Nucleon-pair approximation to the nuclear shell model
Energy Technology Data Exchange (ETDEWEB)
Zhao, Y.M., E-mail: ymzhao@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Arima, A. [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Musashi Gakuen, 1-26-1 Toyotamakami Nerima-ku, Tokyo 176-8533 (Japan)
2014-12-01
Atomic nuclei are complex systems of nucleons–protons and neutrons. Nucleons interact with each other via an attractive and short-range force. This feature of the interaction leads to a pattern of dominantly monopole and quadrupole correlations between like particles (i.e., proton–proton and neutron–neutron correlations) in low-lying states of atomic nuclei. As a consequence, among dozens or even hundreds of possible types of nucleon pairs, very few nucleon pairs such as proton and neutron pairs with spin zero, two (in some cases spin four), and occasionally isoscalar spin-aligned proton–neutron pairs, play important roles in low-energy nuclear structure. The nucleon-pair approximation therefore provides us with an efficient truncation scheme of the full shell model configurations which are otherwise too large to handle for medium and heavy nuclei in foreseeable future. Furthermore, the nucleon-pair approximation leads to simple pictures in physics, as the dimension of nucleon-pair subspace is always small. The present paper aims at a sound review of its history, formulation, validity, applications, as well as its link to previous approaches, with the focus on the new developments in the last two decades. The applicability of the nucleon-pair approximation and numerical calculations of low-lying states for realistic atomic nuclei are demonstrated with examples. Applications of pair approximations to other problems are also discussed.
Nucleon structure study by virtual compton scattering
International Nuclear Information System (INIS)
Berthot, J.; Bertin, P.Y.; Breton, V.; Fonvielle, H.; Hyde-Wright, C.; Quemener, G.; Ravel, O.; Braghieri, A.; Pedroni, P.; Boeglin, W.U.; Boehm, R.; Distler, M.; Edelhoff, R.; Friedrich, J.; Geiges, R.; Jennewein, P.; Kahrau, M.; Korn, M.; Kramer, H.; Krygier, K.W.; Kunde, V.; Liesenfeld, A.; Merle, K.; Neuhausen, R.; Offermann, E.A.J.M.; Pospischil, T.; Rosner, G.; Sauer, P.; Schmieden, H.; Schardt, S.; Tamas, G.; Wagner, A.; Walcher, T.; Wolf, S.
1995-01-01
We propose to study nucleon structure by Virtual Compton Scattering using the reaction p(e,e'p)γ with the MAMI facility. We will detect the scattered electron and the recoil proton in coincidence in the high resolution spectrometers of the hall A1. Compton events will be separated from the other channels (principally π 0 production) by missing-mass reconstruction. We plan to investigate this reaction near threshold. Our goal is to measure new electromagnetic observables which generalize the usual magnetic and electric polarizabilities. (authors). 9 refs., 18 figs., 7 tabs
International Nuclear Information System (INIS)
Jiang Weizhou; Li Baoan; Chen Liewen
2007-01-01
The mean free paths and in-medium scattering cross sections of energetic nucleons in neutron-rich nucleonic matter are investigated using the nucleon optical potential obtained within the relativistic impulse approximation with the empirical nucleon-nucleon scattering amplitudes and the nuclear densities obtained in the relativistic mean-field model. It is found that the isospin-splitting of nucleon mean free paths, sensitive to the imaginary part of the symmetry potential, changes its sign at certain high kinetic energy. The in-medium nucleon-nucleon cross sections are analytically and numerically demonstrated to be essentially independent of the isospin asymmetry of the medium and increase linearly with density in the high-energy region where the relativistic impulse approximation is applicable
Nucleon motion in constant nucleodynamic field (p2 approximation)
International Nuclear Information System (INIS)
Karastoyanov, A.
1979-01-01
It uses the generalized Dirac equation in the form [-ca vector.(p vector - gA vector/c)+E-V-βmc 2 +(μsub(a)/c)β(σ vector.cB vector-iα vector.E vector] PSI = 0, where α vector and β are the Dirac matrices, c is the velocity of light in vacuum, p vector equals i(h/2π)nabla vector is the pulse operator, g is the nuclear charge, A vector is the nuclear vector potential, E is the total energy of the nucleon, V is its nuclear potential energy, m is its rest mass, μsub(a) = -lambdasub(a)g(h/2π)/2m is the value of the anomalous nuclodynamic dipole moment, σ vector is the Pauli matrix, B vector = rot A vector/c is the nucleodynamic field intensity, i is the imaginary unity, E = -grad V/g is the nucleostatic field intensity, PSI is the Dirac wave function and (h/2π) is the Dirac action constant. For a nucleon in rest the potentials at distance r are V 0 = -(g 2 /4π)[esup(-μr)/r+μEi(-μr)], A vector 0 =(lambda sub(a)-1) (g(h/2π)/2mc) (esup(-μr)/4πr 3 ) (σ vector xr vector) with μ=0,684 fm -1 , αsub(g)=g 2 /4π(h/2π)c=1/4, lambda sub(a)=15.96 = 16 - αsub(g)/2π.αsub(g)/2π is the first order radiation correction, while 16 corresponds to a nuclear analogue of the Dirac magnetic monopole gsub(d) = 16 g = n4π(h/2π)c/2g for n = 8. These values are confirmed by calculations. In the Schroedinger equation approach it explains the spin-spin, tensor and spin-orbit forces, the velocity, energy and state dependence of the nuclear forces, the hard potential core, the ''many-body'' nuclear forces and fine effects of the nuclear interactions. (A.K.)
S-wave pion-nucleon phase shifts in PADE approximation
International Nuclear Information System (INIS)
Achuthan, P.; Chandramohan, T.; Venkatesan, K.
1978-01-01
The two S-wave pion nucleon pahse shifts delta( 1 ) (I = 1/2) and delta( 3 ) (I = 3/2) have been calculated in the Pade approximation using epsilon(700), rho(770), f(1260), Δ(1236) and N(938) for the energy range W = 1085 MeV - 1820 MeV in the centre of mass. Contributions from suitable resonance combinations which agree nearest with the delta( 3 ) experimental values are given. (orig.) [de
The virtual environment student. An initial approximation
Federico Borges Sáiz
2007-01-01
The quote at the start of the "Introduction" ("Education follows an agricultural timetable, has an industrial structure and operation and is set in an increasingly digitalised society") illustrates the need for an in-depth understanding of training in virtual environments. This understanding rests on knowing its central element: the student.This article invites the reader to take a look at the figure and the performance of the virtual environment student. One of the features of the twenty-fir...
