator is gauge invariant, unitary, reference frame independent, and describes the existing data reasonably well. Then it is applied in nuclei to predict nuclear cross sections under a variety of kinematic arrangements. Issues such as the effects of gauge-fixing, the interference of the {Delta} resonance with the background, sensitivities to be guadrupole component of the {Delta} excitation and to the electromagnetic form factors, the role of final-state interactions, are studied in detail. Methods on how to experimentally separate the various pieces in the coincidence cross section are suggested. Finally, the model is compared to recent SLAC experiment. (authors) 35 refs., 22 figs.

Strangeness photoproduction

International Nuclear Information System (INIS)

Berthot, J.; Saghai, B.

1989-01-01

A non exhaustive review, about the strangeness photo-production is presented here in relation with the new electrons machines. Accent is put on the elementary reaction γp → K + Λ. The experiments on electroproduction and the study of hypernuclei with the electromagnetic probe are also discussed [fr

Workshop on hadron structure from photo-reactions at intermediate energies: Proceedings

Energy Technology Data Exchange (ETDEWEB)

Nathan, A.M.; Sandorfi, A.M. [eds.

1992-10-01

This report contains papers on the following topics: The proton compton effect: Recent measurements of the electric and magnetic polorizabilities of the proton; experiments on the electric polarizability of the neutron; chiral symmetry and nucleon polarizabilities; chiral model predictions for electromagnetic polarizabilities of the nucleon, a consumer report; the polarizabilities of bound nucleons; nucleon polarizability in free space and in nuclear matter; mechanisms of photon scattering on nucleons at intermediate energies; pion polarizabilities in chiral perturbation theory; pion polarizabilities and the shielding of {sigma}(700)-meson exchange in {gamma}{gamma}{yields}{pi}{pi} processes; pion and kaon polarizabilities in the quark confinement model; radiative pion photoproduction and pion polarizabilities; pion and sigma polarizabilities and radiative transitions; the quadrupole amplitude in the {gamma}{Nu}-{Delta} transition; pion photoproduction and the {gamma}{Nu}-{Delta} amplitudes; effective- lagrangians, Watson`s theorem, and the E2/M1 mixing ratio in the excitation of the delta resonance; new measurements of the p({rvec {gamma}}, {pi}{sup o}) reaction; multipole analyses and photo-decay couplings at intermediate energies; compton scattering off the proton; connections between compton scattering and pion photoproduction in the delta region; single-pion electroproduction and the transverse one-half and scalar helicity transition form factors; relativistic effects, QCD mixing angles, and {Nu} {yields} {Nu}{gamma} and {Delta} {yields} {gamma}{Nu} transition form factors; electroproduction studies of the {Nu} {yields} {Delta} transition at bates and CEBAF.

Electromagnetic Charge Radius of the Pion at High Precision

Science.gov (United States)

Ananthanarayan, B.; Caprini, Irinel; Das, Diganta

2017-09-01

We present a determination of the pion charge radius from high precision data on the pion vector form factor from both timelike and spacelike regions, using a novel formalism based on analyticity and unitarity. At low energies, instead of the poorly known modulus of the form factor, we use its phase, known with high accuracy from Roy equations for π π elastic scattering via the Fermi-Watson theorem. We use also the values of the modulus at several higher timelike energies, where the data from e+e- annihilation and τ decay are mutually consistent, as well as the most recent measurements at spacelike momenta. The experimental uncertainties are implemented by Monte Carlo simulations. The results, which do not rely on a specific parametrization, are optimal for the given input information and do not depend on the unknown phase of the form factor above the first inelastic threshold. Our prediction for the charge radius of the pion is rπ=(0.657 ±0.003 ) fm , which amounts to an increase in precision by a factor of about 2.7 compared to the Particle Data Group average.

Pions scatter by nuclei

International Nuclear Information System (INIS)

Huefner, J.

1975-01-01

Are pions a good tool to study nuclei. If the emphasis of this question rests on ''tool'', the answer must be ''not yet.'' The reason: one does not even understand how a pion interacts with a nucleus. This is part of the many-body problem for strongly interacting particles and its study is a basic problem in physics. One must investigate questions like: Can one understand pion-nucleus interactions from pion-nucleon physics. How does a Δ-resonance look in nuclei. Once one has solved those basic problems, there will be spinoffs in medical, technical and nuclear areas. Then pions can be used as a tool to study nuclear properties

Subthreshold and near-threshold K+-meson photoproduction on nuclei

International Nuclear Information System (INIS)

Paryev, E.Ya.

2000-01-01

The inclusive K + -meson production in photon-induced reactions in the near-threshold and subthreshold energy regimes is analyzed for the one-step (γN → K + Y, Y = Λ, Σ) incoherent production processes on the basis of an appropriate new folding model that takes properly into account the struck-target nucleon-removal energy and the internal momentum distribution (nucleon spectral function), extracted from recent quasielastic-electron-scattering experiments and from many-body calculations based on realistic models of NN interaction. Simple parametrizations of the total and differential cross sections for K + production in photon-nucleon collisions are presented. A comparison of the model calculations of the K + differential cross sections for γ 12 C interactions in the threshold region with existing experimental data is given, which displays the contributions to K + production at considered incident energies from the use of the single-particle part, as well as high momentum and high removal energy part, of the nucleon spectral function. Detailed predictions for the K + total and differential cross sections for γ 2 H, γ 12 C, and γ 208 Pb interactions at subthreshold and near-threshold energies are provided. The effect of the uncertainties in the elementary K + -production cross sections on the K + yield is explored

Reaction πN → ππN near threshold

Energy Technology Data Exchange (ETDEWEB)

Frlez, Emil [Univ. of Virginia, Charlottesville, VA (United States)

1993-11-01

The LAMPF E1179 experiment used the π⁰ spectrometer and an array of charged particle range counters to detect and record π⁺π⁰, π⁰p, and π⁺π⁰p coincidences following the reaction π⁺p → π⁰π⁺p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring π⁺p elastic scattering at 260 MeV. A detailed analysis of the π⁰ detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV π^- beam. All published data on πN → ππN, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter ξ =-0.25±0.10. The threshold matrix element |α₀(π⁰π⁺p)| determined by linear extrapolation yields the value of the s-wave isospin-2 ππ scattering length α$2\\atop{0}$(ππ) = -0.041±0.003 m$-1\\atop{π}$^-1, within the framework of soft-pion theory.

Effect of pion mean-field on properties of pions and kaons from heavy-ion collisions

International Nuclear Information System (INIS)

Zheng Yuming; Chu Zili; Wang Hui; Sa Benhao

1996-01-01

The Relativistic Vlasov-Uehling-Uhlenbeck (RVUU) model is used to study the properties of pions and kaons produced in heavy ion collisions. We include the nuclear medium effect on kaon and pion in the model, and simulate pion production and subthreshold kaon production in Kr + Zr reactions at 1 GeV/u. The calculated results show that the attractive pion optical potential changes the final-state pion momentum spectrum, enhancing the yield of pions with low transverse momenta. At the same time it also increases the kaon abundance and modifies the kaon momentum distribution

Measurements of NN→dπ very near threshold. Pt. 2

International Nuclear Information System (INIS)

Korkmaz, E.; Li, Jin; Elliott, J.B.; Mack, D.J.; Rodning, N.L.; Hutcheon, D.A.; Abegg, R.; Greeniaus, L.G.; Miller, C.A.

1991-01-01

We have measured analyzing powers for the reaction pp→dπ + at beam energies 3 and 7 MeV above pion-production threshold. With the use of Watson's theorem to fix phases and effective range estimates of pion d-wave strength, we have been able to determine the NN→dπ s-wave amplitude and the major p-wave amplitude at these energies. The results are compared to the Faddeev model predictions of Blankleider. (orig.)

Subthreshold pion production study with heavy ions at low and medium energy

International Nuclear Information System (INIS)

Rebreyend, D.

1988-02-01

In the domain of subthreshold pion production with heavy ions at low and medium energy (40-100 MeV/u), only Π 0 have been up to now, extensively studied. The incompleteness of the charged pion data and especially the lack of results for pions of energy less than 30 MeV have led to conceive the magnetic spectrometer SPIC. In the present work, we demonstrate that this spectrometer is particularly well suited for the detection of low energy charged pions (Inferior threshold of detection: T Π = 7 MeV), emitted around 0 0 in heavy ion collisions. Principle and performances, successfully tested at 38 and 93 MeV/u, are described in detail. The main characteristics of a Π 0 spectrometer, that was used to realize a comparative experiment of Π 0 production, are then given. The last chapter is devoted to experimental results. First, we present the results obtained with the 16 0 beam of 38 MeV/u of the SARA accelerator, in charged pions (Al and Ni targets) and in Π 0 (Al and Au targets). A comparison of the data Π - /Π 0 seems to indicate that coulomb effects are surprisingly small. Finally, we report the data obtained with the 16 0 beam of 93 MeV/u of GANIL. In contrast with low energy data, coulomb effects are very strong (ratio Π - /Π + = 100 for pions of low energy with heavy targets) and allowed us to extract informations on the geometry of the collision [fr

Pion form factor in QCD sum rules, local duality approach, and O(A2) fractional analytic perturbation theory

International Nuclear Information System (INIS)

Bakulev, Alexander P.

2010-01-01

Using the results on the electromagnetic pion Form Factor (FF) obtained in the O(α s ) QCD sum rules with non-local condensates [A.P. Bakulev, A.V. Pimikov, and N.G. Stefanis, Phys. Rev. D79 (2009) 093010] we determine the effective continuum threshold for the local duality approach. Then we apply it to construct the O(α s 2 ) estimation of the pion FF in the framework of the fractional analytic perturbation theory.

Isospin violation in low-energy pion-nucleon scattering revisited

Energy Technology Data Exchange (ETDEWEB)

Hoferichter, Martin, E-mail: hoferichter@hiskp.uni-bonn.d [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Kubis, Bastian [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Meissner, Ulf-G. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Institut fuer Kernphysik (IKP-3), Institute for Advanced Simulation, and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany)

2010-02-01

We calculate isospin breaking in pion-nucleon scattering in the threshold region in the framework of covariant baryon chiral perturbation theory. All effects due to quark mass differences as well as real and virtual photons are consistently included. As an application, we discuss the energy dependence of the triangle relation that connects elastic scattering on the proton pi{sup +}-p->pi{sup +}-p with the charge exchange reaction pi{sup -}p->pi{sup 0}n.

Isospin violation in low-energy pion-nucleon scattering revisited

International Nuclear Information System (INIS)

Hoferichter, Martin; Kubis, Bastian; Meissner, Ulf-G.

2010-01-01

We calculate isospin breaking in pion-nucleon scattering in the threshold region in the framework of covariant baryon chiral perturbation theory. All effects due to quark mass differences as well as real and virtual photons are consistently included. As an application, we discuss the energy dependence of the triangle relation that connects elastic scattering on the proton π ± p→π ± p with the charge exchange reaction π - p→π 0 n.

Workshop on hadron structure from photo-reactions at intermediate energies: Proceedings

Energy Technology Data Exchange (ETDEWEB)

Nathan, A.M.; Sandorfi, A.M. (eds.)

1992-01-01

This report contains papers on the following topics: The proton compton effect: Recent measurements of the electric and magnetic polorizabilities of the proton; experiments on the electric polarizability of the neutron; chiral symmetry and nucleon polarizabilities; chiral model predictions for electromagnetic polarizabilities of the nucleon, a consumer report; the polarizabilities of bound nucleons; nucleon polarizability in free space and in nuclear matter; mechanisms of photon scattering on nucleons at intermediate energies; pion polarizabilities in chiral perturbation theory; pion polarizabilities and the shielding of [sigma](700)-meson exchange in [gamma][gamma][yields][pi][pi] processes; pion and kaon polarizabilities in the quark confinement model; radiative pion photoproduction and pion polarizabilities; pion and sigma polarizabilities and radiative transitions; the quadrupole amplitude in the [gamma][Nu]-[Delta] transition; pion photoproduction and the [gamma][Nu]-[Delta] amplitudes; effective- lagrangians, Watson's theorem, and the E2/M1 mixing ratio in the excitation of the delta resonance; new measurements of the p([rvec [gamma

The pion pole term in electroproduction of off-mass-shell pions

International Nuclear Information System (INIS)

McKellar, B.H.; Ellis, R.G.

1983-01-01

The dependence of the invariant amplitudes for electroproduction of off-mass-shell pions on the pion Born term is investigated when current algebra Ward identities and PCAC are used to determine pion electroproduction invariant amplitudes. The authors show that an amplitude satisfying the Ward identities can be constructed starting from the usual Born terms which do not satisfy them and that this same amplitude will be obtained for a large class of input Born terms

Dosimetry of pion beams

International Nuclear Information System (INIS)

Dicello, J.F.

1975-01-01

Negative pion beams are probably the most esoteric and most complicated type of radiation which has been suggested for use in clinical radiotherapy. Because of the limited availability of pion beams in the past, even to nuclear physicists, there exist relatively fewer basic data for this modality. Pion dosimetry is discussed

{eta} meson photoproduction on deuterium; Photoproduction du meson {eta} sur le deuterium

Energy Technology Data Exchange (ETDEWEB)

Hoffmann-Rothe, P.

1996-05-30

Measurements of the total and differential cross sections for {eta}-meson photoproduction on a D{sub 2} liquid target from threshold to 1.2 GeV, have been taken using the tagged Bremsstrahlung photon beam produced by the electrons extracted from the ELSA storage ring at Bonn. The reaction was identified by detecting the eta decay products in the neutral meson spectrometer SPES0-2{pi}, while the recoil baryons (proton, neutron or deuteron) were detected by a variety of large angle scintillator detectors. We succeeded to identify completely the final states corresponding to the production of an {eta} meson on a Quasi-Free (QF) proton, a QF neutron and the coherent deuteron. The differential cross sections corresponding to the production of a coherent deuteron n the final state have been measured, from threshold to 800 MeV; they are 6 times smaller the only previous measurement reported by Anderson and Prepost in 1969. This is consistent with an Isoscalar part of the Amplitude much smaller than the Isovector one. The differential cross sections are in good agreement with the theoretical prediction on the impulse approximation mechanism; indicating in particular, fairly small contributions from rescattering terms. A direct measurement of the neutron to proton cross section ratios has been obtained by integrating the counting rates on the corresponding QF peaks and is 0.70 {+-} 0.03, from 700 MeV to 900 MeV, with a small angular dependence. These two results by comparison to the measured free proton data should allow to reconstruct the free neutron cross sections in a rather model-independent way. (authors). 56 refs., 90 figs., 13 tabs.

Quarkonia Photoproduction at Nucleus Colliders

International Nuclear Information System (INIS)

D'Enterria, David

2008-01-01

Exclusive photoproduction of heavy quarkonia in high-energy ultraperipheral ion-ion interactions (γ A →V A, where V = J/ψ, Y and the nucleus A remains intact) offers a useful means to constrain the small-x nuclear gluon density. We discuss preliminary results on J/ψ photoproduction in Au-Au collisions at RHIC [D. d'Enterria [PHENIX Collaboration], Proceeds. Quark Matter'05, (arXiv:nucl-ex/0601001)], as well as full simulation-reconstruction studies of photo-produced Y in Pb-Pb interactions at the LHC [D. d'Enterria (ed.) et al. [CMS Collaboration], J. Phys. G. 34 2307 (2007)

Pion polarizabilities measurement at COMPASS

CERN Document Server

Guskov, Alexey

2008-01-01

The electromagnetic structure of pions is probed in $\\pi^{−} + (A,Z)\\rightarrow\\pi^{−} + (A,Z) +\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\bar{\\alpha_{\\pi}})$ and the magnetic $(\\bar{\\beta_{\\pi}})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with $a \\pi^{−}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction. The preliminary result for pion polarizabilities under the assumption of $\\bar{\\alpha_{\\pi}} + \\bar{\\beta_{\\pi}} =$ 0 is $\\ba...

Elastic pion-nucleon P-wave scattering in soliton models

International Nuclear Information System (INIS)

Holzwarth, G.

1990-01-01

The equivalence of low-energy P-wave πN scattering in soliton models with the well-established Δ-isobar model is shown to hold even if all constraints on redundant collective variables are ignored. This provides strong support for the unusual (time-derivative) form of meson-baryon coupling in such models, and for the expectation that the soliton description of πN-scattering can be reliably extended down to pion threshold energies in a technically simple way. (orig.)

Measurements on NN → dπ very near threshold. II

International Nuclear Information System (INIS)

Korkmaz, E.; Li, J.; Hutcheon, D.A.; Abegg, R.; Elliott, J.B.; Greeniaus, L.G.; Mack, D.J.; Miller, C.A.; Rodning, N.L.

1991-04-01

We have measured analyzing powers for the reaction pp → dπ + at beam energies 3 and 7 MeV above pion production threshold. With the use of Watson's Theorem to fix phases and effective range estimates of pion d-wave strength, we have been able to determine the NN → dπ s-wave amplitude and the two p-wave amplitudes at these energies. The results are compared to the Faddeev model predictions of Blankleider. (Author) 11 refs., 2 tabs., 11 figs

Pion nucleus scattering lengths

International Nuclear Information System (INIS)

Huang, W.T.; Levinson, C.A.; Banerjee, M.K.

1971-09-01

Soft pion theory and the Fubini-Furlan mass dispersion relations have been used to analyze the pion nucleon scattering lengths and obtain a value for the sigma commutator term. With this value and using the same principles, scattering lengths have been predicted for nuclei with mass number ranging from 6 to 23. Agreement with experiment is very good. For those who believe in the Gell-Mann-Levy sigma model, the evaluation of the commutator yields the value 0.26(m/sub σ//m/sub π/) 2 for the sigma nucleon coupling constant. The large dispersive corrections for the isosymmetric case implies that the basic idea behind many of the soft pion calculations, namely, slow variation of matrix elements from the soft pion limit to the physical pion mass, is not correct. 11 refs., 1 fig., 3 tabs

Far-UV-induced dimeric photoproducts in short oligonucleotides: sequence effects

International Nuclear Information System (INIS)

Douki, T.; Zalizniak, T.; Cadet, J.

1997-01-01

Cyclobutane pyrimidine dimers and pyrimidine (6-4)pyrimidone adducts represent the two major classes of far-UV-induced DNA photoproducts. Because of the lack of appropriate detection methods for each individual photoproduct, little is known about the effect of the sequence on their formaiton. In the present work, the photoproduct distribution obtained upon exposure of a series of dinucleoside monophosphate to 254 nm light was determined. (author)

Pion polarizabilities measurement at COMPASS

CERN Document Server

Guskov, Alexey

2008-01-01

The electromagnetic structure of pions is probed in $\\pi^{−}+(A,Z) \\rightarrow\\pi^{−}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric ($\\bar{\\alpha_{\\pi}}$) and the magnetic ($\\bar{\\beta_{\\pi}}$) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with a $\\pi^{-}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction.

Pion-nuclear many body problems

International Nuclear Information System (INIS)

Weise, W.

1981-01-01

This chapter examines pion-nucleus scattering data produced at the meson factories in order to gain information about the ''optical'' branches of the pion-nuclear excitation spectrum. Discusses basic meson-baryon effective Lagrangians and elementary processes; pion-baryon vertex form factors; the spin-isospin dependent baryon-baryon interaction; pions in nuclear matter; nuclear spin-isospin correlations; the baryon-hole model; photon-induced excitation of baryon-hole states; high momentum transfer properties of pion-like nuclear states; a response function for pionic low-frequency modes in finite nuclei; and applications. Finds that there is no clear evidence for pionic critical opalescence, as in agreement with the expectation that the minimal density for the appearance of a pion condensate is certainly not lower than two or three times nuclear matter density

Experimental study of the pion-xenon nucleus collisions at 3.5 GeV/c. Neutral pion production

International Nuclear Information System (INIS)

Strugalski, Z.; Abrosimov, A.T.; Wosinska, K.; Pawlak, T.; Nluta, J.; Sredniawa, B.; Il'ina, A.N.; Okhrimenko, L.S.; Peryt, W.; Miller, K.

1983-01-01

Experimental investigations of the neutral pion production are performed in pion-xenon collisions at 3.5 GeV/c. It is obtained that: 1) the average neutral pion multiplicity changes with the multiplicity of the protons emitted; 2) nearly 20% of the pions produced are emitted into the backward hemisphere; 3) the energy spectrum of the neutral pions is smooth; 4) the longitudinal component of the neutral pion momentum changes within the limits from -600 MeV/c to +1800 MeV/c; 5) the average value of the transversal component of the neutral pion momentum changes with the multiplicity of the protons emitted from approximately 270 to approximately 170 MeV/c; 6) the average value of the cosine of the neutral pion emission angle decreases with the multiplicity of the protons emitted

Measurement of energy spectra of charged particles emitted after the absorption of stopped negative pions in carbon

International Nuclear Information System (INIS)

Mechtersheimer, G.

1978-06-01

The energy spectra of charged particles (p,d,t, 3 He, 4 He and Li-nuclei) emitted after the absorption of stopped negative pions in carbon targets of different thickness (1.227, 0.307, 0.0202 g/cm 2 ) have been measured from the experimental threshold energy of about 0.5 MeV up to the kinematical limit of about 100 MeV. The experiments have been carried out at the biomedical pion channel πE3 of the Swiss Institute of Nuclear Research (SIN). (orig.) [de

Improved pion pion scattering amplitude from dispersion relation formalism

International Nuclear Information System (INIS)

Cavalcante, I.P.; Coutinho, Y.A.; Borges, J. Sa

2005-01-01

Pion-pion scattering amplitude is obtained from Chiral Perturbation Theory at one- and two-loop approximations. Dispersion relation formalism provides a more economic method, which was proved to reproduce the analytical structure of that amplitude at both approximation levels. This work extends the use of the formalism in order to compute further unitarity corrections to partial waves, including the D-wave amplitude. (author)

Heavy quarks photoproduction

International Nuclear Information System (INIS)

Cacciari, M.

1996-08-01

The state of the art of the theoretical calculations for heavy quarks photoproduction is reviewed. The full next-to-leading order calculation and two possible resummations, the high energy one for total cross sections and the large p T one for differential cross sections, are described. (orig.)

Structure of the φ photoproduction amplitude at a few GeV

International Nuclear Information System (INIS)

Titov, A.I.; Toki, H.; Titov, A.I.; Streltsova, O.; Lee, T.H.

1999-01-01

The structure of the φ photoproduction amplitude in the √ (s) ∼2-5 GeV region is analyzed based on Pomeron-exchange and meson-exchange mechanisms. The SU(3) symmetry and the φ decay widths are exploited to determine the parameters that are needed to predict the amplitudes due to pseudoscalar mesons (π 0 ,η) exchange, scalar mesons (σ,a 0 ,f 0 ) exchange, and the φ radiation from the nucleon. In addition to the universally accepted Pomeron exchange with an intercept α(0)∼1.08, we investigate the role of a second Pomeron with α(0) π =0 + ,M b 2 ∼3 GeV 2 ) predicted by the lattice QCD calculation and dual Ginsburg-Landau model. It is found that the existing limited data at low energies near threshold can accommodate either the second Pomeron or the scalar mesons exchange. The differences between these two competing mechanisms are shown to have profound effects on various density matrices which can be used to calculate the cross sections as well as various single and double polarization observables. We predict a definite isotopic effect: polarization observables of φ photoproduction on the proton and neutron targets can have differences of a factor 2 and more. copyright 1999 The American Physical Society

Pion production in nuclei

International Nuclear Information System (INIS)

Afnan, I.R.; Thomas, A.W.

1976-01-01

A method has been suggested for relating μ-capture in nuclei to pion absorption through partially conserved axial vector current hypothesis. The success of the method relies heavily on the knowledge of the pion absorption amplitude at a momentum transfer equal to the μ-meson mass. That is we need to know the pion absorption amplitude off the mass-shell. The simplest nucleus for which this suggestion can be examined is μ-capture in deuterium. The Koltum-Reitan model is used to determine the pion absorption amplitude off the mass shell. In particular the senstivity of this off-mass-shell extrapolution to details of the N-N interaction is studied. (author)

Coherent diffractive photoproduction of ρ0 mesons on gold nuclei at 200 GeV/nucleon-pair at the Relativistic Heavy Ion Collider

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Klein, S. R.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, W.; Li, Y.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, H.; Liu, P.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, G. L.; Ma, L.; Ma, Y. G.; Ma, R.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y. F.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, C.; Yang, S.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, X. P.; Zhang, J. B.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

2017-11-01

The STAR Collaboration reports on the photoproduction of π+π- pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly real photon emitted by one ion scatters from the other ion. We fit the π+π- invariant-mass spectrum with a combination of ρ0 and ω resonances and a direct π+π- continuum. This is the first observation of the ω in ultraperipheral collisions, and the first measurement of ρ -ω interference at energies where photoproduction is dominated by Pomeron exchange. The ω amplitude is consistent with the measured γ p →ω p cross section, a classical Glauber calculation, and the ω →π+π- branching ratio. The ω phase angle is similar to that observed at much lower energies, showing that the ρ -ω phase difference does not depend significantly on photon energy. The ρ0 differential cross section d σ /d t exhibits a clear diffraction pattern, compatible with scattering from a gold nucleus, with two minima visible. The positions of the diffractive minima agree better with the predictions of a quantum Glauber calculation that does not include nuclear shadowing than with a calculation that does include shadowing.

Differential photoproduction cross sections of the Σ0(1385), Λ(1405), and Λ(1520)

Science.gov (United States)

Moriya, K.; Schumacher, R. A.; Adhikari, K. P.; Adikaram, D.; Aghasyan, M.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bellis, M.; Bennett, R. P.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Collins, P.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Dey, B.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hakobyan, H.; Hanretty, C.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuleshov, S. V.; Lewis, S.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Martinez, D.; Mayer, M.; McCracken, M.; McKinnon, B.; Mestayer, M. D.; Meyer, C. A.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Nasseripour, R.; Nepali, C. S.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Raue, B. A.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S.; Stoler, P.; Strauch, S.; Taiuti, M.; Tang, W.; Taylor, C. E.; Taylor, S.; Tian, Y.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vineyard, M. F.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Weinstein, L. B.; Williams, M.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2013-10-01

We report the exclusive photoproduction cross sections for the Σ0(1385), Λ(1405), and Λ(1520) in the reactions γ+p→K++Y* using the CLAS detector for energies from near the respective production thresholds up to a center-of-mass energy W of 2.85 GeV. The differential cross sections are integrated to give the total exclusive cross sections for each hyperon. Comparisons are made to current theoretical models based on the effective-Lagrangian approach and fit to previous data. The accuracy of these models is seen to vary widely. The cross sections for the Λ(1405) region are strikingly different for the Σ+π-, Σ0π0, and Σ-π+ decay channels, indicating the effect of isospin interference, especially at W values close to the threshold.

Meson photoproduction (CLAS)

Energy Technology Data Exchange (ETDEWEB)

Steffen Strauch

2009-10-01

This is a brief and selective discussion of meson photoproduction measurements with the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Meson photo- production is being used as a tool for various investigations, including the spectroscopy of baryons and mesons and the search for vector-meson medium modifications.

Intermediate-energy nuclear theory. Progress report, July 1, 1977--June 30, 1978

International Nuclear Information System (INIS)

Bryan, R.A.

1978-03-01

The research reported has centered on the nucleon-nucleon interaction at medium energies, with especial emphasis on the reaction NN → NNπ up to 800 MeV. Elastic NN scattering near the pion production threshold was also investigated, both through phase-shift analysis of data and theoretical interpretation of the intermediate-range force. The quasi-elastic amplitude N anti N → ππ for 4m/sub pi/ 2 less than or equal to t less than or equal to 50m/sub pi/ 2 was studied because of its bearing on the NN problem; a simple but useful model was developed. Finally, work on the pion-photoproduction reaction γN → πΔ was completed, and the close correspondence with the amplitude NN → NNπ exploited. A list of publications is included

Chiral Dynamics in Pion-Photon Reactions Habilitation

CERN Document Server

Friedrich, Jan Michael

As the lightest particle of the strong force, the pion plays a central role in the field of strong interactions, and understanding its properties is of prime relevance for understanding the strong interaction in general. The low-energy behaviour of pions is of particular interest. Although the quark-gluon substructure and their quantum chromodynamics is not apparent then, this specific inner structure causes the presence of approximate symmetries in pion-pion interactions and in pion decays, which gives rise to the systematic description of processes involving pions in terms of few low-energy constants. Specifically, the chiral symmetry and its spontaneous and explicit breaking, treated in chiral perturbation theory (ChPT), leads to firm predictions for low-energy properties of the pion. To those belong the electromagnetic polarisabilities of the pion, describing the leading-order structure effect in pion Compton scattering. The research presented in this work is concerned with the interaction of pions and ph...

Measurements of NN → dπ near threshold

International Nuclear Information System (INIS)

Hutcheon, D.A.

1990-09-01

New, precise measurements of the differential cross sections for np → dπ 0 and π + d → pp and of analyzing powers for pp → dπ + have been made at energies within 10 MeV (c.m.) of threshold. They allow the pion s-wave and p-wave parts of the production strength to be distinguished unambiguously, yielding an s-wave strength at threshold which is significantly smaller than the previously accepted value. There is no evidence for charge independence breaking nor for πNN resonances near threshold. (Author) (17 refs., 17 figs., tab.)

Pion condensation in symmetric nuclear matter

International Nuclear Information System (INIS)

Shamsunnahar, T.; Saha, S.; Kabir, K.; Nath, L.M.

1991-01-01

We have investigated the possibility of pion condensation in symmetric nuclear matter using a model of pion-nucleon interaction based essentially on chiral SU(2) x SU(2) symmetry. We have found that pion condensation is not possible for any finite value of the density. Consequently, no critical opalescence phenomenon is likely to be seen in pion-nucleus scattering nor is it likely to be possible to explain the EMC effect in terms of an increased number of pions in the nucleus. (author)

Pion-induced knock-out reactions

International Nuclear Information System (INIS)

Jain, B.K.; Phatak, S.C.

1977-01-01

A strong absorption model for pion-induced Knock-out reactions is proposed. The distortion of the in-coming and out-going pions has been included by (1) computing pion wave number in nuclear medium (dispersive effect) and (2) excluding the central region of the nucleus where the real pion-absorption is dominant (absorption effect). In order to study the dependence of the (π + π + p) reaction on the off-shell pion-nucleon t-matrix, different off-shell extrapolations are used. The magnitude of the cross-sections seems to be sensitive to the type of off-shell extrapolation; their shapes, however, are similar. The theoretical results are compared with experimental data. The agreement between the theoretical results for separable off-shell extrapolation and the data is good. (author)

Real and virtual pions in nuclei

International Nuclear Information System (INIS)

Giraud, N.

1984-02-01

The thesis first part is concerned with physical pion interaction with deuton, studied in a three-body problem frame. The elastic cross-section in the energy range near the resonance (3-3), has been deduced taking in account the pion virtual absorption. The second part is concerned with virtual pion in nuclei. In particular the virtual pion cloud around the nucleus has been studied and the effective constant coupling pion-nucleus has been deduced. This one is strongly reduced by polorazation effects of the nuclear medium (essentially by virtual excitation of the Δ isobar), in relation to its value for free nucleon collection. In the frame of the same polarization model, the pion field inside the nucleus has been studied also. This field is lowered for small momentum transfer. It is increased for large momentum transfer. This last phenomenon corresponds to critical opalescence related to phase transition of pion condensation [fr

Exclusive electroproduction of pion pairs

International Nuclear Information System (INIS)

Warkentin, N.; Schaefer, A.; Diehl, M.; Ivanov, D. Yu.

2007-01-01

We investigate electroproduction of pion pairs on the nucleon in the framework of QCD factorization for hard exclusive processes. We extend previous analyses by taking the hard-scattering coefficients at next-to-leading order in α s . The dynamics of the produced pion pair is described by two-pion distribution amplitudes, for which we perform a detailed theoretical and phenomenological analysis. In particular, we obtain constraints on these quantities by comparing our results with measurements of angular observables that are sensitive to the interference between two-pion production in the isoscalar and isovector channels. (orig.)

Analyses of multi-pion Hanbury Brown–Twiss correlations for the pion-emitting sources with Bose–Einstein condensation

Science.gov (United States)

Bary, Ghulam; Ru, Peng; Zhang, Wei-Ning

2018-06-01

We calculate the three- and four-particle correlations of identical pions in an evolving pion gas (EPG) model with Bose–Einstein condensation. The multi-pion correlation functions in the EPG model are analyzed in different momentum intervals and compared with the experimental data for Pb–Pb collisions at \\sqrt{{s}{NN}}=2.76 {TeV}. It is found that the multi-pion correlation functions and cumulant correlation functions are sensitive to the condensation fraction of the EPG sources in the low average transverse-momentum intervals of the three and four pions. The model results of the multi-pion correlations are consistent with the experimental data in a considerable degree, which gives a source condensation fraction between 16% and 47%.

