Contribution to the study of the antinucleon-nucleon interactions
International Nuclear Information System (INIS)
A potential for the antinucleon-nucleon system is constructed. It has an imaginary part of very short range, respecting theoretical constraints. This implies a significant dependence on spin and isospin, and also on the energy. The spectrum of resonances is computed using an original method. One state (I=0 jPC=0++) could be easily detected. A model is proposed for a class of inelastic reactions: NantiN #-> # 2 mesons. Using a distorted-wave-Born approximation, comparisons with experiment are made. Finally, we consider some aspects of the atomic pantip system (protonium)
Nucleon-antinucleon resonance spectrum in a potential model
Lacombe, M.; Loiseau, B.; Moussallam, B.; Mau, R. Vinh
1984-05-01
We investigate the spectrum of antinucleon-nucleon resonances, using an optical potential we derived recently. An effective method to compute the S-matrix poles is presented. The corresponding phase shifts do not behave as ordinary resonances in the Argand diagram. We show, however, that the poles can be located by extrapolating the phase shifts with the aid of polynomial fits. The annihilation part of our potential is state and energy dependent and of short range. It yields a richer spectrum than that given by a longer ranged annihilation model.
Roles of Antinucleon Degrees of Freedom in the Relativistic Random Phase Approximation
Kurasawa, Haruki
2015-01-01
Roles of antinucleon degrees of freedom in the relativistic random phase approximation(RPA) are investigated. The energy-weighted sum of the RPA transition strengths is expressed in terms of the double commutator between the excitation operator and the Hamiltonian, as in nonrelativistic models. The commutator, however, should not be calculated with a usual way in the local field theory, because, otherwise, the sum vanishes. The sum value obtained correctly from the commutator is infinite, owing to the Dirac sea. Most of the previous calculations takes into account only a part of the nucleon-antinucleon states, in order to avoid the divergence problems. As a result, RPA states with negative excitation energy appear, which make the sum value vanish. Moreover, disregarding the divergence changes the sign of nuclear interactions in the RPA equation which describes the coupling of the nucleon particle-hole states with the nucleon-antinucleon states. Indeed, excitation energies of the spurious state and giant monop...
The signal of $Z^\\pm(4430)$ in nucleon-antinucleon scattering
Ke, Hong-Wei; Liu, Xiang(Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, 730000, Lanzhou , China)
2008-01-01
We study the production of $Z^\\pm(4430)$ at a nucleon-antinucleon scattering experiment. Considering the PANDA experiment to be an ideal platform to explore the production of the charmonium and charmonim-like states, we suggest the forthcoming PANDA experiment to pay attention to the production of $Z^\\pm(4430)$.
Electron-Positron to Nucleon-Antinucleon Pair at Threshold and Proton Form Factor
Yan, Y; Kobdaj, C; Suebka, P
2009-01-01
The reactions of electron-positron to nucleon-antinucleon pair at energy threshold are studied in a non-perturbative quark model. The puzzling experimental result that the ratio of the cross section of electron-positron to proton-antiproton to the one of electron-positron to neutron-antineutron is smaller than 1 can be understood in the framework of the phenomenological nonrelativistic quark model and the theoretical predictions for the time-like proton form factor at energy threshold are well consistent with the experimental data. The work suggests that the two-step process, in which the primary quark-antiquark pair forms first a vector meson which in turn decays into a hadron pair, is dominant over the one-step process in which the primary quark-antiquark pair is directly dressed by additional quark-antiquark pairs to form a hadron pair. The experimental data on the reactions of electron-positron to nucleon-antinucleon strongly suggest the reported vector meson omega(1930) to be a 2D-wave particle, while th...
Antinucleon-nucleus interactions
Energy Technology Data Exchange (ETDEWEB)
Dover, C.B.
1987-01-01
Recent experimental and theoretical results on anti p-nucleus interactions are reviewed. We focus on determinations of the anti p optical potential from elastic scattering, the use of (anti p, anti p') inelastic scattering to reveal aspects of the spin-isospin dependence of N anti N amplitudes, and some puzzling features of (anti p, anti n) charge exchange reactions on nuclei. 47 refs., 7 figs.
有限核真空中的反核子能谱%Spectra of Anti-Nucleons in the Vacuum of Finite Nuclei
Institute of Scientific and Technical Information of China (English)
茅广军
2004-01-01
The quantum vacuum in a many-body system of finite nuclei has been investigated within the relativistic Hartree approach which describes the bound states of nucleons and anti-nucleons consistently. The contributions of the Dirac sea to the source terms of the meson-field equations are taken into account up to the one-nucleon loop and one-meson loop. The tensor couplings for the ω- and ρ-meson are included in the model. After adjusting the parameters of the model to the properties of spherical nuclei, a large effective nucleon mass m */MN ≈ 0. 78 is obtained. The overall nucleon spectra of shell-model states are in agreement with the data. The computed anti-nucleon spectra in the vacuum differ about 20-30MeV with and without the tensor-coupling effects.%通过建立能够自洽地描述核子和反核子束缚态的相对论Hartree模型来研究有限核中的量子真空,其中狄拉克海对介子场方程的贡献由单圈图考虑,模型中还引入了ω介子和ρ介子的张量耦合项.在拟合球形核的性质后得到模型的参数,给出核子有效质量为m*/MN≈0.78;计算得到的核子壳模型能级与实验值相一致,在考虑张量耦合项的效应后真空反核子位阱深度增大了20-30 MeV.