Proton induced nucleon knockout from 40Ca in the Dirac impulse approximation
International Nuclear Information System (INIS)
Maxwell, O.V.; Cooper, E.D.
1989-12-01
The (p,2p) reaction on 40 Ca at incident proton energies of 200 and 300 MeV is examined within a Dirac distorted wave impulse approximation. The relativistic Love-Franey t-matrix is evaluated at the nucleon-nucleon laboratory energy (as defined within the plane wave approximation), rather than the nucleon-nucleus laboratory energy. Particular attention is paid to the sensitivity of the calculated cross sections and analyzing powers to the properties of the bound states employed. It is found that the analyzing powers depend very little on the bound state properties, while the cross sections depend significantly only on the rms radii of the bound state wave functions. A major success of the model is its ability to fit the cross section data over a particular range of momentum transfers at both 200 and 300 MeV with the same bound state potential. Outside this momentum transfer range, the predicted cross sections are too low. The calculated analyzing powers agree well with the data at 200 MeV, but disagree with the data at 300 MeV. Values for the rms radii of the 1D 3/2 and 1D 5/2 states in 40 Ca are derived from the requirement that the peak positions of the calculated cross sections at 300 MeV agree with the empirical peak positions. Some preliminary results are also reported for neutron knockout from 40 Ca at 150 MeV
International Nuclear Information System (INIS)
Niu, Y.; Paar, N.; Vretenar, D.; Meng, J.
2009-01-01
The fully self-consistent relativistic random-phase approximation (RRPA) framework based on effective interactions with a phenomenological density dependence is extended to finite temperatures. The RRPA configuration space is built from the spectrum of single-nucleon states at finite temperature obtained by the temperature dependent relativistic mean field (RMF-T) theory based on effective Lagrangian with density dependent meson-nucleon vertex functions. As an illustration, the dependence of binding energy, radius, entropy and single particle levels on temperature for spherical nucleus 2 08P b is investigated in RMF-T theory. The finite temperature RRPA has been employed in studies of giant monopole and dipole resonances, and the evolution of resonance properties has been studied as a function of temperature. In addition, exotic modes of excitation have been systematically explored at finite temperatures, with an emphasis on the case of pygmy dipole resonances.(author)
The virtual environment student. An initial approximation
Directory of Open Access Journals (Sweden)
Federico Borges Sáiz
2007-05-01
Full Text Available The quote at the start of the "Introduction" ("Education follows an agricultural timetable, has an industrial structure and operation and is set in an increasingly digitalised society" illustrates the need for an in-depth understanding of training in virtual environments. This understanding rests on knowing its central element: the student.This article invites the reader to take a look at the figure and the performance of the virtual environment student. One of the features of the twenty-first century is that of leading increasingly to a learning society, where citizens learn, formally or informally, throughout their lives. Technology sustains many of the behavioural and attitude traits of these citizens, although technology is only the first step; beyond this, the attitudes, skills and motivation required for successfully performing in a virtual environment are necessary.
Nucleon-nucleus inelastic scattering using a relativistic impulse approximation with exchange
International Nuclear Information System (INIS)
Rost, E.; Shepard, J.R.
1987-01-01
We formulate a microscopic relativistic treatment of nucleon-nucleus inelastic scattering in a distorted wave impulse approximation. The interaction is taken from a Lorentz invariant formulation with explicit direct and exchange terms constrained by fitting to experimental NN amplitudes. This procedure allows us to apply the theory in the lower range of intermediate energies (100--400 MeV) where exchange effects are likely to be important. Application to inelastic scattering uses this interaction for both the distorting potentials and the transition interaction. Effects of explicit exchange are studied and a preliminary analysis of /sup 12/C(p,p') data is presented
Extended sudden approximation model for high-energy nucleon removal reactions
Energy Technology Data Exchange (ETDEWEB)
Carstoiu, F.; Sauvan, E.; Orr, N.A. [Caen Univ., Lab. de Physique Corpusculaire, Institut des Sciences de la Matiere et du Rayonnement, IN2P3-CNRS ISMRA, 14 (France); Carstoiu, F. [IFIN-HH, Bucharest-Magurele (Romania); Bonaccorso, A. [Istituto Nazionale di Fisica Nucleare, Pisa (Italy)
2004-04-01
A model based on the sudden approximation has been developed to describe high energy single nucleon removal reactions. Within this approach, which takes as its starting point the formalism of Hansen, the nucleon-removal cross section and the full 3-dimensional momentum distributions of the core fragments including absorption, diffraction, Coulomb and nuclear-Coulomb interference amplitudes, have been calculated. The Coulomb breakup has been treated to all orders for the dipole interaction. The model has been compared to experimental data for a range of light, neutron-rich psd-shell nuclei. Good agreement was found for both the inclusive cross sections and momentum distributions. In the case of {sup 17}C, comparison is also made with the results of calculations using the transfer-to-the-continuum model. The calculated 3-dimensional momentum distributions exhibit longitudinal and transverse momentum components that are strongly coupled by the reaction for s-wave states, whilst no such effect is apparent for d-waves. Incomplete detection of transverse momenta arising from limited experimental acceptances thus leads to a narrowing of the longitudinal distributions for nuclei with significant s-wave valence neutron configurations, as confirmed by the data. Asymmetries in the longitudinal momentum distributions attributed to diffractive dissociation are also explored. (authors)
Extended sudden approximation model for high-energy nucleon removal reactions
International Nuclear Information System (INIS)
Carstoiu, F.; Sauvan, E.; Orr, N.A.; Carstoiu, F.; Bonaccorso, A.
2004-04-01
A model based on the sudden approximation has been developed to describe high energy single nucleon removal reactions. Within this approach, which takes as its starting point the formalism of Hansen, the nucleon-removal cross section and the full 3-dimensional momentum distributions of the core fragments including absorption, diffraction, Coulomb and nuclear-Coulomb interference amplitudes, have been calculated. The Coulomb breakup has been treated to all orders for the dipole interaction. The model has been compared to experimental data for a range of light, neutron-rich psd-shell nuclei. Good agreement was found for both the inclusive cross sections and momentum distributions. In the case of 17 C, comparison is also made with the results of calculations using the transfer-to-the-continuum model. The calculated 3-dimensional momentum distributions exhibit longitudinal and transverse momentum components that are strongly coupled by the reaction for s-wave states, whilst no such effect is apparent for d-waves. Incomplete detection of transverse momenta arising from limited experimental acceptances thus leads to a narrowing of the longitudinal distributions for nuclei with significant s-wave valence neutron configurations, as confirmed by the data. Asymmetries in the longitudinal momentum distributions attributed to diffractive dissociation are also explored. (authors)
Quark-diquark approximation of the three-quark structure of a nucleon and the NN phase shifts
International Nuclear Information System (INIS)
Efimov, G.V.; Ivanov, M.A.