Measurement of the pion form factor

International Nuclear Information System (INIS)

Dally, E.; Hauptman, J.; May, C.

1977-01-01

The pion form factor has been measured in the momentum transfer range of 0.03( 2 by scattering pions from atomic electrons in a liquid hydrogen target. The pion form factor is defined to be the elastic scattering cross section divided by that predicted for a point pion. The experiment has been performed in a 100 GeV/c negative pion beam incident on a 50 cm liquid hydrogen target at Fermi laboratory. The corrected form factor equals 0.33+-0.06 f 2 . Vector dominance predicts 0.40 f 2

Vector meson photoproduction with a linearly polarized beam

Science.gov (United States)

Mathieu, V.; Nys, J.; Fernández-Ramírez, C.; Jackura, A.; Pilloni, A.; Sherrill, N.; Szczepaniak, A. P.; Fox, G.; Joint Physics Analysis Center

2018-05-01

We propose a model based on Regge theory to describe photoproduction of light vector mesons. We fit the SLAC data and make predictions for the energy and momentum-transfer dependence of the spin-density matrix elements in photoproduction of ω , ρ0 and ϕ mesons at Eγ˜8.5 GeV , which are soon to be measured at Jefferson Lab.

Baryon resonances in pion- and photon-induced hadronic reactions

International Nuclear Information System (INIS)

Roenchen, Deborah

2014-01-01

The aim of the present work is the analysis of the baryon spectrum in the medium-energy regime. At those energies, a perturbative treatment of Quantum Chromodynamics, that is feasible in the high-energy regime, is not possible. Chiral perturbation theory, the low-energy effective theory of the strong interaction, is limited to the lowest excited states and does not allow to analyze the complete resonance region. For the latter purpose, dynamical coupled-channel approaches provide an especially suited framework. In the present study, we apply the Juelich model, a dynamical coupled-channel model developed over the years, to analyze pion- and photon-induced hadronic reactions in a combined approach. In the Juelich model, the interaction of the mesons and baryons is built of t- and u-channel exchange diagrams based on an effective Lagrangian. Genuine resonances are included as s-channel states. The scattering potential is unitarized in a Lippmann-Schwinger-type equation. Analyticity is preserved, which is a prerequisite for a reliable extraction of resonance parameters in terms of pole positions and residues in the complex energy plane. Upon giving an introduction to the subject in Chap. 1 and showing selected results in Chap. 2, we will describe the simultaneous analysis of elastic πN scattering and the reactions π - p → ηn, K 0 Λ, K + Σ - , K 0 Σ 0 and π + p→K + Σ + within the Juelich framework in Chap. 3. The free parameters of the model are adjusted to the GWU/SAID analysis of elastic πN scattering and, in case of the inelastic reactions, to experimental data. Partial waves up to J=9/2 are included and we consider the world data set from threshold up to E∝2.3 GeV. We show our fit results compared to differential and total cross sections, to polarizations and to measurements of the spin-rotation parameter. Finally, we present the results of a pole search in the complex energy plane of the scattering amplitude and discuss the extracted resonance

Spectator-velocity pions from heavy ions

International Nuclear Information System (INIS)

Rasmussen, J.; Ridout, J.; Murphy, D.; Radi, H.M.A.

1982-11-01

The discussion centers on pions in the velocity regions of target and projectile, where strong spectral features appear. The topics covered include stopped-pion studies, and convoy pions in the projectile frame

Neutral pion electroproduction off light nuclei in chiral perturbation theory

International Nuclear Information System (INIS)

Lenkewitz, Mark

2013-01-01

Threshold pion electroproduction on tri-nucleon systems is investigated in the framework of baryon Chiral Perturbation Theory (ChPT) at next-to-leading one-loop order O(q 4 ) in the chiral expansion. To this order in small momenta, the production operator is a sum of one- and two-nucleon terms. While the one-nucleon terms resemble the impulse approximation, the two-nucleon contributions represent corrections due to the relevant nuclear interactions, e.g. pion-exchange interactions, which prove to be dominant, and due to recoil effects of the participating nucleons, which appear to be negligible. We calculate the expectation value of the production operator using chiral wave functions in a three-dimensional approach without partial wave expansion. The resulting integrals are evaluated using adaptive Monte Carlo integration, the VEGAS algorithm of Lepage. We obtain results for the threshold production multipoles E 0+ and L 0+ on 3 He and 3 H and comment on the sensitivity to the fundamental neutron amplitude E 0+ π 0 n . 3 He appears to be a particularly promising target to extract information about the neutron amplitude. This idea is usually invoked for spin-dependent quantities since the 3 He wave function is strongly dominated by the principal S-state component which suggests that its spin is largely driven by the one of the neutron.

Photoproduction of hydroxyl radicals in aqueous solution with algae under high-pressure mercury lamp.

Science.gov (United States)

Liu, Xianli; Wu, Feng; Deng, Nansheng

2004-01-01

Photoproduction of hydroxyl radicals (*OH) could be induced in aqueous solution with algae (Nitzschia hantzschiana, etc.) and (or not) Fe3+ under high-pressure mercury lamp with an exposure time of 4 h. *OH was determined by HPLC using benzene as a probe. The photoproduction of *OH increased with increasing algae concentration. Fe3+ could enhance the photoproduction of *OH in aqueous solution with algae. The results showed that the photoproduction of *OH in algal solution with Fe3+ was greater than that in algal solution without Fe3+. The light intensity and pH affected the photoproduction of *OH in aqueous solution with algae with/without Fe3+. The photoproduction of *OH in aqueous solution with algae and Fe3+ under 250 W was greater than that under 125 W HPML. The photoproduction of *OH in algal solution (pH ranged from 4.0 to 7.0) with (or not) Fe3+ at pH 4 was the greatest.

Photo- and pion electroproduction in chiral effective field theory; Photo- und Elektropionproduktion in chiraler effektiver Feldtheorie

Energy Technology Data Exchange (ETDEWEB)

Hilt, Marius

2011-12-13

This thesis is concerned with pion photoproduction (PPP) and pion electroproduction (PEP) in the framework of manifestly Lorentz-invariant baryon chiral perturbation theory. For that purpose two different approaches are used. Firstly, a one-loop-order calculation up to chiral order O(q{sup 4}) including pions and nucleons as degrees of freedom, is performed to describe the energy dependence of the reactions over a large range. To improve the dependence on the virtuality of the photon in PEP, in a second approach vector mesons are included as explicit degrees of freedom. The latter calculation includes one-loop contributions up to chiral order O(q{sup 3}). Only three of the four physical processes of PPP and PEP can be accessed experimentally. These reactions are measured at several different facilities, e.g. Mainz, Bonn, or Saskatoon. The data obtained there are used to explore the limits of chiral perturbation theory. This thesis is the first complete manifestly Lorentz-invariant calculation up to order O(q{sup 4}) for PPP and PEP, and the first calculation ever for these processes including vector mesons explicitly. Beside the calculation of physical observables, a partial wave decomposition is performed and the most important multipoles are analyzed. They may be extracted from the calculated amplitudes and allow one to examine the nucleon and {delta} resonances. The number of diagrams one has to calculate is very large. In order to handle these expressions, several routines were developed for the computer algebra system Mathematica. For the multipole decomposition, two different programs are used. On the one hand, a modified version of the so-called {chi}MAID has been employed. On the other hand, similar routines were developed for Mathematica. In the end, the different calculations are compared with respect to their applicability to PPP and PEP.

Pion condensation in symmetric nuclear matter

Science.gov (United States)

Kabir, K.; Saha, S.; Nath, L. M.

1988-01-01

Using a model which is based essentially on the chiral SU(2)×SU(2) symmetry of the pion-nucleon interaction, we examine the possibility of pion condensation in symmetric nucleon matter. We find that the pion condensation is not likely to occur in symmetric nuclear matter for any finite value of the nuclear density. Consequently, no critical opalescence phenomenom is expected to be seen in the pion-nucleus interaction.

Pion production in nucleus--nucleus collisions

International Nuclear Information System (INIS)

Schroeder, L.S.

1975-06-01

Current work on pion production in high-energy nucleus-nucleus collisions is reviewed. The majority of existing data are of the inclusive variety in which a single final state pion is detected. Experimental data are compared and their possible contributions to obtaining new information on nuclear structure is discussed. Various models which attempt to explain the observed single-inclusive-pion spectra either on the basis of a nucleon-nucleus interaction in which Fermi motion is included or on some type of cooperative model are examined. Other areas of interest involving pion production include tests of charge symmetry and pion multiplicities. (9 figures, 1 table) (U.S.)

Pion condensation in symmetric nuclear matter

International Nuclear Information System (INIS)

Kabir, K.; Saha, S.; Nath, L.M.

1987-09-01

Using a model which is based essentially on the chiral SU(2)xSU(2) symmetry of the pion-nucleon interaction, we examine the possibility of pion condensation in symmetric nucleon matter. We find that the pion condensation is not likely to occur in symmetric nuclear matter for any finite value of the nuclear density. Consequently, no critical opalescence phenomenon is expected to be seen in the pion-nucleus interaction. (author). 20 refs

Study of the pion electromagnetic form factor in the timelike region, from the production threshold to 900 MeV in the center of mass

International Nuclear Information System (INIS)

Quenzer, A.

1977-01-01

The pion form factor is measured in the reaction e + e - →π + π - for center of mass energies in the range 480-900 MeV. The results are first analysed in terms of the conventional Vector Meson Dominance formalism, and then taking into account the ωπ inelastic channel. The results of this later formalisms is a pion form factor (F) which fits quite well all the existing data on F both in the timelike and spacelike regions, and a pion mean square radius [fr

Quark bag coupling to finite size pions

International Nuclear Information System (INIS)

De Kam, J.; Pirner, H.J.

1982-01-01

A standard approximation in theories of quark bags coupled to a pion field is to treat the pion as an elementary field ignoring its substructure and finite size. A difficulty associated with these treatments in the lack of stability of the quark bag due to the rapid increase of the pion pressure on the bad as the bag size diminishes. We investigate the effects of the finite size of the qanti q pion on the pion quark bag coupling by means of a simple nonlocal pion quark interaction. With this amendment the pion pressure on the bag vanishes if the bag size goes to zero. No stability problems are encountered in this description. Furthermore, for extended pions, no longer a maximum is set to the bag parameter B. Therefore 'little bag' solutions may be found provided that B is large enough. We also discuss the possibility of a second minimum in the bag energy function. (orig.)

Future prospects in photon and electron physics at Saclay

International Nuclear Information System (INIS)

Laget, J.M.

1984-12-01

In introduction the two nucleon system is considered. Their interaction is very well described at large distances by the pion exchange potential at intermediate distances by the exchange of two correlated pions. Between the exchange of these two pions, one of the nucleons, or both, can be transformed into a Δ. At small distances the exchange of vector mesons (rho, ω) plays a role, but it is also here that the quark structure of the nucleon is expected to enter the jame. Coincidence experiments performed with the electromagnetic probe are precisely the most strayhtforwad way to answer these questions. This is illustrated by spectra of the electrons inelastically scattered on 3 He which are good examples of the interplay between the many body aspects and the internal degrees of freedom of the nucleon. More exclusive experiments must be performed in order to single out each channel and study the various aspects of the nuclear dynamics. An example in each part of these response functions is given. The first one concerns the pion photoproduction at the top of the Δ peak and has to do with the NΔ interaction. The second concerns the creation of virtual pions near the threshold and has to do with the exchange currents. Typical example choosen is the deuteron electrodisintegration near the threshold when the electric is scattered at a given angle. The third one concern the study of the short range correlations by mean of the (e,e'N) and (e,e'NN) reactions

Photoproduction within the two-component Dual Parton Model: amplitudes and cross sections

International Nuclear Information System (INIS)

Engel, R.; Siegen Univ.

1995-01-01

In the framework of the Dual Parton Model an approximation scheme to describe high energy photoproduction processes is presented. Based on the distinction between direct, resolved soft, and resolved hard interaction processes we construct effective impact parameter amplitudes. In order to treat low mass diffraction within the eikonal formalism in a consistent way a phenomenological ansatz is proposed. The free parameters of the model are determined by fits to high energy hadro- and photoproduction cross sections. We calculate the partial photoproduction cross sections and discuss predictions of the model at HERA energies. Using hadro- and photoproduction data together, the uncertainties of the model predictions are strongly reduced. (orig.)

Twist-2 Light-Cone Pion Wave Function

OpenAIRE

Belyaev, V. M.; Johnson, Mikkel B.

1997-01-01

We present an analysis of the existing constraints for the twist-2 light-cone pion wave function. We find that existing information on the pion wave function does not exclude the possibility that the pion wave function attains its asymptotic form. New bounds on the parameters of the pion wave function are presented.

Pion inelastic scattering and the pion-nucleus effective interaction

International Nuclear Information System (INIS)

Carr, J.A.

1983-01-01

This work examines pion inelastic scattering with the primary purpose of gaining a better understanding of the properties of the pion-nucleus interaction. The main conclusion of the work is that an effective interaction which incorporates the most obvious theoretical corrections to the impulse approximation does a good job of explaining pion elastic and inelastic scattering from zero to 200 MeV without significant adjustments to the strength parameters of the force. Watson's multiple scattering theory is used to develop a theoretical interaction starting from the free pion-nucleon interaction. Elastic scattering was used to calibrate the isoscalar central interaction. It was found that the impulse approximation did poorly at low energy, while the multiple scattering corrections gave good agreement with all of the data after a few minor adjustments in the force. The distorted wave approximation for the inelastic transition matrix elements are evaluated for both natural and unnatural parity excitations. The isoscalar natural parity transitions are used to test the reaction theory, and it is found that the effective interaction calibrated by elastic scattering produces good agreement with the inelastic data. Calculations are also shown for other inelastic and charge exchange reactions. It appears that the isovector central interaction is reasonable, but the importance of medium corrections cannot be determined. The unnatural parity transitions are also reasonably described by the theoretical estimate of the spin-orbit interaction, but not enough systematic data exists to reach a firm conclusion

Drell-Yan lepton pair photoproduction

International Nuclear Information System (INIS)

Badalyan, R.G.; Grabskij, V.O.; Matinyan, S.G.

1989-01-01

The study of photon structure functions by spectra of massive lepton pairs (M l + l - ≥ 2 GeV) in photon fragmentation region in γp-interactions at high energies is suggested. In calculations of Drell-Yan lepton pair inclusive spectra in γp-interactions for photon structure functions there are used results obtained within QCD, data on γγ-interactions in e + e - → e + e - X on colliders as well as results from the analysis of vector meson non-diffractive photoproduction at high energies. It is shown that there exists a sufficienly wide kinematic region over variables X l + l - and M l + l - , wherein photon structure functions can be studied by spectra of Grell-Yan lepton pairs in the processes of their photoproduction. 31 refs.; 6 figs.; 1 tab

Pion observables and QCD

International Nuclear Information System (INIS)

Roberts, C.D.

1995-01-01

Herein the application of the DSE approach to the calculation of pion observables is described using: the π-π scattering lengths (a 0 0 , a 2 0 , a 1 1 , a 0 2 , a 2 2 ) and associated partial wave amplitudes; the π 0 → γγ decay width; and the charged pion form factor, F π (q 2 ), as illustrative examples. Since this approach provides a straightforward, microscopic description of dynamical chiral symmetry breaking (DχSB) and confinement, the calculation of pion observables is a simple and elegant illustrative example of its power and efficacy. (orig.)

A large multi-cell threshold gas Cerenkov counter

International Nuclear Information System (INIS)

Declais, Y.; Aubert, J.J.; Bassompierre, G.; Payre, P.; Thenard, J.M.; Urban, L.

1980-08-01

A large multi-cell threshold gas Cerenkov counter consisting of 78 cells has been built for use in a high energy muon scattering experiment at CERN (European Muon Collaboration). It is used with neon, nitrogen or a mixture of those two gases, allowing the pion threshold to be varied between 6 and 20 GeV/c. The sensitive region of the counter has a length of 4.0 m and entrance and exit windows of 1.1 x 2.4 m 2 and 2.4 x 5.0 m 2 , respectively

MEASUREMENT OF POLARIZATION OBSERVABLES IN VECTOR MESON PHOTOPRODUCTION USING A TRANSVERSELY-POLARIZED FROZEN-SPIN TARGET AND POLARIZED PHOTONS AT CLAS, JEFFERSON LAB

Energy Technology Data Exchange (ETDEWEB)

Roy, Priyashree [Florida State Univ., Tallahassee, FL (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2016-11-30

The study of baryon resonances provides a deeper understanding of the strong interaction because the dynamics and relevant degrees of freedom hidden within them are re ected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c2 are generally predicted to have strong couplings to final states involving a heavier meson, e. g. one of the vector mesons, ρ, ω φ, as compared to a lighter pseudoscalar meson, e. g. π and η. Decays to the ππΝ final states via πΔ also become more important through the population of intermediate resonances. We observe that nature invests in mass rather than momentum. The excited states of the nucleon are usually found as broadly overlapping resonances which may decay into a multitude of final states involving mesons and baryons. Polarization observables make it possible to isolate single resonance contributions from other interference terms. The CLAS g9 (FROST) experiment, as part of the N* spectroscopy program at Je?erson Laboratory, accumulated photoproduction data using circularly- & linearly-polarized photons incident on a transversely-polarized butanol target (g9b experiment) in the photon energy range 0:3-2:4 GeV & 0:7-2:1 GeV, respectively. In this work, the analysis of reactions and polarization observables which involve two charged pions, either in the fully exclusive reaction γρ -> ρπ+π- or in the semi-exclusive reaction with a missing neutral pion, γρ -> ρπ+π-(π0) will be presented. For the reaction ρπ+π-, eight polarization observables (Is, Ic, Px, Py, Psx; y, Pcx; y) have been extracted. The high statistics data rendered it possible to extract these observables in three dimensions. All of them are first-time measurements. The fairly good agreement of Is, Ic obtained from this analysis with the experimental results from a previous CLAS experiment provides support for the first-time measurements. For the reaction γρ -> ρω -> ρπ+π(π0, five polarization

Search for Odderon induced contributions to exclusive Meson Photoproduction at HERA

International Nuclear Information System (INIS)

Olsson, J.

2001-01-01

A search for exclusive photoproduction of π 0 , f 2 (1270) and a 2 (1320), induced by Odderon exchange, was performed using multi-photon final states. No signal was found. Upper limits for the cross sections are below the predictions of a model based on non-perturbative QCD. Exclusive ω and ωπ 0 photoproduction is observed in three and five photon final states, at levels consistent with the expectations from Pomeron exchange and consistent with other observations of exclusive vector and axial vector meson photoproduction

Double recharge of pions on a deuterium

International Nuclear Information System (INIS)

Nichitiu, F.; Falomkin, I.V.; Shcherbakov, Yu.A.

1987-01-01

Assumptions on the dibaryon nature of the existing narrow resonances below the threshold of the NΔ-state with masses 1935, 1965, 2015 MeV are considered. New proposals on construction of the particle systematics with a new particle (R-particle of mass 1025 MeV, J=1/2, T=3/2) are used to draw a conclusion that double charge exchange is possible on deuterium and helium-3 if dibaryons or new R-particles are born in the final state. Attention is paid to a possible decay of these particles through a weak channel. A search for double charge exchange of pions on hydrogen and deuterium using a laser-illuminated streamer chamber of high pressure is proposed

Eta meson photoproduction on hydrogen from threshold up to 1100 MeV: Measurement of the {Sigma} beam asymmetry; Photoproduction du meson eta sur l`hydrogene du seuil jusqu`a 1100 MeV: Mesure de l`asymetrie faisceau {Sigma}

Energy Technology Data Exchange (ETDEWEB)

Ajaka, Jassem [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

1997-12-12

The photoproduction of {eta} meson on hydrogen has been measured from threshold to 1100 MeV in GRAAL experiment performed in 1996 - 1997 at the ESRF in Grenoble by a collaboration of Italian, French and Russian groups. A tagged and linearly polarized photon beam has been produced by back-scattering a laser beam on the 6 GeV electron beam of the ESRF ring. The target was a liquid hydrogen target of 3 cm. A 4{pi} detection system was used. It is composed of three layers of detectors: wire chambers, scintillator counters and calorimeters. We had in charge to install and calibrate a double wall of scintillator bars (3 x 3 m) designed to detect at forward angles (1 deg. - 25 deg.) the charged particles and to measure their loss of energy and their time of flight. We analyzed the results of the reaction {gamma}p {yields} {eta}p by identifying the {eta} in the lateral calorimeter which is a BGO ball and by detecting the proton in the scintillation counters. The {Sigma} beam asymmetry was extracted from {phi} distribution of {eta} meson and was plotted against {theta}{sub CM} of {eta} for 6 intervals of energy between the threshold and 1100 MeV. The interpretation of {Sigma} beam asymmetry was performed in the frame of the isobaric model. The use of two resonances S11(1535) and D13(1520) to explain our results was not sufficient. We had to take into account in addition the excitation of the resonances P13(1720), D15(1675) and P13(1880). The last being missing in the table of resonances and recently revealed by quark models. (author) 94 refs., 56 figs., 20 tabs.

Strangeness photoproduction at the BGO-OD experiment

Energy Technology Data Exchange (ETDEWEB)

Jude, Thomas [Physikalisches Institut, Bonn University (Germany); Collaboration: BGO-OD-Collaboration

2016-07-01

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the internal structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. Compared to constituent quark models (CQMs), models including psuedoscalar meson-baryon interactions have had improved success in describing baryon excitation spectra. For example, the Λ(1405) appears to be dynamically generated from meson-baryon interactions at least to some extent. Vector-meson baryon interactions have also been predicted to dynamically generate states, which may have been observed in photoproduction reactions. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. This enables the investigation of degrees of freedom not derived from CQMs, and in particular, strangeness photoproduction where t-channel exchange mechanisms play a dominant role. With the first major data taking periods for BGO-OD complete, an extensive programme for the investigation of associated strangeness photoproduction has begun.

Simulation of inelastic hadron collisions below 5 GeV

International Nuclear Information System (INIS)

Pedroni, P.

1988-01-01

To evaluate the detector characteristics in an experiment designed to study photoproduction and photodisintegration at energies above pion production threshold at the Saclay linear accelerator (ALS), a Monte Carlo simulation program has been written. The CEREN FORTRAN package GEANT3 which has been modified to correctly generate hadronic interactions of particle with momenta below a few GeV has been used. In this note is described a simulation program in which GEANT3 has been corrected with the addition of a new hadronic library. Some comparisons between simulated and experimental data for detector has been provided

Helicity-dependent reaction γd → π0d near the η-threshold and its contribution to the E-asymmetry and the GDH sum rule for the deuteron

International Nuclear Information System (INIS)

Darwish, Eed M.; Hemmdan, A.; El-Shamy, N.T.

2015-01-01

The helicity-dependent coherent π 0 -photoproduction in the reaction γd → π 0 d near the η-threshold is investigated. The calculations are performed within an approach which includes the reaction amplitudes of the impulse approximation (IA), two-step process with intermediate πN- and ηN-rescattering, and the higher order terms in the multiple scattering series for the intermediate ηNN interaction. The contribution of γd → π 0 d to the deuteron spin asymmetry is calculated and its contribution to the Gerasimov–Drell–Hearn (GDH) integral is explicitly evaluated by integration up to a photon energy of 900 MeV. In addition, the helicity E-asymmetry is calculated. The results revealed that the doubly polarized differential cross-sections and the helicity E-asymmetry are sensitive to the interference of rescattering effects, specially at photon energies 600–800 MeV and extreme backward pion angles. The sensitivity of the obtained results for the GDH integral to the choice of NN potential model governing the deuteron wave function is discussed. We find that the deviation among results obtained for the deuteron GDH integral using different deuteron wave functions is quite large. (author)

Can one distinguish τ-neutrinos from antineutrinos in neutral-current pion production processes?

International Nuclear Information System (INIS)

Hernandez, E.; Nieves, J.; Valverde, M.

2007-01-01

A potential way to distinguish τ-neutrinos from antineutrinos, below the τ-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral-current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing τ-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves, etc.). We show that neutrino-antineutrino asymmetries occur both in the totally integrated cross sections and in the pion azimuthal differential distributions. To define the asymmetries for the latter distributions we just rely on Lorentz-invariance. All these asymmetries are independent of the lepton family and can be experimentally measured by using electron or muon neutrinos, due to the lepton family universality of the neutral-current neutrino interaction. Nevertheless and to estimate their size, we have also used the chiral model of [E. Hernandez, J. Nieves, M. Valverde, hep-ph/0701149] at intermediate energies. Results are really significant since the differences between neutrino and antineutrino induced reactions are always large in all physical channels

Characteristic aspects of pion-condensed phases

International Nuclear Information System (INIS)

Takatsuka, Tatsuyuki; Tamagaki, Ryozo; Tatsumi, Toshitaka.

1993-01-01

Characteristic aspects of pion-condensed phases are described in a simple model, for the system involving only nucleons and pions which interact through the π-N P-wave interaction. We consider one typical version in each of three kinds of pion condensation; the one of neutral pions (π 0 ), the one of charged pions (π C ) and the combined one in which both the π 0 and π C condensations are coexistent. Emphasis is put on the description to clarify the novel structures of the nucleon system which are realized in the pion-condensed phases. At first, it is shown that the π 0 condensation is equivalent to the particular nucleonic phase realized by a structure change of the nucleon system, where the attractive first-order effect of the one-pion-exchange (OPE) tensor force is brought about coherently. The aspects of this phase are characterized by the layered structure with a specific spin-isospin order with one-dimensional localization (named the ALS structure in short), which provides the source function for the condensed π 0 field. We utilize both descriptions with use of fields and potentials for the π 0 condensation. Next, the π C condensation realized in neutron-rich matter is described by adopting a version of the traveling condensed wave. In this phase, the nucleonic structure becomes the Fermi gas consisting of quasi-neutrons described by a superposition of neutron and proton. In this sense the structure change of the nucleon system for the π C condensation is moderate, and the field description is suitable. Finally, we describe a coexistent pion condensation, in which both the π 0 and π C condensations coexist without interference in such a manner that the π C condensation develops in the ALS structure. The model adopted here provides us with the characteristic aspects of the pion-condensed phases persisting in the realistic situation, where other ingredients affecting the pion condensation are taken into account. (author)

Strangeness photoproduction at the BGO-OD experiment

Energy Technology Data Exchange (ETDEWEB)

Jude, Thomas [Physikalisches Institut, Universitaet Bonn, Nussallee 12, Bonn (Germany); Collaboration: BGO-OD-Collaboration

2015-07-01

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the internal structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. The BGO-OD is ideal for investigating the photoproduction of hadrons of non-zero strangeness. The high momentum resolution at forward angles covers a kinematic region where t-channel exchange mechanisms play a dominant role. This is complemented by the neutral and charged particle identification in the BGO calorimeter for the identification of hyperon decays. The first part of an extensive physics programme includes measurements of the differential cross section at forward angles for γp → K{sup +}Λ and, using linearly polarised photons, the beam asymmetry, Σ, for γp → K{sup 0}Σ{sup +}. This latter measurement is focussed on the K* threshold region where a cusp-like structure was recently observed in the total cross section. Analysis of these reaction channels for both real and simulated data is presented.

Lambda-neutron interaction in kaon photoproduction from the deuteron

International Nuclear Information System (INIS)

Adelseck, R.A.; Wright, L.E.

1989-01-01

The importance of hyperon-nucleon final-state interaction in kaon photoproduction from the deuteron is examined. By calculating the deuteron wave function using the Reid, Paris, or Bonn NN potentials, the uncertainty of this process due to the nucleonic wave function is found to be negligible. The insignificance of off-shell and relativistic effects is demonstrated by employing a completely relativistic wave function and comparing various approximations. We find the influence of the kaon production operator to be the most critical ingredient in this calculation. Final-state effects, which are included via a distorted-wave formalism, involve partial waves up to l = 3. They produce a sharp rise of the cross section near threshold resulting in an enhancement by about a factor of 3, but diminish rapidly as the energy increases. Different ΛN potential models show variations of the effect by up to 10%

The pion: an enigma within the Standard Model

Energy Technology Data Exchange (ETDEWEB)

Horn, Tanja; Roberts, Craig D.

2016-05-27

Almost 50 years after the discovery of gluons & quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons, protons, and the pions that bind them. QCD is characterised by two emergent phenomena: confinement & dynamical chiral symmetry breaking (DCSB). They are expressed with great force in the character of the pion. In turn, pion properties suggest that confinement & DCSB are closely connected. As both a Nambu-Goldstone boson and a quark-antiquark bound-state, the pion is unique in Nature. Developing an understanding of its properties is thus critical to revealing basic features of the Standard Model. We describe experimental progress in this direction, made using electromagnetic probes, highlighting both improvements in the precision of charged-pion form factor data, achieved in the past decade, and new results on the neutral-pion transition form factor. Both challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, first explaining how DCSB works to guarantee that the pion is unnaturally light; but also, nevertheless, ensures the pion is key to revealing the mechanisms that generate nearly all the mass of hadrons. Our discussion unifies the charged-pion elastic and neutral-pion transition form factors, and the pion's twist-2 parton distribution amplitude. It also indicates how studies of the charged-kaon form factor can provide significant contributions. Importantly, recent predictions for the large-$Q^2$ behaviour of the pion form factor can be tested by experiments planned at JLab 12. Those experiments will extend precise charged-pion form factor data to momenta that can potentially serve in validating factorisation theorems in QCD, exposing the transition between the nonperturbative and perturbative domains, and thereby reaching a goal that has long driven hadro-particle physics.

Photoproduction of Neutral Kaons on Deuterons

Science.gov (United States)

Beckford, Brian

2006-11-01

Experimentation to greater understand the strangeness production mechanism can be performed by observing the electromagnetic interaction that leads to Kaon photoproduction. The n (γ, K^0) λ reaction may assist in answering questions about the strangeness photo-production process. An experiment into the elementary Kaon photoproduction process was investigated in an experiment conducted at the Laboratory of Nuclear Science of Tohoku University (LNS) using the Neutral Kaon Spectrometer. (NKS). The experiment was conducted by the d (γ, K^0) reaction. K^0 will be measured in the K^0->π^+π^- decay chain by the NKS. The NKS implements many detectors working in coincidence: These ranging from the Tagged Photon Beam generated by the 1.2 GeV Electron beam via bremsstrahlung, an Inner Plastic Scintillator Hodoscope (IH), a Straw Drift Chamber (SDC), a Cylindrical Drift Chamber (CDC), and an Outer Plastic Scintillator Hodoscope. Due to the background produced through the γ-> e+e- process, electron veto counters (EV) were placed in the middle of the OH to reject charged particles in the horizontal plane of the beam line. Preliminary analysis of the data indicates the need for pulse height correction. This was achieved by analysis of the Inner and Outer hodoscopes, and determining the energy deposit in the scintillators.

Photoproduction of π0ω off protons at energies up to 3 GeV. Measurements with the Crystal-Barrel detector at ELSA

International Nuclear Information System (INIS)

Junkersfeld, J.

2005-05-01

The CB-ELSA collaboration measured in 2001 photoproduction of mesons off a hydrogen target. From the data, events due to the reaction γp→pπ 0 ω were selected; 2000 events of this type were identified. The differential cross sections of the reaction γp→pπ 0 ω were determined for the first time. The differential cross section dσ/dΩ (cos θ ω ) shows a strong rise in the forward direction and an offset of nearly constant magnitude. The differential cross section dσ/dt (vertical stroke t-t min vertical stroke), where t is the squared four momentum transfer to the ω meson shows an exponential drop off characteristic for a diffractive production of the meson. The corresponding slope parameter is nearly constant in the energy regions covered. The differential cross sections dσ/dΩ and dσ/dt of the pion were also determined. They show no significant structures and demonstrate that pion production in the t-channel provides no or only a small contribution to the cross section of γp→pπ 0 ω. For the first time the total cross section for this reactions was determined. The total cross section for γp→pπ 0 ω shows a slow rise from threshold up to 2400 MeV. Between 2500 and 3000 MeV the variation of the data points is in the same order as the errors. The cross section has a maximum of 6.57±0.57 stat ±0.35 syst μb at 2450 MeV. To determine resonant contributions the invariant masses were examined. The differential cross sections dσ/dm of the pπ 0 system show a strong Δ contribution. This affects also the differential cross sections dσ/dm of the pω and π 0 ω systems, which show mainly kinematical reflections due to the Δ in the pπ 0 system. The dσ/dm spectra of pπ 0 were fitted with a Breit-Wigner and a phase space distribution. The cross section of γp→Δω and the cross section of γp→pπ 0 ω without Δω contributions were determined. (Orig.)

Pion electroproduction at threshold in the inverse channel: π-p → ne+e-. Determination method of the longitudinal multipole Lsub(0+)sup(π-) at small transfer. Preparation of the experiment

International Nuclear Information System (INIS)

Fonvieille, H.