Nucleon-antinucleon annihilation in chiral soliton model
International Nuclear Information System (INIS)
We investigate annihilation process of nucleons in the chiral soliton model by the path integral method. A soliton-antisoliton pair is shown to decay into mesons at range of about 1fm, defined by the S bar S potential. Contribution of the annihilation channel to the elastic scattering is discussed
Nucleon-antinucleon annihilation in chiral soliton model
International Nuclear Information System (INIS)
We investigate annihilation process of nucleons in chiral soliton model by path integral method. Soliton-antisoliton pair is shown to decay into pions at range of order of about 1 fm, defined by SS-bar potential. Contribution of annihilation channel into elastic scattering is discussed. (author). 14 refs, 1 fig
Conference summary: antinucleon- and nucleon-nucleus interactions
International Nuclear Information System (INIS)
Topics summarized include: the hadronic substructure, the EMC effect, observations on relativity and the Dirac equation, and relativistic Lagrangian field theories for N-N interactions and nuclear matter
Coupled-channel analysis of low energy nucleon-antinucleon interactions
International Nuclear Information System (INIS)
Multichannel M-matrix method is applied to an NN-bar-system with taking into account elastic pp-bar-scattering, charge-exchange pp-bar→nn-bar reaction and pp-bar annihilation. It is shown that contrary to standard assumptions the isotopic invariance due the large influence of the charge exchange channel affects very significantly the parameters of strong interactions. Contrary to previous descriptions, M-matrix elements are treated as real functions. The differential and total cross-sections for pp-bar→pp-bar and pp-bar→nn-bar processes, cross-section δtot(pp-bar) and the real-to-imaginary ratio of the forward amplitude of elastic pp-bar scattering up to beam momenta plab=600 MeV/c are described. The fitting leads to a resonance in the s-wave at about plab=500 MeV/c and to bound states in p-wave near the pp-bar threshold. 33 refs.; 8 figs.; 3 tabs
Baryonic Effect on XcJ Suppression in Au+Au Collisions at RHIC Energies
Institute of Scientific and Technical Information of China (English)
PENG Ru; XU Xiao-Ming; ZHOU Dai-Cui
2004-01-01
@@ We predict that xcJ mesons at low transverse momentum in the central rapidity region are almost dissociated by nucleons and antinucleons in hadronic matter produced in central Au+Au collisions at relativistic high-ion collider (RHIC) energies √SNN = 130 and 200 GeV. In the calculations the nucleon and antinucleon distributions in hadronic matter are results of evolution from their freeze-out distributions which well fit the experimental transverse momentum spectra of proton and antiproton.
Antiproton-proton resonant like channels in J/Psi decays into photon, proton and antiproton
Loiseau, B
2005-01-01
The BES collaboration has recently observed a strong enhancement close to the proton-antiproton threshold in the J/Psi decays into photon, proton and antiproton. Such a structure can be explained by a traditional nucleon-antinucleon model. The near threshold 1S0 bound state and/or the well-established 3P0 resonant state found in this nucleon-antinucleon interaction can adequately describe the BES data.
Pion interactions at medium energies. Progress report, December 1, 1982-January 31, 1984
International Nuclear Information System (INIS)
Research summaries are given on the following topics: spin dependence of nucleon-nucleon amplitudes, kaon and hypernuclear physics, kaon reactions at higher momentum, anti-nucleon reactions, and double charge exchange with heavy ions. A feasibility study for a 1 to 2 GeV separated kaon beam at the AGS is included. Publications are listed
Pion interactions at medium energies. Progress report, February 1, 1984-January 31, 1985
International Nuclear Information System (INIS)
Our research program has developed into two major thrusts. The first uses kaons produced at the Brookhaven National Laboratory (BNL) Alternating Gradient Synchrotron (AGS) to study the properties of hyperons embedded in nuclear matter. Specifically we have had under investigation for some time the spectra of both lambda and sigma hypernuclei and the extraction of the hyperon-nucleon interaction parameters. The second thrust uses antinucleons produced by the AGS to study the antinucleon nucleon interaction and the properties of the annihilation reaction. Both thrusts have an approved program at the AGS which will last several years. Experiments are listed and abstracts of current research are given. Some preliminary results from experiments are presented, and new approved proposals are detailed
Measurement of interaction between antiprotons
,
2015-01-01
One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force since acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered and their masses measured, we have no direct knowledge of the nuclear force between antinucleons. Here, we study antiproton pair correlations among data taken by the STAR experiment at the Relativistic Heavy Ion Collider and show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: namely, the scattering length (f0) and effective range (d0). As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, our result provides a fundamental ingr...
International Nuclear Information System (INIS)
Progress is briefly reported on a number of experiments on hadron and photon interactions. Stand-alone bubble chamber experiments were completed, and current efforts focus on hybrid chamber research. Two new projects are being proposed-mu neutrinos in the Kitigaki bubble chamber at Fermilab, and a search for a threshold enhancement in the production of sigma particles in the SLAC 40 hybrid chamber. Photoproduction and antinucleon physics are covered. Experiments at CERN were run to observe diffractive strange particle production
Verifying Unmatter by Experiments, More Types of Unmatter, and a Quantum Chromodynamics Formula
Directory of Open Access Journals (Sweden)
Smarandache F.
2005-07-01
Full Text Available As shown, experiments registered unmatter: a new kind of matter whose atoms include both nucleons and anti-nucleons, while their life span was very short, no more than 10^−20 sec. Stable states of unmatter can be built on quarks and anti-quarks: applying the unmatter principle here it is obtained a quantum chromodynamics formula that gives many combinations of unmatter built on quarks and anti-quarks.
Search for baryonium and the physics at FAIR
Directory of Open Access Journals (Sweden)
Wycech S.
2014-01-01
Full Text Available The existence of nucleon-antinucleon quasi-bound state is indicated in two decay modes of the J/ψ meson studied by BES. We discuss an explanation in a fairly traditional Paris-potential model of the NN̄ interactions. A broad, S-wave and a narrow P-wave quasi-bound states are predicted by this model. Some existing experimental evidence and possible verifications in the future are indicated.
Physics with antiprotons at LEAR in the ACOL ERA. Proceedings of the 3. LEAR Workshop
Energy Technology Data Exchange (ETDEWEB)
Gastaldi, U.; Klapisch, R.; Richard, J.M.; Tran Thanh Van, J. (eds.)
1985-01-01
The programme covered the following topics: accelerator aspects (anti-p production, LEAR, advanced developments, cooling, LEAR design inspired machines). Nucleon antinucleon interactions (panti-p atom, scattering, annihilation, spin effects, antineutron physics, antibaryon physics). Spectroscopy (light mesons, hybrids, glueballs, baryonia, quarkonia). Rare channels (form factors, CP, CPT, C, T violation, quantum mechanics tests) anti-p nucleus interactions (exotic atoms, scattering, annihilation, hypernuclei). New ideas (antigravity, high precision experiments). New detectors (new experiments, general and/or technical aspects).
πN TDAs from charmonium production in association with a forward pion at P̅ANDA
Directory of Open Access Journals (Sweden)
Ma B.
2014-06-01
Full Text Available Charmonium production in association with a forward or backward pion in nucleon-antinucleon annihilation is one of the most promising reaction to access nucleon-to-pion transition distribution amplitudes (TDAs at P̅ANDA. We briefly review the description of this reaction in terms of πN TDAs within the collinear factorization approach and present the first results of dedicated feasibility studies for the P̅ANDA experimental setup.