1988-01-01
The quark-diquark approximations of the three-quark structure of a nucleon are considered in the framework of the quark confinement model (QCM) based on definite concepts of the hadronization and quark confinement. The static nucleon characteristics (magnetic moments, ratio G A /G V and strong meson-nucleon coupling constants) are calculated. The behaviour of the electromagnetic and strong nucleon form factors is obtained at the low energy (0≤0 2 =-q 2 2 , where q is a transfer momentum). The one-boson exchange potential is constructed and the NN-phase-shifts are computed. Our results are compared with experiment and the Bonn potential model. 45 refs.; 7 figs.; 3 tabs
International Nuclear Information System (INIS)
Kazarnovskij, M.V.; Matushko, G.K.; Matushko, V.L.; Par'ev, Eh.Ya.; Serezhnikov, S.V.
1981-01-01
The problem on propagation of the internuclear cascade initiated by nucleons of 0.1-1 GeV energy in accelerator schielding is solved approximately in the analytical form. Analytical expressions for the function of spatial, angular and energy distribution of the flux density of nucleons with the energy above 20 MeV and some functionals from it are obtained. The results of the calculations obtained by the developed methods are compared with calculations obtained by the method of direct simulation. It is shown that at the atomic mass of shielding material [ru
Medium energy nucleon-nucleus scattering theory by semi-classical distorted wave approximation
Energy Technology Data Exchange (ETDEWEB)
Ogata, Kazuyuki [Kyushu Univ., Fukuoka (Japan)
1998-07-01
The semiclassical distorted wave model (SCDW) is one of the quantum mechanical models for nucleon inelastic and charge exchange scattering at intermediate energies. SCDW can reproduce the double differential inclusive cross sections for multi-step direct processes quite well in the angular and outgoing energy regions where the model is expected to work. But the model hitherto assumed on-the-energy-shell (on-shell) nucleon-nucleon scattering in the nucleus, neglecting the difference in the distorting potentials for the incoming and the outgoing particles and also the Q-value in the case of (p,n) reactions. There had also been a problem in the treatment of the exchange of colliding nucleons. Now we modify the model to overcome those problems and put SCDW on sounder theoretical foundations. The modification results in slight reduction (increase) of double differential cross sections at forward (backward) angles. We also examine the effect of the in-medium modification of N-N cross sections in SCDW and find it small. A remedy of the disagreement at very small and large angles in terms of the Wigner transform of the single particle density matrix is also discussed. This improvement gives very promising results. (author)
Energy Technology Data Exchange (ETDEWEB)
Kivel, N.; Mankiewicz, L. E-mail: lech@cft.edu.pl
2003-11-10
We computed the NLO corrections to twist-3, L{yields}T, flavor nonsinglet amplitude in DVCS on a nucleon in the Wandzura-Wilczek approximation. Explicit calculation shows that factorization holds for NLO contribution to this amplitude, although the structure of the factorized amplitude at the NLO is more complicated than in the leading-order formula. Next-to-leading order coefficient functions for matrix elements of twist-3 vector and axial-vector quark string operators and their LO evolution equations are presented.
International Nuclear Information System (INIS)
Kivel, N.; Mankiewicz, L.
2003-01-01
We computed the NLO corrections to twist-3, L→T, flavor nonsinglet amplitude in DVCS on a nucleon in the Wandzura-Wilczek approximation. Explicit calculation shows that factorization holds for NLO contribution to this amplitude, although the structure of the factorized amplitude at the NLO is more complicated than in the leading-order formula. Next-to-leading order coefficient functions for matrix elements of twist-3 vector and axial-vector quark string operators and their LO evolution equations are presented
International Nuclear Information System (INIS)
Kabulov, A.B.
2003-01-01
Atomic nuclei display different kinds of collective motion. The well known example - is the collective model arising from valent nucleons motion. The other a special kind of collective motion is cluster mode. If a collective model has quadrupole character, then cluster one has dipole character. In the boson formalism this model is describing by dynamic symmetry U(6) direct X U(4). The common Hamiltonian symmetrical to U(6) direct X U(4) group has a form H=H d +H p +V pd . In the paper the asymptotical wave function for dipole states connected with (N-1) bosons of s- and d-types is presented. In this case the problem for Hamiltonian eigenvalues is solving by analytical way. With use Elliot method and wave functions asymptotical form the operators for matrix elements of E2-, E1-, M1-transitions are cited
Nucleon spin-averaged forward virtual Compton tensor at large {Q}^{2}
Energy Technology Data Exchange (ETDEWEB)
Hill, Richard J.; Paz, Gil
2017-05-01
The nucleon spin-averaged forward virtual Compton tensor determines important physical quantities such as electromagnetically-induced mass differences of nucleons, and two-photon exchange contributions in hydrogen spectroscopy. It depends on two kinematic variables: $\
Virtual meson cloud of the nucleon and intrinsic strangeness and charm
International Nuclear Information System (INIS)
Navarra, F.S.; Nielsen, M.; Duraes, F.O.; Barz, L.L.; Paiva, S.
1996-09-01
We have applied the Meson Cloud Model (MCM) to calculate the charm and strange antiquark distribution in the nucleon. The resulting distribution, in the case of charm, is very similar to the intrinsic charm momentum distribution in the nucleon. This seems to corroborate the hypothesis that the intrinsic charm is in the cloud and, at the same time, explains why other calculations with the MCM involving strange quark distributions fail in reproducing the low x region data. From the intrinsic strange distribution in the nucleon we have extracted the strangeness radius of the nucleon, which is in agreement with other meson cloud calculations. (author). 28 refs., 4 figs
Lowest order Virtual Element approximation of magnetostatic problems
Beirão da Veiga, L.; Brezzi, F.; Dassi, F.; Marini, L. D.; Russo, A.