1984-01-01

Our main is to give for the first time an experimental value of the longitudinal multipole Lsub(0+)sup(π - ) (k 2 ) for small transfers in the time-like region (/k 2 / -2 ) by studying the process: π - p → ne + e - at threshold. The pion beam is stopped in a liquid hydrogen target, and the lepton pair is detected in a double arm high-resolution, large-acceptance spectrometer (magnet + drift chambers). We describe here the preparating phases of the experiment. After a brief review of the theoretical approaches, we discuss the method for selecting the events from the background (due to: π - p → nγ, γ → e + e - , and π - p → π 0 n, π 0 → γe + e - ) and present a method for analyzing our data, from which the multiple Lsub(0+)sup(π - ) (k 2 ) is to be determined with an average 10% precision. For that purpose, we give an approximate calculation of the experimental resolution. The choice of the experimental set-up and its realization are then described. The experiment (a Clermont-LPC, Saclay-DPhN/HE, Lyon-IPN Collaboration) takes place on the ALS-pion Beam (Saclay). The whole experimental set-up has been recently checked satisfactorily [fr

Relating inclusive and exclusive meson photoproduction at large transverse momentum

International Nuclear Information System (INIS)

Scott, D.M.

1975-01-01

Inclusive and exclusive meson photoproduction at large transverse momentum are related by a local application of the correspondence principle of Bjorken and Kogut. The recent predictions for the inclusive process by Escobar are thus compared with wide angle exclusive data. The inclusive photoproduction of (rho 0 +ω) at large transverse momentum is discussed. (Auth.)

The pion form factor within the hidden local symmetry model

International Nuclear Information System (INIS)

Benayoun, M.; David, P.; DelBuono, L.; Leruste, P.; O'Connell, H.B.

2003-01-01

We analyze a pion form factor formulation which fulfills the Analyticity requirement within the Hidden Local Symmetry (HLS) Model. This implies an s-dependent dressing of the ρ-γ VMD coupling and an account of several coupled channels. The corresponding function F π (s) provides nice fits of the pion form factor data from s=-0.25 to s=1 GeV 2 . It is shown that the coupling to KK has little effect, while ωπ 0 improves significantly the fit probability below the φ mass. No need for additional states like ρ(1450) shows up in this invariant-mass range. All parameters, except for the subtraction polynomial coefficients, are fixed from the rest of the HLS phenomenology. The fits show consistency with the expected behaviour of F π (s) at s=0 up to O(s 2 ) and with the phase shift data on δ 1 1 (s) from threshold to somewhat above the φ mass. The ω sector is also examined in relation with recent data from CMD-2. (orig.)

Charge dependence of the pion-nucleon coupling constant

Directory of Open Access Journals (Sweden)

V. A. Babenko

2015-07-01

Full Text Available On the basis of the Yukawa potential we study the pion-nucleon coupling constants for the neutral and charged pions assuming that nuclear forces at low energies are mainly determined by the exchange of virtual pions. We obtain the charged pseudovector pion-nucleon coupling constant f2π± = 0.0804(7 by making the use of experimental low-energy scattering parameters for the singlet pp- and np-scattering, and also by use of the neutral pseudovector pion-nucleon coupling constant f2π0 = 0.0749(7. Corresponding value of the charged pseudoscalar pion-nucleon coupling constant g2π0 / 4π = 14.55(13 is also determined. This calculated value of the charged pseudoscalar pion-nucleon coupling constant is in fully agreement with the experimental constant g2π0 / 4π = 14.52(26 obtained by the Uppsala Neutron Research Group. Our results show considerable charge splitting of the pion-nucleon coupling constant.

Pion-nucleus scattering in the isobar formalism

International Nuclear Information System (INIS)

Moniz, E.J.

1978-06-01

Lectures on the isobar-hole model for pion reactions include the isobar as an explicit degree of freedom and the connection with a purely pion and nucleon system, the formalism and its relation to the pion optical potential, the extended schematic model for pion scattering, a simple spinless s-wave model, application to pion-oxygen 16 scattering and comparison with elastic scattering data. In this way the extent is shown to which microscopic treatment of the many-body dynamics explains the data and the extent to which additional physical input is required. Another test is the various inelastic processes. Inclusive reactions are briefly discussed. 37 references

Hadronic form factors in kaon photoproduction

Energy Technology Data Exchange (ETDEWEB)

Syukurilla, L., E-mail: tmart@fisika.ui.ac.id; Mart, T., E-mail: tmart@fisika.ui.ac.id [Department Fisika, FMIPA, Universitas Indonesia, Depok, 164242 (Indonesia)

2014-09-25

We have revisited the effect of hadronic form factors in kaon photoproduction process by utilizing an isobaric model developed for kaon photoproduction off the proton. The model is able to reproduce the available experimental data nicely as well as to reveal the origin of the second peak in the total cross section, which was the main source of confusion for decades. Different from our previous study, in the present work we explore the possibility of using different hadronic form factors in each of the KΛN vertices. The use of different hadronic form factors, e.g. dipole, Gaussian, and generalized dipole, has been found to produce a more flexible isobar model, which can provide a significant improvement in the model.

Magnetic polarizability of pion

Energy Technology Data Exchange (ETDEWEB)

Luschevskaya, E.V., E-mail: luschevskaya@itep.ru [Institute for Theoretical and Experimental Physics, Bolshaia Cheremushkinskaia 25, 117218 Moscow (Russian Federation); School of Biomedicine, Far Eastern Federal University, 690950 Vladivostok (Russian Federation); Solovjeva, O.E., E-mail: olga.solovjeva@itep.ru [Institute for Theoretical and Experimental Physics, Bolshaia Cheremushkinskaia 25, 117218 Moscow (Russian Federation); Teryaev, O.V., E-mail: teryaev@theor.jinr.ru [Joint Institute for Nuclear Research, Dubna, 141980 (Russian Federation); National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Kashirskoe highway, 31, 115409 Moscow (Russian Federation)

2016-10-10

We explore the energy dependence of π mesons off the background Abelian magnetic field on the base of quenched SU(3) lattice gauge theory and calculate the magnetic dipole polarizability of charged and neutral pions for various lattice volumes and lattice spacings. The contribution of the magnetic hyperpolarizability to the neutral pion energy has been also found.

On electron and pion identification using a multilayer perceptron in the transition radiation detector of the CBM experiment

International Nuclear Information System (INIS)

Akishina, T.P.; Denisova, O.Yu.; Ivanov, V.V.

2009-01-01

The problem of pion-electron identification based on their energy losses in the TRD is considered in the frame of the CBM experiment. For particles identification an artificial neural network (ANN) was used, a multilayer perceptron realized in JETNET and ROOT packages. It is demonstrated that, in order to get correct and comparable results, it is important to define the network structure correctly. The recommendations for such a selection are given. In order to achieve an acceptable level of pions suppression, the energy losses need to be transformed to more 'effective' variables. The dependency of ANN output threshold for a fixed portion of electron loss on the particle momentum is presented

Study of the isospin properties of single-pion production by neutrinos

International Nuclear Information System (INIS)

Barnes, V.E.; Carmony, D.D.; Garfinkel, A.F.

1978-01-01

Results are presented on the three single-pion production reactions νP-μ - Pπ + , νn-μ - nπ + , and νn-μ - Pπ 0 . Measurements were made from threshold to a neutrino energy of 1.5 GeV using the Argonne National Laboratory 12-foot bubble chamber filled with deuterium and exposed to a broad band neutrino beam. In addition to a resonant isospin I = 3/2 N/sub π/ amplitude, a large I = 1/2 amplitude was found as predicted by Adler

Charm photoproduction and quantum chromodynamics

International Nuclear Information System (INIS)

Novikov, V.A.; Shifman, M.A.; Vainshtein, A.I.; Zakharov, V.I.

1977-01-01

It is shown that charm photoproduction can be consistently described within asymptotically free field theory. Quantum chromodynamics is used to derive sum rules for the total cross section sigmasub(c)sup(γ) which includes both production of mesons with hidden charm (J/PIS, PIS' and so on) and of charmed particles (pairs DantiD, FantiF and so on). An estimate of sigmasub(c)sup(γ) as a function of energy is given and fast growth is discovered up to energies approximately 1000 GeV. In this energy range sigmasub(c)sup(γ) turns out to be equal to several microbarns. It is argued that measurements of charm photoproduction would give the most direct information on the gluon distribution within a nucleon. All the results are generalized to production of heavier particles containing new quarks. In particular, a simple rescaling law is derived connecting the cross sections for charm and beauty

Single nucleon-nucleon collision model for subthreshold pion production in heavy ion collisions

International Nuclear Information System (INIS)

Bellini, V.; Di Toro, M.; Bonasera, A.

1985-01-01

We show that inclusive experimental data on subthreshold pion production in 12 C + 12 C and 16 O + 12 C collisions can be reproduced using a first chance Nucleon-Nucleon (NN) collision mechanism. Pauli blocking effects are extremely important while π-resorption can be safely neglected for these light systems. We apply our method at various beam energies. The possible importance of collective dynamical effects around the physical threshold is finally suggested

Longitudinal Electroproduction of Charged Pions from

International Nuclear Information System (INIS)

David Gaskell; Abdellah Ahmidouch; Pawel Ambrozewicz; H. Anklin; John Arrington; K. Assamagan; Steven Avery; Kevin Bailey; Oliver K. Baker; Shelton Beedoe; Elizabeth Beise; Herbert Breuer; D. S. Brown; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cowley; Samuel Danagoulian; D. De Schepper; Jim Dunne; Dipangkar Dutta; Rolf Ent; Liping Gan; Ashot Gasparian; Donald Geesaman; Ron Gilman; Charles Glashausser; Paul Gueye; M. Harvey; O. Hashimoto; Wendy Hinton; G. Hofman; Ceasar Jackson; Hal Jackson; Cynthia Keppel; Ed Kinney; Doug Koltenuk; G. Kyle; Allison Lung; David Mack; D. McKee; Joseph Mitchell; Hamlet Mkrtchyan; B. Mueller; Gabriel Niculescu; Ioana Niculescu; Tom O'Neill; V. Papavassiliou; Dave Potterveld; Juerg Reinhold; Philip Roos; Reyad Sawafta; Ralph Segel; Stepan Stepanyan; Vardan Tadevosyan; T. Takahashi; Liguang Tang; B. Terburg; D. Van Westrum; J. Volmer; T. P. Welch; Stephen Wood; Lulin Yuan; Ben Zeidman; Beni Zihlmann

2001-01-01

Separated longitudinal and transverse cross sections for charged pion electroproduction from 1 H, 2 H, and 3 He were measured at Q 2 = 0.4 (GeV/c) 2 for two values of the invariant mass, (bar W) = 1.15 GeV and (bar W) = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in 3> He at (bar W) = 1.60 GeV. The (bar W) = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production

Pions in the nuclear medium

International Nuclear Information System (INIS)

Chanfray, G.

1996-07-01

We discuss various aspects of pion physics in the nuclear medium. We first study s-wave pion-nucleus interaction in connection with chiral symmetry restoration and quark condensate in the nuclear medium. We then address the question of p-wave pion-nucleus interaction and collective pionic modes in nuclei and draw the consequences for in medium ππ correlations especially in the scalar-isoscalar channel. We finally discuss the modification of the rho meson mass spectrum at finite density and/or temperature in connection with relativistic heavy ion collisions

Strangeness photoproduction and hadronic resonances; Photoproduction d`etrangete et resonances hadroniques

Energy Technology Data Exchange (ETDEWEB)

David, J C

1994-09-01

The purpose of this thesis is to study the kaon photoproduction off a proton ({gamma}p {yields} K{sup +}{Lambda},{gamma}p {yields} K{sup +}{Sigma}{sup 0}, {gamma}p {yields} K{sup 0}{Sigma}{sup +}), with a photon energy between 0.9 and 2.1 GeV. We use an isobaric model where the amplitudes are computed with Feynman diagrams. The insertion of nucleonic resonances with spin 3/2 and 5/2 is necessary to improve the existing models beyond 1.5 GeV. This step is also necessary to extend the elementary process of photoproduction to electroproduction where the data have been taken with photon energies above 2.0 GeV. The parameters of our models are the coupling constants which appear at each Feynman diagram vertex. They are determined by fitting our models to the experimental data (cross sections, polarization asymmetries). Before performing the minimization we drew some informations about coupling constants from mesonic and electromagnetic decays, and from SU(3) and SU(6) symmetries. In conclusion, the models developed here reproduce the experimental data (E{sub {gamma}} {<=} 2.0 GeV) and the two main coupling constants are in good agreement with broken SU(3)-symmetry predictions. (author). 47 refs.

Quasi-free K+ photo-production in 12C

International Nuclear Information System (INIS)

Maeda, K.; Yamazaki, H.; Asano, S.; Emura, T.; Endo, I.; Endo, S.; Ito, S.; Itoh, H.; Ifuku, K.; Konno, O.; Koike, M.; Maruyama, K.; Niki, K.; Niwa, K.; Okuno, H.; Sakaguchi, A.; Sasaki, T.; Suda, T.; Sumi, Y.; Takeya, M.; Terasawa, T.; Uchida, H.; Yamashita, H.; Yoshida, K.

1994-01-01

Quasi-free K + photo-production in the 12 C(γ,K + ) reaction has been investigated in a photon energy range of 0.7-1.1GeV. Differential cross sections for the quasi-free process of the 12 C(γ,K + ) reaction have been obtained and they are compared with a calculation of a quasi-free K + photo-production. The effective proton number Z eff =4.2±0.6 obtained from the experiment was in good agreement with a calculation of a semi-classical attenuation model. ((orig.))

The pion form factor from first principles

International Nuclear Information System (INIS)

Heide, J. van der

2004-01-01

We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the O(a) improved current. We calculate form factor for pion masses down to mπ = 380 MeV. We compare the mean square radius for the pion extracted from our form factors to the value obtained from the 'Bethe Salpeter amplitude'. Using (quenched) chiral perturbation theory, we extrapolate our results towards the physical pion mass

Radiation quality of beams of negative pions

International Nuclear Information System (INIS)

Dicello, J.F.; Brenner, D.J.

1981-01-01

As a negative pion stops in tissue, it attaches itself to an adjacent atom to form a mesonic atom. Subsequently, the wave function of the pion interacts with that of the nucleus and the pion is absorbed. Because the energy associated with the rest mass of the pion is greater than the separation energy of the nuclear particles, the nucleus disintegrates (pion star). In tissue, approximately 40 MeV goes into overcoming the binding energies; 20 MeV goes into kinetic energy of charged particles; 80 MeV goes into kinetic energy of neutrons. In cases where biological studies are performed with beams of negative pions, as much as 20% of the total absorbed dose in the treatment volume and about 50% of the high-LET dose (> 100 keV/μm) can result from neutrons. The degree of biological response and the variation of that response throughout the treatment volume can be altered by the neutron dose

Scrutinizing the pion condensed phase

Energy Technology Data Exchange (ETDEWEB)

Carignano, Stefano; Mammarella, Andrea; Mannarelli, Massimo [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Lepori, Luca [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Universita dell' Aquila, Dipartimento di Scienze Fisiche e Chimiche, Coppito-L' Aquila (Italy); Pagliaroli, Giulia [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Gran Sasso Science Institute, L' Aquila (Italy)

2017-02-15

When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the ''radial'' fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition. (orig.)

Quantum signature in heavy-ion pion production

International Nuclear Information System (INIS)

Buvel, R.L.

1985-01-01

A revised model for pion production in heavy-ion peripheral collisions is presented. The pion-production mechanism investigated here is a two step process involving the formation and subsequent decay of an isobar resonance in the projectile nucleus. The independent-particle shell model with harmonic oscillator states is used to approximate the internal structure of the nucleus. The inclusion of the internal structure of the projectile nucleus led to the discovery of a quantum signature in the pion-production differential cross section. The quantum signature involves a matching condition where the pion-production differential cross section goes to zero for a particular value of the pion kinetic energy. The theory is compared to a recent experiment, but the results of this comparison are inconclusive

Physics of the pion liquid

International Nuclear Information System (INIS)

Shuryak, E.V.

1990-01-01

Excited hadronic matter in the temperature interval T = 100-200 MeV is not an ideal pion gas, but ratehr a liquid, in which attractive interaction among particles plays an important role. Pion dispersion curve is in this case essentially modified by a kind of collective momentum-dependent potential, which becomes important as the quasipion comes to the boundary of the system. The author shows that these effects can provide an explanation for a number of recent experimental puzzles, in particular, for the observed copious production of soft pions and soft photons in high energy hadronic reactions

Physics of the pion liquid

International Nuclear Information System (INIS)

Shuryak, E.V.

1990-04-01

Excited hadronic matter in the temperature interval T = 100--200 MeV is not an ideal pion gas, but rather a liquid, in which attractive interaction among particles plays an important role. Pion dispersion curve is in this case essentially modified by a kind of collective momentum-dependent potential, which becomes important as the ''quasipion'' comes to the boundary of the system. We show that effects can provide and explanation for a number of recent experimental puzzles, in particular, for the observed copious production of soft pions and soft photons in high energy hadronic reactions. 31 refs., 13 figs

Pion-nucleon scattering in covariant baryon chiral perturbation theory with explicit Delta resonances

Energy Technology Data Exchange (ETDEWEB)

Yao, De-Liang [Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany); Siemens, D. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Bernard, V. [Groupe de Physique Théorique, Institut de Physique Nucléaire, UMR 8606,CNRS, University Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex (France); Epelbaum, E. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Gasparyan, A.M. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); SSC RF ITEP, Bolshaya Cheremushkinskaya 25, 117218 Moscow (Russian Federation); Gegelia, J. [Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany); Tbilisi State University, 0186 Tbilisi (Georgia); Krebs, H. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Meißner, Ulf-G. [Helmholtz Institut für Strahlen- und Kernphysik andBethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn (Germany); Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany)

2016-05-05

We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the S- and P-partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the D and F waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.

Pion distribution in the nucleon

International Nuclear Information System (INIS)

Lee, T.-S.H.

1989-01-01

A model is presented for calculating the pion wave function inside the nucleon. By assuming that all pions around a core of the nucleon are in the lowest eigenstate of the system, it is shown that both the bound state and πN scattering amplitude can be consistently described by an exactly soluble model defined in the subspace spanned by the core state and the physical πN state. The parameters of the model are determined by fitting the data of the nucleon mass, πNN coupling constant and low energy πN scattering phase shifts. The model predicts that the probability of finding the pion component inside the nucleon is about 20%. The calculated πNN form factor differs significantly from the conventional monopole form. The dynamical consequences of the differences are demonstrated in a calculation of electromagnetic production of pions from the nucleon and the deuteron. 7 refs., 4 figs., 1 tab

Measuring pion beta decay with high-energy pion beams

International Nuclear Information System (INIS)

McFarlane, W.K.; Hoffman, C.M.

1993-01-01

Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay π + → π 0 e + vε is predicted by the Standard Model (SM) to be R(π + → π 0 e + vε) = 0.3999±0.0005 s -1 . The best experimental number, obtained using in-flight decays, is R(π + → π 0 e + vε) = 0.394 ± 0.015 s -1 . A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required

Design and simulation of the nuSTORM pion beamline

Energy Technology Data Exchange (ETDEWEB)

Liu, A., E-mail: aoliu@fnal.gov; Neuffer, D.; Bross, A.

2015-11-21

The nuSTORM (neutrinos from STORed Muons) proposal presents a detailed design for a neutrino facility based on a muon storage ring, with muon decay in the production straight section of the ring providing well defined neutrino beams. The facility includes a primary high-energy proton beam line, a target station with pion production and collection, and a pion beamline for pion transportation and injection into a muon decay ring. The nuSTORM design uses “stochastic injection”, in which pions are directed by a chicane, referred to as the Orbit Combination Section (OCS), into the production straight section of the storage ring. Pions that decay within that straight section provide muons within the circulating acceptance of the ring. The design enables injection without kickers or a separate pion decay transport line. The beam line that the pions traverse before being extracted from the decay ring is referred to as the pion beamline. This paper describes the design and simulation of the pion beamline, and includes full beam dynamics simulations of the system.

Nucleon multiplicities after pion absorption in 160

International Nuclear Information System (INIS)

Hamers, R.

1989-01-01

The experiment described in this thesis concerns a simultaneous measurement of two- and higher-fold coincidences following positive and negative pion absorption in 16 0. The detected particles are protons, neutrons and deuterons. The detection and analysis of charged particles is discussed. The incident pion energy was 65 MeV, thus well below the delta resonance. The low pion energy was 65 MeV, thus well below the delta resonance. The low pion energy ensures that contributions of initial state interactions, i.e. pion-nucleon scattering preceding absorption, are minimized. The following reaction channels were selected and analyzed: π + ,pp), (π + ,pd). Evidence for quasifree reaction precessed has been investigated by comparing the data with phase-space calculations incorporating the geometry of the experimental setup. (author). 36 refs.; 1 figs.; 3 tabs

Effective pion--nucleon interaction in nuclear matter

International Nuclear Information System (INIS)

Celenza, L.S.; Liu, L.C.; Nutt, W.; Shakin, C.M.

1976-01-01

We discuss the modification of the interaction between a pion and a nucleon in the presence of an infinite medium of nucleons (nuclear matter). The theory presented here is covariant and is relevant to the calculation of the pion--nucleus optical potential. The specific effects considered are the modifications of the nucleon propagator due to the Pauli principle and the modification of the pion and nucleon propagators due to collisions with nucleons of the medium. We also discuss in detail the pion self-energy in the medium, paying close attention to off-shell effects. These latter effects are particularly important because of the rapid variation with energy of the fundamental pion--nucleon interaction. Numerical results are presented, the main feature being the appearance of a significant damping width for the (3, 3) resonance

Electron linac design for pion radiotherapy

International Nuclear Information System (INIS)

Loew, G.A.; Brown, K.L.; Miller, R.H.; Walz, D.R.

1977-03-01

The electron linac provides a straightforward, state-of-the-art method of producing the primary beam required for a hospital-based multiport pion radiotherapy facility for cancer treatment. The accelerator and associated beam transport system described are capable of generating an electron beam of about 250 kW and delivering it alternately to one of several pion generators and treatment areas. Each pion generator, a prototype of which now exists at the Stanford W. W. Hansen Laboratory, would contain a target for the electron beam and sixty separate superconducting magnet channels which focus the pions in the patient. The considerations which enter the design of a practical linac are presented together with a possible layout of a flexible beam transport system

Charged pions polarizability measurement at COMPASS

CERN Document Server

Guskov, A

2010-01-01

The pion electromagnetic structure can be probed in $\\pi^{−}+(A,Z)\\rightarrow\\pi^{-}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\alpha_{\\pi})$ and the magnetic $(\\beta_{\\pi})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of point-like pions with the measured cross section. The opportunity to measure pion polarizability via the Primakoff reaction at the COMPASS experiment was studied with $a$ $\\pi^{-}$ beam of 190 GeV during pilot run 2004. The obtained results were used for preparation of the new data taking which was performed in 2009.

Critical opalescence of the nuclear pion field: a possible evidence in the M1 (15.11 MeV) form factor of 12C

International Nuclear Information System (INIS)

Delorme, J.; Ericson, M.; Figureau, A.; Giraud, N.

1979-07-01

The nuclear pion field for the transition to the 15.11 MeV (1 + , T= 1) state of 12 C has been computed, evaluating the nuclear polarization with a large basis of nucleon- and isobar-hole excitations. The field shows an enhancement (or critical opalescence) in the momentum region beyond 1.5msub(π) which leads to a substantial increase of the second maximum of the M1 form factor. Agreement with experiment can be obtained if the 12 C nucleus is much closer to the pion condensation threshold than currently expected

Pion-nucleus scatter and the Pauli principle

International Nuclear Information System (INIS)

Dover, C.B.; Lemmer, R.H.

1976-01-01

A density expansion of the pion self-energy for pions in nuclear matter is reexamined. It is shown that a single hole-line expansion of the self-energy (i) is equivalent to using a strongly quenched πN scattering amplitude in the medium, and (ii) results in an inconsistent treatment of the virtual pions necessarily present in a field-theoretic description of the problem. Exchange of intermediate pions gives rise to nucleon-nucleon, as well as pion-nucleon scattering diagrams that both contribute to the pion self-energy in an essential way. The nucleon-nucleon scattering proceeds, for instance, via a one-pion-exchange potential that is, however, highly nonstatic for energy transfers between nucleons close to the incident energy. Such interactions are singled out automatically for special treatment in a field-theory approach to the problem, and should not be introduced in an ad hoc manner as part of an empirical NN interaction in nuclear matter. We evaluate the coherent and charge exchange contributions to the pion-nucleus optical potential, proportional to the total density and the neutron-proton density difference, respectively. The Pauli principle is found to provide a small correction to the coherent part, both in the hole-line and density expansion formalisms. However, the charge exchange part of the potential is almost completely damped at low energies in the hole-line expansion, while the inclusion of backward-going graphs (random-phase-approximation-type correlations) restores it to its value based on free space πN charge exchange amplitudes (i.e., no net Pauli effect)

Pion structure from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Javadi Motaghi, Narjes

2015-05-12

In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.

Pion radiation therapy

International Nuclear Information System (INIS)

Kligerman, M.M.

1975-01-01

Results are summarized from studies on the relative biological effects as compared with x or γ radiation and OER of negative pi mesons produced by the Berkeley 184-inch synchrocyclotron or the NIMROD 7-GeV proton synchrocyclotron at the Rutherford High Energy Laboratory in England using cultured animal cells or Vicia faba cells as the test system. Preliminary results are reported from similar radiobiological studies at the Los Alamos Meson Physics Facility. The relative response of human tissues to peak pion irradiation was compared with 140 kV x rays in a single patient with multiple malignant melanoma by observing the acute response of the skin surrounding metastatic modules following exposure to either pions or x radiation. Color photographs of the irradiated areas made at least twice weekly and densitometry measurements and observations by radiation therapists indicated that maximum erythemia occurred during the fifth, sixth, or seventh week after the start of a schedule of fractionated exposure to 15 fractions over 19 elapsed days. X irradiation was delivered at a dose rate of 500 rads/min to modules to deliver 55, 66, or 75 percent of a skin surface dose of 5,200 rads and pion irradiation, at doses numerically 50 percent of the x ray dose, was delivered at a dose rate of 5 to 7 rads/min. Dose response curves were plotted. Results of histological examinations of skin samples taken 24 weeks following irradiation are reported. Results are discussed relative to the destruction of melanoma cells following pion or x ray treatment

Exclusive vector meson production at HERA

International Nuclear Information System (INIS)

Szuba, Dorota

2013-01-01

The exclusive photoproduction of Υ has been studied with the ZEUS detector in ep collisions at HERA. The exponential slope, b, of the |t|-dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured. This constitutes the first measurement of the |t|-dependence of the γp→Υp cross section. The differential crosssections as a function of t at lower energies of γp centre-of-mass has been studied in exclusive diffractive photoproduction of J/ψ mesons with the H1 detector. The exclusive electroproduction of two pions has been measured by the ZEUS experiment. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, assuming that the studied mass range includes the contributions of the ρ, ρ′ and . ρ'' vector-meson states.

Measurement of the charged-pion polarisability at COMPASS

CERN Multimedia

CERN. Geneva

2015-01-01

For more than a decade, COMPASS has been tackling the measurement of the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in electromagnetic fields. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method for realizing interactions of charged pions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous results, roughly by a factor two, with the smallest uncertainties realized so far. The pion polarisability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and dynamics of the pion, the lightest bound system of strong interaction.

Mechanism of the alkali degradation of (6-4) photoproduct-containing DNA.

Science.gov (United States)

Arichi, Norihito; Inase, Aki; Eto, Sachise; Mizukoshi, Toshimi; Yamamoto, Junpei; Iwai, Shigenori

2012-03-21

The (6-4) photoproduct is one of the major damaged bases produced by ultraviolet light in DNA. This lesion is known to be alkali-labile, and strand breaks occur at its sites when UV-irradiated DNA is treated with hot alkali. We have analyzed the product obtained by the alkali treatment of a dinucleoside monophosphate containing the (6-4) photoproduct, by HPLC, NMR spectroscopy, and mass spectrometry. We previously found that the N3-C4 bond of the 5' component was hydrolyzed by a mild alkali treatment, and the present study revealed that the following reaction was the hydrolysis of the glycosidic bond at the 3' component. The sugar moiety of this component was lost, even when a 3'-flanking nucleotide was not present. Glycosidic bond hydrolysis was also observed for a dimer and a trimer containing 5-methyl-2-pyrimidinone, which was used as an analog of the 3' component of the (6-4) photoproduct, and its mechanism was elucidated. Finally, the alkali treatment of a tetramer, d(GT(6-4)TC), yielded 2'-deoxycytidine 5'-monophosphate, while 2'-deoxyguanosine 3'-monophosphate was not detected. This result demonstrated the hydrolysis of the glycosidic bond at the 3' component of the (6-4) photoproduct and the subsequent strand break by β-elimination. It was also shown that the glycosidic bond at the 3' component of the Dewar valence isomer was more alkali-labile than that of the (6-4) photoproduct.

Mechanism of pion absorption in complex nuclei

International Nuclear Information System (INIS)

Doss, K.G.N.; Wharton, W.R.

Basic geometrical arguments are used to analyze the A dependence of the total pion absorption cross section, the effective number of nucleons sharing the pion momentum and energy, and the proton yields from π + - and π - -induced reactions. The results are consistent with the pions penetrating some distance through the nuclear volume and annihilating on a pair of nucleons. 3 figures

Real-pion states formed by virtual-pion beam

International Nuclear Information System (INIS)

Yamazaki, Toshimitsu.

1990-04-01

Deeply bound pionic states are discussed from various points of view; highly excited nuclear states as a cluster family of pionic bound states, Σ atom/Σ hypernuclei, halo-like density distributions, virtual pion beam to produce pionic states, etc. (author)

Pion production cross sections and associated parameters

International Nuclear Information System (INIS)

Bradbury, J.N.

1985-01-01

Negative pions have been used for radiotherapy at the meson factories LAMPF (USA), SIN (Switzerland), and TRIUMF (Canada) and have been planned for use at new meson facilities under construction (USSR) and at proposed dedicated medical facilities. Providing therapeutically useful dose rates of pions requires a knowledge of the pion production cross sections as a function of primary proton energy (500 to 1000 MeV), pion energy (less than or equal to100 MeV), production angle, and target material. The current status of the data base in this area is presented including theoretical guidelines for extrapolation purposes. The target material and geometry, as well as the proton and pion beam parameters, will affect the electron (and muon) contamination in the beam which may have an important effect on both the LET characteristics of the dose and the dose distribution. In addition to cross-section data, channel characteristics such as length of pion trajectory, solid-angle acceptance, and momentum analysis will affect dose rate, distribution, and quality. Such considerations are briefly addressed in terms of existing facilities and proposed systems. 16 refs., 6 figs

Invariant potential for elastic pion--nucleus scattering

International Nuclear Information System (INIS)

Cammarata, J.B.; Banerjee, M.K.

1976-01-01

From the Wick-Dyson expansion of the exact propagator of a pion in the presence of a nucleus, an invariant potential for crossing symmetric elastic pion-nucleus scattering is obtained in terms of a series of pion-nucleon diagrams. The Chew-Low theory is used to develop a model in which the most important class of diagrams is effectively summed. Included in this model is the exclusion principle restriction on the pion-bound nucleon interaction, the effects of the binding of nucleons, a kinematic transformation of energy from the lab to the πN center of mass frame, and the Fermi motion and recoil of the target nucleons. From a numerical study of the effects of these processes on the π- 12 C total cross section, the relative importance of each is determined. Other processes contributing to the elastic scattering of pions not included in the present model are also discussed

Evidence for a ωrhosup(+-)πsup(+-) state in diffractive photoproduction

International Nuclear Information System (INIS)

Atkinson, M.; Davenport, M.; Flower, P.; Hutton, J.S.; Kumar, B.R.; Morris, J.A.G.; Morris, J.V.; Sharp, P.H.; Brodbeck, T.J.; Clegg, A.B.; Flynn, P.J.; Henderson, R.C.W.; Newton, D.; Brookes, G.R.; Bunn, J.J.; Galbraith, W.; McClatchey, R.H.; Bussey, P.J.; Dainton, J.B.; Paterson, C.; Raine, C.; Skillicorn, I.O.; Smith, K.M.; Diekmann, B.; Heinloth, K.; Jakob, H.P.; Jung, M.; Liebenau, V.; Paul, E.; Reidenbach, M.; Rotscheidt, H.; Schloesser, A.; Laberrigue, J.; La Vaissilere, C. de; Yiou, T.P.

1985-01-01

The photoproduction of the final state ωπ + π - π 0 has been studied as part of a survey of photoproduction in the energy range 20-70 GeV in the Omega spectrometer at CERN. The π + π - π 0 system produced with the ω meson has a strong rhosup(+-)πsup(+-) component which is predominantly I=1 and Jsup(π)=1+. For the ωrhosup(+-)π + state a spin-parity analysis favours Jsup(π)=1-, and the mass spectrum peaks at 2.28+-0.05 GeV. The fitted width is GAMMA=0.44+-0.11 GeV. The photoproduction cross-section of the ωrhosup(+-)rhosup(+-) state, averaged over the energy range 25-60 GeV, is 150+-50 nb. (orig.)