Revisiting big-bang nucleosynthesis constraints on dark-matter annihilation
Directory of Open Access Journals (Sweden)
Masahiro Kawasaki
2015-12-01
Full Text Available We study the effects of dark-matter annihilation during the epoch of big-bang nucleosynthesis on the primordial abundances of light elements. We improve the calculation of the light-element abundances by taking into account the effects of anti-nucleons emitted by the annihilation of dark matter and the interconversion reactions of neutron and proton at inelastic scatterings of energetic nucleons. Comparing the theoretical prediction of the primordial light-element abundances with the latest observational constraints, we derive upper bounds on the dark-matter pair-annihilation cross section. Implication to some of particle-physics models are also discussed.
International Nuclear Information System (INIS)
The predictions are made for relative yields kaons, hyperons, antinucleons, and lightest sub(ΛΛ)sup(4)He, sub(ΛΛ)sup(6)He and sub(ΛΛ)sup(10)B hyperfragments for various combinations of colliding nuclei up to 10 GeV/nucleon within the firestreak model taking account of the associated nature of the strange particle production. These results may be used to identify the signs of a possible phase transition of hadrons into the quark-gluon plasma
Mass shift of -meson in nuclear matter
Indian Academy of Sciences (India)
J R Morones-Ibarra; Mónica Menchaca Maciel; Ayax Santos-Guevara; Felipe Robledo Padilla
2013-03-01
The propagation of -meson in nuclear matter is studied in the Walecka model, by assuming that the sigma couples to a pair of nucleon–antinucleon states and to particle–hole states. The in-medium effect of - mixing is also studied. For completeness, the coupling of sigma to two virtual pions was also considered. It is found that the -meson mass decreases with respect to its value in vacuum and that the contribution of the - mixing effect on the mass shift is relatively small.
Spin Symmetry for Anti-Lambda Spectrum in atomic nucleus
Song, Chunyan; Meng, Jie
2009-01-01
The spin symmetry of anti-Lambda spectrum in nucleus ^{16}O has been studied in the relativistic mean field theory. The spin-orbit splittings of spin doublets are found to be around 0.03-0.07 MeV and the dominant components of the Dirac spinor for the anti-Lambda spin doublets are found to be near identical. It indicates that there is an even better spin symmetry in the anti-Lambda spectrum than that in the anti-nucleon spectrum.
Mass shift of σ-meson in nuclear matter
International Nuclear Information System (INIS)
The propagation of σ-meson in nuclear matter is studied in the Walecka model, by assuming that sigma couples to a pair of nucleon-antinucleon states to particle-hole states. The in-medium effect of σ-ω mixing is also studied. For completeness, the coupling of sigma to two virtual pions was also considered. It is found that the σ-meson mass decreases with respect to its value in vacuum and that the contribution of the σ-ω mixing effect on the mass shift is relatively small. (author)
Spin Symmetry for Anti-Lambda Spectrum in Atomic Nucleus
Institute of Scientific and Technical Information of China (English)
SONG Chun-Yan; YAO Jiang-Ming; MENG Jie
2009-01-01
The spin symmetry of the anti-Lambda spectrum in nucleus ~(16)O is studied in the relativistic mean field theory.The spin-orbit splittings of spin doublets are found to be around 0.03-0.07 MeV and the dominant components of the Dirac spinor for the anti-Lambda spin doublets are found to be near identical.It is indicated that there is an even better spin symmetry in the anti-Lambda spectrum than that in the anti-nucleon spectrum.
Gotta, D
1999-01-01
The Lyman and Balmer transitions from antiprotonic hydrogen and deuterium were studied extensively at the low-energy-antiproton ring LEAR at CERN in order to determine the strong interaction effects. A first series of experiments $9 was performed with semiconductor and gaseous X-ray detectors. In the last years of LEAR operation using a Bragg crystal spectrometer, strong interaction parameters in the 2p states of antiprotonic hydrogen and deuterium were measured $9 directly. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction. (39 refs).
Study of anti-neutron annihilations at low energy
International Nuclear Information System (INIS)
The results of a total cross section measurement for the reactions anti np and anti pn are plotted. These results indicate that the annihilation amplitudes are predominantly I = 1 at low energy. The S-wave unitarity limit is shown, and the data support the conclusion drawn from anti pp data that even at the lowest momenta P-wave and higher waves are very important. The technique of using antineutrons to study very low energy antineutrons to study very low energy antinucleon interactions is demonstrated to be feasible
Revisiting big-bang nucleosynthesis constraints on dark-matter annihilation
Kawasaki, Masahiro; Kohri, Kazunori; Moroi, Takeo; Takaesu, Yoshitaro
2015-12-01
We study the effects of dark-matter annihilation during the epoch of big-bang nucleosynthesis on the primordial abundances of light elements. We improve the calculation of the light-element abundances by taking into account the effects of anti-nucleons emitted by the annihilation of dark matter and the interconversion reactions of neutron and proton at inelastic scatterings of energetic nucleons. Comparing the theoretical prediction of the primordial light-element abundances with the latest observational constraints, we derive upper bounds on the dark-matter pair-annihilation cross section. Implication to some of particle-physics models are also discussed.
Effective meson masses in a non-linear relativistic mean field model
International Nuclear Information System (INIS)
Full text: Relativistic mean field theories, with (σ, ω)-fields mediating the baryonic interaction, reproduce many important properties of the symmetric nuclear matter. This kind of models, where the nonlinear Walecka's model is a prototype, also has been widely applied to the description of the hadron phase for the thermodynamic treatment of the hadron to quark-gluon phase transition. However the conventional theory does not consider the interaction between the mesonic fields. This kind of interaction could be relevant when applying the theory to the situation involving nucleon and antinuclear matter. In this work we discuss the inclusion of meson-meson interaction in the theory in order to investigate the properties of nucleon-antinucleon matter at high temperature and low net baryonic density regime. This situation is of interest in describing the highest energy density states of the heavy ion collision at ultra-relativistic energies. Our present study includes the interaction between σ-ω mesons for different net baryonic densities by changing the ratio of nucleons to antinucleons densities. The particular scenario with null net baryonic density (the so-called 'no-sea' approximation) was already studied in Refs., but without taking into account the interaction between mesons. In the present work, with the interaction between meson included, we also determine the effective masses of the (σ, ω)-fields. (author)
Search for narrow lines in photon spectra from proton-antiproton annihilations at rest
International Nuclear Information System (INIS)
Inclusive photon spectra from annihilation of antiprotons stopped in a liquid hydrogen target were measured at LEAR (CERN) with a magnetic pair spectrometer. The FWHM energy resolution of the spectrometer in the region from 100-700 MeV was in the range from 2 to 4.5%. A total number of about 4.8.106 events with energies up to 1 GeV have been reconstructed. The photon spectra were scanned for possible lines with widths comparable to spectrometer resolution indicating the existence of bound nucleon-antinucleon states. No such structures were found with branching ratios greater than 4 to 8.10-4 at 95% confidence level. Results of former experiments could not be confirmed. (orig.)