2018-04-01
We give here a simplified presentation of the lowest order Serendipity Virtual Element method, and show its use for the numerical solution of linear magneto-static problems in three dimensions. The method can be applied to very general decompositions of the computational domain (as is natural for Virtual Element Methods) and uses as unknowns the (constant) tangential component of the magnetic field $\\mathbf{H}$ on each edge, and the vertex values of the Lagrange multiplier $p$ (used to enforce the solenoidality of the magnetic induction $\\mathbf{B}=\\mu\\mathbf{H}$). In this respect the method can be seen as the natural generalization of the lowest order Edge Finite Element Method (the so-called "first kind N\\'ed\\'elec" elements) to polyhedra of almost arbitrary shape, and as we show on some numerical examples it exhibits very good accuracy (for being a lowest order element) and excellent robustness with respect to distortions.
International Nuclear Information System (INIS)
Bensafa, I.K.
2006-05-01
The first part of this work presents the analysis and results of the VCS-SSA (virtual Compton scattering - single spin asymmetry) experiment at MAMI (Mainz). It was carried out with beam energy 883 MeV and longitudinal polarization (about 80%), at virtual photon four-momentum transfer squared (Q 2 = 0.35 GeV 2 ) to measure the beam asymmetry in the ep → epγ and ep → epπ 0 reactions. The asymmetry obtained in photon (resp. pion) electro-production is between 0-15% (resp. 0-2%). The dispersion relation model for virtual Compton scattering and MAID model (for π 0 ) reproduce the amplitude globally but not completely the shape of the asymmetry. Perhaps this discrepancy is due to an imperfect parameterization of some pion production multipoles (γ * N → πN). The second part is dedicated to the study of the nucleon energy spectrum in ground-state L=0 and excited-state L=1 in the quark model, using the Coulomb + linear potential type (CL) and a relativistic correction. The hyperfine correction is applied to discriminate the nucleon masses. The values of the mass found for the proton and the Δ(1232) are respectively equal to (968 MeV, 1168 MeV), and the masses of the excited states are between 1564 - 1607 MeV. This part is completed by an application of the CL model to an approximate calculation of generalized polarizabilities of the proton. (author)
Polarized lepton-nucleon scattering
International Nuclear Information System (INIS)
Hughes, E.
1994-01-01
The author provides a summary of the proposed and published statistical (systematic) uncertainties from the world experiments on nucleon spin structure function integrals. By the time these programs are complete, there will be a vast resource of data on nucleon spin structure functions. Each program has quite different experimental approaches regarding the beams, targets, and spectrometers thus ensuring systematically independent tests of the spin structure function measurements. Since the field of spin structure function measurements began, there has been a result appearing approximately every five years. With advances in polarized target technology and high polarization in virtually all of the lepton beams, results are now coming out each year; this is a true signature of the growth in the field. Hopefully, the experiments will provide a consistent picture of nucleon spin structure at their completion. In summary, there are still many open questions regarding the internal spin structure of the nucleon. Tests of QCD via the investigation of the Bjorken sum rule is a prime motivator for the field, and will continue with the next round of precision experiments. The question of the origin of spin is still a fundamental problem. Researchers hope is that high-energy probes using spin will shed light on this intriguing mystery, in addition to characterizing the spin structure of the nucleon
Polarized lepton-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Hughes, E. [Stanford Univ., CA (United States)
1994-12-01
The author provides a summary of the proposed and published statistical (systematic) uncertainties from the world experiments on nucleon spin structure function integrals. By the time these programs are complete, there will be a vast resource of data on nucleon spin structure functions. Each program has quite different experimental approaches regarding the beams, targets, and spectrometers thus ensuring systematically independent tests of the spin structure function measurements. Since the field of spin structure function measurements began, there has been a result appearing approximately every five years. With advances in polarized target technology and high polarization in virtually all of the lepton beams, results are now coming out each year; this is a true signature of the growth in the field. Hopefully, the experiments will provide a consistent picture of nucleon spin structure at their completion. In summary, there are still many open questions regarding the internal spin structure of the nucleon. Tests of QCD via the investigation of the Bjorken sum rule is a prime motivator for the field, and will continue with the next round of precision experiments. The question of the origin of spin is still a fundamental problem. Researchers hope is that high-energy probes using spin will shed light on this intriguing mystery, in addition to characterizing the spin structure of the nucleon.
On the sensitivity of nucleon-nucleon correlations to the form of short-range potential
International Nuclear Information System (INIS)
Gmitro, M.; Kvasil, J.; Lednicky, R.; Lyuboshitz, V.L.
1986-01-01
Nucleon-nucleon correlation characteristics are calculated for several phenomenological and realistic strong potentials. The results show that a square-well potential reasonably well approximates the nucleon-nucleon interaction if one calculates the correlations between nucleons generated in a region with an r.m.s. radius larger than 1.5-2 fm. Vice versa, the correlations of nucleons emitted from a smaller generation region are sensitive to the form of the assumed nucleon-nucleon potential. (author)
High-energy electroweak neutrino-nucleon deeply virtual Compton scattering
International Nuclear Information System (INIS)
Machado, Magno V. T.
2007-01-01
In this work we estimate the differential and total cross sections for the high-energy deeply virtual Compton scattering in the weak sector. In the weak neutral sector one considers neutrino scattering off an unpolarized proton target through the exchange of Z 0 . We numerically compute the process Z*p→γp within the QCD color dipole formalism, which successfully describes the current high-energy electromagnetic DVCS experimental data. We also discuss possible applications for the weak charged sector and perform predictions for scattering on nuclear targets
Toy model for pion production in nucleon-nucleon collisions
International Nuclear Information System (INIS)
Hanhart, C.; Miller, G. A.; Myhrer, F.; Sato, T.; Kolck, U. van
2001-01-01
We develop a toy model for pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations
International Nuclear Information System (INIS)
Guegan, B.