Pion broadening and low-mass dilepton production

International Nuclear Information System (INIS)

Schulze, H.-J.; Blaschke, D.

2002-01-01

Mass and transverse momentum spectra of dileptons produced in Pb + Au (158 GeV/u) collisions within a pion annihilation model are determined. A fit to the data requires simultaneous mass reduction and broadening of the in-medium rho propagator. The introduction of a finite pion width, as required within self-consistent approaches to the interacting pion gas, further improves the agreement with the data

Measurement of the total cross section for the photoproduction of omega mesons on the proton; Messung des totalen Wirkungsquerschnitts fuer die Photoproduktion von Omegamesonen am Proton

Energy Technology Data Exchange (ETDEWEB)

Hoeffgen, S.K.

2007-06-15

The photoproduction of omega mesons on the proton ({gamma}p {yields} {omega}p) directly at the production threshold was investigated during the first phase of the CB-ELSA experiment in Bonn. In experiments directly at the threshold the protons are strongly focussed in forward direction due to kinematic reasons. Therefore the forward detector, a large area time of flight detector, plays a prominent role and there is a detailed description of the reconstruction and measuring capabilities of this spectrometer. Thereafter follows the extraction of the total cross section of the reaction {gamma}p {yields} {omega}p in the decay channel with {omega} {yields} {pi}{sup 0}{pi}{sup +}{pi}{sup -} directly at the production threshold with previously unequaled accuracy. (orig.)

Pion interferometric tests of transport models

Energy Technology Data Exchange (ETDEWEB)

Padula, S.S.; Gyulassy, M.; Gavin, S. (Lawrence Berkeley Lab., CA (USA). Nuclear Science Div.)

1990-01-08

In hadronic reactions, the usual space-time interpretation of pion interferometry often breaks down due to strong correlations between spatial and momentum coordinates. We derive a general interferometry formula based on the Wigner density formalism that allows for arbitrary phase space and multiparticle correlations. Correction terms due to intermediate state pion cascading are derived using semiclassical hadronic transport theory. Finite wave packets are used to reveal the sensitivity of pion interference effects on the details of the production dynamics. The covariant generalization of the formula is shown to be equivalent to the formula derived via an alternate current ensemble formalism for minimal wave packets and reduces in the nonrelativistic limit to a formula derived by Pratt. The final expression is ideally suited for pion interferometric tests of Monte Carlo transport models. Examples involving gaussian and inside-outside phase space distributions are considered. (orig.).

Pion interferometric tests of transport models

International Nuclear Information System (INIS)

Padula, S.S.; Gyulassy, M.; Gavin, S.

1990-01-01

In hadronic reactions, the usual space-time interpretation of pion interferometry often breaks down due to strong correlations between spatial and momentum coordinates. We derive a general interferometry formula based on the Wigner density formalism that allows for arbitrary phase space and multiparticle correlations. Correction terms due to intermediate state pion cascading are derived using semiclassical hadronic transport theory. Finite wave packets are used to reveal the sensitivity of pion interference effects on the details of the production dynamics. The covariant generalization of the formula is shown to be equivalent to the formula derived via an alternate current ensemble formalism for minimal wave packets and reduces in the nonrelativistic limit to a formula derived by Pratt. The final expression is ideally suited for pion interferometric tests of Monte Carlo transport models. Examples involving gaussian and inside-outside phase space distributions are considered. (orig.)

Hadron photoproduction at medium energy

International Nuclear Information System (INIS)

Dainton, J.B.

1985-04-01

Results from measurements of multibody photoproduction at medium incident photon energy (2.8 to 4.8 GeV) are presented and discussed. Particular emphasis is placed on topics which are not well understood and which therefore motivate experiments with the upgraded electron accelerator and storage ring ELSA at the University of Bonn, FR Germany. (author)

Landau-Migdal parameters and pion condensation

Energy Technology Data Exchange (ETDEWEB)

Tatsumi, Toshitaka [Department of Physics, Kyoto Univ., Kyoto (Japan)

1999-08-01

The possibility of pion condensation, one of the long-standing issues in nuclear physics, is reexamined in the light of the recent experimental data on the giant Gamow-Teller resonance. The experimental result tells that the coupling of nucleon particle-hole states with {delta} isobar-hole states in the spin-isospin channel should be weaker than that previously believed. It, in turn, implies that nuclear matter has the making of pion condensation at low densities. The possibility and implications of pion condensation in the heavy-ion collisions and neutron stars should be seriously reconsidered. (author)

Virtual-pion and two-photon production in pp scattering

International Nuclear Information System (INIS)

Scholten, O.; Korchin, A.Yu.

2002-01-01

Two-photon production in pp scattering is proposed as a means of studying virtual-pion emission. Such a process is complementary to real-pion emission in pp scattering. The virtual-pion signal is embedded in a background of double-photon bremsstrahlung. We have developed a model to describe this background process and show that in certain parts of phase space the virtual-pion signal gives significant contributions. In addition, through interference with the two-photon bremsstrahlung background, one can determine the relative phase of the virtual-pion process

RAYPHOTON version 2. 0 - an interface for HERA photoproduction physics

Energy Technology Data Exchange (ETDEWEB)

Brook, N.H.; Doyle, A.T. (Glasgow Univ. (United Kingdom). Dept. of Physics and Astronomy); DeRoeck, A. (Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg Inst.)

1992-04-01

RAYPHOTON allows photoproduction of both light and heavy quarks for the direct and resolved photon. It is a convolution of the Weiszaecker-Williams approximation with the cross section for the hard interaction. The hard interaction cross sections and colour flows are set up using the generators for real photoproduction LUCIFER, for the direct photon, and TWISTER, for the resolved photon. It includes QCD cascades in the colour dipole formalism, via an interface, RADIATE, to the ARIADNE package. (orig.).

In vitro residual anti-bacterial activity of difloxacin, sarafloxacin and their photoproducts after photolysis in water

International Nuclear Information System (INIS)

Kusari, Souvik; Prabhakaran, Deivasigamani; Lamshoeft, Marc; Spiteller, Michael

2009-01-01

Fluoroquinolones like difloxacin (DIF) and sarafloxacin (SARA) are adsorbed in soil and enter the aquatic environment wherein they are subjected to photolytic degradation. To evaluate the fate of DIF and SARA, their photolysis was performed in water under stimulated natural sunlight conditions. DIF primarily degrades to SARA. On prolonged photodegradation, seven photoproducts were elucidated by HR-LC-MS/MS, three of which were entirely novel. The residual anti-bacterial activities of DIF, SARA and their photoproducts were studied against a group of pathogenic strains. DIF and SARA revealed potency against both Gram-positive and -negative bacteria. The photoproducts also exhibited varying degrees of efficacies against the tested bacteria. Even without isolating the individual photoproducts, their impact on the aquatic environment could be assessed. Therefore, the present results call for prudence in estimating the fate of these compounds in water and in avoiding emergence of resistance in bacteria caused by the photoproducts of DIF and SARA. - Assessment of the residual anti-bacterial efficacies of difloxacin, sarafloxacin and their photoproducts in water, and estimating their impact on the aquatic environment in inducing resistance to microorganisms.

Factorization and pion form factor in QCD

International Nuclear Information System (INIS)

Efremov, A.V.; Radyushkin, A.V.

1979-01-01

The behaviour of the pion electromagnetic form factor (EMFF) in the framework of quantum chromodynamics (QCD) is discussed. Pion is considered to be a quark-antiquark bound state. It is proposed to use an OPE description of the bound state structure by matrix elements of certain local gauge-invariant operators. Short-distance quark interactions is proved using a direct analysis of perturbation theory in the α-parametric representation of the Feynman diagrams. It is shown that the short-distance parton picture privides a self-consistent description of the large Q 2 momentum behaviour of the pion EMFF in QCD. Pion EMFF asymptotics is expressed in terms of fu fundamental constants of the theory

Effects of the pion string at heavy ion collisions

International Nuclear Information System (INIS)

Mao Hong; Li Yunde; East China Normal Univ., Shanghai

2005-01-01

The authors study the possible signals of the pion string associated with the QCD chiral phase transition in LHC Pb-Pb collision at energy √s=5.5 TeV. The authors follow the Kibble-Zurek mechanism to discuss the production and evolution of the pion string. The authors will show that if the QCD chiral phase transition really takes place in the LHC Pb-Pb collision process and the phase transition is in the second order, the pion string will be inevitably produced and subsequently decay. The main effect of this phenomenon is that there is a generation of a large number of pions in the final state produced by the decay of the pion string, and these pions are mostly distributed in a low momentum region with p-143 MeV; also there are lots of neutral pions distributed in a low momentum region with the mean momentum at p-21 MeV. (authors)

Effects of the pion string at heavy ion collisions

CERN Document Server

Mao, Hong

2005-01-01

We study the possible signals of the pion string associated with the QCD chiral phase transition in LHC Pb-Pb collision at energy square root s=5.5 TeV. We follow the Kibble-Zurek mechanism to discuss the production and evolution of the pion string. We will show that if the QCD chiral phase transition really takes place in the LHC Pb-Pb collision process and the phase transition is in the second order, the pion string will be inevitably produced and subsequently decay. The main effect of this phenomenon is that there is a generation of a large number of pions in the final state produced by the decay of the pion string, and these pions are mostly distributed in a low momentum region with p143 MeV; also there are lots of neutral pions distributed in a low momentum region with the mean momentum at p21 Me V.

The future IKO-PION-MUON-facility

International Nuclear Information System (INIS)

Goudsmit, P.F.A.; Arnold, H.; Dantzig, R. van; Konijn, J.

1975-09-01

Information is given on the pion and muon physics facility planned at the Institute for Nuclear Physics Research (IKO) with special notice of the fluxes of pions and muons expected at this facility, as well as on the structure of these secondary beams

Studies on the charge asymmetry in inclusive photoproduction of mesons in forward direction in the momentum range of 60-170 GeV/c at the CERN Ω-spectrometer

International Nuclear Information System (INIS)

Koersgen, G.

1988-09-01

This thesis describes in its first part the construction and the calibration of a Transition Radiation Detector (TRD) which was used in the photoproduction experiment WA69 at CERN (Geneva). The energy range of the incident photons was 65 GeV to 170 GeV. The detector consisted of 12 radiator-chamber systems. The radiators are of irregular radiator type, made of polypropylen fibres. The chambers are multiwire proportional chambers of thickness 1 cm and driven with a Xe/methane mixture of 90/10. The analysis of hadronic test beams has shown that the pion contamination of a data sample identified as kaons is 20% (8%) at 100 (150) GeV, both numbers given for a kaon efficiency of 80%. This is in agreement with theoretical expectation. The physics analysis deals with charge asymmetries in photoproduction of mesons in the beam fragmentation region. A positive excess has been found of the size 2.2±0.3% overall and 6.0±0.6% for strange particles. The dependence of the charge asymmetry upon the energy of the incident photons and on x F has been examined. It is in agreement with the assumption that the asymmetry found is caused by the annihilation reaction mentioned above. The same tendency occurs in a comparison with SLAC data taken at 20 GeV photon energy. (orig./HSI) [de

J/Psi and Gamma Photoproduction in Pb-Pb Collisions at LHC

CERN Document Server

Li Yun De; CERN. Geneva

1996-01-01

abstractINT-96-01 Hard photoproduction of J/psi and upsilon at LHC Pb-Pb collisions with cms energy 6300 AGeV, is discussed in the process Pb+Pb--Pb + J/psi (upsilon) + X with three types of equivalent photon spectrum function. It turns out that in hard photoproduction the J/psi cross section is dominated by the gluon and heavy quark fragmentation, especially the gluon fragmentation is very important at large pt; while the Upsilon cross section is dominated by the leading order process. It may be concluded from the result that the hard photoproduction processes can be used to test several important problems such as the gluon distribution in nucleus, gluon and heavy quark fragmentation of J/psi , etc. In addition, these processes also provide a new way of testing the EMC effects.

In-medium pion valence distributions in a light-front model

Energy Technology Data Exchange (ETDEWEB)

Melo, J.P.B.C. de, E-mail: joao.mello@cruzeirodosul.edu.br [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); Tsushima, K. [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); Ahmed, I. [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); National Center for Physics, Quaidi-i-Azam University Campus, Islamabad 45320 (Pakistan)

2017-03-10

Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

Multipole analyses and photo-decay couplings at intermediate energies

International Nuclear Information System (INIS)

Workman, R.L.; Arndt, R.A.; Zhujun Li

1992-01-01

The authors describe the results of several multipole analyses of pion-photoproduction data to 2 GeV in the lab photon energy. Comparisons are made with previous analyses. The photo-decay couplings for the delta are examined in detail. Problems in the representation of photoproduction data are discussed, with an emphasis on the recent LEGS data. 16 refs., 4 tabs

Anisotropy of the pion emission in relativistic nucleus-nucleus collisions

International Nuclear Information System (INIS)

Babinet, R.; Cavata, C.; Demoulins, M.; Fanet, H.; Gosset, J.; Lemaire, M.C.; Le Merdy, A.; L'Hote, D.; Lucas, B.; Poitou, J.; Alard, J.P.; Augerat, J.; Bastid, N.; Charmensat, P.; Dupieux, P.; Fraysse, L.; Marroncle, J.; Montarou, G.; Parizet, M.J.; Ramani, A.; Brochard, F.; Gorodetzky, P.; Racca, C.

1990-01-01

The production of pions and baryons from Ne and Ar induced reactions on Ca, NaF, Nb and Pb targets, in the range of .2 to 1 GeV per nucleon, is discussed. The 4π detector Diogenes at the Saturne accelerator facility is applied. The reaction plane is determined from the baryon momenta distribution and used as a reference for the pion triple differential cross-sections. A transverse momentum analysis is carried out for baryons and pions. The pion squared reduced impact parameter and the flow characteristics are given. The results show that the azimuthal anisotropy of pion emission increases with the asymmetry of the system. The evidence that pion absorption effects may be responsible for the azimuthal anisotropy of the pion emission is provided

The pion mass: Looking for its origins

International Nuclear Information System (INIS)

Peccei, R.D.

1985-10-01

After explaining why pions are special excitations in QCD, I discuss how the pion mass reflects directly the dynamical scale of the strong interactions (Λsub(QCD)) and the scale of breaking of the weak interactions (Λsub(F)). To actually calculate the pion mass, however, requires understanding the origin of the quark masses and so I compare and contrast approaches to this latter problem, based on composite models and on superstrings. (orig.)

Funny hills in pion spectra from heavy-ion collisions

International Nuclear Information System (INIS)

Rasmussen, J.O.

1982-03-01

A discussion of some of the systematic features of the pion spectra in heavy-ions reactions is given. A discussion of the hills and valleys in heavy ion pion spectra that show up at the lower pion energies is given. The following topics are discussed: (1) three kinds of funny hills; (2) π - / + ratios near center of mass; (3) new Monte Carlo studies of charged pion spectra; and (4) pion orbiting about fireballs and Bose-Einstein behavior as explanation for the mid-rapidity P/sub perpendicular to/ approx. = 0.4 to 0.5 m/sub π/c hill

Negative pion irradiation of mammalian cells

International Nuclear Information System (INIS)

Dertinger, H.; Luecke-Huhle, C.; Schlag, H.; Weibezahn, K.F.

1976-01-01

Monolayers and spheroids of Chinese hamster cells (V79) were subjected to negative pion irradiation under aerobic conditions. R.b.e. values in the pion peak of 1.8 and 1.5 were obtained for monolayers and spheroids, respectively, whereas the r.b.e. for the plateau was found to be slightly higher than 1. In addition, it was observed that the higher resistance of the V79 spheroid cells than the monolayers to γ-irradiation is not diminished in the pion peak, suggesting that the underlying phenomenon of intercellular communication influences cell survival even after high-LET irradiation. (author)

Beauty Photoproduction

International Nuclear Information System (INIS)

Turcato, M.

2002-01-01

Beauty photoproduction in ep collisions has been studied with the ZEUS detector at HERA, at a center-of-mass energy of 300 GeV. Beauty quarks are tagged via their semi-leptonic decay into a muon or an electron. Events are selected by requiring the presence of two high-transverse energy jets and one high - p T lepton in the final state. The discrimination between beauty and background events is done by a fit to the p rel T variable, the transverse momentum of the lepton with respect to the jet axis. Total and differential cross sections are presented and compared to leading order Monte Carlo simulations and next-to-leading order QCD predictions. (author)

Covariant density functional theory: The role of the pion

International Nuclear Information System (INIS)

Lalazissis, G. A.; Karatzikos, S.; Serra, M.; Otsuka, T.; Ring, P.

2009-01-01

We investigate the role of the pion in covariant density functional theory. Starting from conventional relativistic mean field (RMF) theory with a nonlinear coupling of the σ meson and without exchange terms we add pions with a pseudovector coupling to the nucleons in relativistic Hartree-Fock approximation. In order to take into account the change of the pion field in the nuclear medium the effective coupling constant of the pion is treated as a free parameter. It is found that the inclusion of the pion to this sort of density functionals does not destroy the overall description of the bulk properties by RMF. On the other hand, the noncentral contribution of the pion (tensor coupling) does have effects on single particle energies and on binding energies of certain nuclei.

Measurement of the charged-pion polarizability.

Science.gov (United States)

Adolph, C; Akhunzyanov, R; Alexeev, M G; Alexeev, G D; Amoroso, A; Andrieux, V; Anosov, V; Austregesilo, A; Badełek, B; Balestra, F; Barth, J; Baum, G; Beck, R; Bedfer, Y; Berlin, A; Bernhard, J; Bicker, K; Bieling, J; Birsa, R; Bisplinghoff, J; Bodlak, M; Boer, M; Bordalo, P; Bradamante, F; Braun, C; Bressan, A; Büchele, M; Burtin, E; Capozza, L; Chiosso, M; Chung, S U; Cicuttin, A; Colantoni, M; Crespo, M L; Curiel, Q; Dalla Torre, S; Dasgupta, S S; Dasgupta, S; Denisov, O Yu; Dinkelbach, A M; Donskov, S V; Doshita, N; Duic, V; Dünnweber, W; Dziewiecki, M; Efremov, A; Elia, C; Eversheim, P D; Eyrich, W; Faessler, M; Ferrero, A; Filin, A; Finger, M; Finger, M; Fischer, H; Franco, C; du Fresne von Hohenesche, N; Friedrich, J M; Frolov, V; Gautheron, F; Gavrichtchouk, O P; Gerassimov, S; Geyer, R; Gnesi, I; Gobbo, B; Goertz, S; Gorzellik, M; Grabmüller, S; Grasso, A; Grube, B; Grussenmeyer, T; Guskov, A; Guthörl, T; Haas, F; von Harrach, D; Hahne, D; Hashimoto, R; Heinsius, F H; Herrmann, F; Hinterberger, F; Höppner, Ch; Horikawa, N; d'Hose, N; Huber, S; Ishimoto, S; Ivanov, A; Ivanshin, Yu; Iwata, T; Jahn, R; Jary, V; Jasinski, P; Jörg, P; Joosten, R; Kabuss, E; Ketzer, B; Khaustov, G V; Khokhlov, Yu A; Kisselev, Yu; Klein, F; Klimaszewski, K; Koivuniemi, J H; Kolosov, V N; Kondo, K; Königsmann, K; Konorov, I; Konstantinov, V F; Kotzinian, A M; Kouznetsov, O; Krämer, M; Kroumchtein, Z V; Kuchinski, N; Kuhn, R; Kunne, F; Kurek, K; Kurjata, R P; Lednev, A A; Lehmann, A; Levillain, M; Levorato, S; Lichtenstadt, J; Maggiora, A; Magnon, A; Makke, N; Mallot, G K; Marchand, C; Martin, A; Marzec, J; Matousek, J; Matsuda, H; Matsuda, T; Meshcheryakov, G; Meyer, W; Michigami, T; Mikhailov, Yu V; Miyachi, Y; Moinester, M A; Nagaytsev, A; Nagel, T; Nerling, F; Neubert, S; Neyret, D; Nikolaenko, V I; Novy, J; Nowak, W-D; Nunes, A S; Olshevsky, A G; Orlov, I; Ostrick, M; Panknin, R; Panzieri, D; Parsamyan, B; Paul, S; Peshekhonov, D; Platchkov, S; Pochodzalla, J; Polyakov, V A; Pretz, J; Quaresma, M; Quintans, C; Ramos, S; Regali, C; Reicherz, G; Rocco, E; Rossiyskaya, N S; Ryabchikov, D I; Rychter, A; Samoylenko, V D; Sandacz, A; Sarkar, S; Savin, I A; Sbrizzai, G; Schiavon, P; Schill, C; Schlüter, T; Schmidt, K; Schmieden, H; Schönning, K; Schopferer, S; Schott, M; Shevchenko, O Yu; Silva, L; Sinha, L; Sirtl, S; Slunecka, M; Sosio, S; Sozzi, F; Srnka, A; Steiger, L; Stolarski, M; Sulc, M; Sulej, R; Suzuki, H; Szabelski, A; Szameitat, T; Sznajder, P; Takekawa, S; ter Wolbeek, J; Tessaro, S; Tessarotto, F; Thibaud, F; Uhl, S; Uman, I; Virius, M; Wang, L; Weisrock, T; Wilfert, M; Windmolders, R; Wollny, H; Zaremba, K; Zavertyaev, M; Zemlyanichkina, E; Ziembicki, M; Zink, A

2015-02-13

The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q(2)<0.0015  (GeV/c)(2). From a sample of 63,000 events, the pion electric polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4)  fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.

Autumn photoproduction of carbon monoxide in Jiaozhou Bay, China

Science.gov (United States)

Ren, Chunyan; Yang, Guipeng; Lu, Xiaolan

2014-06-01

Carbon monoxide (CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter (CDOM). In this study, the effects of photobleaching, temperature and the origin (terrestrial or marine) of CDOM on the apparent quantum yields (AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%-6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.

Exclusive vector meson production at HERA

Energy Technology Data Exchange (ETDEWEB)

Szuba, Dorota [Hamburg University, Hamburg (Germany); Collaboration: H1 Collaboration; ZEUS Collaboration

2013-04-15

The exclusive photoproduction of {Upsilon} has been studied with the ZEUS detector in ep collisions at HERA. The exponential slope, b, of the |t|-dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured. This constitutes the first measurement of the |t|-dependence of the {gamma}p{yields}{Upsilon}p cross section. The differential crosssections as a function of t at lower energies of {gamma}p centre-of-mass has been studied in exclusive diffractive photoproduction of J/{psi} mesons with the H1 detector. The exclusive electroproduction of two pions has been measured by the ZEUS experiment. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, assuming that the studied mass range includes the contributions of the {rho}, {rho} Prime and . {rho}'' vector-meson states.

Strangeness photoproduction on the deuterium target

NARCIS (Netherlands)

Shende, Sugat Vyankatesh

2007-01-01

More information on the nucleon excitation function can be gained by studying the photoproduction experiments. In these experiments, the nucleon inside the nucleous is excited by shooting a high energy photon beam. The excited spectrum of the nucleon is then studied by measuring the energy and

High-energy photoproduction of neutral mesons

CERN Document Server

Charity, Tim

1987-01-01

This thesis presents results from the first full period of data-taking of the experiment WA69 at the Omega^'^ectrometer, CERN, Geneva. The experiment used a tagged photon beam of energy 60-180 GeV incident on a liquid hydrogen target to study photoproduction of hadronic states. The various components of the experiment are described, with particular emphasis on the electromagnetic calorimeters, and the associated offline software for event reconstruction and acceptance calculation. The performance of the outer calorimeter is discussed, and the pi^0 detection and reconstruction efficiency is examined by comparison with pi^{+/- } production. Searches for photoproduction of neutral meson states reveal a clear signal for the pi^0, eta^0 , and omega^0 mesons. The cross-section for elastic omega^0 production is estimated, and found to be consistent with the established value of 1 mub. The cross-section for inclusive pi^0 and eta^0 production is studied using the variable Feynman-x (x_{F }), and pi^0 production as a ...

Pion-nucleon vertex function and the Chew-Low model

International Nuclear Information System (INIS)

Nutt, W.T.

1977-01-01

We provide an interpretation of the cutoff function used in the Chew-Low theory of pion-nucleon scattering. It is shown that this function may be related to the pion-pion interaction which is not explicitly considered in the Chew-Low approach. Using a previously developed model for the pion-nucleon vertex function, we then perform a ''parameter-free'' Chew-Low calculation which predicts the P 33 resonance quite well

Gravitational wave from dark sector with dark pion

Energy Technology Data Exchange (ETDEWEB)

Tsumura, Koji [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Yamada, Masatoshi [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Yamaguchi, Yuya, E-mail: ko2@gauge.scphys.kyoto-u.ac.jp, E-mail: m.yamada@thphys.uni-heidelberg.de, E-mail: yy@particle.sci.hokudai.ac.jp [Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)

2017-07-01

In this work, we investigate the spectra of gravitational waves produced by chiral symmetry breaking in dark quantum chromodynamics (dQCD) sector. The dark pion (π) can be a dark matter candidate as weakly interacting massive particle (WIMP) or strongly interacting massive particle (SIMP). For a WIMP scenario, we introduce the dQCD sector coupled to the standard model (SM) sector with classical scale invariance and investigate the annihilation process of the dark pion via the 2π → 2 SM process. For a SIMP scenario, we investigate the 3π → 2π annihilation process of the dark pion as a SIMP using chiral perturbation theory. We find that in the WIMP scenario the gravitational wave background spectra can be observed by future space gravitational wave antennas. On the other hand, when the dark pion is the SIMP dark matter with the constraints for the chiral perturbative limit and pion-pion scattering cross section, the chiral phase transition becomes crossover and then the gravitational waves are not produced.

A measurement of the pion charge radius

International Nuclear Information System (INIS)

Amendolia, S.R.; Badelek, B.; Batignani, G.; Bedeschi, F.; Bertolucci, E.; Bettoni, D.; Bosisio, L.; Bradaschia, C.; Dell'Orso, M.; Fidecaro, F.; Foa, L.; Focardi, E.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Scribano, A.; Tonelli, G.; Codino, A.; Fabbri, F.L.; Laurelli, P.; Satta, L.; Spillantini, P.; Zallo, A.; Counihan, M.J.; Frank, S.G.F.; Harvey, J.; Storey, D.; Menasce, D.; Meroni, E.; Moroni, L.

1984-01-01

We report a measurement of the negative pion electromagnetic form factor in the range of space-like four-momentum transfer 0.014 2 2 . The measurement was made by the NA7 collaboration at the CERN SPS, by observing the interaction of 300 GeV pions with the electrons of a liquid hydrogen target. The form factor is fitted by a pole form with a pion radius of (rho 2 )sup(1/2) = 0.657 +- 0.012 fm. (orig.)

Fast pion production in exclusive neutrino processes

International Nuclear Information System (INIS)

Gershtein, S.S.; Komachenko, Yu.Ya.; Khlopov, M.Yu.

1980-01-01

Single pion production in exclusive neutrino reactions with small momentum transfer to nucleon, induced by neutrino scattering on virtual mesons (reggeons), is considered. The estimation of the contributions to process νA → μπA where A is a nucleon or the target nucleus made by various virtual mesons is presented. In the experimental investigation of such processes the contributions of different mesons may be singled out, thus providing information on the weak; meson-pion (reggeon-pion) transitions

Experiments at INS electron synchrotron

International Nuclear Information System (INIS)

Kato, Sadayuki

1982-01-01

Photoproduction of pion and proton on nuclei in 1 GeV energies region are discussed in order to study the nuclear structure. We illustrate how those reactions can be used to obtain information on short range nature of the pion wave function and on nuclear wave functions. Also we discuss about the dibaryon resonances and the deutron wave function

Capture and transfer of pions in hydrogenous materials

International Nuclear Information System (INIS)

Armstrong, D.S.

1990-05-01

Pionic hydrogen is a short-lived exotic hydrogen isotope in which a negative pion replaces the atomic electron. The formation and subsequent interactions of pionic hydrogen are discussed, with emphasis on the process of pion transfer. Recent results using the pion charge-exchange reaction (π - , π 0 ) obtained at TRIUMF are reviewed. (Author) (35 refs., 3 tabs., 9 figs.)

Diagrammatic Approach to Meson Production in Proton-Proton Collisions near Threshold

International Nuclear Information System (INIS)

Kaiser, Norbert

2000-01-01

We evaluate the threshold T-matrices for the reactions pp → ppπ 0 , pnπ + , ppη, ppω,pΛK + , and pn → pnη in a relativistic Feynman diagram approach. We employ an effective range approximation to take care of the strong S-wave pN and pΛ final-state interaction. We stress that the heavy baryon formalism is not applicable in the NN-system above π-production threshold due to the large external momentum, vertical-bar rvec p vertical-bar ≅ √(Mm π ). The magnitudes of the experimental threshold amplitudes extracted from total cross section data, script-A = (2.7 - 0.3i)fm 4 , script-B = (2.8 - 1.5i)fm 4 , vertical-bar script-C vertical-bar = 1.32 fm 4 , vertical-bar Omega vertical-bar = 0.53 fm 4 , script-K = √(2(vertical-bar)K s (vertical-bar) 2 + (vertical-bar)K t (vertical-bar) 2 ) = 0.38 fm 4 and (vertical-bar)script-D(vertical-bar) = 2.3 fm 4 can be reproduced by (long-range) o ne-pion exchange and short-range vector meson exchanges, with the latter giving the largest contributions. Pion loop effects in pp → ppπ 0 appear to be small. The presented diagrammatic approach requires further tests via studies of angular distributions and polarization observables

The relative cytotoxicity and mutagenicity of cyclobutane pyrimidine dimers and photoproducts in Escherichia coli cells

International Nuclear Information System (INIS)

Tang, Moon-shong; Hrncir, J.; Mitchell, D.; Ross, J.; Clarkson, J.

1986-01-01

In order to calculate the relative cytotoxicity and mutagenicity of cyclobutane pyrimidine dimers and photoproducts, the authors have measured survival and mutation induction in UV-irradiated excision-deficient E. coli uvrA cells, with or without complete photoreactivation of the dimers. Radioimmunoassays with specificity for dimers or photoproducts have shown that maximum photoreactivation eliminates all of the dimers produce up to 10 Jm -2 254-nm light, while it has no effect on photoproducts. These results were confirmed by measuring the frequency of T4 endonuclease V-sensitive sites. Based on the best fit equations for survival and mutation induction, the authors have found that the calculated cytotoxicity of photoproducts is similar to that of dimers; however, the former is much more mutagenic than the latter. (Auth.)

Remarks on the pion-nucleon σ-term

Science.gov (United States)

Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.

2016-09-01

The pion-nucleon σ-term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about 3σ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms.

Goldberger-Treiman discrepancy and the momentum variation of the pion-nucleon form factor and pion decay constant

International Nuclear Information System (INIS)

Coon, S.A.; Scadron, M.D.

1981-01-01

We suggest that the observed 6% Goldberger-Treiman discrepancy is due in part to a 3% variation in the pion-nucleon form factor and in part due to a 3% variation in the pion decay form factor from q 2 =m/sub π/ 2 to q 2 =0

Proton compton scattering in the resonance region

International Nuclear Information System (INIS)

Ishii, Takanobu.

1979-12-01

Differential cross sections of the proton Compton scattering have been measured in the energy range between 400 and 1150 MeV at CMS angles of 130 0 , 100 0 and 70 0 . The recoil proton was detected with a magnetic spectrometer using multi-wire proportional chambers and wire spark chambers. In coincidence with the proton, the scattered photon was detected with a lead glass Cerenkov counter of the total absorption type with a lead plate converter, and horizontal and vertical scintillation counter hodoscopes. The background due to the neutral pion photoproduction, was subtracted by using the kinematic relations between the scattered photon and the recoil proton. Theoretical calculations based on an isobar model with two components, that is, the resonance plus background, were done, and the photon couplings of the second resonance region were determined firstly from the proton Compton data. The results are that the helicity 1/2 photon couplings of P 11 (1470) and S 11 (1535), and the helicity 3/2 photon coupling of D 13 (1520) are consistent with those determined from the single pion photoproduction data, but the helicity 1/2 photon coupling of D 13 (1520) has a somewhat larger value than that from the single pion photoproduction data. (author)

I. Surface properties of neutron-rich nuclei. II. Pion condensation at finite temperature

International Nuclear Information System (INIS)

Kolehmainen, K.A.