Pseudospin Dynamical Symetry in Nuclei
Ginocchio, Joseph N
2014-01-01
Pseudospin symmetry has been useful in understanding atomic nuclei. We review the arguments that this symmetry is a relativistic symmetry. The condition for this symmetry is that the sum of the vector and scalar potentials in the Dirac Hamiltonian is a constant. We give the generators of pseudospin symmetry. We review some of the predictions that follow from this insight into the relativistic origins of pseudospin symmetry. Since in nuclei the sum of the scalar and vector potentials is not zero but is small, we discuss preliminary investigations into the conditions on the potentials to produce partial dynamic pseudospin symmetry. Finally we show that approximate pseudospin symmetry in nuclei predicts approximate spin symmetry in anti-nucleon scattering from nuclei.
Philippe Bloch
2012-01-01
By providing an intense and clean source of antiprotons for the first time, LEAR has opened many fields of research. Although it is not easy to summarise its versatile physics programme in a few lines, this article is an attempt to do justice to the 27 experiments performed during 14 years of running and to their successful results. LEAR complex, September 1983. In the early days of LEAR operation, the antiproton intensity was quite limited and the machine was mostly used for studying antiprotonic atoms and interactions of low-energy antiprotons with nuclei. Physicists were also performing measurements of cross-sections (total, elastic, charge exchange) as a function of the antiproton momentum. These first experiments provided valuable insights into the properties of nucleon-antinucleon interactions, including their spin structure, and ruled out the existence of hypothesized multiquark states of matter referred to as “baryonium”. The ASTERIX experiment...
23rd Annual seminar on theoretical physics, Grahamstown, 5-8 July 1988
International Nuclear Information System (INIS)
This seminar contains 18 papers. Twelve papers are indexed separately. Topics covered include: the Dirac equation in arbitrary space-time dimensions; next-to-leading corrections to jet multiplicity distributions in QCD; propagators and one loop diagrams in cavity field theory; cavity quantum chromodynamics in the presence of a classical background field; quark gluon plasma and hadronic matter in the early universe; deconfinement and chiral transitions in lattice QCD; J/Ψ suppression as a signal for quark deconfinement; geometrical interpretation of boson models of nuclear structure; the interacting boson model, BCS-RPA theory and the theory of pairing interactions applied to the Ge-nuclei; fluctuations and chaotic behaviour; test of the Bonn nucleon-nucleon potential in nucleon-antinucleon scattering; and new relativistic centre-of-mass corrections for the nucleon
The 3rd Nordic meeting on high energy reactions in nuclei
International Nuclear Information System (INIS)
Abstracts of the 31 lectures given at the meeting are presented. Major emphasis was placed on the nucleon-nucleon and nucleon-antinucleon interaction in bound and unbound systems. Four of the ten sessions were devoted to this subject. Two sessions contained lecture and seminars on 'Isobars in nuclei', two were devoted to hadron-nucleus reactions, one to high-energy heavy-ion reactions and one to new developments of experimental tools. This latter session had two talks, one about channeling with GeV particles and the other about the planned low-energy antiproton facility LEAR at CERN. Talks of more general character were 'The experimental programme at the CERN SC', 'Accelerator produced nuclear fuel' and 'The upsilons, a new family of quark-antiquark bound state'. (JIW)
High energy nucleonic component of cosmic rays at mountain altitudes
Stora, Raymond Félix
The diffusion equations describing the unidimensional propagation of .the high energy nucleonic component of cosmic rays throughout the atmosphere are sol"V'ed under two assumptions: (l) The nucleon-nucleon collisions are described according to Fermi's therlnOdynamical model involving completely inelastic pion and.nucleon-antinucleon pair production. (2) A somewhat opposite assumption is made assuming partially elastic collisions without nucleon-anti.nucleon pair production. Due to the present inaccuracy of experiments, we are able to derive only tentati v.e conclusions. The values computed under both hypotheses for the absorption mean free path and the charged to neutral particles ratio are found in acceptable ranges when compared to experimental data. The diffeential energy spectrum at a given depth is always found steeper than the primary, and steeper than indicated by experimental values if the primary is taken proportional to the 2.5 inverse power of energy.
Investigation of silicon sensors for their use as antiproton annihilation detectors
Energy Technology Data Exchange (ETDEWEB)
Pacifico, N., E-mail: nicola.pacifico@cern.ch [University of Bergen, Institute of Physics and Technology, Allégaten 55, 5007 Bergen (Norway); Aghion, S. [Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare, Sez. di Milano, Via Celoria 16, 20133 Milano (Italy); Ahlén, O. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Belov, A.S. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312 (Russian Federation); Bonomi, G. [University of Brescia, Department of Mechanical and Industrial Engineering, Via Branze 38, 25133 Brescia (Italy); Istituto Nazionale di Fisica Nucleare, Sez. di Pavia, Via Agostino Bassi 6, 27100 Pavia (Italy); Bräunig, P. [Kirchhoff Institute for Physics, Im Neuenheimer Feld 227, 69120 Heidelberg (Germany); Bremer, J. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Brusa, R.S. [Department of Physics, University of Trento, via Sommarive 14, 38123 Povo, Trento (Italy); INFN-TIFPA, via Sommarive 14, 38123 Povo, Trento (Italy); Burghart, G. [European Organisation for Nuclear Research, Physics Department, 1211 Geneva 23 (Switzerland); Cabaret, L. [Laboratoire Aimé Cotton, CNRS, Université Paris Sud, ENS Cachan, Bâtiment 505, Campus d' Orsay, 91405 Orsay Cedex (France); Caccia, M. [University of Insubria, Dipartimento di Scienza ed Alta Tecnologia, via Valleggio 11, Como (Italy); Canali, C. [University of Zurich, Physics Institute, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Caravita, R. [Istituto Nazionale di Fisica Nucleare, Sez. di Genova, Via Dodecaneso 33, 16146 Genova (Italy); University of Genoa, Department of Physics, Via Dodecaneso 33, 16146 Genova (Italy); Castelli, F. [University of Milano, Department of Physics, Via Celoria 16, 20133 Milano (Italy); and others
2014-11-21
We present here a new application of silicon sensors aimed at the direct detection of antinucleons annihilations taking place inside the sensor's volume. Such detectors are interesting particularly for the measurement of antimatter properties and will be used as part of the gravity measurement module in the AEg{sup ¯}IS experiment at the CERN Antiproton Decelerator. One of the goals of the AEg{sup ¯}IS experiment is to measure the gravitational acceleration of antihydrogen with 1% precision. Three different silicon sensor geometries have been tested with an antiproton beam to investigate their properties as annihilation detection devices: strip planar, 3D pixels and monolithic pixel planar. In all cases we were successfully detecting annihilations taking place in the sensor and we were able to make a first characterization of the clusters and tracks.