2012-11-01
The Generalized Parton Distributions (GPDs) provide a new description of the nucleon structure in terms of its elementary constituents, the quarks and the gluons. The GPDs give access to a unified picture of the nucleon, correlating the information obtained from the measurements of the Form Factors and the Parton Distribution Functions. They describe the correlation between the transverse position and the longitudinal momentum fraction of the partons in the nucleon. Deeply Virtual Compton Scattering (DVCS), the electroproduction of a real photon on a single quark of the nucleon eN → e'N'γ, is the most straightforward exclusive process allowing access to the GPDs. A dedicated experiment to study DVCS with the CLAS detector of Jefferson Lab has been carried out using a 5.883 GeV polarized electron beam and an unpolarized hydrogen target, allowing to collect DVCS events in the widest kinematic range ever explored in the valence region: 1 2 2 , 0.1 B 2 . In this work, we present the extraction of three different DVCS observables: the unpolarized cross section, the difference of polarized cross sections and the beam spin asymmetry. We present comparisons with GPD model. We show a preliminary extraction of the GPDs using the latest fitting code procedure on our data, and a preliminary interpretation of the results in terms of parton density. (author)
On the validity of the equivalent-photon approximation for virtual photon-photon collisions
International Nuclear Information System (INIS)
Carimalo, C.; Kessler, P.; Parisi, J.
1979-05-01
For virtual photon-photon collisions in electron storage rings, one derive the equivalent-photon approximation from a helicity treatment, and present it in two forms, involving respectively (i) polarized transverse photons ('transverse-photon approximation') and (ii) unpolarized ones ('Williams-Weizsaecker approximation'). One first postulates the conditions of validity of the approximation on the basis of analytic considerations, and then check them numerically in the case of the process e e → e e μ + μ - . For this check, we consider the completely differentiated cross section as far as approximation (i) is concerned; and in the case of approximation (ii), the cross section differentiated with respect to all variables except the azimuthal angles. The results are given in the form of Tables showing the lower and higher limit of the error involved in the approximation for a large variety of kinematic configurations (i. e., energy losses and scattering angles of both electrons). Those Tables are discussed in detail, and conclusions are drawn as to the applicability of the equivalent-photon approximation to future experiments to be performed with high-energy electron storage rings
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
Charge and finite size corrections for virtual photon spectra in second order Born approximation
International Nuclear Information System (INIS)
Durgapal, P.
1982-01-01
The purpose of this work is to investigate the effects of finite nuclear size and charge on the spectrum of virtual photons emitted when a relativistic electron is scattered in the field of an atomic nucleus. The method consisted in expanding the scattering cross section in terms of integrals over the nuclear inelastic form factor with a kernel which was evaluated in second order Born approximation and was derived from the elastic-electron scattering form factor. The kernel could be evaluated analytically provided the elastic form factor contained only poles. For this reason the author used a Yukawa form factor. Before calculating the second order term the author studied the first order term containing finite size effects in the inelastic form factor. The author observed that the virtual photon spectrum is insensitive to the details of the inelastic distribution over a large range of energies and depends only on the transition radius. This gave the author the freedom of choosing an inelastic distribution for which the form factor has only poles and the author chose a modified form of the exponential distribution, which enabled the author to evaluate the matrix element analytically. The remaining integral over the physical momentum transfer was performed numerically. The author evaluated the virtual photon spectra for E1 and M1 transitions for a variety of electron energies using several nuclei and compared the results with the distorted wave calculations. Except for low energy and high Z, the second order results compared well with the distorted wave calculations
Jets in high energy nucleon-nucleon collisions
International Nuclear Information System (INIS)
Strugalski, Z.
1982-01-01
From the experimental studies of high-energy hardon-nucleon and nucleon-nucleon collisions, by means of nuclear targets applied as detectors, it follows that particles are produced via intermediate objects created first in a 2 → 2 type endoergic reaction. These objects, called generons, decay in flight into finally observed particles and resonances after their lifetime tausub(g) > or approximately 10 - 22 s. The jet structure of the outcome in nucleon-nucleon collisions is a simple and indispensable consequence of this particle production mechanism. The picture of the jet structure in the collision outcome observed in the CMS of the colliding nucleons depends on the energy of these nUcleons. New particle production scheme is proposed, which can be tested experimentally; corresponding simple relations between characteristics of colliding nucleons and of produced jets are proposed for a testing
Elastic scattering of virtual photons via a quark loop in the double-logarithmic approximation
Ermolaev, B. I.; Ivanov, D. Yu.; Troyan, S. I.
2018-04-01
We calculate the amplitude of elastic photon-photon scattering via a single quark loop in the double-logarithmic approximation, presuming all external photons to be off-shell and unpolarized. At the same time we account for the running coupling effects. We consider this process in the forward kinematics at arbitrary relations between t and the external photon virtualities. We obtain explicit expressions for the photon-photon scattering amplitudes in all double-logarithmic kinematic regions. Then we calculate the small-x asymptotics of the obtained amplitudes and compare them with the parent amplitudes, thereby fixing the applicability regions of the asymptotics, i.e., fixing the applicability region for the nonvacuum Reggeons. We find that these Reggeons should be used at x <10-8 only.
International Nuclear Information System (INIS)
Jo, H.S.
2007-03-01
The Generalized Parton Distributions (GPDs), introduced in the 1990's, provide the most complete description of the structure (in quarks and gluons) of the nucleon. The Deeply Virtual Compton Scattering (DVCS), which corresponds to the 'hard' exclusive electroproduction of photons on the nucleon, is a key process among the reactions allowing access to the GPDs. A DVCS-dedicated experiment was carried out in 2005 with the CLAS detector of Jefferson Lab, using a polarized electron beam of 5.776 GeV and a hydrogen target. For this experiment, we built and used a dedicated electromagnetic calorimeter capable of detecting the final-state photon. The collected data allowed us to study the DVCS in the widest kinematic range ever accessed for this reaction: 1 2 2 , 0.1 B 2 . The work performed during this PhD includes simulation work done for the preparation of the experiment, timing calibration of one of the CLAS subsystems, and data analysis. The aim of the data analysis was the extraction of the unpolarized cross sections of the studied reaction and of the difference of the polarized cross sections, this latter observable being linearly proportional to the GPDs. The obtained results were compared to DVCS theoretical calculations based on one of the most up-to-date GPD parametrizations. (author)
Nucleon-nucleon scattering in the functional quantum theory of the non-linear spinor field
International Nuclear Information System (INIS)
Philipp, W.