1983-01-01

In part I, the energy density formalism, the Thomas-Fermi approximation, and Skyrme-type interactions were used to describe the energy density of a semi-infinite slab of neturon-rich nuclear matter at zero temperature. The existence of a drip phase at low proton fractions is allowed in addition to the more dense nuclear phase, and various bulk properties of both phases are found when the system is in equilibrium. The usual definition of the surface energy is extended to apply to the case where drip is present. Assuming a Fermi function type density profile, a constrained variational calculation is performed to determine the neutron and proton surface diffuseness parameters, the thickness of the neutron skin, and the surface energy. Results are obtained for proton fractions reanging from 0.5 (symmetric nuclear matter) to zero (pure neutron matter) for most Skyrme-type interactions in common use. The results are in close agreement with the predictions of the droplet model, as well as with the results of more exact calculations in those cases where the more exact results exist (only for symmetric or nearly symmetric matter in most cases). Significantly different asymmetry dependences for different interactions are found. In part II, several simple but increasingly complex models are used to calculate the threshold for charged pion condensation in neutron-rich nuclear matter at finite temperature. Unlike in mean field theory descriptions of pion condensation, the effects of thermal excitations of the pion field are included. The thermal pion excitations have two important effects: first, to modify the phase diagram qualitatively from that predicted by mean field theory, and second, to make the phase transition to a spatially nonuniform condensed state at finite temperature always first, rather than second, order

Strangeness photoproduction and hadronic resonances

International Nuclear Information System (INIS)

David, J.C.

1994-09-01

The purpose of this thesis is to study the kaon photoproduction off a proton (γp → K + Λ,γp → K + Σ 0 , γp → K 0 Σ + ), with a photon energy between 0.9 and 2.1 GeV. We use an isobaric model where the amplitudes are computed with Feynman diagrams. The insertion of nucleonic resonances with spin 3/2 and 5/2 is necessary to improve the existing models beyond 1.5 GeV. This step is also necessary to extend the elementary process of photoproduction to electroproduction where the data have been taken with photon energies above 2.0 GeV. The parameters of our models are the coupling constants which appear at each Feynman diagram vertex. They are determined by fitting our models to the experimental data (cross sections, polarization asymmetries). Before performing the minimization we drew some informations about coupling constants from mesonic and electromagnetic decays, and from SU(3) and SU(6) symmetries. In conclusion, the models developed here reproduce the experimental data (E γ ≤ 2.0 GeV) and the two main coupling constants are in good agreement with broken SU(3)-symmetry predictions. (author)

Study of the incident pion deflection in passing through atomic nucleus

International Nuclear Information System (INIS)

Strugalski, Z.; Pawlak, T.; Pluta, J.

1982-01-01

Pion-xenon nucleus collision events at 3.5 GeV/c momentum are studied in which the incident pion is deflected only, without particle production; the deflection is accompanied by emission of nucleons. The multiplicity of the protons emitted is a measure of the nuclear matter layer thickness passed by the pion. It can be concluded that: a) a definite simple relation exists between the pion deflection angle and the thickness of the nuclear matter layer traversed by this pion; b) the deflection angle of the incident pion increases in a definite manner with increasing the thickness of the nuclear matter layer traversed by this pion; c) the average kinetic energy, average longitudinal momentum and average transverse momentum of the protons emitted do not depend on the pion deflection angle

Photoproduction of Phi-mesons at small momentum transfer

International Nuclear Information System (INIS)

Hirschmann, H.

1975-09-01

The differential cross section of the γp → PHI, p → K + K - p reaction is determined for four-momentum transfer (0 - 0.23) GeV 2 and for photon energies (4.6 - 6.62) GeV with very small error. The differential cross section is independent of energy, the dependence on four-momentum transfer is described by an exponential function with a slope parameter (5.2 +- 0.4) GeV -2 . The total cross section of the PHI-meson as well as its differential cross section for elastic scattering at the proton comes out too small by a factor of 0.6 - 0.7 and 0.5 relative to predictions of a combined vector-dominance-quark model. The trajectories of the forward-going K-mesons are recorded in proportional and spark chambers, a threshold Cherenkov counter discriminates against fast pions and electrons, the principle of track reconstruction out of spark coordinates are explained in detail. (BJ) [de

Investigation of pion-nucleus interactions

International Nuclear Information System (INIS)

Moore, C.F.

1992-09-01

This report summarizes the work carried out by personnel from the University of Texas at Austin at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF). The research activities involved experiments done with the Energetic Pion Channel and Spectrometer (EPICS), the Low Energy Pion Channel (LEP), the Pion and Particle Physics Channel (P 3 ), the High Resolution Spectrometer (HRS), and planning a new experimental program associated with the new high-resolution Neutral Meson Spectrometer (NMS) at LAMPF. A brief overview of work supported by this grant is given followed by an account of the study of the double giant resonances in pion double charge exchange on 51 V, 115 In, and 197 Au. This report contains a list of published papers and preprints, abstracts, and invited talks. These papers summarize experiments involving participants supported by this grant and indicate the work accomplished by these participants in this program of medium energy nuclear physics research. Lists of the most recent proposals on which we have participation at LAMPF, proposals which have been approved this past year to run as experiments, personnel who have participated in this research program are included. The research cited in this report is, in many cases, the collaborative effort of many groups associated with research at LAMPF

Experimental studies of pion-nucleus interactions at intermediate energies

International Nuclear Information System (INIS)

1991-01-01

This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting π 0 mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized 3 He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure

Measurement of np→dπ0 cross sections very near threshold

International Nuclear Information System (INIS)

Hutcheon, D.A.; Abegg, R.; Greeniaus, L.G.; Miller, C.A.; Korkmaz, E.; Moss, G.A.; Edwards, G.W.R.; Mack, D.; Olsen, W.C.; Ye, Y.

1989-06-01

We have measured np→dπ 0 cross sections at ten beam energies within 16 MeV of threshold. Total cross sections followed closely the relationship σ tot (np→dπ 0 ) = (1/2)[(184±5)η 3 ]μb, where η is the c.m. pion momentum in units of m π c. The differential cross sections are anisotropic at only 1 MeV (c.m.) above threshold. These results are predicted by Faddeev model calculations and by a perturbative model. Our cross sections are in fair agreement with previous π + d→pp data. (Author) 12 refs., tab., 4 figs

Rho0 Photoproduction in Ultra-Peripheral Relativistic Heavy Ion Collisions with STAR

Energy Technology Data Exchange (ETDEWEB)

STAR Coll

2007-12-20

Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR collaboration presents a measurement of {rho}{sup 0} and direct {pi}{sup +}{pi}{sup -} photoproduction in ultra-peripheral relativistic heavy ion collisions at {radical}s{sub NN} = 200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross-section of {sigma}(AuAu {yields} Au*Au* {rho}{sup 0}) = 530 {+-} 19 (stat.) {+-} 57 (syst.) mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The {rho}{sup 0} transverse momentum spectrum (p{sub T}{sup 2}) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find {sigma}{sub inc}/{sigma}{sub coh} = 0.29 {+-} 0.03 (stat.) {+-} 0.08 (syst.). The ratio of direct {pi}{sup +}{pi}{sup -} production is comparable to that observed in {gamma}p collisions at HERA, and appears to be independent of photon energy. Finally, the measured {rho}{sup 0} spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.

Disoriented chiral condensates and anomalous production of pions

International Nuclear Information System (INIS)

Martinis, M.; Mikuta-Martinis, V.; Crnugelj, J.

1999-01-01

The leading-particle effect and the factorization property of the scattering amplitude in the impact parameter space are used to study semiclassical production of pions in the central region. The mechanism is related to the isospin-uniform solution of the nonlinear σ-model coupled to quark degrees of freedom. The multipion exchange potential between two quarks is derived. It is shown that the soft chiral pion Bremsstrahlung also leads to anomalously large fluctuations in the ratio of neutral to charged pion.. We show that only direct production of pions in the form of an isoscalar coherent pulse without isovector pairs can lead to large neutral-charged fluctuations. (Authors)

Galileo-invariant theory of low energy pion-nucleus scattering

International Nuclear Information System (INIS)

Mach, R.

1980-01-01

Two classes of Galileo-invariant optical models are constructed for pion elastic scattering by nuclei. The first, the two-body model, has been obtained assuming that the pion-bound nucleon dynamics is determined by the pion-nucleon kinetic energy. In deriving the second model, the (A+1)-body dynamics has been taken into account. The technique of effective nucleon momenta maintains the nonlocal propagation of the pion-target nucleon subsystem through the nucleus in contrast with the standard static approximation

Measurement of the Charged-Pion Polarizability

CERN Document Server

Adolph, C.; Alexeev, M.G.; Alexeev, G.D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Austregesilo, A.; Badelek, B.; Balestra, F.; Barth, J.; Baum, G.; Beck, R.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Buchele, M.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Colantoni, M.; Crespo, M.L.; Curiel, Q.; Dalla Torre, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dinkelbach, A.M.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; Finger, M., Jr.; Fischer, H.; Franco, C.; von Hohenesche, N. du Fresne; Friedrich, J.M.; Frolov, V.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Gnesi, I.; Gobbo, B.; Goertz, S.; Gorzellik, M.; Grabmuller, S.; Grasso, A.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Guthorl, T.; Haas, F.; von Harrach, D.; Hahne, D.; Hashimoto, R.; Heinsius, F.H.; Herrmann, F.; Hinterberger, F.; Hoppner, Ch.; Horikawa, N.; d'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Jorg, P.; Joosten, R.; Kabuss, E.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kroumchtein, Z.V.; Kuchinski, N.; Kuhn, R.; Kunne, F.; Kurek, K.; Kurjata, R.P.; Lednev, A.A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G.K.; Marchand, C.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Moinester, M.A.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.I.; Novy, J.; Nowak, W.D.; Nunes, A.S.; Olshevsky, A.G.; Orlov, I.; Ostrick, M.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Peshekhonov, D.; Platchkov, S.; Pochodzalla, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Rocco, E.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Rychter, A.; Samoylenko, V.D.; Sandacz, A.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schluter, T.; Schmidt, K.; Schmieden, H.; Schonning, K.; Schopferer, S.; Schott, M.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Wolbeek, J. ter; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Uhl, S.; Uman, I.; Virius, M.; Wang, L.; Weisrock, T.; Wilfert, M.; Windmolders, R.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.

2015-02-10

The COMPASS collaboration at CERN has investigated pion Compton scattering, $\\pi^-\\gamma\\rightarrow \\pi^-\\gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction $\\pi^-\\mathrm{Ni}\\rightarrow\\pi^-\\gamma\\;\\mathrm{Ni}$, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, $Q^2<0.0015$ (GeV/$c$)$^2$. From a sample of 63 000 events the pion electric polarisability is determined to be $\\alpha_\\pi = (2.0 \\pm 0.6_{\\mbox{stat}} \\pm 0.7_{\\mbox{syst}}) \\times 10^{-4} \\mbox{fm}^3$ under the assumption $\\alpha_\\pi=-\\beta_\\pi$, which relates the electric and magnetic dipole polarisabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction, that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is fou...

High-energy pion beams: Problems and prospects

International Nuclear Information System (INIS)

Chrien, R.E.

1992-01-01

The investigation of relatively unexplored research areas with high energy pion beams requires new facilities. Presently existing meson factories such as LAMPF, TRIUMF and PSI provide insufficient pion fluxes above the 3,3 resonance region for access to topics such as strangeness production with the (π, K) reaction, baryon resonances, rare meson decays, and nuclear studies with penetrating pion beams. The problems and prospects of useful beams for these studies will be reviewed, both for existing facilities such as the AGS and KEK, and for possible future facilities like KAON and PILAC

A new determination of the pion mass

International Nuclear Information System (INIS)

Anagnastopoulos, D.; Belmiloud, D.; El-Khoury, P.; Indelicato, P.; Borchert, G.; Gorke, H.; Gotta, D.; Lenz, S.; Siems, T.; Daum, M.; Frosch, R.; Hauser, P.; Kirch, K.; Simons, L.M.

1996-01-01

Initial measurements concerning the feasibility of a new pion mass determination are described. In a first step, a high-resolution crystal spectrometer was coupled to a cyclotron trap which provides a high pion stopping density, sufficient to check predictions for the cascade process and to measure the stability of the apparatus. A comparison with the measured Cu K α fluorescence line resolves an ambiguity in the value of the pion mass. The preliminary result from this experiment is m π -=(139.57040±0.00045) MeV/c 2 . (orig.)

On two-particle correlations of identical pions

International Nuclear Information System (INIS)

Podgoretskij, M.I.

1991-01-01

The pion generation processes, in which the interference term describing the correlations of identical pions seems to be negative, have been analyzed. It is shown that similar processes can take place, in particular, in nuclear collisions at intermediate energies

Incorporating pion effects into the naive quark model

International Nuclear Information System (INIS)

Nogami, Y.; Ohtuska, N.

1982-01-01

A hybrid of the naive nonrelativistic quark model and the Chew-Low model is proposed. The pion is treated as an elementary particle which interacts with the ''bare baryon'' or ''baryon core'' via the Chew-Low interaction. The baryon core, which is the source of the pion interaction, is described by the naive nonrelativistic quark model. It turns out that the baryon-core radius has to be as large as 0.8 fm, and consequently the cutoff momentum Λ for the pion interaction is < or approx. =3m/sub π/, m/sub π/ being the pion mass. Because of this small Λ (as compared with Λapprox. nucleon mass in the old Chew-Low model) the effects of the pion cloud are strongly suppressed. The baryon masses, baryon magnetic moments, and the nucleon charge radii can be reproduced quite well. However, we found it singularly difficult to fit the axial-vector weak decay constant g/sub A/

Inclusive production of ρ0 mesons on protons with photons, pion and kaon beams in the energy range from 65 to 175 GeV

International Nuclear Information System (INIS)

Hofmann, R.P.

1991-03-01

Cross sections of the inclusive photoproduction and hadroproduction of the ρ 0 (770) meson on a liquid hydrogen target are given as functions of p perpendicular to (varying from 0 to 2 GeV) and x F (-0.1 to 1.0) where the photon energy range is 65 to 175 GeV and the hadrons are charged π and K of the energies 80 and 140 GeV. The ρ-signal is quantified in fits to the π + π - -mass distributions accounting for a downward mass shift of the ρ 0 peak known from the diffractive ρ 0 -production. This mass shift is shown to be significantly different from zero also in the low-x F -low-p perpendicular to region in both photon and hadron data. The ratios d 2 σ/dp perpendicular to dx F (γp→ρ 0 X)/d 2 σ/dp perpendicular to dx F (π/Kp→ρ 0 X) give an x F - and π perpendicular to - dependent VMD-factor. Comparison of hadron and photon cross sections shows a difference due to the pointlike photon-hadron-coupling at large p perpendicular to . This onset is in good quantitative agreement with the predictions of the LUCIFER-Monte-Carlo. The low and medium x F -range can be described by a quark-antiquark-fusion-model. The high x F -regions show distinct decay angular distributions matching the predictions for diffractive photoproduction and the one-pion-exchange model respectively. (orig.) [de

Measurement of elastic φ photoproduction at HERA

International Nuclear Information System (INIS)

Derrick, M.; Krakauer, D.; Magill, S.

1996-01-01

The production of φ mesons in the reaction e + p→e + φp(φ→K + K - ) at a median Q 2 of 10 -4 GeV 2 has been studied with the ZEUS detector at HERA. The differential φ photoproduction cross section dσ/dt has an exponential shape and has been determined in the kinematic range 0.1 2 and 60 γp→φp 0.96±0.19 -0.18 +0.21 μb has been obtained by extrapolating to t=0. When compared to lower energy data, the results show a weak energy dependence of both σ γp→φp and the slope of the t distribution. The φ decay angular distributions are consistent with s-channel helicity conservation. From lower energies to HERA energies, the features of φ photoproduction are compatible with those of a soft diffractive process. (orig.)

Low energy pion detection by a silicon surface barrier telescope

International Nuclear Information System (INIS)

Sealock, R.M.; Caplan, H.S.; Leung, M.K.

1978-01-01

Four telescopes of three (2-ΔE, 1-E) silicon surface barrier detectors each, mounted in the focal plane of a magnetic spectrometer, have been used to detect positive pions in the energy range from 4.7-17.9 MeV and negative pions from 14.1-17.9 MeV. Positive pions from 4.7-12.7 MeV were stopped in the third detector while positive and negative pions from 14.1-17.9 MeV were detected in transmission. For energies greater than 7.4 MeV aluminum moderators were placed in front of the first detector to degrade the pion energy. Energy spectra show well resolved pion peaks with extremely low background. Double differential cross sections for the 12 C(e,π + ) 12 B,e' reaction have been measured. (Auth.)

Characteristics of the pion production and nucleon emission processes in pion-carbon nuclear collisions at 40 GeV/.c

International Nuclear Information System (INIS)

Strugalski, Z.; Sultanov, M.

1992-01-01

Experimental data on pion-carbon nucleus collisions are presented. The momentum and energy spectra of protons emitted from the target nucleus do not depend on the intensity of the pion production in the collisions. 6 refs.; 12 figs.; 12 tabs

Investigation of Compton effect on π-meson and charged pion polarizability

International Nuclear Information System (INIS)

Antipov, Yu.M.; Batarin, V.A.; Bezzubov, V.A.

1986-01-01

The results of an experiment aimed at the study of the 40 GeV/c pion radiative scattering on nuclei at small momentum transfers are presented. Compton effect on the pion was investigated and the charged pion polarizability was measured. The pion Compton-effect cross section dependence on the incident photon energy ω' 1 (rest pion frame) was measured in the 100 - 600 MeV range. The polarizability of charged pion from the analysis of Compton-effect events has been found to be β π =-α π =(-6.9 ± 1.4 stat. ± 1.2 syst. )x10 -43 cm 3 and the sun of pion electrical α π and magnetic β π polarizability has been estimated to be in agreement with theoretical predictions: α π +β π ≅ 0

Status of PILAC: A pion linac facility for 1-GeV pion physics at LAMPF

International Nuclear Information System (INIS)

Thiessen, H.A.

1990-01-01

A Pion Linac (PILAC) is being designed for LAMPF. Together with its high resolution beam line and spectrometer, the system is optimized to provide 10 9 pions per second on target and 200-keV resolution for the (π + ,K + ) reaction at 920, MeV. There will also be an achromatic beam line capable of utilizing the maximum energy available, thus opening up the possibility of a broad experimental program as is being discussed at this workshop. 12 figs

Chiral pion dynamics for spherical nucleon bags

International Nuclear Information System (INIS)

Vento, V.; Rho, M.; Nyman, E.M.; Jun, J.H.; Brown, G.E.; CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette

1980-01-01

A chirally symmetric quark-bag model for the nucleon is obtained by introducing an explicit, classical, pion field exterior to the bag. The coupling at the bag surface is determined by the requirement of a conserved axial-vector current. The pion field satisfies equations of motion corresponding to the non-linear sigma-model. We study on this paper the simplified case where the bag and the pion field are spherically symmetric. Corrections due to gluon exchange between the quarks are ignored along with other interactions which split the N- and Δ-masses. The equations of motion for the pion field are solved and we find a substantial pion pressure at the bag surface, along with an attractive contribution to the nucleon self-energy. The total energy of the system, bag plus meson cloud, turns out to be approximately Msub(n)c 2 for a wide range of bag radii, from 1.5 fm down to about 0.5 fm. Introduction of a form factor for the pion would extend the range of possible radii to even smaller values. We propose that the bag with the smallest allowed radius be identified with the 'little bag' discussed before. One surprising result of the paper is that as long as one restricts to spherically symmetric bags, restoring chiral symmetry to the bag model makes the axial-vector current coupling constant gsub(A) to be always too large compared with the experimental value for any bag radius, suggesting a deviation from spherical symmetry for the intrinsic bag wave functions of the 'ground-state' hadrons. (orig.)

Strangeness production with protons and pions

International Nuclear Information System (INIS)

Dover, C.B.

1993-01-01

We discuss the spectrum of physics questions related to strangeness which could be addressed with intense beams of protons and pions in the few GeV region. We focus on various aspects of strangeness production, including hyperon production in pp collisions, studies of hyperon-nucleon scattering, production of hypernuclei in proton and pion-nucleus collisions, and spin phenomena in hypernuclei

Coherent and chaotic generation of pions from relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Nakamura, Hiroki; Seki, Ryoichi

2002-01-01

Based on the recent NA44 and WA98 two- and three-pion interferometry data together with the WA98 pion multiplicity information, we observe that the pions may be mostly emitted from chaotic sources in the peripheral events and coherent pions are mostly generated in the central events. A more refined analysis would be needed, however, to make our observation conclusive by quantifying various effects such as resonance formation of the emerging pions and also experimental uncertainties

Quantum effects and colour transparency in charmonium photoproduction on nuclei

International Nuclear Information System (INIS)

Kopeliovich, B.Z.; Zakharov, B.G.

1991-01-01

A rigorous quantum-mechanical treatment of colour transparency effects in diffractive photoproduction of c-barc-pairs on nuclei was developed. The evolution of the c-barc wave function during propagating through a nucleus is rather a considerable distortion of its form, than a trivial attenuation. One of the manifestations of the quantum effects is a nuclear antishadowing of Ψ' yield, i.e. transparency above one. On the contrary, a considerable nuclear shadowing is predicted for the photoproduction of J/Ψ, which has a much smaller absorption cross section than Ψ'. 26 refs.; 5 figs.; 1 tab

Tensor polarization in pion-deuteron elastic scattering

International Nuclear Information System (INIS)

Holt, R.J.; Freeman, W.S.; Geesaman, D.F.

1985-01-01

During this year the analysis of measurements of t 20 in π-d elastic scattering was completed and a final summary manuscript was prepared for publication. The results consists of angular distributions of the deuteron tensor polarization in π-d elastic scattering at pion energies of 140, 180, 220 and 256 MeV. Theoretical calculations in which the effects of pion absorption on the elastic channel are small reproduce the data. No rapid angular or energy dependence was found near a pion energy of 134 MeV, where another experiment at SIN has suggested the existence of dibaryon resonances

Single pion production in neutrino-nucleon interactions

Science.gov (United States)

Kabirnezhad, M.

2018-01-01

This work represents an extension of the single pion production model proposed by Rein [Z. Phys. C 35, 43 (1987)., 10.1007/BF01561054]. The model consists of resonant pion production and nonresonant background contributions coming from three Born diagrams in the helicity basis. The new work includes lepton mass effects, and nonresonance interaction is described by five diagrams based on a nonlinear σ model. This work provides a full kinematic description of single pion production in the neutrino-nucleon interactions, including resonant and nonresonant interactions in the helicity basis, in order to study the interference effect.

Induction of UV photoproducts and DNA damage by solar simulator UV irradiation

International Nuclear Information System (INIS)

Wolfreys, A.; Henderson, L.; Clingen, P.

1997-01-01

The recent increased incidence of skin cancer and the depletion of the ozone layer has increased interest in the ultraviolet (UV) component of natural sunlight and its role in the induction of skin cancer. Previous research on UV radiation has concentrated on UVC (254nm) but, as only UVB and UVA are present in natural sunlight, its relevance is unknown. We have investigated the induction of two forms of direct DNA damage - the pyrimidine dimer and the (6-4) photoproduct - in human DNA repair deficient XP-G (Xeroderma pigmentosum group G) lymphoblastoid cells following exposure to simulated sunlight. As exposure to natural sunlight is highly variable, a solar simulator lamp was used which is known to mimic natural sunlight at midday in Central Europe. Cells were irradiated on ice to minimise DNA repair and the relative induction of pyrimidine dimers and (6-4) photoproducts was measured using specific monoclonal antibodies and a computer assisted image analysis system. A time dependent increase in both cyclobutane dimer and (6-4) photoproduct antibody binding sites was seen. The increases in pyrimidine dimer and (6-4) photoproduct antibody binding sites differed to that reported with natural sunlight in the UK but was similar to that seen with a similar solar simulator lamp

High-energy photoproduction and electroproduction of π+ on nuclei

International Nuclear Information System (INIS)

Kuz'menko, V.S.; Mitrofanova, A.V.; Noga, V.I.; Ranyuk, Y.N.; Sorokin, P.V.; Telegin, Y.N.; Blomqvist, I.; Jonsson, G.G.; Freed, N.

1977-01-01

Cross sections for photoproduction and electroproduction of π + on 27 Al and 51 V leading to bound states in the daughter nuclei have been measured at Kharkov in the energy range 600--1200 MeV by use of the activation method. Careful comparison is made to other recent results obtained at intermediate and high energies. Agreement is found between the present data and results of earlier work carried out at Lund and DESY. Discrepancies between photoproduction data taken at different laboratories are attributed to differences between methods of background subtraction. Relative bremsstrahlung-induced to electron-induced yield ratios are compared with predictions based on the Dalitz-Yennie formalism for virtual-photon spectra

Roy-Steiner-equation analysis of pion-nucleon scattering

Science.gov (United States)

Meißner, U.-G.; Ruiz de Elvira, J.; Hoferichter, M.; Kubis, B.

2017-03-01

Low-energy pion-nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion-nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion-nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.

Mechanisms for pion production in heavy ion collisions

International Nuclear Information System (INIS)

Pfeiffer, M.

1991-01-01

In the following contribution some aspects concerning pion production in heavy ion collisions will be discussed. After a general introduction the properties of pions and the Δ-resonance will be briefly mentioned. In the following section some points refering to the pion production in a relativistic heavy ion collision will be discussed. In addition, the basic ideas of the applied models will be shown. In the last part results from existing experiments and possible interpretations will be presented. (orig.)

A possible form of the pion's structure function

International Nuclear Information System (INIS)

Long Ming; Huang Tao

1986-01-01

The pion's structure function behaviour is discussed by using the Fock state expansion of the hadronic wave function in QCD in this paper. As an example, we employ a model wave function of the Fock state in the light-cone and assume a Regge behaviour of a weight function for higher Fock states, and we get a possible form of the pion's structure function. This form is consistent with experimental data of the pion's structure function

Pion condensation and instabilities: current theory and experiment

International Nuclear Information System (INIS)

Gyulassy, M.

1980-05-01

Current calculations of pion condensation phenomena in symmetric nuclear matter are reviewed. The RPA and MFA methods are compared. Latest results [LBL-10572] with a relativistic MFA theory constrained by bulk nuclear properties are presented. The differences between equilibrium (condensation) and nonequilibrium (dynamic) instabilities are discussed. Finally, two-proton correlation experiments aimed at looking for critical scattering phenomena and two-pion correlation experiments aimed at looking for pion field coherence are analyzed. 10 figures, 2 tables

Radiative pion-proton scattering

International Nuclear Information System (INIS)

Ho-Kim, Q.; Lavine, J.P.

1977-01-01

The results are presented of a non-relativistic calculation of the π +- proton bremsstrahlung cross section at the pion kinetic energy of 298 MeV for backward photon angles. The pion-nucleon interaction is given by models that are based on the p-wave Chew-Low theory. An interaction current is included in an attempt to make the overall bremsstrahlung amplitude gauge-invariant. The predicted cross sections show little of the expected resonance, and are in fair agreement with the data. The authors have also calculated the cross sections at other kinetic energies, and have studied effects of the off-mass-shell electromagnetic vertex. (Auth.)

Pion scattering and nuclear dynamics

International Nuclear Information System (INIS)

Johnson, M.B.

1988-01-01

A phenomenological optical-model analysis of pion elastic scattering and single- and double-charge-exchange scattering to isobaric-analog states is reviewed. Interpretation of the optical-model parameters is briefly discussed, and several applications and extensions are considered. The applications include the study of various nuclear properties, including neutron deformation and surface-fluctuation contributions to the density. One promising extension for the near future would be to develop a microscopic approach based on powerful momentum-space methods brought to existence over the last decade. In this, the lowest-order optical potential as well as specific higher-order pieces would be worked out in terms of microscopic pion-nucleon and delta-nucleon interactions that can be determined within modern meson-theoretical frameworks. A second extension, of a more phenomenological nature, would use coupled-channel methods and shell-model wave functions to study dynamical nuclear correlations in pion double charge exchange. 35 refs., 11 figs., 1 tab

Exclusive photoproduction of Upsilon in pPb collisions at LHC energies

International Nuclear Information System (INIS)

Dutta, Dipanwita; Chudasama, Ruchi; Mohanty, A.K.

2014-01-01

Recent results of exclusive photoproduction of heavy vector mesons at LHC energies by ALICE and LHCb in pp, pPb and PbPb Ultraperipheral collisions (UPC) confirmed the expectations that UPCs are a very promising probe to study the gluon distributions in nucleons and in nuclei at small x. In this work, we have estimated the photoproduction of γ in pPb collisions at √s NN = 5.02 TeV in the framework of perturbative two-gluon exchange formalism employing various parametrization of gluon distributions functions

Charged pion coherent production in nucleus-nucleus collisions at incident energies between 86 and 330 MeV/nucleon

International Nuclear Information System (INIS)

Fassnacht, P.

1984-01-01

We have studied pion production in nucleus-nucleus collisions at foward angles for about twenty projectile target combinations. The incident energies were below or around 300 MeV/nucleon which is the threshold of the elementary reaction NN → NNπ. The study of the inclusive spectra shows some new ideas: shell effects in pion production, collective resonances excitations. These spectra have been analyzed following different models: hard-scattering models which describe the interaction on the basis of the elementary reaction NN → NNπ, statistical model and the pionic cloud model which is a coherent description of the interaction. In the study of the exclusive reactions, we established some empiric rules concerning the cross-section variations. These exclusive spectra were then analyzed in the framework of two-models: the semi-phenomenological model and the pionic fusion [fr

Probing nuclear correlations with pion-nucleus double charge exchange

International Nuclear Information System (INIS)

Ginocchio, J.N.

1988-01-01

In this paper we have calculated the lowest order pion double charge reaction mechanism using shell model wavefunctions of medium weight nuclei. We have the sequential reaction mechanism in which the pion undergoes two single-charge exchange scatterings on the valence neutrons. The distortion of the incoming, intermediate, and outgoing pion are included. The closure approximation is made for the intermediate states with an average excitation energy used in the pion propagator. The double-charge exchange is assumed to take place on the valence nucleons which are assumed to be in one spherical shell model orbital. 34 refs., 5 figs., 3 tabs

Pion double charge exchange and nuclear structure

International Nuclear Information System (INIS)

Ginocchio, J.N.

1987-01-01

Pion double charge exchange to both the double-analog state and the ground state is studied for medium weight nuclei. The relative cross section of these two transitions and the importance of nuclear structure as a function of pion kinetic energy is examined. 16 figs., 5 tabs

The bag model and the Nambu-Goldstone pion

International Nuclear Information System (INIS)

Lee, H.C.; Ho-Kim, Q.

1983-01-01

The MIT bag model for the pion is improved and extended in such a way that the pion does not have spurious center-of-mass motions; perturbative gluon contributions to the pion mass msub(π) and decay constant fsub(π) are both calculated to lowest order in αsub(s). The pion is a Nambu-Goldstone boson in the sense that the vacuum in the bag refers to massive constituent quarks, but not so massless current quarks. The transformation of Nambu and Jona-Lasinio between massive and massless quarks is utilized in the computation of fsub(π), the result of which strongly suggests that quarks in the pion are correlated, characterized by a correlation momentum which is proportional 300 MeV/c. The vacuum expectation value for the massless quark condensate is calculated to be proportional0.04 GeV 3 , corresponding to a current quark mass of proportional4 MeV. The requirement that msub(π) approaches zero in a manner consistent with PCAC constrains the bag energy to be msub(π)/4. (orig.)

Distortion of two-pion interferometry by multipion correlations

International Nuclear Information System (INIS)

Zhang, W.N.; Liu, Y.M.; Wang, S.; Liu, Q.J.; Jiang, J.; Keane, D.; Shao, Y.; Chu, S.Y.; Fung, S.Y.

1993-01-01

Multipion correlations arising from the symmetrization of the n-pion wave function affect the extracted information from two-pion correlation measurements. The influence of multipion correlations on a sample of like-pion pairs can be expressed as a multipion correlation factor, the distribution of which offers good sensitivity to the multipion correlation effect. Analyses of the multipion correlation factor for two Bevalac streamer chamber data samples of 2.1A GeV Ne+Pb and 1.8A GeV Ar+Pb collisions show that the multipion correlation effect in the former sample is greater than in the latter. This result mainly arises from the fact that the pion source for Ne projectiles is smaller than for Ar projectiles. The residual correlations in the reference sample are related to the multipion correlation factor in multipion events, which can be expressed as a residual correlation factor. The influence of multipion correlations on two-pion interferometry analyses arises from the ratio of the residual correlation factor to the multipion correlation factor

Exclusive electroproduction of two pions at HERA

International Nuclear Information System (INIS)

Abramowicz, H.; Ashery, D.; Gueta, O.; Gurvich, E.; Ingbir, R.; Kananov, S.; Levy, A.; Stern, A.

2012-01-01

The exclusive electroproduction of two pions in the mass range 0.4 ππ -1 . The analysis was carried out in the kinematic range of 2 2 2 , 32 2 , where Q 2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, vertical stroke F(M ππ ) vertical stroke, assuming that the studied mass range includes the contributions of the ρ, ρ' and ρ'' vector-meson states. The masses and widths of the resonances were obtained and the Q 2 dependence of the cross-section ratios σ(ρ'→ππ)/ σ(ρ) and σ(ρ''→ππ)/ σ(ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e + e - →π + π - . (orig.)