Aspects of meson spectroscopy with N N annihilation
Energy Technology Data Exchange (ETDEWEB)
Dover, C.B.
1990-04-01
We focus on the potentialities of nucleon-antinucleon ({bar N}N) annihilation as a means of producing new mesonic states. The case for the existence of quasinuclear {bar N}N bound states is discussed in detail. Strong evidence for a 2{sup ++}(0{sup +}) state of this type has been obtained at LEAR in annihilation from the p-wave (L = 1) {bar N}N system, in support of earlier sightings of this object in L = 0 annihilation at Brookhaven. In the next generation of LEAR experiments, the emphasis shifts to the search for mesons containing dynamical excitations of the gluonic field, namely glueballs and hybrids (Q{bar Q}g). We discuss some features of the masses, decay branching ratios and production mechanisms for these states, and suggest particular {bar N}N annihilation channels which are optimal for their discovery. 59 refs., 15 figs.
Antiproton-Nucleus Interaction and Coulomb Effect at High Energies
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; WU Qing; GU Yun-Ting; MA Wei-Xing; TAN Zhen-Qiang; HU Zhao-Hui
2005-01-01
The Coulomb effect in high energy antiproton-nucleus elastic and inelastic scattering from 12C and 16O is studied in the framework of Glauber multiple scattering theory for five kinetic energies ranged from 0.23 to 1.83 GeV.A microscopic shell-model nuclear wave functions, Woods-Saxon single-particle wave functions, and experimental pN amplitudes are used in the calculations. The results show that the Coulomb effect is of paramount importance for filling up the dips of differential cross sections. We claim that the present result for inelastic scattering of antiproton-12C is sufficiently reliable to be a guide for measurements in the very near future. We also believe that antiproton nucleus elastic and inelastic scattering may produce new information on both the nuclear structure and the antinucleon-nucleon interaction, in particular the p-neutron interaction.
2008-01-01
Dear Colleagues, It is with deep sorrow and regret that we inform you that our colleague and friend Ludwig Tauscher passed away on Sunday 23 November after a heart attack. Ludwig studied physics at the University of Heidelberg, where he obtained his PhD in 1966. After several postdoctoral appointments at the MPI Heidelberg, and the Universities of Konstanz and Karlsruhe, he joined the University of Basel, where he became Professor of Physics in 1985. Ludwig devoted his entire professional life to teaching and experimental physics. He arrived at CERN in the early seventies, where he performed several experiments at the SC and at the PS, studying exotic atoms with various probes such as μ-, π-, K-, and Σ-. In the early eighties he searched for the production of nucleon-antinucleon bound states at the PS, a subject that was the main motivation for the construction of the LEAR storage ring. At LEAR he studied neutral meson productio...
Energy Technology Data Exchange (ETDEWEB)
El-Khoury, P
1998-04-15
The study of exotic atoms, in which an orbiting electron of a normal atom is replaced by a negatively charged particle ({pi}{sup -}, {mu}{sup -}, p, {kappa}{sup -}, {sigma}{sup -},...) may provide information on the orbiting particle and the atomic nucleus, as well as on their interaction. In this work, we were interested in pionic atoms ({pi}{sup -14} N) on the one hand in order to determine the pion mass with high accuracy (4 ppm), and on the other hand in antiprotonic atoms (pp-bar) in order to study the strong nucleon-antinucleon interaction at threshold. In this respect, a high-resolution crystal spectrometer was coupled to a cyclotron trap which provides a high stop density for particles in gas targets at low pressure. Using curved crystals, an extended X-ray source could be imaged onto the detector. Charge-Coupled Devices were used as position sensitive detectors in order to measure the Bragg angle of the transition to a high precision. The use of gas targets resolved the ambiguity owing to the number of K electrons for the value of the pion mass, and, for the first time, strong interaction shift and broadening of the 2p level in antiprotonic hydrogen were measured directly. (author)
Theory of the low-energy pion--nucleon interaction
Energy Technology Data Exchange (ETDEWEB)
Banerjee, M.K.; Cammarata, J.B.
1977-08-01
A once-subtracted form of the Low equation for the pion-nucleon scattering amplitude is derived, with PCAC 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 mod(g/sub ..pi../(4M/sup 2/)) = 11.69 and 25.5 MeV for the ..pi..N sigma-commutator. The implications of this work for the analysis of low-energy elastic scattering of pions from nuclei are discussed. In particular, it is pointed 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.