1975-01-01
The nucleon-nucleon and nucleon-antinucleon scattering cross sections are calculated in the frame of the functional quantum field theory by means of two different approximation methods: averaging by integration of indefinite integrals and pulse averaging. The results for nucleon-nucleon scattering are compared with experimental data, with calculations using a modified functional scalar product and with results in first order perturbation theory (V-A-coupling). As for elastic nucleon-antinucleon scattering, the S matrix is investigated for crossing symmetry. Scattering of 'nucleons' of different mass results in different cross sections even in the lowest-order approximation. (BJ) [de
Energy Technology Data Exchange (ETDEWEB)
Bensafa, I.K
2006-05-15
The first part of this work presents the analysis and results of the VCS-SSA (virtual Compton scattering - single spin asymmetry) experiment at MAMI (Mainz). It was carried out with beam energy 883 MeV and longitudinal polarization (about 80%), at virtual photon four-momentum transfer squared (Q{sup 2} = 0.35 GeV{sup 2}) to measure the beam asymmetry in the ep {yields} ep{gamma} and ep {yields} ep{pi}{sup 0} reactions. The asymmetry obtained in photon (resp. pion) electro-production is between 0-15% (resp. 0-2%). The dispersion relation model for virtual Compton scattering and MAID model (for {pi}{sup 0}) reproduce the amplitude globally but not completely the shape of the asymmetry. Perhaps this discrepancy is due to an imperfect parameterization of some pion production multipoles ({gamma}{sup *}N {yields} {pi}N). The second part is dedicated to the study of the nucleon energy spectrum in ground-state L=0 and excited-state L=1 in the quark model, using the Coulomb + linear potential type (CL) and a relativistic correction. The hyperfine correction is applied to discriminate the nucleon masses. The values of the mass found for the proton and the {delta}(1232) are respectively equal to (968 MeV, 1168 MeV), and the masses of the excited states are between 1564 - 1607 MeV. This part is completed by an application of the CL model to an approximate calculation of generalized polarizabilities of the proton. (author)
Nucleon-nucleon scattering data
International Nuclear Information System (INIS)
Bystricky, J.; Lehar, F.
1981-01-01
The present review contains a compilation of p-p, n-n, n-p and p-n elastic scattering data, total cross sections for elastic and inelastic nucleon-nucleon processes as well as the slope parameters and the ratios of the real to the imaginary part of the forward scattering amplitude measured at all energies. The data are given in detailed tables with comments on each measurement. Summary tables, nucleon-nucleon kinematics formulae, transformation tables for kinematics, a detailed list of references and an author index complete the paper. (orig.)
International Nuclear Information System (INIS)
Bond, A.
1977-01-01
The present position of nucleonic techniques for process measurements, is considered from the technical and cost viewpoints. Systems considered include level, density, thickness (including coating thickness), moisture, and sulphur in hydrocarbons gauges and also belt weighers. The advantages of such systems are discussed and the cost-benefit position considered. The combination of nucleonic measuring equipment with a microcomputer is examined. (U.K.)
Energy Technology Data Exchange (ETDEWEB)
Ye, Zhenyu
2007-02-15
In this thesis we report on the rst results on the transverse target-spin asymmetry associated with deeply virtual Compton scattering on the proton. It is shown that this asymmetry can provide one of the rare possibilities to access the Generalized Parton Distribution (GPD) E of the nucleon, and thus, through models for E, also to the total angular momentum of u and d quarks in the nucleon. The measurement was performed using the 27.6 GeV positron beam of the HERA storage ring and the transversely polarized hydrogen target of the HERMES experiment at DESY. The two leading azimuthal amplitudes of the asymmetry are extracted from the HERMES 2002-2004 data, corresponding to an integrated luminosity of 65.3 pb.1. By comparing the results obtained at HERMES and theoretical predictions based on a phenomenological model of GPDs, we obtain a model-dependent constraint on the total angular momentum of quarks in the nucleon. (orig.)
International Nuclear Information System (INIS)
Ye, Zhenyu
2007-02-01
In this thesis we report on the rst results on the transverse target-spin asymmetry associated with deeply virtual Compton scattering on the proton. It is shown that this asymmetry can provide one of the rare possibilities to access the Generalized Parton Distribution (GPD) E of the nucleon, and thus, through models for E, also to the total angular momentum of u and d quarks in the nucleon. The measurement was performed using the 27.6 GeV positron beam of the HERA storage ring and the transversely polarized hydrogen target of the HERMES experiment at DESY. The two leading azimuthal amplitudes of the asymmetry are extracted from the HERMES 2002-2004 data, corresponding to an integrated luminosity of 65.3 pb.1. By comparing the results obtained at HERMES and theoretical predictions based on a phenomenological model of GPDs, we obtain a model-dependent constraint on the total angular momentum of quarks in the nucleon. (orig.)
Nucleon-nucleon interaction of a chiral σ-ω model at finite temperature
International Nuclear Information System (INIS)
Rukeng Su
1994-01-01
By using the imaginery time Green's function method, the nucleon-nucleon interaction of the chiral σ-ω model has been investigated under the one-loop approximation. The effective masses of the pion, σ-meson and ω-meson at finite temperature are given. We have found that the potential well of the nucleon-nucleon interaction becomes shallow as the temperature increases. At a critical temperature T c (70 MEV) the potential well disappears. (author)
The effect of including tensor forces in nucleon-nucleon interaction on three-nucleon binding energy
International Nuclear Information System (INIS)
Osman, A.; Ramadan, S.
1986-01-01
Separable two-body interactions are used in considering the three-nucleon problem. The nucleon-nucleon potentials are taken to include attraction and repulsion as well as tensor forces. The separable approximation is used in order to investigate the effect of the tensor forces. The separable expansion is introduced in the three-nucleon problem, by which the Faddeev equations are reduced to a well-behaved set of coupled integral equations. Numerical calculations are carried out for the obtained integral equations using potential functions of the Yamaguchi, Gaussian, Takabin, Mongan and Reid forms. The present calculated values of the binding energies of the 3 H and 3 He nuclei are in good agreement with the experimental values. The effect of including the tensor forces in the nucleon-nucleon interactions is found to improve the three-nucleon binding energy by about 4.490% to 8.324%. 37 refs., 2 tabs. (author)
Radial excitations in nucleon-nucleon scattering
International Nuclear Information System (INIS)
Silvestre-Brac, B.; Carbonell, J.; Gignoux, C.
1986-01-01
In the non-relativistic constituent quark model, the role of the radial excitations of the nucleon is studied within a resonating group approach of the nucleon-nucleon scattering. It is shown that, rather than the inclusion of new channels, it is important to include mixed-symmetry spin-isospin components in the nucleon wave function. It is also found that during the collision there is no significant deformation of the nucleon. (orig.)