Antiquark distributions in pion and nucleon

International Nuclear Information System (INIS)

Arakelian, G.G.; Boreskov, K.G.; Kaidalov, A.B.

1980-01-01

Relation between the antiquark distributions in pion and nucleon, based on the π-exchange hypothesis, is derived. The antiquark distributions in proton are calculated with the data on the valence antiquark distribution in pion as input. Results of the calculation agree with the experimental data. The role of the peripheral mechanism in formulation of the initial conditions for the chromodynamical evolution equations is discussed

Pion condensation and neutron star dynamics

International Nuclear Information System (INIS)

Kaempfer, B.

1983-01-01

The question of formation of pion condensate via a phase transition in nuclear matter, especially in the core of neutron stars is reviewed. The possible mechanisms and the theoretical restrictions of pion condensation are summarized. The effects of ultradense equation of state and density jumps on the possible condensation phase transition are investigated. The possibilities of observation of condensation process are described. (D.Gy.)

Galileo-invariant theory of low energy pion-nucleus scattering. II

International Nuclear Information System (INIS)

Mach, R.

1983-01-01

Two classes of Galileo-invariant optical models are constructed for pion elastic scattering by nuclei. The former, the two-body model, was obtained assuming that the pion-bound nucleon dynamics is determined by the pion-nucleon kinetic energy. In deriving the latter model, the (A+1)-body dynamics was taken into account. The technique of effective nucleon momenta maintains the nonlocal propagation of the pion-target nucleon subsystem through the nucleus in contrast with the standard static approximation. (author)

First measurement of the helicity asymmetry E in η photoproduction on the proton

Science.gov (United States)

Senderovich, I.; Morrison, B. T.; Dugger, M.; Ritchie, B. G.; Pasyuk, E.; Tucker, R.; Brock, J.; Carlin, C.; Keith, C. D.; Meekins, D. G.; Seely, M. L.; Rönchen, D.; Döring, M.; Collins, P.; Adhikari, K. P.; Adikaram, D.; Akbar, Z.; Anderson, M. D.; Anefalos Pereira, S.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Credé, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Joosten, S.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Klein, F. J.; Kubarovsky, V.; Kunkel, M. C.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Mattione, P.; McKinnon, B.; Meyer, C. A.; Mineeva, T.; Mokeev, V.; Montgomery, R. A.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Net, L. A.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Park, K.; Park, S.; Peng, P.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Simonyan, A.; Skorodumina, Iu.; Smith, G. D.; Sober, D. I.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Tian, Ye; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2016-04-01

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the η photoproduction reaction γp → ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.

First measurement of the helicity asymmetry E in η photoproduction on the proton

Energy Technology Data Exchange (ETDEWEB)

Senderovich, I.; Morrison, B. T.; Dugger, M.; Ritchie, B. G.; Pasyuk, E.; Tucker, R.; Brock, J.; Carlin, C.; Keith, C. D.; Meekins, D. G.; Seely, M. L.; Rönchen, D.; Döring, M.; Collins, P.; Adhikari, K. P.; Adikaram, D.; Akbar, Z.; Anderson, M. D.; Anefalos Pereira, S.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Credé, V.; D' Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Joosten, S.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Klein, F. J.; Kubarovsky, V.; Kunkel, M. C.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Mattione, P.; McKinnon, B.; Meyer, C. A.; Mineeva, T.; Mokeev, V.; Montgomery, R. A.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Net, L. A.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Park, K.; Park, S.; Peng, P.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Simonyan, A.; Skorodumina, Iu.; Smith, G. D.; Sober, D. I.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Tian, Ye; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wei, X.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2016-01-26

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the η photoproduction reaction γ p → ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich–Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.

Virtual photons in the pion form factors and the energy-momentum tensor

Energy Technology Data Exchange (ETDEWEB)

Kubis, Bastian E-mail: b.kubis@fz-juelich.de; Meissner, Ulf-G. E-mail: ulf-g.meissner@fz-juelich.de

2000-05-22

We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii.

Virtual photons in the pion form factors and the energy-momentum tensor

International Nuclear Information System (INIS)

Kubis, Bastian; Meissner, Ulf-G.

2000-01-01

We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii

Matching Pion-Nucleon Roy-Steiner Equations to Chiral Perturbation Theory

Science.gov (United States)

Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.

2015-11-01

We match the results for the subthreshold parameters of pion-nucleon scattering obtained from a solution of Roy-Steiner equations to chiral perturbation theory up to next-to-next-to-next-to-leading order, to extract the pertinent low-energy constants including a comprehensive analysis of systematic uncertainties and correlations. We study the convergence of the chiral series by investigating the chiral expansion of threshold parameters up to the same order and discuss the role of the Δ (1232 ) resonance in this context. Results for the low-energy constants are also presented in the counting scheme usually applied in chiral nuclear effective field theory, where they serve as crucial input to determine the long-range part of the nucleon-nucleon potential as well as three-nucleon forces.

Measurement of π-p→ηn from threshold to pπ-=747 MeV/c

International Nuclear Information System (INIS)

Prakhov, S.; Nefkens, B.M.K.; Clajus, M.; Marusic, A.; McDonald, S.; Phaisangittisakul, N.; Price, J.W.; Starostin, A.; Tippens, W.B.; Allgower, C.E.; Spinka, H.; Arndt, R.A.; Briscoe, W.J.; Shafi, A.; Strakovsky, I.I.; Workman, R.L.; Bekrenev, V.; Koulbardis, A.; Kozlenko, N.; Kruglov, S.

2005-01-01

The differential cross section for η production in reaction π - p→ηn has been measured over the full angular range at seven incident π - beam momenta from threshold to p π - =747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total η production cross section σ tot is obtained by integration of dσ/dΩ. Starting at threshold, σ tot rises rapidly, as expected for S-wave-dominated production. The features of the π - p→ηn cross section are strikingly similar to those of the SU(3) flavor-related process K - p→ηΛ. Comparison of the π - p→ηn reaction is made with η photoproduction

Various models for pion probability distributions from heavy-ion collisions

International Nuclear Information System (INIS)

Mekjian, A.Z.; Mekjian, A.Z.; Schlei, B.R.; Strottman, D.; Schlei, B.R.

1998-01-01

Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases which will be mentioned. The pion probability distributions for these various cases are compared. Comparison of the pion laser model and Bose-Einstein condensation in a laser trap and with the thermal model are made. The thermal model and hydrodynamic model are also used to illustrate why the number of pions never diverges and why the Bose-Einstein correction effects are relatively small. The pion emission strength η of a Poisson emitter and a critical density η c are connected in a thermal model by η/n c =e -m/T <1, and this fact reduces any Bose-Einstein correction effects in the number and number fluctuation of pions. Fluctuations can be much larger than Poisson in the pion laser model and for a negative binomial description. The clan representation of the negative binomial distribution due to Van Hove and Giovannini is discussed using the present description. Applications to CERN/NA44 and CERN/NA49 data are discussed in terms of the relativistic hydrodynamic model. copyright 1998 The American Physical Society

Carbon Monoxide Photoproduction from Particles and Solutes in the Delaware Estuary under Contrasting Hydrological Conditions.

Science.gov (United States)

Song, Guisheng; Richardson, John D; Werner, James P; Xie, Huixiang; Kieber, David J

2015-12-15

Full-spectrum, ultraviolet (UV), and visible broadband apparent quantum yields (AQYs) for carbon monoxide (CO) photoproduction from chromophoric dissolved organic matter (CDOM) and particulate organic matter (POM) were determined in the Delaware Estuary in two hydrologically contrasting seasons in 2012: an unusually low flow in August and a storm-driven high flow in November. Average AQYs for CDOM and POM in November were 10 and 16 times the corresponding AQYs in August. Maximum AQYs in November occurred in a midestuary particle absorption maximum zone. Although POM AQYs were generally smaller than CDOM AQYs, the ratio of the former to the latter increased substantially from the UV to the visible. In both seasons, UV solar radiation was the primary driver for CO photoproduction from CDOM whereas visible light was the principal contributor to POM-based CO photoproduction. CDOM dominated CO photoproduction in the uppermost water layer while POM prevailed at deeper depths. On a depth-integrated basis, the Delaware Estuary shifted from a CDOM-dominated system in August to a POM-dominated system in November with respect to CO photoproduction. This study reveals that flood events may enhance photochemical cycling of terrigenous organic matter and switch the primary photochemical driver from CDOM to POM.

Exclusive photoproduction of quarkonium at the LHC energies within the color dipole approach

Energy Technology Data Exchange (ETDEWEB)

Ducati, M. B. Gay; Griep, M. T.; Machado, M. V. T. [High Energy Physics Phenomenology Group, GFPAE IF-UFRGS, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil)

2015-04-10

The exclusive photoproduction of ψ(2S) meson was investigated and the coherent and the incoherent contributions were evaluated. The light-cone dipole formalism was considered in this analysis and predictions are done for PbPb collisions at the CERN-LHC energy of 2.76 TeV. A comparison is done to the recent ALICE Collaboration data for the ψ(1S) state photoproduction with good agreement.

Study on Charged Top-Pion Decay Processes

Institute of Scientific and Technical Information of China (English)

WANG Xue-Lei; XU Wen-Na; DU Lin-Lin

2004-01-01

In the framework of top-color assisted technicolor (TC2) theory, we study the four decay processes of charged top-pion, i.e., П+t → t-b, П+t → c-b, П+t → W+γ П+t → W+ Z0. The decay branching ratio of these modes are calculated. The results show that the main decay channels of charged top-pion are the tree level modes: П+t → t-b and П+t → c-b. Light П+t is easier to be detected than heavy one at future coliders. So, the study provides us with some useful informations to search for charged top-pion.

On the use of distributions of stopping pions as an indicator of the spatial distribution of the high-LET dose in negative pion radiotherapy

International Nuclear Information System (INIS)

Brenner, D.J.

1991-01-01

A semi-empirical across the treatment volume of a therapeutic negative pion beam. Such beams deliver dose partially at high LET (through alphas and heavier particles produced both directly in pion stars and via intermediate star-produced neutrons), and partially at low LET (through scattering of pions, electrons and muons, as well as protons produced directly from pion stars and via intermediate neutrons). The problem is how to understand the spatial distribution of the high-LET dose, which is responsible for the potentially improved biological response in the treatment volume

Data on the electromagnetic pion form factor and p-wave

International Nuclear Information System (INIS)

Dubnicka, S.; Meshcheryakov, V.A.; Milko, J.

1980-01-01

The pion form factor absolute value data (free of the omega meson contribution) are unified with the P-wave isovector ππ phase shift. The resultant real and imaginary parts of the pion form factor are described by means of the Pade approximation. All the data, which involve the pion form factor experimental points from the range of momenta - 0.8432 GeV 2 2 , the pion charge radius, and the P-wave isovector ππ phase shift in the elastic region (including also the generally accepted value of the scattering length) are mutually consistent. The data themselves through the Pade approximation reveal that the aforementioned consistency can be achieved only if the pion form factor left-hand cut from the second Riemann sheet is taken into account. Almost in all of the considered Pade approximations one stable pion form factor zero is found in the space-like region, which might indicate the existence of a diffraction minimum in the differential cross section for elastic e - π scattering as a consequence of the constituent structure of the pion like in the case of the electron elastic scattering on nuclei

Measurement of antideuteron photoproduction and a search for heavy stable charged particles at HERA

CERN Document Server

Aktas, A; Anthonis, T; Asmone, A; Babaev, A; Backovic, S; Bähr, J; Baranov, P; Barrelet, E; Bartel, Wulfrin; Baumgartner, S; Becker, J; Beckingham, M; Behnke, O; Behrendt, O; Belousov, A; Berger, Christoph; Berndt, T; Bizot, J C; Boenig, M O; Böhme, J; Boudry, V; Bracinik, J; Brisson, V; Broker, H B; Brown, D P; Bruncko, Dusan; Bunyatyan, A; Buschhorn, G; Büsser, F W; Bystritskaya, L; Campbell, A J; Caron, S; Cassol-Brunner, F; Cerny, K; Chekelian, V; Collard, Caroline; Contreras, J G; Coppens, Y R; Coughlan, J A; Cox, B E; Cozzika, G; Cvach, J; Dainton, J B; Dau, W D; Daum, K; de Roeck, A; De Wolf, E A; Delcourt, B; Demirchyan, R; Desch, Klaus; Diaconu, C; Dingfelder, J; Dodonov, V; Dubak, A; Duprel, C; Eckerlin, G; Efremenko, V; Egli, S; Eichler, R; Eisele, F; Ellerbrock, M; Elsen, E; Erdmann, M; Erdmann, W; Faulkner, P J W; Favart, L; Fedotov, A; Felst, R; Ferencei, J; Fleischer, M; Fleischmann, P; Fleming, Y H; Flucke, G; Flügge, G; Fomenko, A; Foresti, I; Formánek, J; Franke, G; Frising, G; Gabathuler, E; Gabathuler, K; Garutti, E; Garvey, J; Gayler, J; Gerhards, R; Gerlich, C; Ghazaryan, S; Görlich, L; Gogitidze, N; Gorbounov, S; Grab, C; Grassler, J; Greenshaw, T; Gregori, M; Grindhammer, G; Gwilliam, C; Haidt, D; Hajduk, L; Haller, J; Hansson, M; Heinzelmann, G; Henderson, R C W; Henschel, H; Henshaw, O; Heremans, R; Herrera-Corral, G; Herynek, I; Heuer, R D; Hildebrandt, M; Hiller, K H; Hoffmann, D; Horisberger, R P; Hoting, P; Hovhannisyan, A; Ibbotson, M; Ismail, M; Jacquet, M; Janauschek, L; Janssen, X; Jemanov, V; Johnson, D P; Jönsson, L B; Jung, H; Kant, D; Kapichine, M; Karlsson, M; Katzy, J; Keller, N; Kennedy, J; Kenyon, I R; Kiesling, C; Klein, M; Kleinwort, C; Klimkovich, T; Kluge, T; Knies, G; Knutsson, A; Koblitz, B; Korbel, V; Kostka, P; Koutouev, R; Kropivnitskaya, A; Kroseberg, J; Kuckens, J; Kuhr, T; Landon, M P J; Lange, W; Lastoviicka, T; Laycock, P; Lebedev, A; Leissner, B; Lemrani, R; Lendermann, V; Levonian, S; Lindfeld, L; Lipka, K; List, B; Lobodzinska, E; Loktionova, N; López-Fernandez, R; Lubimov, V; Lüders, H; Lüke, D; Lux, T; Lytkin, L; Makankine, A; Malden, N; Malinovski, E; Mangano, S; Marage, P; Marks, J; Marshall, R; Martisikova, M; Martyn, H U; Maxfield, S J; Meer, D; Mehta, A; Meier, K; Meyer, A B; Meyer, H; Meyer, J; Michine, S; Mikocki, S; Milcewicz, I; Milstead, D; Mohamed, A; Moreau, F; Morozov, A; Morozov, I; Morris, J V; Mozer, M U; Müller, K; Murín, P; Nagovizin, V; Naroska, Beate; Naumann, J; Naumann, Th; Newman, P R; Niebuhr, C; Nikiforov, A; Nikitin, D; Nowak, G; Nozicka, M; Oganezov, R; Olivier, B; Olsson, J E; Ossoskov, G; Ozerov, D; Pascaud, C; Patel, G D; Peez, M; Pérez, E; Perieanu, A; Petrukhin, A; Pitzl, D; Placakyte, R; Portheault, B; Pöschl, R; Povh, B; Raicevic, N; Ratiani, Z; Reimer, P; Reisert, B; Rimmer, A; Risler, C; Rizvi, E; Robmann, P; Roland, B; Roosen, R; Rostovtsev, A; Rurikova, Z; Rusakov, S; Rybicki, K; Sankey, D P C; Sauvan, E; Schatzel, S; Scheins, J; Schilling, F P; Schleper, P; Schmidt, S; Schmitt, S; Schneider, M; Schoeffel, L; Schöning, A; Schröder, V; Schultz Coulon, H C; Schwanenberger, C; Sedlak, K; Sefkow, F; Shevyakov, I; Shtarkov, L N; Sirois, Y; Sloan, T; Smirnov, P; Soloviev, Yu V; South, D; Spaskov, V; Specka, A; Spitzer, H; Stamen, R; Stella, B; Stiewe, J; Strauch, I; Straumann, U; Tchoulakov, V; Thompson, G; Thompson, P D; Tomasz, F; Traynor, D; Trevino, A V; Truöl, P; Tsipolitis, G; Tsuri, I; Turnau, J; Tzamariudaki, E; Uraev, A; Urban, M; Usik, A; Utkin, D; Valkár, S; Valkárová, A; Vallée, C; Van Mechelen, P; Van Remortel, N; Vazdik, Ya A; Veelken, C; Vest, A; Vinokurova, S; Volchinski, V; Wacker, K; Wagner, J; Weber, G; Weber, R; Wegener, D; Werner, C; Werner, N; Wessels, M; Wessling, B; Winter, G G; Wissing, C; Woerling, E E; Wolf, R; Wünsch, E; Xella, S M; Yan, W; Yeganov, V; Zácek, J; Zaleisak, J; Zhang, Z; Zhokin, A; Zohrabyan, H; Zomer, F; 10.1140/epjc/s2004-01978-x

2004-01-01

The cross section for antideuteron photoproduction is measured at HERA at a mean centre-of-mass energy of W/sub gamma p/=200 GeV in the range 0.2

photoproduction to those in central proton-proton collisions at the CERN ISR but much lower than those in central Au-Au collisions at RHIC. The coalescence parameter B/sub 2/, which characterizes the likelihood of antideuteron production, is measured in photoproduction to be 0.010+or-0.002+or-0.001, which is much higher than in Au-Au collisions at a similar nucleon-nucleon centre-of-mass energy. No significant production of particles heavier than deuterons is observed and upper limits are set on the photoproduction cross sections for such particles.

Processes involved in pion capture in hydrogen-containing molecules

International Nuclear Information System (INIS)

Horvath, D.

1983-03-01

A systematic analysis is presented of the possible elementary processes determining the fate of negative pions stopped in hydrogen-containing samples. Using a phenomenological description in comparison with the available experimental information on pion capture in hydrogen, it is shown that the formation and decay of pπ - atoms in compounds Zsub(m)Hsub(n) are determined mainly by the processes of Auger capture in a molecular orbit ZHπ - , transition from molecular to atomic orbit, transfer of pions to atoms Z in collisions pπ - +Z, and nuclear capture in collisions pπ - +H. The recent assumption of a considerable role of the processes of radiative atomic capture in bound hydrogen atoms, nuclear capture of pions by protons from the molecular state ZHπ - , or 'inner' transfer of the pion via tunnelling through the bond Z-H is not supported by the theory and contradicts the experimental data

Beauty in photoproduction at HERA II with the ZEUS detector

International Nuclear Information System (INIS)

Boutle, Sarah

2010-02-01

The production of beauty quarks in ep collisions should be accurately calculable in perturbative Quantum Chromodynamics (QCD) since the large mass of the b quark provides a hard scale. Therefore it is interesting to compare such predictions to results using photoproduction events where a low-virtuality photon, emitted by the incoming lepton, collides with a parton from the incoming proton. A measurement of beauty in photoproduction has been made at HERA with the ZEUS detector using an integrated luminosity of 126 pb - 1. Beauty was identified in events with a muon in the final state by using the transverse momentum of the muon relative to the closest jet. Lifetime information from the silicon vertex detector was also used; the impact parameter of the muon with respect to the primary vertex was exploited to discriminate between signal and background. Cross sections for beauty production as a function of the muon and the jet variables were measured and compared to QCD predictions and to previous measurements. The data were found to be well described by the predictions from next-to-leading-order QCD. The dijet sample of beauty photoproduction events was also used to study higher-order QCD topologies. At leading order, the two jets in the event are produced back-to-back in azimuthal angle, such that Δφ jj =φ j1 -φ j2 =π. Additional soft radiation causes small azimuthal decorrelations, whilst Δφ jj significantly lower than π is evidence of additional hard radiation. In this thesis, the cross section versus Δφ jj for beauty photoproduction and the comparison to NLO QCD predictions and Monte Carlo models are presented. (orig.)

An unusual diphosphatase from the PhnP family cleaves reactive FAD photoproducts.

Science.gov (United States)

Beaudoin, Guillaume A W; Li, Qiang; Bruner, Steven D; Hanson, Andrew D

2018-01-11

Flavins are notoriously photolabile, but while the photoproducts derived from the iso -alloxazine ring are well known the other photoproducts are not. In the case of FAD, typically the main cellular flavin, the other photoproducts are predicted to include four- and five-carbon sugars linked to ADP. These FAD photoproducts were shown to be potent glycating agents, more so than ADP-ribose. Such toxic compounds would require disposal via an ADP-sugar diphosphatase or other route. Comparative analysis of bacterial genomes uncovered a candidate disposal gene that is chromosomally clustered with genes for FAD synthesis or transport and is predicted to encode a protein of the PhnP cyclic phosphodiesterase family. The representative PhnP family enzyme from Koribacter versatilis (here named Fpd, F AD p hotoproduct d iphosphatase) was found to have high, Mn 2+ -dependent diphosphatase activity against FAD photoproducts, FAD, and ADP-ribose, but almost no phosphodiesterase activity against riboflavin 4',5'-cyclic phosphate, a chemical breakdown product of FAD. To provide a structural basis of the unique Fpd activity, the crystal structure of K. versatilis Fpd was determined. The results place Fpd in the broad metallo-β-lactamase-like family of hydrolases, a diverse family commonly using two metals for hydrolytic catalysis. The active site of Fpd contains two Mn 2+ ions and a bound phosphate, consistent with a diphosphatase mechanism. Our results characterize the first PhnP family member that is a diphosphatase rather than a cyclic phosphodiesterase and suggest its involvement in a cellular damage-control system that efficiently hydrolyzes the reactive, ADP-ribose-like products of FAD photodegradation. © 2018 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Determination of the pion-nucleon coupling constant and scattering lengths

CERN Document Server

Ericson, Torleif Eric Oskar; Thomas, A W

2002-01-01

We critically evaluate the isovector GMO sum rule for forward pion-nucleon scattering using the recent precision measurements of negatively charged pion-proton and pion-deuteron scattering lengths from pionic atoms. We deduce the charged-pion-nucleon coupling constant, with careful attention to systematic and statistical uncertainties. This determination gives, directly from data a pseudoscalar coupling constant of 14.17+-0.05(statistical)+-0.19(systematic) or a pseudovector one of 0.0786(11). This value is intermediate between that of indirect methods and the direct determination from backward neutron-proton differential scattering cross sections. We also use the pionic atom data to deduce the coherent symmetric and antisymmetric sums of the negatively charged pion-proton and pion-neutron scattering lengths with high precision. The symmetric sum gives 0.0017+-0.0002(statistical)+-0.0008 (systematic) and the antisymmetric one 0.0900+-0.0003(statistical)+-0.0013(systematic), both in units of inverse charged pi...

Low-energy photo- and electroproduction for physical pions

International Nuclear Information System (INIS)

MacMullen, J.T.

1979-02-01

The Ward identities of current algebra are combined with gauge invariance constraints, on-shell PCAC and the Bjorken limit to obtain the low-energy expressions of the pion photo- and electroproduction invariant amplitudes for physical pions

[Measurements of observables of pion-nucleon reactions]. Progress report

International Nuclear Information System (INIS)

Sadler, M.E.

1985-01-01

This document reports the progress of the research of pion reactions. These include (1) a study to measure observables in the pion-nucleon system in the momentum interval 400 to 700 MeV/c, (2) differential cross section measurements at low energy for pion-nucleon charge exchange, and (3) elastic and inelastic scattering of π +- on 3 H and 3 He. Individual experiments will be indexed separately

The pion polarisability and more measurements on chiral dynamics at COMPASS

CERN Document Server

Friedrich, Jan

2016-01-01

Within the physics program of the COMPASS experiment at CERN pion-photon reactions are measured via the Primakoff effect, referring to processes in which high-energetic pions react with the quasi-real photon field that surrounds the target nuclei. The production of a single hard photon in such a pion scattering at lowest momentum transfer to the nucleus is related to pion Compton scattering. From the measured cross-section shape, the pion polarisability has been determined, a result that has been published meanwhile as a Physical Review Letter [ 1 ]. The COMPASS measurement is in tension with the earlier dedicated measurements, and rather in agreement with the theoretical expectation from chiral perturbation theory. The analysis of a more recent high-statistics data taking is underway. Reactions with neutral and more charged pions in the final state are measured and analyzed as well. At low energy in the pion-photon centre-of-momentum system, these reactions are governed by chiral dynamics and contain informa...

Crystal physics with positive pions

International Nuclear Information System (INIS)

Flik, G.

1983-01-01

The π + /μ + lattice channeling is a new method of investigation in solid state physics. In the present thesis axial and planar channeling effects could be observed for the first time in monocrystalline Tantalum for 4, 12 MeV Muons generated by the decay of implanted positive pions. It is found that pions for T + /μ + channeling is investigated in Germanium for low temperatures. For T > 80 K tetrahedral sites are found, but for T < 80 K hexaedral sites or sites in the middle of the Ge-Ge bond are preferred. (BHO)

Measurement of Anti-Deuteron Photoproduction and a Search for Heavy Stable Charged Particles at HERA

CERN Document Server

Aktas, A.; Anthonis, T.; Asmone, A.; Babaev, A.; Backovic, S.; Bahr, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Baumgartner, S.; Becker, J.; Beckingham, M.; Behnke, O.; Behrendt, O.; Belousov, A.; Berger, Ch.; Berger, N.; Berndt, T.; Bizot, J.C.; Bohme, J.; Boenig, M.O.; Boudry, V.; Bracinik, J.; Brisson, V.; Broker, H.B.; Brown, D.P.; Bruncko, D.; Busser, F.W.; Bunyatyan, A.; Buschhorn, G.; Bystritskaya, L.; Campbell, A.J.; Caron, S.; Cassol-Brunner, F.; Cerny, K.; Chekelian, V.; Collard, C.; Contreras, J.G.; Coppens, Y.R.; Coughlan, J.A.; Cousinou, M.C.; Cox, B.E.; Cozzika, G.; Cvach, J.; Dainton, J.B.; Dau, W.D.; Daum, K.; Delcourt, B.; Demirchyan, R.; De Roeck, A.; Desch, K.; De Wolf, E.A.; Diaconu, C.; Dingfelder, J.; Dodonov, V.; Dubak, A.; Duprel, C.; Eckerlin, Guenter; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Ellerbrock, M.; Elsen, E.; Erdmann, M.; Erdmann, W.; Faulkner, P.J.W.; Favart, L.; Fedotov, A.; Felst, R.; Ferencei, J.; Fleischer, M.; Fleischmann, P.; Fleming, Y.H.; Flucke, G.; Flugge, G.; Fomenko, A.; Foresti, I.; Formanek, J.; Franke, G.; Frising, G.; Gabathuler, E.; Gabathuler, K.; Garutti, E.; Garvey, J.; Gayler, J.; Gerhards, R.; Gerlich, C.; Ghazaryan, Samvel; Goerlich, L.; Gogitidze, N.; Gorbounov, S.; Grab, C.; Grassler, H.; Greenshaw, T.; Gregori, M.; Grindhammer, Guenter; Gwilliam, C.; Haidt, D.; Hajduk, L.; Haller, J.; Hansson, M.; Heinzelmann, G.; Henderson, R.C.W.; Henschel, H.; Henshaw, O.; Heremans, R.; Herrera, G.; Herynek, I.; Heuer, R.D.; Hildebrandt, M.; Hiller, K.H.; Hladky, J.; Hoting, P.; Hoffmann, D.; Horisberger, R.; Hovhannisyan, A.; Ibbotson, M.; Ismail, M.; Jacquet, M.; Janauschek, L.; Janssen, X.; Jemanov, V.; Jonsson, L.; Johnson, D.P.; Jung, H.; Kant, D.; Kapichine, M.; Karlsson, M.; Katzy, J.; Keller, N.; Kennedy, J.; Kenyon, I.R.; Kiesling, Christian M.; Klein, M.; Kleinwort, C.; Kluge, T.; Knies, G.; Knutsson, A.; Koblitz, B.; Korbel, V.; Kostka, P.; Koutouev, R.; Kropivnitskaya, A.; Kroseberg, J.; Kuckens, J.; Kuhr, T.; Landon, M.P.J.; Lange, W.; Lastovicka, T.; Laycock, P.; Lebedev, A.; Leiner, B.; Lemrani, R.; Lendermann, V.; Levonian, S.; Lindfeld, L.; Lipka, K.; List, B.; Lobodzinska, E.; Loktionova, N.; Lopez-Fernandez, R.; Lubimov, V.; Lueders, H.; Luke, D.; Lux, T.; Lytkin, L.; Makankine, A.; Malden, N.; Malinovski, E.; Mangano, S.; Marage, P.; Marks, J.; Marshall, R.; Martisikova, M.; Martyn, H.U.; Maxfield, S.J.; Meer, D.; Mehta, A.; Meier, K.; Meyer, A.B.; Meyer, H.; Meyer, J.; Michine, S.; Mikocki, S.; Milcewicz, I.; Milstead, D.; Mohamed, A.; Moreau, F.; Morozov, A.; Morozov, I.; Morris, J.V.; Mozer, Matthias Ulrich; Muller, K.; Murin, P.; Nagovizin, V.; Naroska, B.; Naumann, J.; Naumann, Th.; Newman, Paul R.; Niebuhr, C.; Nikiforov, A.; Nikitin, D.; Nowak, G.; Nozicka, M.; Oganezov, R.; Olivier, B.; Olsson, J.E.; Ossoskov, G.; Ozerov, D.; Pascaud, C.; Patel, G.D.; Peez, M.; Perez, E.; Perieanu, A.; Petrukhin, A.; Pitzl, D.; Placakyte, R.; Poschl, R.; Portheault, B.; Povh, B.; Raicevic, N.; Ratiani, Z.; Reimer, P.; Reisert, B.; Rimmer, A.; Risler, C.; Rizvi, E.; Robmann, P.; Roland, B.; Roosen, R.; Rostovtsev, A.; Rurikova, Z.; Rusakov, S.; Rybicki, K.; Sankey, D.P.C.; Sauvan, E.; Schatzel, S.; Scheins, J.; Schilling, F.P.; Schleper, P.; Schmidt, S.; Schmitt, S.; Schneider, M.; Schoeffel, L.; Schoning, A.; Schroder, V.; Schultz-Coulon, H.C.; Schwanenberger, C.; Sedlak, K.; Sefkow, F.; Sheviakov, I.; Shtarkov, L.N.; Sirois, Y.; Sloan, T.; Smirnov, P.; Soloviev, Y.; South, D.; Spaskov, V.; Specka, Arnd E.; Spitzer, H.; Stamen, R.; Stella, B.; Stiewe, J.; Strauch, I.; Straumann, U.; Thompson, Graham; Thompson, P.D.; Tomasz, F.; Traynor, D.; Truoel, Peter; Tsipolitis, G.; Tsurin, I.; Turnau, J.; Tzamariudaki, E.; Uraev, A.; Urban, Marcel; Usik, A.; Utkin, D.; Valkar, S.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Vargas Trevino, A.; Vassiliev, S.; Vazdik, Y.; Veelken, C.; Vest, A.; Vichnevski, A.; Vinokurova, S.; Volchinski, V.; Wacker, K.; Wagner, J.; Weber, G.; Weber, R.; Wegener, D.; Werner, C.; Werner, N.; Wessels, M.; Wessling, B.; Winter, G.G.; Wissing, Ch.; Woehrling, E.E.; Wolf, R.; Wunsch, E.; Xella, S.; Yan, W.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhokin, A.; Zohrabyan, H.; Zomer, F.

2004-01-01

The cross section for anti-deuteron photoproduction is measured at HERA at a mean centre-of-mass energy of W_{\\gamma p} = 200 GeV in the range 0.2 < p_T/M < 0.7 and |y| < 0.4, where M, p_T and y are the mass, transverse momentum and rapidity in the laboratory frame of the anti-deuteron, respectively. The numbers of anti-deuterons per event are found to be similar in photoproduction to those in central proton-proton collisions at the CERN ISR but much lower than those in central Au-Au collisions at RHIC. The coalescence parameter B_2, which characterizes the likelihood of anti-deuteron production, is measured in photoproduction to be 0.010 \\pm 0.002 \\pm 0.001, which is much higher than in Au-Au collisions at a similar nucleon-nucleon centre-of-mass energy. No significant production of particles heavier than deuterons is observed and upper limits are set on the photoproduction cross sections for such particles.

CLAS+FROST: new generation of photoproduction experiments at jefferson lab

International Nuclear Information System (INIS)

Pasyuk, E.