Precision measurement of the mass difference between light nuclei and anti-nuclei
Adam, Jaroslav; Aggarwal, Madan Mohan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agrawal, Neelima; Ahammed, Zubayer; Ahmed, Ijaz; Ahn, Sang Un; Aimo, Ilaria; Aiola, Salvatore; Ajaz, Muhammad; Akindinov, Alexander; Alam, Sk Noor; Aleksandrov, Dmitry; Alessandro, Bruno; Alexandre, Didier; Alfaro Molina, Jose Ruben; Alici, Andrea; Alkin, Anton; Alme, Johan; Alt, Torsten; Altinpinar, Sedat; Altsybeev, Igor; Alves Garcia Prado, Caio; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshaeuser, Harald; Arcelli, Silvia; Armesto Perez, Nestor; Arnaldi, Roberta; Aronsson, Tomas; Arsene, Ionut Cristian; Arslandok, Mesut; Augustinus, Andre; Averbeck, Ralf Peter; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bagnasco, Stefano; Bailhache, Raphaelle Marie; Bala, Renu; Baldisseri, Alberto; Ball, Markus; Baltasar Dos Santos Pedrosa, Fernando; Baral, Rama Chandra; Barbano, Anastasia Maria; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Ramillien Barret, Valerie; Bartalini, Paolo; Bartke, Jerzy Gustaw; Bartsch, Esther; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batista Camejo, Arianna; Batyunya, Boris; Batzing, Paul Christoph; Bearden, Ian Gardner; Beck, Hans; Bedda, Cristina; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bello Martinez, Hector; Bellwied, Rene; Belmont Iii, Ronald John; Belmont Moreno, Ernesto; Belyaev, Vladimir; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Bertens, Redmer Alexander; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhat, Inayat Rasool; Bhati, Ashok Kumar; Bhattacharjee, Buddhadeb; Bhom, Jihyun; Bianchi, Livio; Bianchi, Nicola; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Biswas, Saikat; Bjelogrlic, Sandro; Blanco, Fernando; Blau, Dmitry; Blume, Christoph; Bock, Friederike; Bogdanov, Alexey; Boggild, Hans; Boldizsar, Laszlo; Bombara, Marek; Book, Julian Heinz; Borel, Herve; Borissov, Alexander; Borri, Marcello; Bossu, Francesco; Botje, Michiel; Botta, Elena; Boettger, Stefan; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Broker, Theo Alexander; Browning, Tyler Allen; Broz, Michal; Brucken, Erik Jens; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Buncic, Predrag; Busch, Oliver; Buthelezi, Edith Zinhle; Buxton, Jesse Thomas; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calero Diaz, Liliet; Caliva, Alberto; Calvo Villar, Ernesto; Camerini, Paolo; Carena, Francesco; Carena, Wisla; Castillo Castellanos, Javier Ernesto; Castro, Andrew John; Casula, Ester Anna Rita; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Chartier, Marielle; Charvet, Jean-Luc Fernand; Chattopadhyay, Subhasis; Chattopadhyay, Sukalyan; 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Zyzak, Maksym
2015-01-01
The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons (d) and anti-deuterons ($\\bar{d}$), and $^{3}{\\rm He}$ and $^3\\overline{\\rm He}$ nuclei carried out with the ALICE (A Large Ion Collider Experiment) detector in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge differences confirm CPT invariance to an unprecedented precision in the sector of light nuclei. This funda...
Hidden pseudospin and spin symmetries and their origins in atomic nuclei
Liang, Haozhao; Zhou, Shan-Gui
2014-01-01
Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals $(n, l, j = l + 1/2)$ and $(n-1, l + 2, j = l + 3/2)$ indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from ce...
Measurement of the Spin–Dependence of the $\\overline{p}-p$ Interaction at the AD–Ring
Barschel, C; Dietrich, J; Dolfus, N; Engels, R; Gebel, R; Hadamek, H; Haidenbauer, J; Hanhart, C; Kacharava, A; Krol, G; Küven, M; Langenberg, G; Lehrach, A; Lorentz, B; Maier, R; Martin, S; Meissner, U G; Nekipelov, M; Nikolaev, N N; Oellers, D; d'Orsaneo, G; Prasuhn, D; Rathmann, F; Retzlaff, M; Sarkadi, J; Schleichert, R; Seyfarth, H; Sibirtsev, A; Spölgen, D; Stein, H J; Stockhorst, H; Ströher, H; Weidemann, Chr; Welsch, D; Wieder, P; Barion, L; Bertelli, S; Carassiti, V; Ciullo, G; Contalbrigo, M; Cotta-Ramusino, A; Dalpiaz, P F; Drago, A; Guidoboni, G; Lenisa, P; Pappalardo, L; Stancari, G; Stancari, M; Statera, M; Azarian, T; Kulikov, A; Kurbatov, V; Macharashvili, G; Merzliakov, S; Meshkov, I N; Smirnov, A; Tsirkov, D; Uzikov, Yu; Barsov, S; Belostotskii, S; Grigoryev, K; Kravtsov, P; Mikirtychiants, M; Mikirtychiants, S; Vasilyev, A; Esser, F M; Greven, R; Hansen, G; Jadgfeld, F; Klehr, F; Soltner, H; Straatmann, H; Chiladze, D; Garishvili, A; Lomidze, N; Mchedlishvili, D; Nioradze, M; Tabidze, M; Akopov, N; Avetisyan, A; Elbakyan, G; Marukyan, H; Taroian, S; Benati, P; Erven, W; Kayser, F J; Kleines, H; Wüstner, P; Bruncko, D; Ferencei, J; Musinsky, J; Urbán, J; Augustyniak, W; Marianski, B; Trzcinski, A; Zupranski, P; Dymov, S; Nass, A; Steffens, E; Rathsman, K; Tegnér, P E; Engblom, P Thoerngren; De Leo, R; Tagliente, G; Kämpfer, B; Trusov, S; Buttimore, N; Meyer, H O; CERN. Geneva. SPS and PS Experiments Committee; SPSC
2009-01-01
We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin–dependent pbar-p cross sections σ1 and σ2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin–spin dependence of the nucleon–antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double–polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide access to a wealt...
Antimatter H4Λ hypernucleus production and the H3Λ /3He puzzle in relativistic heavy-ion collisions
Sun, Kai-Jia; Chen, Lie-Wen
2016-06-01
We show that the measured yield ratio H3Λ /3He(H¯3¯Λ /¯3He ) in Au +Au collisions at √{sN N}=200 GeV and in Pb +Pb collisions at √{sN N}=2.76 TeV can be understood within a covariant coalescence model if (anti-)Λ particles freeze out earlier than (anti-)nucleons but their relative freeze-out time is closer at √{sN N}=2.76 TeV than at √{sN N}=200 GeV. The earlier (anti-)Λ freeze-out can significantly enhance the yield of (anti)hypernucleus H4Λ (H¯4¯Λ ), leading to that H¯4¯Λ has a comparable abundance with ¯4He and thus provides an easily measured antimatter candidate heavier than ¯4He. The future measurement on H4Λ (H¯4¯Λ ) would be very useful to understand the (anti-)Λ freeze-out dynamics and the production mechanism of (anti)hypernuclei in relativistic heavy-ion collisions.