Jia, Mengyu; Chen, Xueying; Zhao, Huijuan; Cui, Shanshan; Liu, Ming; Liu, Lingling; Gao, Feng
2015-01-26
Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we herein report on an improved explicit model for a semi-infinite geometry, referred to as "Virtual Source" (VS) diffuse approximation (DA), to fit for low-albedo medium and short source-detector separation. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the near-field to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. This parameterized scheme is proved to inherit the mathematical simplicity of the DA approximation while considerably extending its validity in modeling the near-field photon migration in low-albedo medium. The superiority of the proposed VS-DA method to the established ones is demonstrated in comparison with Monte-Carlo simulations over wide ranges of the source-detector separation and the medium optical properties.
General aspects of the nucleon-nucleon interaction and nuclear matter properties
Energy Technology Data Exchange (ETDEWEB)
Plohl, Oliver
2008-07-25
decreased in the chiral limit. The present formalism allows within chEFT to perform a consistent comparison of the in-medium nucleon mass and the density dependence of the scalar condensate derived from the Hellmann-Feynman theorem (in HF and BHF approximation). A decoupling of the in-medium nucleon mass and the scalar condensate is observed. It turns out that in contrast to QCD sum rules the effective nucleon mass in matter is mainly determined by short-range contact terms while virtual low-momentum pions provide the essential contributions responsible for the reduction of the in-medium scalar condensate. (orig.)
General aspects of the nucleon-nucleon interaction and nuclear matter properties
International Nuclear Information System (INIS)
Plohl, Oliver
2008-01-01
decreased in the chiral limit. The present formalism allows within chEFT to perform a consistent comparison of the in-medium nucleon mass and the density dependence of the scalar condensate derived from the Hellmann-Feynman theorem (in HF and BHF approximation). A decoupling of the in-medium nucleon mass and the scalar condensate is observed. It turns out that in contrast to QCD sum rules the effective nucleon mass in matter is mainly determined by short-range contact terms while virtual low-momentum pions provide the essential contributions responsible for the reduction of the in-medium scalar condensate. (orig.)
Nuclear friction calculated from nucleon currents
International Nuclear Information System (INIS)
Pi, M.; Vinas, X.; Barranco, M.; La Rana, G.; Leray, S.; Lucas, R.; Ngo, C.; Tomasi, E.
1984-01-01
Nuclear friction can be connected to the number of nucleons exchanged between two interacting nuclei. The proximity scaling allows to reduce this problem to a calculation of the nucleon current between two semi infinite slabs of nuclear matter facing each other. In this paper we review the approximations and the results concerning this problem with a special emphasis on the physical ideas. Applications of nucleons currents to Fermi jets and to the calculation of a part of the imaginary potential are also discussed
Dressing the nucleon propagator
International Nuclear Information System (INIS)
Fishman, S.; Gersten, A.
1976-01-01
The nucleon propagator in the ''nested bubbles'' approximation is analyzed. The approximation is built from the minimal set of diagrams which is needed to maintain the unitarity condition under two-pion production threshold in the two-nucleon Bethe--Salpeter equation. Recursive formulas for subsets of ''nested bubbles'' diagrams calculated in the framework of the pseudoscalar interaction are obtained by the use of dispersion relations. We prove that the sum of all the ''nested bubbles'' diverges. Moreover, the successive iterations are plagued with ghost poles. We prove that the first approximation--which is the so-called chain approximation--has ghost poles for any nonvanishing coupling constant. In an earlier paper we have shown that ghost poles lead to ghost cuts. These cuts are present in the ''nested bubbles.'' Ghost elimination procedures are discussed. Modifications of the ''nested bubbles'' approximation are introduced in order to obtain convergence and in order to eliminate the ghost poles and ghost cuts. In a similar way as in the Lee model, cutoff functions are introduced in order to eliminate the ghost poles. The necessary and sufficient conditions for the absence of ghost poles are formulated and analyzed. The spectral functions of the modified ''nested bubbles'' are analyzed and computed. Finally, we present a theorem, similar in its form to Levinson's theorem in scattering theory, which enables one to compute in a simple way the number of ghost poles
Where does the nucleon spin come from?
International Nuclear Information System (INIS)
Frois, B.; CEA Centre d'Etudes de Saclay, 91 - Gif-sur-Yvette; Karliner, M.
1994-01-01
This article describes current thinking on exactly how quarks form neutrons and protons, and where nucleon spin is derived. The European Muon Collaboration has recently shown that, contrary to previous thinking, little of the proton spin is carried by quarks, rather that virtual strange quarks in a sea contribute to nucleon spin. Thus a fundamental gap is revealed in our understanding of nucleon structure which is explored in this article, by looking at several ways of accounting for these surprising results using the ''axiaanomaly'' and the idea of gluon polarization. Future experiments already planned, on polarized scattering, should resolve the enigma of proton spin. (UK)
Nucleon-nucleon theory and phenomenology
International Nuclear Information System (INIS)
Signell, P.
1981-03-01
This project involves five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the πN and ππ physical regions of the N anti N → ππ amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 0-1200 MeV range that can be used by all nucleon-nucleon reseachers
Energy Technology Data Exchange (ETDEWEB)
Burkert, Volker D.
2016-07-25
Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $\\Delta$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^2 > 1.5GeV^2$. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.
Energy Technology Data Exchange (ETDEWEB)
Jo, H.S
2007-03-15
The Generalized Parton Distributions (GPDs), introduced in the 1990's, provide the most complete description of the structure (in quarks and gluons) of the nucleon. The Deeply Virtual Compton Scattering (DVCS), which corresponds to the 'hard' exclusive electroproduction of photons on the nucleon, is a key process among the reactions allowing access to the GPDs. A DVCS-dedicated experiment was carried out in 2005 with the CLAS detector of Jefferson Lab, using a polarized electron beam of 5.776 GeV and a hydrogen target. For this experiment, we built and used a dedicated electromagnetic calorimeter capable of detecting the final-state photon. The collected data allowed us to study the DVCS in the widest kinematic range ever accessed for this reaction: 1 < Q{sup 2} < 4.6 GeV{sup 2}, 0.1 < x{sub B} < 0.58, 0.09 < -t < 2 GeV{sup 2}. The work performed during this PhD includes simulation work done for the preparation of the experiment, timing calibration of one of the CLAS subsystems, and data analysis. The aim of the data analysis was the extraction of the unpolarized cross sections of the studied reaction and of the difference of the polarized cross sections, this latter observable being linearly proportional to the GPDs. The obtained results were compared to DVCS theoretical calculations based on one of the most up-to-date GPD parametrizations. (author)
Nucleon structure functions, resonance form factors, and duality
International Nuclear Information System (INIS)
Davidovsky, V.V.; Struminsky, B.V.