2009-01-01

A large part of the experimental program in Hall B of the Jefferson Lab is dedicated to baryon spectroscopy. Photoproduction experiments are essential part of this program. CEBAF Large Acceptance Spectrometer (CLAS) and availability of circularly and linearly polarized tagged photon beams provide unique conditions for this type of experiments. Recent addition of the Frozen Spin Target (FROST) gives a remarkable opportunity to measure double and triple polarization observables for different pseudo-scalar meson photoproduction processes. For the first time, a complete or nearly complete experiment becomes possible and will allow model independent extraction of the reaction amplitude. An overview of the experiment and its current status is presented. (author)

Pion correlation from Skyrmion--anti-Skyrmion annihilation

International Nuclear Information System (INIS)

Lu, Y.; Amado, R.D.

1995-01-01

We study two pion correlations from Skyrmion and anti-Skyrmion collision, using the product ansatz and an approximate random grooming method for nucleon projection. The spatial-isospin coupling inherent in the Skyrme model, along with empirical averages, leads to correlations not only among pions of like charges but also among unlike charge types

Pionic retardation effects in two-pion-exchange three-nucleon forces

International Nuclear Information System (INIS)

Coon, S.A.; Friar, J.L.

1986-01-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v/c) 2 relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential

Pionic retardation effects in two-pion-exchange three-nucleon forces

Science.gov (United States)

Coon, S. A.; Friar, J. L.

1986-09-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v/c)2 relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential.

Pionic retardation effects in two-pion-exchange three-nucleon forces

Energy Technology Data Exchange (ETDEWEB)

Coon, S.A.; Friar, J.L.

1986-09-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v-italic/c-italic)/sup 2/ relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential.

Charged pion photoproduction from 10B

International Nuclear Information System (INIS)

Rowley, D.; LeRose, J.; Min, K.; Sapp, B.O.; Stoler, P.; Winhold, E.J.; Yergin, P.F.; Bernstein, A.M.; Blomqvist, K.I.; Caplan, H.S.; Dytman, S.A.; Franklin, G.; Pauli, M.

1982-01-01

Measurements were made of dsigma/dΩ [theta/sub π/ = 90 0 (lab)] for 10 B(γ,π + ) 10 Be(g.s.) at T/sub π/ = 17, 29, and 42 MeV, for 10 B(γ,π + ) 10 Be(E/sub x/ = 3.37 MeV) at T/sub π/ = 29 and 42 MeV, and for 10 B(γ,π - ) 10 C(g.s.) at T/sub π/ = 29 MeV. The results disagree significantly with several recent distorted-wave impulse approximation calculations

Polarization Measurements in Neutral Pion Photoproduction

International Nuclear Information System (INIS)

C. Jones; Krishni Wijesooriya; B. Fox; Andrei Afanasev; Moscov Amaryan; Konrad Aniol; Stephen Becher; Kamal Benslama; Louis Bimbot; Peter Bosted; Edward Brash; John Calarco; Zhengwei Chai; C. Chang; Ting Chang; Jian-Ping Chen; Seonho Choi; Eugene Chudakov; Steve Churchwell; Domenick Crovelli; Sonja Dieterich; Scott Dumalski; Dipangkar Dutta; Martin Epstein; Kevin Fissum; Salvatore Frullani; Haiyan Gao; Juncai Gao; Franco Garibaldi; Olivier Gayou; Ronald Gilman; Oleksandr Glamazdin; Charles Glashausser; Javier Gomez; Viktor Gorbenko; Ole Hansen; Roy Holt; Jordan Hovdebo; Garth Huber; Kees de Jager; Xiaodong Jiang; Mark Jones; Jim Kelly; Edward Kinney; Edgar Kooijman; Gerfried Kumbartzki; Michael Kuss; John LeRose; Meme Liang; Richard Lindgren; Nilanga Liyanage; Sergey Malov; Demetrius Margaziotis; Pete Markowitz; Kathy McCormick; Dave Meekins; Zein-Eddine Meziani; Robert Michaels; Joe Mitchell; Ludyvine Morand; Charles Perdrisat

2002-01-01

We present measurements of the recoil proton polarization for the 1 H(gamma-vector,p-vector)pi 0 reaction for theta c.m. pi = 60 o -135 o and for photon energies up to 4.1 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. Various theoretical models are compared with the results. No evidence for hadron helicity conservation is observed. Models that employ factorization are not favored. It appears from the strong angular dependence of the induced polarization at photon energies of 2.5 and 3.1 GeV that a relatively high spin resonance or background amplitude might exist in this energy region

Chiral symmetry breaking and the pion quark structure

International Nuclear Information System (INIS)

Bernard, V.

1986-01-01

The mechanism of dynamical breaking of chiral symmetry in hadronic matter is first studied in the framework of the Nambu and Jona-Lasinio model on one hand and its generalisation to finite hadron size on the other hand. The analysis uses a variational procedure modelled after the BCS superconductor. Our study indicates for example, a great sensitivity of various quantities characterizing the breaking of symmetry to the shape of the interaction. Also the mechanism of breaking of chiral symmetry is essentially related to the mechanism of confinement. When a symmetry is spontaneously broken, there exists a Goldstone particle of zero mass. This is true in our model. This particle, the pion, is obtained as solution of a Bethe Salpeter equation for a qantiq bound state. This enables us to establish a connection between the pion as a Goldstone boson related to spontaneous symmetry breaking and the quark-antiquark structure of the pion. The finite mass of the physical pion is obtained with non zero current quark mass. Various properties of this particle are then studied in the RPA formalism. One important point of our model is the highly collective character of the pion. 85 refs [fr

Collective flow of pions in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Russkikh, V.N.; Ivanov, Yu.B.

1995-02-01

The transverse-momentum distributions of pions in the Au(1 GeV/nucleon)+Au collisions are analyzed. The calculations are carried out within relativistic meanfield one- and two-fluid models. The rapidity distributions of the mean transverse momentum of pions are found to be fairly sensitive to the nuclear equation of state and, especially, to the stopping power. It is shown that the collective flow of pions in the reaction plane always correlates with the 'hot' flow of nucleons (i.e. those emitted from hot regions of nuclear system), while not always, with the total nucleon flow. This 'hot' nucleon flow can be experimentally singled out by selecting nucleons with sufficiently high transverse momenta. We predict that the 'hot' nucleon flow selected in this way will always correlate with the pion flow. Available experimental data on transverse-momentum spectra of pions are compared with calculations employing various equations of state and stopping power. (orig.)

A coupled-channels analysis of pion scattering and pion-induced eta production on the nucleon

International Nuclear Information System (INIS)

Pratt, R.K.; Bennhold, C.; Surya, Y.

1995-01-01

Motivated by new, upcoming Brookhaven data, pion scattering and pion-induced eta production on the nucleon in the S 11 (1535) resonance region is studied in an extension of the unitary, relativistic resonance model by Surya and Gross. The Kernel of the relativistic wave equation includes the nucleon, Roper, δ(1232), D 13 (1520) and S 11 (1535) pole terms along with contact σ- and ρ-like exchange terms. The formalism includes a coupling between the πN and ηN channels. The resonance parameters are adjusted to reproduce the experimental πN phase shifts

Pion condensation and density isomerism in nuclear matter

International Nuclear Information System (INIS)

Hecking, P.; Weise, W.

1979-01-01

The possible existence of density isomers in nuclear matter, induced by pion condensation, is discussed; the nuclear equation of state is treated within the framework of the sigma model. Repulsive short-range baryon-baryon correlations, the admixture of Δ (1232) isobars and finite-range pion-baryon vertex form factors are taken into account. The strong dependence of density isomerism on the high density extrapolation of the equation of state for normal nuclear matter is also investigated. We find that, once finite range pion-baryon vertices are introduced, the appearance of density isomers becomes unlikely

Universal pion freeze-out in heavy-ion collisions.

Science.gov (United States)

Adamová, D; Agakichiev, G; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Castillo, A; Cherlin, A; Damjanović, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Z; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B; Ludolphs, W; Maas, A; Marín, A; Milosević, J; Milov, A; Miśkowiec, D; Panebrattsev, Yu; Petchenova, O; Petrácek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Sako, H; Schmitz, W; Schukraft, J; Sedykh, S; Shimansky, S; Slívová, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, I; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V

2003-01-17

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.

Use of reiterative primer extension methodology to map UV-induced photoproducts at the nucleotide level in the laci gene from genomic DNA

International Nuclear Information System (INIS)

Chandrasekhar, D.; Houten, B. Van

1994-01-01

A newly developed reiterative primer extension assay has been employed to examine photoproduct formation and repair at the nucleotide level. Analysis of UV-induced DNA photoproduct hotspots in the first 184 base pairs of the laci genes of genomic E. coli DNA has revealed that photoproducts are formed linearly with dose and display a sequence-dependent increase. Generally, pyrimdine dimers were twice as frequent as all other UV-induced photoproducts. However, specific sites showed differing distributions. A post-irradiation recovery period revealed differences in the repair efficiency at individual nucleotides. Repair of photoproducts on the transcribed strand was generally twice as efficient as repair of photoproducts on the nontranscribed strand, indicating that strand-specific DNA repair occurs in the constitutively transcribed laci gene of E. coli. The UV-induced DNA photoproduct distribution following repair was well correlated with an established UV-induced mutation spectrum for wild-type E. coli cells. This analysis revealed that photoproduct hotspots on the efficiently repaired transcribed strand did not correlate with mutagenic hotspots. These data strongly support the hypothesis that mutations arise at inefficiently repaired sites on the nontranscribed strand

Electro- and Photoproduction of Omega(783) Mesons using CLAS at Jefferson Lab

International Nuclear Information System (INIS)

Manak, J.J.; Volker Burkert; Franz Klein; Bernhard Mecking; Alan Coleman; Herb Funsten

2000-01-01

Electro- and photoproduction of w(783) from a proton target have been measured in the CLAS detector at the Thomas Jefferson National Accelerator Facility in Newport News VA. The photoproduction data were taken over a photon energy range from 0.5 to 2.3 GeV, while the electroproduction data was obtained over a W range of 1.8-2.5 GeV/c2. Preliminary acceptance corrected center-of-mass angular distributions have been examined for both data sets

Exclusive electroproduction of two pions at HERA

CERN Document Server

Abramowicz, H.

2012-01-25

The exclusive electroproduction of two pions in the mass range 0.4 < M{\\pi}{\\pi} < 2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(M{\\pi}{\\pi})|, assuming that the studied mass range includes the contributions of the {\\rho}, {\\rho}' and {\\rho}" vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios {\\sigma}({\\rho}' \\rightarrow {\\pi}{\\pi})/{\\sigma}({\\rho}) and {\\sigma}({\\rho}" \\rightarrow {\\pi}{\\pi})/{\\sigma}({\\rho}) was extracted. The pion form factor obtained in the present analysis is compared to that obtained...

Low energy scattering with a nontrivial pion

International Nuclear Information System (INIS)

Fariborz, Amir H.; Jora, Renata; Schechter, Joseph

2007-01-01

An earlier calculation in a generalized linear sigma model showed that the well-known current algebra formula for low energy pion-pion scattering held even though the massless Nambu Goldstone pion contained a small admixture of a two-quark two-antiquark field. Here we turn on the pion mass and note that the current algebra formula no longer holds exactly. We discuss this small deviation and also study the effects of a SU(3) symmetric quark mass type term on the masses and mixings of the eight SU(3) multiplets in the model. We calculate the s-wave scattering lengths, including the beyond current algebra theorem corrections due to the scalar mesons, and observe that the effect of the scalar mesons is to improve the agreement with experiment. In the process, we uncover the way in which linear sigma models give controlled corrections (due to the presence of scalar mesons) to the current algebra scattering formula. Such a feature is commonly thought to exist only in the nonlinear sigma model approach

Pion-nucleon scattering and isospin violation

International Nuclear Information System (INIS)

Meissner, U.G.

1999-01-01

The paper discusses low-energy pion-nucleon scattering in the framework of chiral perturbation theory. It is argued that using this theoretical method one is able to match the in some cases impressive experimental accuracy (for the low partial waves). It is also shown how strong and electromagnetic isospin violation can be treated simultaneously. Some first results for neutral pion scattering and the σ-term are given. Copyright (1999) World Scientific Publishing Co. Pte. Ltd

The possibility for a pion polarizability measurement at COMPASS

CERN Document Server

Guskov, A

2010-01-01

The pion electromagnetic structure can be probed in $\\pi^{−}+(A,Z)\\rightarrow\\pi^{-}+(A,Z) + \\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\alpha_{\\pi})$ and the magnetic $(\\beta_{\\pi})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of point-like pions with the measured cross section. The opportunity to measure pion polarizability via the Primakoff reaction at the COMPASS experiment was studied with a $\\pi^{−}$ beam of 190 GeV. The obtained results are used for preparation of the new measurement.

On the role of secondary pions in spallation targets

Energy Technology Data Exchange (ETDEWEB)

Mancusi, Davide [Paris-Saclay Univ., Gif-sur-Yvette (France). Den-Service d' Etude des Reacteurs et de Mathematiques Appliquees (SERMA); Lo Meo, Sergio [ENEA, Research Centre ' ' Ezio Clementel' ' , Bologna (Italy); INFN, Bologna (Italy); Colonna, Nicola [INFN, Bari (Italy); Boudard, Alain; David, Jean-Christophe; Leray, Sylvie [Paris-Saclay Univ., Gif-sur-Yvette (France). IRFU, CEA; Cortes-Giraldo, Miguel Antonio; Lerendegui-Marco, Jorge [Sevilla Univ. (Spain). Facultad de Fisica; Cugnon, Joseph [Liege Univ. (Belgium). AGO Dept.; Massimi, Cristian [INFN, Bologna (Italy); Bologna Univ. (Italy). Physics and Astronomy Dept.; Vlachoudis, Vasilis [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

2017-05-15

We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the nTOF lead spallation target, irradiated with 20 GeV/c protons, neutral pions are involved in the production of ∝ 90% of the high-energy photons; charged pions participate in ∝ 40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets. (orig.)

On the role of secondary pions in spallation targets

CERN Document Server

Mancusi, Davide; Colonna, Nicola; Boudard, Alain; Cortés-Giraldo, Miguel Antonio; Cugnon, Joseph; David, Jean-Christophe; Leray, Sylvie; Lerendegui-Marco, Jorge; Massimi, Cristian; Vlachoudis, Vasilis

2017-01-01

We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the n_TOF lead spallation target, irradiated with 20-GeV/c protons, neutral pions are involved in the production of ~90% of the high-energy photons; charged pions participate in ~40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets.

Relativistic generalizations of simple pion-nucleon models

International Nuclear Information System (INIS)

McLeod, R.J.; Ernst, D.J.

1981-01-01

A relativistic, partial wave N/D dispersion theory is developed for low energy pion-nucleon elastic scattering. The theory is simplified by treating crossing symmetry only to lowest order in the inverse nucleon mass. The coupling of elastic scattering to inelastic channels is included by taking the necessary inelasticity from experimental data. Three models are examined: pseudoscalar coupling of pions and nucleons, pseudovector coupling, and a model in which all intermediate antinucleons are projected out of the amplitude. The phase shifts in the dominant P 33 channel are quantitatively reproduced for P/sub lab/ 33 phase shifts. Thus a model of the pion-nucleon interaction which does not include antinucleon degrees of freedom is found to be unphysical

Phi Photoproduction in a Coupled-Channel Approach

NARCIS (Netherlands)

Ozaki, S.; Nagahiro, H.; Hosaka, A.; Scholten, O.

2010-01-01

We investigate photoproduction of phi-mesons off protons within a coupled-channel effective-Lagrangian method which is based on the K-matrix approach. We take into account pi N, rho N, eta N, K Lambda, K Sigma, K Lambda (1520) and phi N channels. Especially we focus on K Lambda(1520) channel. We

Detecting the neutral top-pion at e+e- colliders

International Nuclear Information System (INIS)

Wang Xuelei; Yang Yueling; Li Bingzhong

2004-01-01

We investigate some processes of the associated production of a neutral top-pion Π t 0 with a pair of fermions (e + e - →ff-barΠ t 0 ) in the context of top-color-assisted technicolor (TC2) theory in the future e + e - colliders. The studies show that the largest cross sections of the processes e + e - →f ' f ' Π t 0 (f ' =u,d,c,s,μ,τ) could only reach the level of 0.01 fb; we can hardly detect a neutral top-pion through these processes. For the processes e + e - →e + e - Π t 0 , e + e - →tt-barΠ t 0 , and e + e - →bb-barΠ t 0 , the cross sections of these processes are at the level of a few fb for the favorable parameters, and a few tens, even hundreds, of neutral top-pion events can be produced at future e + e - colliders each year through these processes. With the clean background of the flavor-changing tc-bar channel, the top-pion events can possibly be detected at the planned high luminosity e + e - colliders. Therefore, such neutral top-pion production processes provide a useful way to detect a neutral top-pion and test the TC2 model directly

Possibility of investigation of pion degrees of freedom in atomic nuclei with the help of quasielastic pions knocking out by high energy electrons

CERN Document Server

Neudachin, V G; Sviridova, L L

2002-01-01

The attention is paid to the interesting possibilities of studying the pion degrees of freedom in the atomic nuclei by means of the quasielastic knocking out of pion (e, ep) from the nuclei by the electrons with the energy of several GeV. It appears, that the pulse distribution of the pions, knocked out from the separate nucleons and the nuclei, is in the whole differ essentially different

Measurement of the pion form factor in the time-like region for q2 values between 0.1 (GeV/c)2 and 0.18 (GeV/c)2

International Nuclear Information System (INIS)

Amendolia, S.R.; Badelek, B.; Bertolucci, E.; Bettoni, D.; Bizzeti, A.; Bosisio, L.; Bradaschia, C.; Dell'Orso, M.; Foa, L.; Focardi, E.; Giannetti, P.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Scribano, A.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Frank, S.G.F.; Harvey, J.; Menasce, D.; Meroni, E.; Moroni, L.; Milan Univ.

1984-01-01

The EM form factor of the pion has been studied in the time-like region by measuring sigma(e + e - ->π + π - ) normalization to sigma(e + e - ->μ + μ - ). Results have been obtained for q 2 down to the physical threshold. (orig.)

Diffractive photoproduction of D*±(2010) at HERA

International Nuclear Information System (INIS)

Chekanov, S.; Derrick, M.; Magill, S.

2007-03-01

Diffractive photoproduction of D *± (2010) mesons was measured with the ZEUS detector at the ep collider HERA, using an integrated luminosity of 78.6 pb -1 . The D * mesons were reconstructed in the kinematic range: transverse momentum p T (D * )>1.9 GeV and pseudorapidity vertical stroke η(D * ) vertical stroke *+ → D 0 π + s followed by D 0 → K - π + (+c.c.). Diffractive events were identified by a large gap in pseudorapidity between the produced hadronic state and the outgoing proton. Cross sections are reported for photon-proton centre-of-mass energies in the range 130 2 2 , in two ranges of the Pomeron fractional momentum x P P *± (2010) photoproduction cross section is about 6%. The data are in agree- ment with perturbative QCD calculations based on various parameterisations of diffractive parton distribution functions. The results are consistent with diffractive QCD factorisation. (orig.)

Production and decay of baryonic resonances in pion induced reactions

Directory of Open Access Journals (Sweden)

Przygoda Witold

2016-01-01

Full Text Available Pion induced reactions give unique opportunities for an unambiguous description of baryonic resonances and their coupling channels. A systematic energy scan and high precision data, in conjunction with a partial wave analysis, allow for the study of the excitation function of the various contributions. A review of available world data unravels strong need for modern facilities delivering measurements with a pion beam. Recently, HADES collaboration collected data in pion-induced reactions on light (12C and heavy (74W nuclei at a beam momentum of 1.7 GeV/c dedicated to strangeness production. It was followed by a systematic scan at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c in π− − p reaction in order to tackle the role of N(1520 resonance in conjunction with the intermediate ρ production. First results on exclusive channels with one pion (π− p and two pions (nπ+π−, pπ−π0 in the final state are discussed.

Relativistic quantum kinetic analysis of a pion--nucleon system

International Nuclear Information System (INIS)

Alonso, J.D.

1985-01-01

A relativistic plasma of nucleons interacting through pions via the usual isospin-invariant Yukawa coupling is analyzed in the framework of the covariant Wigner function technique. The method is manifestly covariant and the temperature effects are considered. The relativistic quantum BBGKY hierarchy for the pion--nucleon system is derived. By generalizing the Bogolioubov analysis of the classical BBGKY hierarchy a non-perturbative renormalizable method is elaborated which allows the solution of the kinetic problem in form of power series of two cluster parameters which measure the importance of correlations. In the lowest order of the cluster expansion (Hartree approximation of zero-order approximation) the quasi-nucleon Fock space is introduced, the fermion Wigner function in the thermodynamic equilibrium is obtained and the vacuum effects are renormalized. In this approximation the plasma behaves as a perfect Fermi gas of nucleons and antinucleons, but there exists an abnormal configuration with a uniform pion condensate which is unstable. In the next approximation (quadratic in the small parameters) the quasi-pion dispersion relation is obtained and the vacuum polarization tensor is renormalized. The quasi-pion rest-mass spectra (''plasma frequency'') and the effective-coupling behaviour as functions of the thermodynamic state are given. By estimating the size of the cluster parameters the self-consistency of the approximation scheme is proved. The quasi-pion Fock space is introduced and the quasi-pion equilibrium Wigner function is obtained. From these results the problem of the higher-order corrections to the Hartree thermodynamics is outlined

Beauty in photoproduction at HERA II with the ZEUS detector

Energy Technology Data Exchange (ETDEWEB)

Boutle, Sarah

2010-02-15

The production of beauty quarks in ep collisions should be accurately calculable in perturbative Quantum Chromodynamics (QCD) since the large mass of the b quark provides a hard scale. Therefore it is interesting to compare such predictions to results using photoproduction events where a low-virtuality photon, emitted by the incoming lepton, collides with a parton from the incoming proton. A measurement of beauty in photoproduction has been made at HERA with the ZEUS detector using an integrated luminosity of 126 pb{sup -}1. Beauty was identified in events with a muon in the final state by using the transverse momentum of the muon relative to the closest jet. Lifetime information from the silicon vertex detector was also used; the impact parameter of the muon with respect to the primary vertex was exploited to discriminate between signal and background. Cross sections for beauty production as a function of the muon and the jet variables were measured and compared to QCD predictions and to previous measurements. The data were found to be well described by the predictions from next-to-leading-order QCD. The dijet sample of beauty photoproduction events was also used to study higher-order QCD topologies. At leading order, the two jets in the event are produced back-to-back in azimuthal angle, such that {delta}{phi}{sup jj}={phi}{sup j1}-{phi}{sup j2}={pi}. Additional soft radiation causes small azimuthal decorrelations, whilst {delta}{phi}{sup jj} significantly lower than {pi} is evidence of additional hard radiation. In this thesis, the cross section versus {delta}{phi}{sup jj} for beauty photoproduction and the comparison to NLO QCD predictions and Monte Carlo models are presented. (orig.)

High pT charm photoproduction

International Nuclear Information System (INIS)

Abbiendi, G.; Butterworth, J.M.

1996-09-01

The expected rates for charm-tagged jet photoproduction are evaluated for a number of tagging procedures, and some of the physics potential is discussed. Charm in jets is tagged using D * 's, μ's, or tracks from secondary vertices which might be identified in a microvertex detector. We find high expected event rates, leading to the possibility of placing strong constraints on the kinematics of charm production and on the gluon content of the proton and the charm content of the photon. (orig.)

Two pion correlation from SPACER

International Nuclear Information System (INIS)

Csoergoe, T.; Zimanyi, J.; Pratt, S.

1989-12-01

The correlation function for neutral and negative pions produced in ultrarelativistic heavy ion collisions was calculated without free parameters based on a space-time version of the LUND model, called SPACER: Simulation of Phase space distribution of Atomic nuclear Collisions in Energetic Reactions. This method includes the effect of Bose correlations for the emitted pion pair. Effects arising from correlations between space-time and momentum space distributions are investigated. The results are compared to the data of two different experiments. The role and interpretation of the chaocity parameter are discussed. (D.G.) 14 refs.; 4 figs

Photoproduction of events with rapidity gaps between jets at HERA

Energy Technology Data Exchange (ETDEWEB)

Chekanov, S.; Derrick, M.; Magill, S. [Argonne National Laboratory, Argonne, IL (US)] (and others)

2006-12-15

The photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 39 pb{sup -1}. Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value E{sub T}{sup C}UT. The data show a clear excess over the predictions of standard photoproduction models. This is interpreted as evidence for a strongly interacting exchange of a color-singlet object. Monte Carlo models which include such a color-singlet exchange are able to describe the data. (orig.)

Photoproduction of events with rapidity gaps between jets at HERA

International Nuclear Information System (INIS)

Chekanov, S.; Derrick, M.; Magill, S.

2006-12-01

The photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 39 pb -1 . Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value E T C UT. The data show a clear excess over the predictions of standard photoproduction models. This is interpreted as evidence for a strongly interacting exchange of a color-singlet object. Monte Carlo models which include such a color-singlet exchange are able to describe the data. (orig.)

Dijet angular distributions in direct and resolved photoproduction at HERA

International Nuclear Information System (INIS)

Derrick, M.; Krakauer, D.; Magill, S.

1996-05-01

Jet photoproduction, where the two highest transverse energy (E T jet ) jets have E T jet above 6 GeV and a jet-jet invariant mass above 23 GeV, has been studied with the ZEUS detector at the HERA ep collider. Resolved and direct photoproduction samples have been separated. The cross section as a function of the angle between the jet-jet axis and the beam direction in the dijet rest frame has been measured for the two samples. The measured angular distributions differ markedly from each other. They agree with the predictions of QCD calculations, where the different angular distributions reflect the different spins of the quark and gluon exchanged in the hard subprocess. (orig.)

CLEAR: Prospects for a low threshold neutrino experiment at the Spallation Neutron Source

International Nuclear Information System (INIS)

Scholberg, Kate

2008-01-01

A low-threshold neutrino scattering experiment at a high intensity stopped-pion neutrino source has the potential to measure coherent neutral current neutrino-nucleus elastic scattering. A promising prospect for the measurement of this process is a proposed noble-liquid-based experiment, dubbed CLEAR (Coherent Low Energy A (Nuclear) Recoils), at the Spallation Neutron Source. This poster will describe the CLEAR proposal and its physics reach.

Pion interactions with light nuclei and applications to radiotherapy

International Nuclear Information System (INIS)

Brenner, D.J.

1979-02-01

In the light of the current interest in negative pion radiotherapy particle spectra have been obtained after negative pion absorption in oxygen. Using a multiple foil activation technique, measurements were made of neutron spectra from the pion interactions and also from background sources from which it appears that the technique is a potentially useful tool for routine dosimetry. Theoretical predictions are made of the energy spectra of particles emitted after stopped pion absorption on oxygen based on an alpha cluster model and using a plane-wave impulse approximation. A method of considering residual interactions with the nucleus is described which has the potential to treat the low energy particles and also final channels not expected as a result of a single interaction. (UK)

Deeply virtual compton scattering on a virtual pion target

International Nuclear Information System (INIS)

Amrath, D.; Diehl, M.; Lansberg, J.P.; Heidelberg Univ.

2008-07-01

We study deeply virtual Compton scattering on a virtual pion that is emitted by a proton. Using a range of models for the generalized parton distributions of the pion, we evaluate the cross section, as well as the beam spin and beam charge asymmetries in the leading-twist approximation. Studying Compton scattering on the pion in suitable kinematics puts high demands on both beam energy and luminosity, and we find that the corresponding requirements will first be met after the energy upgrade at Jefferson Laboratory. As a by-product of our study, we construct a parameterization of pion generalized parton distributions that has a non-trivial interplay between the x and t dependence and is in good agreement with form factor data and lattice calculations. (orig.)

Universal pion freeze-out in heavy-ion collisions

CERN Document Server

Adamova, D; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Castillo, A; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B C; Ludolphs, W; Maas, A; Marin, A; Milosevic, J; Milov, A; Miskowiec, D; Panebratsev, Yu A; Petchenova, O Yu; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Sako, H; Schükraft, Jürgen; Sedykh, S; Shimansky, S S; Slivova, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V; Schmitz, W

2003-01-01

Based on an evaluation of recent systematic data on two-pion interferometry and on measured particle yields at mid-rapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda_f reaches a value of approximately 2.5 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and its value is constant at all currently available beam energies from AGS to RHIC.

Photonuclear physics at the Bonn synchrotrons. Present status and future plans at the Bonn synchrotron

International Nuclear Information System (INIS)

Mecking, B.A.

1983-11-01

The activities in the field of photonuclear physics at the Bonn 500 MeV and 2.5 GeV synchrotrons are reviewed. The experiments concentrate on photodisintegration and pion-photoproduction reactions on light nuclei. (orig.)

Scattering of low-energy pions by p-shell nuclei

International Nuclear Information System (INIS)

Khankhasaev, M.Kh.

1987-01-01

Low-energy pion-carbon scattering (up to 50 MeV) is analysed in the framework of the unitary approach based on the method of evolution in the coupling constant. It is shown that at pion energy ∼ 50 MeV the differential cross section arises as a result of the strong interference between the pure potential scattering and absorption channels. In this energy region the scattering data are very sensitive to the dynamics of the pion-nucleus interaction

Basic features of the pion valence-quark distribution function

Energy Technology Data Exchange (ETDEWEB)

Chang, Lei [CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005 (Australia); Mezrag, Cédric; Moutarde, Hervé [Centre de Saclay, IRFU/Service de Physique Nucléaire, F-91191 Gif-sur-Yvette (France); Roberts, Craig D. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Rodríguez-Quintero, Jose [Departamento de Física Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, Huelva E-21071 (Spain); Tandy, Peter C. [Center for Nuclear Research, Department of Physics, Kent State University, Kent, OH 44242 (United States)

2014-10-07

The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow–ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, q{sup π}(x); namely, at a characteristic hadronic scale, q{sup π}(x)∼(1−x){sup 2} for x≳0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.

THE ETA-MESON PHOTOPRODUCTION ON PROTON

Czech Academy of Sciences Publication Activity Database

Donoval, Jan; Bydžovský, Petr

2011-01-01

Roč. 26, 3-4 (2011), s. 645-646 ISSN 0217-751X. [11th International Workshop on Meson Production , Properties and Interaction. Krakow, 10.06.2010-15.06.2010] R&D Projects: GA ČR GA202/08/0984 Institutional research plan: CEZ:AV0Z10480505 Keywords : Eta-meson photoproduction * form factors * nucleon resonances Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.053, year: 2011

Photoproduction of π{sup 0} -pairs off protons and off neutrons

Energy Technology Data Exchange (ETDEWEB)

Dieterle, M.; Oberle, M.; Garni, S.; Kaeser, A.; Keshelashvili, I.; Krusche, B.; Maghrbi, Y.; Pheron, F.; Rostomyan, T.; Strub, T.; Walford, N.K.; Werthmueller, D.; Witthauer, L. [University of Basel, Department of Physics, Basel (Switzerland); Ahrens, J.; Arends, H.J.; Bartolome, P.A.; Heid, E.; Jahn, O.; Ostrick, M.; Otte, P.; Schumann, S.; Thomas, A. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); Annand, J.R.M.; Glazier, D.I.; Hamilton, D.; Howdle, D.; Livingston, K.; MacGregor, I.J.D.; Mancell, J.; McGeorge, J.C.; McNicoll, E.; Robinson, J. [University of Glasgow, SUPA School of Physics and Astronomy, Glasgow (United Kingdom); Bantawa, K.; Manley, D.M. [Kent State University, Kent, Ohio (United States); Beck, R.; Nikolaev, A. [University of Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Bekrenev, V. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Berghaeuser, H.; Drexler, P.; Metag, V.; Novotny, R.; Thiel, M. [University of Giessen, II. Physikalisches Institut, Giessen (Germany); Braghieri, A.; Costanza, S.; Mushkarenkov, A.; Pedroni, P. [INFN Sezione di Pavia, Pavia (Italy); Branford, D.; Jude, T.C.; Sikora, M.H.; Watts, D.P. [University of Edinburgh, SUPA School of Physics, Edinburgh (United Kingdom); Briscoe, W.J.; Demissie, B.; Marinides, Z. [The George Washington University, Center for Nuclear Studies, Washington, DC (United States); Brudvik, J.; Starostin, A. [University of California Los Angeles, Los Angeles, California (United States); Cherepnya, S.; Fil' kov, L.V. [Lebedev Physical Institute, Moscow (Russian Federation); Downie, E.J. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); University of Glasgow, SUPA School of Physics and Astronomy, Glasgow (United Kingdom); The George Washington University, Center for Nuclear Studies, Washington, DC (United States); Fix, A. [Tomsk Polytechnic University, Laboratory of Mathematical Physics, Tomsk (Russian Federation); Hornidge, D.; Middleton, D.G. [Mount Allison University, New Brunswick (Canada); Huber, G.M. [University of Regina, Regina (Canada); Kashevarov, V.L. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); Lebedev Physical Institute, Moscow (Russian Federation); Kondratiev, R.; Lisin, V.; Polonski, A. [Institute for Nuclear Research, Moscow (Russian Federation); Korolija, M.; Mekterovic, D.; Micanovic, S.; Supek, I. [Rudjer Boskovic Institute, Zagreb (Croatia); Oussena, B. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); The George Washington University, Center for Nuclear Studies, Washington, DC (United States); Prakhov, S. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); The George Washington University, Center for Nuclear Studies, Washington, DC (United States); University of California Los Angeles, Los Angeles, California (United States); Sober, D.I. [The Catholic University of America, Washington, DC (United States); Unverzagt, M. [University of Mainz, Institut fuer Kernphysik, Mainz (Germany); University of Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Collaboration: The A2 Collaboration

2015-11-15

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of π{sup 0}π{sup 0} pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400 MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to ∼ 1550 MeV), where both reactions are dominated by the N(1520)3/2{sup -} → Δ(1232)3/2{sup +}π decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an N{sup *} → Nσ decay for the proton, while the reaction is dominated by a sequential decay via a Δπ intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis. (orig.)