Bianconi, Andrea
2009-01-01
Here a preliminary study is presented concerning the detection of the normally unseen Drell-Yan fragments, possible in the PANDA experiment. To work as a multi-purpose apparatus, this experiment will record all the particles produced in the collisions between the antiproton beam and the target, with a rather wide acceptance. So detecting Drell-Yan dileptons with or without analyzing the other fragments is just a matter of applying cutoffs in the data analysis stage. The distribution of the products of 50,000 typical Drell-Yan events is here simulateded using a well-known generator code (Pythia-8). The resulting distributions are inserted within the PANDA acceptance region, to analyze the chances of missing some searched fragment combinations, or of confusing different sets of particles. The most interesting result is that, due to the reduced phase space, the produced states are much simpler than one could imagine: (i) almost 50 \\% of the events just consist of a dilepton plus a nucleon-antinucleon pair; (ii) ...
A Meson Emission Model of Psi to N Nbar m Charmonium Strong Decays
Barnes, T; Roberts, W
2010-01-01
In this paper we consider a sequential "meson emission" mechanism for charmonium decays of the type Psi -> N Nbar m, where Psi is a generic charmonium state, N is a nucleon and m is a light meson. This decay mechanism, which may not be dominant in general, assumes that an NNbar pair is created during charmonium annihilation, and the light meson m is emitted from the outgoing nucleon or antinucleon line. A straightforward generalization of this model can incorporate intermediate N* resonances. We derive Dalitz plot event densities for the cases Psi = eta_c, J/psi, chi_c0, chi_c1} and psi' and m = pi0, f0 and omega (and implicitly, any 0^{-+}, 0^{++} or 1^{--} final light meson). It may be possible to separate the contribution of this decay mechanism to the full decay amplitude through characteristic event densities. For the decay subset Psi -> p pbar pi0 the two model parameters are known, so we are able to predict absolute numerical partial widths for Gamma(Psi -> p pbar pi0). In the specific case J/psi -> p ...
Bressani, Tullio
2003-01-01
Antineutrons ($\\overline{n}$'s) have been used only in the last few years as projectiles for nuclear and particle physics experiments, mainly in the low momentum region. The reason is that, in spite of some undoubted advantages (absence of Coulomb corrections, pure I=1 state for the ($\\overline{n}p$) system), the difficulties in obtaining beams of $\\overline{n}$'s of suitable intensity and energy definition were overwhelming. The setting-up of suitable beams at BNL and mainly at CERN LEAR (with momentum lower than 400 MeV/c) allowed a first round of interesting experiments. In this review a summary of the most important experimental issues obtained in this field will be presented. They range from studies on the antineutron annihilation dynamics, intended to shed light on the mechanisms responsible for the particles production as well as for the possible formation of quasinuclear nucleon-antinucleon bound states, to meson spectroscopy researches, aiming to identify the existence of new, possibly exotic, resona...
Exact solution of a model for πd induced reactions and its application to pion-nucleon reactions
International Nuclear Information System (INIS)
Reduction techniques are applied to πd elastic scattering and π absorption in a theory without anti-nucleons. In the one-pion approximation we derive two sets of exact coupled-channel equations for respectively the amplitudes Tsub(πd,NN), Tsub(NΔ,NN) and Tsub(π,πdsup3) Tsub(πd,NΔ). Alternatively are expressed all amplitudes in terms of the absorption amplitude Tsub(πd,NΔ) and available solutions for a three-body problem restricted to the πd and NΔ channels. It is explicity demonstrated that the model (which comes close to the one of Thomas, Mutzutani and Koltun) strictly respects the Pauli principle and avoids double-counting. Using the same technique amplitudes for the (π,2N) reaction and for π(in) elastic scattering on general nuclei in terms of amplitudes amongst the NN, NNπ channels are determined. Both the elastic amplitude and the πA optical potential are shown to decompose into a multiple scattering part based on an input πN amplitude without the Psub(11) partial wave and calculable absorption corrections. (author)
Energy Technology Data Exchange (ETDEWEB)
Haidenbauer, J. [Institut fuer Kernphysik (Theorie), Forschungszentrum Juelich, D-52425 Juelich (Germany); Hammer, H.-W. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)]. E-mail: hammer@itkp.uni-bonn.de; Meissner, Ulf-G. [Institut fuer Kernphysik (Theorie), Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany); Sibirtsev, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)
2006-11-30
We study the energy dependence of the e{sup +}e{sup -}{yields}pp-bar cross section close to the two-nucleon threshold, recently reported by the BaBar Collaboration. Our analysis also includes the p-bar p{yields}e{sup +}e{sup -} data collected by PS170 Collaboration and the e{sup +}e{sup -}{yields}NN-bar data from the FENICE Collaboration. We show that the near-threshold enhancement in the e{sup +}e{sup -}{yields}pp-bar cross section can be explained by the final-state interaction between proton and antiproton in the {sup 3}S{sub 1} partial wave, utilizing the Julich nucleon-antinucleon model. As a consequence, the strong dependence of the proton electromagnetic form factors on the momentum transfer close to the two-nucleon threshold is then likewise driven by this final-state interaction effect. This result is in line with our previous studies of the near-threshold enhancement of the pp-bar invariant mass spectrum seen in the J/{psi}{yields}{gamma}pp-bar decay by the BES Collaboration and in the B{sup +}{yields}pp-bar K{sup +} decay by the BaBar Collaboration.
Production of antimatter $^{5,6}$Li nuclei in central Au+Au collisions at $\\sqrt{s_{NN}} = 200$ GeV
Sun, Kai-Jia
2015-01-01
Combining the covariant coalescence model and a blast-wave-like analytical parametrization for (anti-)nucleon phase-space freezeout configuration, we explore light (anti-)nucleus production in central Au+Au collisions at $\\sqrt{s_{NN}} = 200$ GeV. Using the nucleon freezeout configuration (denoted by FO1) determined from the measured spectra of protons (p), deutrons (d) and $^{3}$He, we find the predicted yield of $^{4}$He is significantly smaller than the experimental data. We show this disagreement can be removed by using a nucleon freezeout configuration (denoted by FO2) in which the nucleons are assumed to freeze out earlier than those in FO1 to effectively consider the effect of large binding energy value of $^{4}$He. Assuming the binding energy effect also exists for the production of $^5\\text{Li}$, $^5\\overline{\\text{Li}}$, $^6\\text{Li}$ and $^6\\overline{\\text{Li}}$ due to their similar binding energy values as $^{4}$He, we find the yields of these heavier (anti-)nuclei can be enhanced by a factor of a...