Microscopic approach to subthreshold pion production in heavy-ion collisions

International Nuclear Information System (INIS)

Tohyama, M.; Kaps, R.; Masak, D.; Mosel, U.

1985-01-01

A microscopic approach to subthreshold pion production in heavy-ion collisions is proposed, in which the wave function of the nucleon system is approximated in the time-dependent Hartree-Fock theory and an effective interaction for the pion-production process is taken from (p,π) reaction theories. The model is applied to pion production in 16 O + 16 O collisions. (orig.)

Pion form factor within QCD instanton vacuum model

International Nuclear Information System (INIS)

Dorokhov, A.E.

1997-01-01

Instanton induced pion wave function is constructed. It provides an intrinsic k 1 dependence which suppress soft virtual one-gluon exchanges and thus legitimate the perturbative QCD (pQCD) calculations of the pion electromagnetic form factor in the region of momentum transfers above the scale. (author)

Theory of the low-energy pion-nucleon interaction

International Nuclear Information System (INIS)

Banerjee, M.K.; Cammarata, J.B.

1978-01-01

A once-subtracted form of the Low equation for the pion-nucleon scattering amplitude is derived, with partial conservation of axial-vector current used to define the amplitude when one pion is off the mass shell. The static approximation is not made and both the seagull terms and the antinucleon contribution (z graphs) are retained. The theory is applied to calculate the S-wave amplitudes in the elastic scattering region. Good agreement is found with the phase shift fits to the data when we use vertical-barg/sub π/(4M 2 ) vertical-bar = 11.69 and 25.5 MeV for the πN sigma commutator. The implications of this work for the analysis of low-energy elastic scattering of pions form nuclei are discussed. In particular, we point out how this work establishes the presence of a Laplacian term in the pion-nucleus optical potential with a magnitude that is fixed from the value of the sigma commutator

Dosimetry and radiobiology of negative pions and heavy ions

International Nuclear Information System (INIS)

Raju, M.R.

1978-01-01

The depth dose distribution of pion beams has not been found superior to protons. Pion radiation quality at the plateau region is comparable to conventional low-LET radiations, and radiobiology results also indicate RBE values close to unity. In the pion stopping region, the radiation quality increases considerably. Radiobiology data for negative pions at the Bragg peak position clearly indicate the increase in RBE and the reduction in OER. Even at the Bragg peak position, compared to fast neutrons, the average LET of negative pions is lower. Pion radiobiology data have indicated lower RBE values and higher OER values compared to fast neutrons. The radiation quality of fast neutrons is in between that of carbon and neon ions at the peak region and that of neon ions at the plateau is lower than for fast neutrons. The mean LET value for helium ions, even at the distal end of the peak, is lower than for fast neutrons. Dose localization of heavy ions has been found to decrease slowly with increasing charge of the heavy ion. The intercellular contact that protects cells after exposure to low-LET radiations is not detected after exposure to heavy ions. Single and fractionated doses of heavy ions produce dose-response curves for heavy ions having reduced shoulders but similar slopes when compared to gamma rays. Fractionated treatments of heavy ions produce an enhanced effect in the peak region compared to the plateau region and could lead to a substantial gain in therapeutic ratio. The OER for protons was similar to that for x rays. The OER values for negative pions, helium ions, and carbon ions were larger, for neon ions similar, and for argon ions smaller when compared to fast neutrons.Negative pions, helium ions, and carbon ions may be very effective clinically because the radiation quality of these beams is similar to that of the mixed scheme of neutrons and x rays

Radiative corrections to the charged pion-pair production process {pi}{sup -}{gamma} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup -} at low energies

Energy Technology Data Exchange (ETDEWEB)

Kaiser, N.; Petschauer, S. [Technische Universitaet Muenchen, Physik-Department T39, Garching (Germany)

2013-12-15

We calculate the one-photon loop radiative corrections to the charged pion-pair production process {pi}{sup -}{gamma} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup -}. In the low-energy region this reaction is governed by the chiral pion-pion interaction. The pertinent set of 42 irreducible photon-loop diagrams is calculated by using the package FeynCalc. Electromagnetic counterterms with two independent low-energy constants k{sub 1} and k{sub 2} are included in order to remove the ultraviolet divergences generated by the photon loops. Infrared finiteness of the virtual radiative corrections is achieved by including soft photon radiation below an energy cut-off {Lambda}. The purely electromagnetic interaction of the charged pions mediated by one-photon exchange is also taken into account. The radiative corrections to the total cross section (in the isospin limit) vary between +10% close to threshold and about -1% at a center-of-mass energy of 7m{sub {pi}}. The largest contribution comes from the simple one-photon exchange. Radiative corrections to the {pi}{sup +}{pi}{sup -} and {pi}{sup -}{pi}{sup -} mass spectra are studied as well. The Coulomb singularity of the final-state interaction produces a kink in the dipion mass spectra. The virtual radiative corrections to elastic {pi}{sup -}{pi}{sup -} scattering are derived additionally. (orig.)

Elastic photoproduction of ρ0 mesons at HERA

International Nuclear Information System (INIS)

Aid, S.; Andreev, V.; Andrieu, B.

1995-12-01

The cross section for the elastic photoproduction of ρ 0 mesons (γp→ρ 0 p) has been measured with the H1 detector at HERA for two average photon-proton centre-of-mass energies of 55 and 187 GeV. The lower energy point was measured by observing directly the ρ 0 decay giving a cross section of 9.1±0.9 (stat.)±2.5 (syst.) μb. The logarithmic slope parameter of the differential cross section, dσ/dt, is found to be 10.9±2.4 (stat.)±1.1 (syst.) GeV -2 . The ρ 0 decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be 13.6±0.8 (stat.)±2.4 (syst.) μb. (orig.)

Quarkonium momentum distributions in photoproduction and B decay

CERN Document Server

Beneke, Martin; Wolf, S

2000-01-01

According to our present understanding many $J/\\psi$ production processes proceed through a coloured $c\\bar{c}$ state followed by the emission of soft particles in the quarkonium rest frame. The kinematic effect of soft particle emission is usually a higher-order effect in the non-relativistic expansion, but becomes important near the kinematic endpoint of quarkonium energy (momentum) distributions. In an intermediate region a systematic resummation of the non-relativistic expansion leads to the introduction of so-called `shape functions'. In this paper we provide an implementation of the kinematic effect of soft gluon emission which is consistent with the non-relativistic shape function formalism in the region where it is applicable and which models the extreme endpoint region. We then apply the model to photoproduction of $J/\\psi$ and $J/\\psi$ production in $B$ meson decay. A satisfactory description of $B$ decay data is obtained. For inelastic charmonium photoproduction we conclude that a sensible comparis...

Study of ultraviolet light-induced DNA damage and repair: the role of the (6-4) photoproduct

International Nuclear Information System (INIS)

Franklin, W.A.

1985-01-01

Ultraviolet light induces lethal, mutagenic, and carcinogenic effects to cells. These effects are a result of the induction of photoproducts in the cellular DNA. One class of photoproducts was found as alkaline labile lesions in DNA, and it was proposed that such lesions were precursor products to the 6,4'-[pyrimidin-2'-one]-pyrimidine class of photoproducts that have been previously shown to occur in UV light-irradiated DNA. Using a series of dinucleotide compounds, the precursor compounds were isolated, and were demonstrated to be alkaline labile. These products were named the UV light-induced pyrimidine-pyrimidone (6-4) photoproducts, and their chemistry of formation in dinucleotides and DNA was studied. The formation of these photoproducts under conditions of chemical photosensitization was also measured. The most abundant of the (6-4) photoproducts is the thymine-cytosine (6-4) product, and the molecular structure of this compounds was determined by the use of infrared spectroscopy, proton NMR, and mass spectroscopy. The (6-4) products have been recently shown to be the major UV light-induced premutagenic lesions in E. coli. In E. coli, the repair of the (6-4) products is under the control of the uvrABC excision pathway. The rate of removal of (6-4) products was measured in a series of human cells lines. The rate of removal of (6-4) products from the DNA of a xeroderma pigmentosum complementation group A cell line was nearly that of the normal cells, yet these cells are unable to excise cyclobutane pyrimidine dimers. These results suggest that the removal of cyclobutane pyrimidine dimers and (6-4) products may be controlled by separate enzymatic pathways

Neutral Pion Rejection at L2 using the CMS Endcap Preshower

CERN Document Server

Kyriakis, Aristotelis; Loukas, Demetrios; Mousa, Jehad; Seez, Christopher

1999-01-01

Applying a general Artificial Neural Network approach, we have examined the possibility of neutral pion rejection at the Level 2 Trigger stage ( L2) principally using information from the CMS Endcap Preshower. We have studied both pion/photon and pion/electron discrimination. For L2 the hope was to achieve some useful pion/electron discrimination for a high electron efficiency. For a single electron/photon efficiency of 95% the results show that no useful rejection of neutral pions against electrons/photons can be obtained using this algorithm alone, due to the presence of tracker material. If the efficiency is lowered or information from the tracker is available, the rejection can increase dramatically. This will be the case for off-line analyses.

Low-energy photo- and electroproduction for physical pions

International Nuclear Information System (INIS)

MacMullen, J.T.

1979-02-01

The background resonance Δ(1230), Nsup(*)(1520), Nsup(*)(1470) and Nsup(*)(1535)pion and axial-vector amplitudes are first calculated in the soft pion and on-shell configuration, respectively. Then a comparison is made with the usual soft pion theorems and on-shell low-energy expansions of current algebra as worked out in the previous paper. The agreement is good and we also deduce a nucleon dipole form factor axial-vector mass of msub(A)approximately equal to 1,23 GeV. Finally an approximate value for the non-strange current quark mass of m equal to 0,64 +- 1,11μ is extracted from the data

Photoproduction of the f1(1285 ) meson

Science.gov (United States)

Dickson, R.; Schumacher, R. A.; Adhikari, K. P.; Akbar, Z.; Amaryan, M. J.; Anefalos Pereira, S.; Badui, R. A.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Cao, T.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Chetry, T.; Ciullo, G.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dugger, M.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fanchini, E.; Fedotov, G.; Filippi, A.; Fleming, J. A.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gothe, R. W.; Griffioen, K. A.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Holtrop, M.; Hicks, K.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, H.; Jo, H. S.; Joosten, S.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Kuleshov, S. V.; Lanza, L.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Mattione, P.; McKinnon, B.; Meyer, C. A.; Mirazita, M.; Markov, N.; Mokeev, V.; Moriya, K.; Munevar, E.; Murdoch, G.; Nadel-Turonski, P.; Net, L. A.; Ni, A.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Phelps, W.; Pisano, S.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Raue, B. A.; Ripani, M.; Rizzo, A.; Rosner, G.; Roy, P.; Salgado, C.; Seder, E.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, E. S.; Smith, G. D.; Sober, D.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Strakovsky, I. I.; Stankovic, I.; Strauch, S.; Sytnik, V.; Taiuti, M.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Weygand, D.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zonta, I.; CLAS Collaboration

2016-06-01

The f1(1285 ) meson with mass 1281.0 ±0.8 MeV/c2 and width 18.4 ±1.4 MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson Lab. Differential cross sections were obtained via the η π+π-,K+K¯0π- , and K-K0π+ decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the η π+π- final-state Dalitz distribution are consistent with the axial-vector JP=1+ f1(1285 ) identity, rather than the pseudoscalar 0- η (1295 ) . The production mechanism is more consistent with s -channel decay of a high-mass N* state and not with t -channel meson exchange. Decays to η π π go dominantly via the intermediate a0±(980 ) π∓ states, with the branching ratio Γ [a0π (noK ¯K )] /Γ [η π π (all)] =0.74 ±0.09 . The branching ratios Γ (K K ¯π ) /Γ (η π π ) =0.216 ±0.033 and Γ (γ ρ0) /Γ (η π π ) =0.047 ±0.018 were also obtained. The first is in agreement with previous data for the f1(1285 ) , while the latter is lower than the world average.

Pion condensation in cold dense matter and neutron stars

International Nuclear Information System (INIS)

Haensel, P.; Proszynski, M.

1982-01-01

We study possible influence, on the neutron star structure, of a pion condensation occurring in cold dense matter. Several equations of state with pion-condensed phase are considered. The models of neutron stars are calculated and confronted with existing observational data on pulsars. Such a confrontation appears to rule out the models of dense matter with an abnormal self-bound state, and therefore it seems to exclude the possibility of the existence of abnormal superheavy neutron nuclei and abnormal neutron stars with a liquid pion-condensed surface

Coherent pion production induced by protons and light ions

International Nuclear Information System (INIS)

Fernandez de Cordoba, P.; Oset, E.; Vicente-Vacas, M.J.

1995-01-01

We study coherent pion production by means of the (p,n) and (He,t) reactions on different nuclei and at different energies of the projectile. Energy and angular distributions are calculated. The angular distributions are rather narrow along the direction of the momentum transfer, particularly in heavy nuclei. The reaction is sensitive to the longitudinal part of the elementary NN→NΔ interaction. It also provides a new tool to obtain information on the pion-nuclear interaction, complementary to that offered by reactions with real pions. (orig.)

Correlations of neutral pions in ultrarelativistic heavy ion collisions

International Nuclear Information System (INIS)

Peitzmann, T.; Beckmann, P.; Berger, F.; Glewing, G.; Dragon, L.; Glasow, R.; Kampert, K.H.; Loehner, H.; Purschke, M.; Santo, R.; Albrecht, R.; Bock, R.; Claesson, G.; Gutbrod, H.H.; Kolb, B.W.; Lund, I.; Schmidt, H.R.; Siemiarczuk, T.; Awes, T.C.; Baktash, C.; Ferguson, R.L.; Lee, I.Y.; Obenshain, F.E.; Plasil, F.; Soerensen, S.P.; Young, G.R.; Eklund, A.; Garpman, S.; Gustafsson, H.A.; Idh, J.; Kristiansson, P.; Oskarsson, A.; Otterlund, I.; Persson, S.; Stenlund, E.; Franz, A.; Poskanzer, A.M.; Ritter, H.G.

1989-01-01

Correlations of 4 photons representing neutral pions have been studied in ultrarelativistic heavy ion collisions. Data were taken in the WA80 experiment at the CERN-SPS with a 200 A GeV oxygen beam. The π 0 are detected via their decay photons with a high-granularity lead glass array. Special features of interferometry using neutral pions will be discussed. The extracted preliminary parameters for high p T pions emitted near midrapidity in O+Au collisions lead to rather small effective source sizes. (orig.)

Pion-induced damage in silicon detectors

CERN Document Server

Bates, S; Glaser, M; Lemeilleur, F; León-Florián, E; Gössling, C; Kaiser, B; Rolf, A; Wunstorf, R; Feick, H; Fretwurst, E; Lindström, G; Moll, Michael; Taylor, G; Chilingarov, A G

1995-01-01

The damage induced by pions in silicon detectors is studied for positive and negative pions for fluence up to 10(14)cm-2 and 10(13) cm-2 respectively. Results on the energy dependence of the damage in the region of 65-330 MeV near to the  resonance are presented. The change in detector characteristics such as leakage current, charge collection efficiency and effective impurity concentration including long-term annealing effects have been studied. Comparisons to neutron and proton-induced damage are presented and discussed.

Photon flux determination for a precision measurement of the neutral pion lifetime

Energy Technology Data Exchange (ETDEWEB)

Teymurazyan, Aram [Univ. of Kentucky, Lexington, KY (United States)

2008-01-01

The Jefferson Lab Hall B PrimEx Collaboration is using tagged photons to perform a 1.4% level measurement of the absolute cross section for the photo-production of neutral pions in the Coulomb field of a nucleus as a test of Chiral Perturbation Theory. Such a high precision pushes the limits of the photon tagging technique in regards to the determination of the absolute photon flux. A multifaceted approach to this problem has included measuring the absolute tagging ratios with a Total Absorption Counter (TAC) as well as relative tagging ratios with a Pair Spectrometer (PS), and determining the rate of the tagging counters using multi-hit TDC's and a clock trigger. This enables the determination of the absolute tagged photon flux for the PrimEx experiment with uncertainty of ~ 1.0%, which is unprecedented. In view of the stringent constraints on the required precision of the photon flux for this experiment, periodicmeasurements of the pair production cross section were performed throughout the run. In these measurements, both the photon energy and flux were determined by the Jefferson Lab Hall B tagger, and the electron-positron pairs were swept by a magnetic field and detected in the new 1728 channel hybrid calorimeter (HyCal). The pair production crosssection was extracted with an uncertainty of ~ 2%, producing an agreement with theoretical calculations at the level of ~ 2%. This measurement provided a unique opportunity to verify the photon flux determination procedure for the PrimEx experiment.

The Λ(1520) photoproduction from proton

International Nuclear Information System (INIS)

He, Jun

2014-01-01

The Λ(1520) photoproduction from proton target is investigated within the effective Lagrangian method and well compared with the experimental data. The D 13 state N(2120) plays the most important role among the nucleon resonances. Besides N(2120), a nucleon resonance [5/2 - ] 2 (2080) predicted by the constituent quark model is found also important to reproduce the experimental data. Other nucleon resonances give negligible contributions in the channel considered in this work. (author)

Aspects of the heavy-quark photoproduction in the semihard approach

International Nuclear Information System (INIS)

Mariotto, C. Brenner; Ducati, M.B. Gay; Machado, M.V.T.

2002-01-01

In this contribution we report on the calculations of heavy-quark photoproduction using the K p erpendicular to-factorization (semihard) approach, emphasizing the results obtained with the phenomenological saturation model. (author)

Recent developments in the understanding of pion-nucleus scattering

International Nuclear Information System (INIS)

Johnson, M.B.

1983-01-01

A development of the theory of pion-nucleus scattering is given in a field theoretical framework. The theory is designed to describe pion elastic scattering and single- and double-charge exchange to isobaric analog states. An analysis of recent data at low and resonance energies is made. Strong modifications to the simple picture of the scattering as a succession of free pion-nucleon interactions are required in order to understand the data. The extent to which the experiment is understood in terms of microscopic theory is indicated. 71 references

Negative pion capture in chemical compounds

International Nuclear Information System (INIS)

Butsev, V.S.; Chultem, D.; Gavrilov, Yu.K.; Ganzorig, Dz.; Norseev, Yu.V.; Presperin, V.

1976-01-01

The results are reported of an experiment of determination of the probability of capture of resting negative pions by iodine nuclei in alkali metal iodides (LiI, NaI, KI, RbI, CsI). The yield of an isomer sup(116m)(Sb/8 - ) with a high spin number, formed in the reaction 127 I(π - , lp 10n) allows to determine the relative probability of the nuclear capture of pions in the above compounds. The results obrained are compared with the predictions of the Fermi-Teller Z-law

Calculation of the pion-nucleon double spectral functions and applications

International Nuclear Information System (INIS)

Grether, D.

1986-01-01

In the present thesis the latest results from pion-pion and pion-nucleon phase analyses are applied in order to calculate the pion-nucleon double spectral functions which belong to the elastic unitarity in the t-channel. The equivalence of the partial wave projection of these spectral functions in the s-channel with the elastic t-channel unitarity is extensively discussed. After we summarize the aspects of the pion-nucleon system seeming in this connection interesting we discuss the Mandelstam method for the calculation of the spectral functions by means of the elastic t-channel unitarity as well as the applied input and present the results. Thereafter we use these results in order to calculate by means of a fixed t-channel dispersion relation the real parts of the t-channel cuts. Partial wave projections into the t-channel are proved as equivalent to the elastic t-channel unitarity. We study the compatibility of the asymptotic behaviour of the spectral functions relative to the energy with current Regge pole models. Finally we use our results in order to calculate the pion-nucleon partial waves by means of their Froissart-Gribov representations which follow from their analyticity at fixed energy. (orig./HSI) [de

Beam asymmetry Σ for π0 and η photoproduction on the proton at GlueX

Science.gov (United States)

Zhang, Zhenyu; GlueX Collaboration

2016-09-01

Measurements of meson photoproduction at high energies began almost 50 years ago with bubble chamber experiments at SLAC, DESY, and Cambridge. These data have been successfully described through Regge theory in terms of t-channel quasi-particle exchange. High statistics measurements of pseudoscalar meson photoproduction at GlueX, using the 9 GeV linearly-polarized, tagged photon beam in Jefferson Lab's Hall D, will provide important new constraints on these Regge models. These measurements will test our understanding of the photoproduction mechanism at high energy, which is a necessary first step toward the broader meson spectroscopy program at GlueX. Through finite energy sum rules, these measurements can also impose new constraints on the extraction of nucleon resonances from low energy photoproduction data. In this talk, preliminary results for the linearly polarized photon beam asymmetry Σ for the exclusive reactions γp -> pπ0 and γp -> pη will be presented. These are the first measurements of the η beam asymmetry at these energies. Supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and the China Scholarship Council No. 201506275156.

Pion production in high energy heavy ion collisions

International Nuclear Information System (INIS)

Wolf, K.L.; Bock, R.; Brockmann, R.

1984-01-01

Experimental data for heavy ion pion production reactions are compared with the predictions of a number of versions of cascade models. Pion suppression effects observed in the experimental data are fit by introducing refinements into cascade theory. Impact parameter adjustment, off-shell effects on the potential and perturbations due to nuclear matter are considered

Production of pions and anomalous projectile fragments in heavy ion collisions

International Nuclear Information System (INIS)

Noren, B.

1988-05-01

Results are presented from investigations of the mean free path (mfp) of multiply charged fragments, produced by 1.8 A GeV argon nuclei. The mfp's have been studied experimentally, and no dependence of the mfp on the distance from the preceeding collision is observed. In a Monte Carlo simulation, the mfp estimators are investigated for different statistics, with or without an enhanced reaction probability. Intermediate energy heavy ion collisions have been studied using the carbon beam produced at the CERN SC-accelerator. Cross-sections for pion + and pion - have been measured over a wide range of angles and targets. Also, coincidence measurements with projectile-like fragments have been performed. The pion - /pion + ratio has been studied for C+Li, C+C, C+Pb, C+ 116 Sn and C+ 124 Sn. Inconsistencies in the target mass dependence of the pion yield disappear if a correction for reabsorption in the target nucleus is included. The projectile breakup is significantly stronger for pion producing collisions than for the average collision, thus indicating a much stronger abundance of central collisions. (With 32 refs.) (author)

UV-visible degradation of boscalid--structural characterization of photoproducts and potential toxicity using in silico tests.

Science.gov (United States)

Lassalle, Yannick; Kinani, Aziz; Rifai, Ahmad; Souissi, Yasmine; Clavaguera, Carine; Bourcier, Sophie; Jaber, Farouk; Bouchonnet, Stéphane

2014-05-30

Boscalid is a carboximide fungicide mainly used for vineyard protection as well as for tomato, apple, blueberry and various ornamental cultivations. The structural elucidation of by-products arising from the UV-visible photodegradation of boscalid has been investigated by gas chromatography/multi-stage mass spectrometry (GC/MS(n) ) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) couplings. The potential toxicities of transformation products were estimated by in silico calculations. Aqueous solutions of boscalid were irradiated up to 150 min in a self-made reactor equipped with a mercury lamp. Analyses were carried out using a gas chromatograph coupled with an ion trap mass spectrometer operated in both electron ionization (EI) and chemical ionization (CI) modes and a liquid chromatograph coupled with a quadrupole time-of-flight (Q-TOF) mass spectrometer operated in electrospray ionization (ESI) mode. Multiple-stage collision-induced dissociation (CID) experiments were performed to establish dissociation pathways of ions. The QSAR (Quantitative Structure-Activity Relationship) T.E.S.T. program allowed the estimation of the toxicities of the by-products. Eight photoproducts were investigated. Chemical structures were proposed not only on the interpretation of multi-stage CID experiments, but also on kinetics data. These structures led us to suggest photodegradation pathways. Three photoproducts were finally detected in Lebanon in a real sample of grape leaves for which routine analysis had led to the detection of boscalid at 4 mg kg(-1). With one exception, the structures proposed for the photoproducts on the basis of mass spectra interpretation have not been reported in previous studies. In silico toxicity predictions showed that two photoproducts are potentially more toxic than the parent compound considering oral rat LD50 while five photoproducts may induce mutagenic toxicity. With the exception of one compound, all photoproducts may

UV-visible degradation of boscalid- structural characterization of photoproducts and potential toxicity using in silico tests

International Nuclear Information System (INIS)

Rifai, A.; Jaber, F.; Lassalle, Y.; Kinani, A.; Souissi, Y.; Clavaguera, C.; Bourcier, S.; Bouchonnet, St.

2014-01-01

RATIONALE: Boscalid is a carboximide fungicide mainly used for vineyard protection as well as for tomato, apple, blueberry and various ornamental cultivations. The structural elucidation of by-products arising from the UV-visible photodegradation of boscalid has been investigated by gas chromatography/multi-stage mass spectrometry (GC/MSn) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) couplings. The potential toxicities of transformation products were estimated by in silico calculations. METHODS: Aqueous solutions of boscalid were irradiated up to 150 min in a self-made reactor equipped with a mercury lamp. Analyses were carried out using a gas chromatograph coupled with an ion trap mass spectrometer operated in both electron ionization (EI) and chemical ionization (CI) modes and a liquid chromatograph coupled with a quadrupole time-of-flight (Q-TOF) mass spectrometer operated in electrospray ionization (ESI) mode. Multiple-stage collision-induced dissociation (CID) experiments were performed to establish dissociation pathways of ions. The QSAR (Quantitative Structure-Activity Relationship) T.E.S.T. program allowed the estimation of the toxicities of the by-products. RESULTS: Eight photoproducts were investigated. Chemical structures were proposed not only on the interpretation of multi-stage CID experiments, but also on kinetics data. These structures led us to suggest photodegradation pathways. Three photoproducts were finally detected in Lebanon in a real sample of grape leaves for which routine analysis had led to the detection of boscalid at 4 mg kg1. CONCLUSIONS: With one exception, the structures proposed for the photoproducts on the basis of mass spectra interpretation have not been reported in previous studies. In silico toxicity predictions showed that two photoproducts are potentially more toxic than the parent compound considering oral rat LD50 while five photoproducts may induce mutagenic toxicity. With the exception of one compound

Photoproduction of events with rapidity gaps between jets with ZEUS at HERA

Energy Technology Data Exchange (ETDEWEB)

Ryan, P.D.

2006-11-15

Cross sections for the photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 38.6 pb{sup -1}. Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value E{sup CUT}{sub T}. The data show a clear excess above the predictions of standard photoproduction models. Models which include color-singlet exchange are able to describe the data. (orig.)

Photoproduction of events with rapidity gaps between jets with ZEUS at HERA

International Nuclear Information System (INIS)

Ryan, P.D.

2006-11-01

Cross sections for the photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 38.6 pb -1 . Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value E CUT T . The data show a clear excess above the predictions of standard photoproduction models. Models which include color-singlet exchange are able to describe the data. (orig.)

Dynamical chiral symmetry breaking and pion decay constant

International Nuclear Information System (INIS)

Gogohia, V.Sh.; Kluge, Gy.

1991-08-01

Flavour non-singlet, chiral axial-vector Ward-Takahashi identity is investigated in the framework of dynamical chiral symmetry breaking. The use of the condition of stationarity for the bound-state amplitude is proposed in order to fully determine this quantity and the regular piece of the corresponding axial vertex. This makes it possible to express the pion decay constant in terms of the quark propagator variables only. An exact expression was found for the pion decay constant in current algebra and in Jackiw-Johnson representation as well. We also find a new expression for the pion decay constant in the Pagels-Stokar-Cornwall variables within the framework of Jackiw-Johnson representation. (author) 22 refs.; 2 figs

Pions to Quarks

Science.gov (United States)

Brown, Laurie Mark; Dresden, Max; Hoddeson, Lillian

2009-01-01

Part I. Introduction; 1. Pions to quarks: particle physics in the 1950s Laurie M Brown, Max Dresden and Lillian Hoddeson; 2. Particle physics in the early 1950s Chen Ning Yang; 3. An historian's interest in particle physics J. L. Heilbron; Part II. Particle discoveries in cosmic rays; 4. Cosmic-ray cloud-chamber contributions to the discovery of the strange particles in the decade 1947-1957 George D. Rochester; 5. Cosmic-ray work with emulsions in the 1940s and 1950s Donald H. Perkins; Part III. High-energy nuclear physics; Learning about nucleon resonances with pion photoproduction Robert L. Walker; 7. A personal view of nucleon structure as revealed by electron scattering Robert Hofstadter; 8. Comments on electromagnetic form factors of the nucleon Robert G. Sachs and Kameshwar C. Wali; Part IV. The new laboratory; 9. The making of an accelerator physicist Matthew Sands; 10. Accelerator design and construction in the 1950s John P. Blewett; 11. Early history of the Cosmotron and AGS Ernest D. Courant; 12. Panel on accelerators and detectors in the 1950s Lawrence W. Jones, Luis W. Alvarez, Ugo Amaldi, Robert Hofstadter, Donald W. Kerst, Robert R. Wilson; 13. Accelerators and the Midwestern Universities Research Association in the 1950s Donald W. Kerst; 14. Bubbles, sparks and the postwar laboratory Peter Galison; 15. Development of the discharge (spark) chamber in Japan in the 1950s Shuji Fukui; 16. Early work at the Bevatron: a personal account Gerson Goldhaber; 17. The discovery of the antiproton Owen Chamberlain; 18. On the antiproton discovery Oreste Piccioni; Part V. The Strange Particles; 19. The hydrogen bubble chamber and the strange resonances Luis W. Alvarez; 20. A particular view of particle physics in the fifties Jack Steinberger; 21. Strange particles William Chinowsky; 22. Strange particles: production by Cosmotron beams as observed in diffusion cloud chambers William B. Fowler; 23. From the 1940s into the 1950s Abraham Pais; Part VI. Detection of the

Photodissociation thresholds of OH produced from CH sub 3 OH in solid neon and argon

CERN Document Server

Cheng, B M; Lo, W J; Lee, Y P

2001-01-01

Photodissociation thresholds of OH from CH sub 3 OH in solid Ne and Ar were determined via photolysis of CH sub 3 OH/Ne and CH sub 3 OH/Ar (1/200) samples in situ at 4 K. The samples were irradiated with VUV synchrotron radiation after dispersion by a Seya-Namioka monochromator. The OH photo-product was detected by means of laser-induced fluorescence technique. The increase of fluorescent intensity of OH was monitored and recorded after the matrix sample was irradiated at different wavelengths for 3-5 min. Photodissociation threshold energies of 7.13+-0.02 eV (174.0+-0.5 nm) and 7.08+-0.04 eV (175.0+-1.0 nm) were measured for OH production of CH sub 3 OH in solid Ne and Ar, respectively.

Comparison of a two-body threshold (π,2π) reaction mechanism with the usual one-body mechanism in the deuteron

International Nuclear Information System (INIS)

Rockmore, R.

1984-01-01

A two-body threshold (π +- ,π +- π -+ ) reaction mechanism is suggested in direct analogy with pion absorption. The mechanism involves boson rescattering via Δ excitation. The relative importance of this mechanism and the ordinary one-body mechanism in nuclei is studied in the particular case of S-wave deuteron targets. The contribution of the two-body mechanism to the threshold reaction cross section is found to be less than 1% of the simple one-body estimate

Pion in a box

International Nuclear Information System (INIS)

Bietenholz, W.; Rakow, P.E.L.; Schierholz, G.; Regensburg Univ.

2010-02-01

The residual mass of the pion in a finite spatial box at vanishing quark masses is computed with two flavors of dynamical clover fermions. The result is compared with predictions of chiral perturbation theory in the δ regime. (orig.)

Pion double charge exchange

International Nuclear Information System (INIS)

Cooper, M.D.

1978-01-01

The pion double charge exchange data on the oxygen isotopes is reviewed and new data on 9 Be, 12 C, 24 Mg, and 28 Si are presented. Where theoretical calculations exist, they are compared to the data. 9 references