Inclusive Lambda_c Production in e+e- Annihilations at sqrt{s}=10.54 GeV and in Upsilon(4S) Decays
Energy Technology Data Exchange (ETDEWEB)
Aubert, B.
2006-09-07
We present measurements of the total production rates and momentum distributions of the charmed baryon {Lambda}{sub c}{sup +} in e{sup +}e{sup -} {yields} hadrons at a center-of-mass energy of 10.54 GeV and in {Upsilon}(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e{sup +}e{sup -} {yields} c{bar c} events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for {Lambda}{sub c}{sup +} baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of (x{sub p}) = 0.574 {+-} 0.009 and a total rate of N{sub {Lambda}{sub c}}{sup q{bar q}} = 0.057 {+-} 0.002(exp.) {+-} 0.015(BF) {Lambda}{sub c}{sup +} per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK{sup -} {pi}{sup +}. In {Upsilon}(4S) decays we measure a total rate of N{sub {Lambda}{sub c}}{sup {Upsilon}} = 0.091 {+-} 0.006(exp.) {+-} 0.024(BF) per {Upsilon}(4S) decay, and find a much softer momentum distribution than expected from B decays into a {Lambda}{sub c}{sup +} plus an antinucleon and one to three pions.
Hadronic wavefunctions in light-cone quantization
Energy Technology Data Exchange (ETDEWEB)
Hyer, T.
1994-05-01
The analysis of light-cone wavefunctions seems the most promising theoretical approach to a detailed understanding of the structure of relativistic bound states, particularly hadrons. However, there are numerous complications in this approach. Most importantly, the light-cone approach sacrifices manifest rotational invariance in exchange for the elimination of negative-energy states. The requirement of rotational invariance of the full theory places important constraints on proposed light-cone wavefunctions, whether they are modelled or extracted from some numerical procedure. A formulation of the consequences of the hidden rotational symmetry has been sought for some time; it is presented in Chapter 2. In lattice gauge theory or heavy-quark effective theory, much of the focus is on the extraction of numerical values of operators which are related to the hadronic wavefunction. These operators are to some extent interdependent, with relations induced by fundamental constraints on the underlying wavefunction. The consequences of the requirement of unitarity are explored in Chapter 3, and are found to have startling phenomenological relevance. To test model light-cone wavefunctions, experimental predictions must be made. The reliability of perturbative QCD as a tool for making such predictions has been questioned. In Chapter 4, the author presents a computation of the rates for nucleon-antinucleon annihilation, improving the reliability of the perturbative computation by taking into account the Sudakov suppression of exclusive processes at large transverse impact parameter. In Chapter 5, he develops the analysis of semiexclusive production. This work focuses on processes in which a single isolated meson is produced perturbatively and recoils against a wide hadronizing system. At energies above about 10 GeV, semiexclusive processes are shown to be the most sensitive experimental probes of hadronic structure.
Energy Technology Data Exchange (ETDEWEB)
Noyes, H.P.
1990-01-29
We construct discrete space-time coordinates separated by the Lorentz-invariant intervals h/mc in space and h/mc{sup 2} in time using discrimination (XOR) between pairs of independently generated bit-strings; we prove that if this space is homogeneous and isotropic, it can have only 1, 2 or 3 spacial dimensions once we have related time to a global ordering operator. On this space we construct exact combinatorial expressions for free particle wave functions taking proper account of the interference between indistinguishable alternative paths created by the construction. Because the end-points of the paths are fixed, they specify completed processes; our wave functions are born collapsed''. A convenient way to represent this model is in terms of complex amplitudes whose squares give the probability for a particular set of observable processes to be completed. For distances much greater than h/mc and times much greater than h/mc{sup 2} our wave functions can be approximated by solutions of the free particle Dirac and Klein-Gordon equations. Using a eight-counter paradigm we relate this construction to scattering experiments involving four distinguishable particles, and indicate how this can be used to calculate electromagnetic and weak scattering processes. We derive a non-perturbative formula relating relativistic bound and resonant state energies to mass ratios and coupling constants, equivalent to our earlier derivation of the Bohr relativistic formula for hydrogen. Using the Fermi-Yang model of the pion as a relativistic bound state containing a nucleon-antinucleon pair, we find that (G{sub {pi}N}{sup 2}){sup 2} = (2m{sub N}/m{sub {pi}}){sup 2} {minus} 1. 21 refs., 1 fig.
Institute of Scientific and Technical Information of China (English)
张家伟; 刘春兰; 陈学文
2013-01-01
In the work,we make a detailed discussion on the reaction,via nucleon-antinucleon propagator,within the SU (2)-invariant coupling model between charged mesons and nucleons (π± N) of perturbation theory of quantum field theory.The renormalized loop-chain propagator of nucleon-antinucleon (N-(N)) was strictly calculated and given an analytical expression with the large momentum integral limitation method.Furthermore,we obtain a simple and analytic expression of the differential cross-section of p(p)→ π+ π with nucleon-antinucleon (N-N) renormalized loop-chain propagator,i.e.dσ(chain)/dΩ=G4/641/(2π)21/P20√P20-μ2 1/√P20-m2(2P20-μ2-2√P20-m2√P20-μ2cos θ)2T(q2).We also calculate and obtain numerical results of the differential cross-section of p(p)→π+ π at tree,one-loop and chain diagram in different center-of-mass energy,respectively,and make a detailed comparison and discussion and show some important information about radiative correction.In large energy within 2.5 GeV≤p0 ≤100 GeV,these corrections are in the reasonable range,i.e.R(chain) (or R(locp))＜2.0.The results provide a significant reference to understand in-depth of the SU(2)-invariant coupling model of strong interactions theory and to explore the reaction cross-section between mesons and nucleons (πN).In addition,it will provide effective reference to the applicability of the perturbation theory of quantum field theory in nucleon interactions,the renormalized calculation in different ways and approaches.%本文在量子场论微扰理论框架下,利用荷电介子与核子(π±N)强相互作用的SU(2)-不变耦合模型,系统研究了p(p)→π+π-物理反应过程.采用“大动量积分极限法”对核子—反核子(N-N)重正化圈 链图传播子做了相关物理分析并作了严格解析计算,获得了精确理论计算结果.进而利用该结果系统计算了在核子—反核子(N-N)重整化圈—链图传播子下p(p)→π+π-反应