2003-01-01
The behavior of nucleon structure functions in the resonance region is explored. For form factors that describe resonance production, expressions are obtained that are dependent on the photon virtuality Q 2 , which have a correct threshold behavior, and which take into account available experimental data on resonance decay. Resonance contributions to nucleon structure functions are calculated. The resulting expressions are used to investigate quark-hadron duality in electron-nucleon scattering by taking the example of the structure function F 2
Covariant computation of e+e- production in nucleon-nucleon collisions
International Nuclear Information System (INIS)
Haglin, K.; Kapusta, J.; Gale, C.
1989-01-01
Electron-positron production differential cross sections in nucleon-nucleon collisions are calculated analytically via meson exchange with a realistic pseudovector coupling including strong interaction form factors. These results are compared with newly obtained data from the DLS at the BEVALAC of proton on beryllium. A comparison with the soft photon approximation is also made. (orig.)
Qualitative treatment of three-nucleon properties
International Nuclear Information System (INIS)
Efimov, V.
1981-01-01
An attempt is made at consistent qualitative treatment of the three-nucleon system. The approach used is based on the physical concept of effective three-nucleon long-range interaction resulting from the existence of the deuteron and the virtual singlet deuteron. Within the framework of the approach, a qualitative treatment of the triton properties, nucleon-deuteron scattering, and triton-disintegration reactions is carried out. The following topics are dealt with: the Phillips line, the triton D-wave admixture, the doublet effective range of the n-d scattering, the triton virtual state, the anomaly of the n-d elastic cross section near the three-body threshold, and the partial cross sections of the inelastic n-d scattering and of the triton photo- and electrodisintegration. The discussion of these topics includes the evaluation of three-nucleon parameters and the qualitative interpretation of experimental data and calculation results; some predictions are also made. The results of our analysis lead to the conclusion that the concept of effective three-nucleon long-range interaction can indeed serve as grounds for consistent qualitative treatment of the three-nucleon phenomena. (orig.)
Future exploration of the nucleon structure at COMPASS
International Nuclear Information System (INIS)
Marchand, Claude
2011-01-01
Up to now, COMPASS experiment essentially focussed, in it's program with muon beams, on studying aspects of the longitudinal momentum structure of the nucleon in the collinear approximation, like Δq(x) and ΔG/G(x). However, quarks can also have intrinsic transverse momentum in the nucleon, which give rise to a new class of Transverse Momentum Distribution (TMD) Parton Distribution Functions. As an example, Sievers function has been measured by both COMPASS and HERMES to be non zero on the proton, paving thus the way for more precise investigations. It is precisely the goal of the new COMPASS phase II proposal to investigate in more detail new transverse description of the nucleon structure. Deeply Virtual Compton Scattering (DVCS) will allow studies in the transverse space via Generalized Parton Distributions (GPDs). Transverse Mometum Dependent PDFs will essentially be studied in Drell-Yan (DY) reaction and SIDIS, and some universality arguments in QCD imply different signs for Sievers and Boer-Mulders functions in DY and SIDIS.
Energy Technology Data Exchange (ETDEWEB)
Simula, S. [Instituto Nazionale di Fisica Nucleare, Roma (Italy)
1994-04-01
Semi-inclusive deep inelastic lepton scattering off nuclei is investigated assuming that virtual boson absorption occurs on a hadronic cluster which can be either a two-nucleon correlated pair or a six-quark bag. The differences in the energy distribution of nucleons produced in backward and forward directions are analyzed both at x<1 and x>1.
Isospin breaking in the pion-nucleon scattering lengths
International Nuclear Information System (INIS)
Hoferichter, Martin; Kubis, Bastian; Meissner, Ulf-G.
2009-01-01
We analyze isospin breaking through quark mass differences and virtual photons in the pion-nucleon scattering lengths in all physical channels in the framework of covariant baryon chiral perturbation theory.
Isospin breaking in the pion-nucleon scattering lengths
Energy Technology Data Exchange (ETDEWEB)
Hoferichter, Martin [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)], E-mail: kubis@itkp.uni-bonn.de; 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 (Theorie), Institute for Advanced Simulation, and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany)
2009-07-06
We analyze isospin breaking through quark mass differences and virtual photons in the pion-nucleon scattering lengths in all physical channels in the framework of covariant baryon chiral perturbation theory.
International Nuclear Information System (INIS)
Tezuka, Hirokazu.
1984-10-01
Scattering of a particle by bound nucleons is discussed. Effects of nucleons that are bound in a nucleus are taken as a structure function. The way how to calculate the structure function is given. (author)
International Nuclear Information System (INIS)
Sauer, P.U.
2014-01-01
In this paper, the role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries toward calculationally converged results. Genuine forces make up the Hamiltonian. They represent the chosen underlying dynamics. The hierarchy of contributions arising from genuine two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the description of some observables. Their contributions to observables are small on the scale set by two-nucleon forces. (author)
Pionic background for nucleon-nucleon observables
International Nuclear Information System (INIS)
Ballot, J.L.; Robilotta, M.R.
1992-01-01
A method is presented that allows the unambiguous definition of the one pion exchange contribution to nucleon-nucleon scattering observables and then use it to determine those waves where values of phase shifts and mixing parameters may be understood as sums of pionic and non-pionic dynamical effects. This helps the assessment of the explicative power of the various existing phenomenological potentials and may eventually lead to ways of discriminating their effectiveness. (author) 16 refs.; 19 figs.; 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Bouchigny, S
2004-04-01
The first part describe my work on the frozen spin target project HYDILE. This target has to be made of very pure HD (Hydrogen Deuterium), better than 99.95%. However, commercial HD is never found with a concentration better than 98%. The goal was, then, to build an HD distillation facility which could produce pure HD. We describe, in this thesis, the design of the distillator and the implementation of a quadrupole mass spectrometer to monitor the HD purity during the distillation process. The second part of the thesis concerns the analysis taken at the electron accelerator facility TJNAF (Virginia, USA). We look at the electroproduction of Delta resonances involving Deep Virtual Compton Scattering (DeltaVCS). The interpretation of this reaction in terms of GPDs (Generalized Parton Distribution) can provide new insights to the nucleon structure. We focus on the measurement of the beam spin asymmetry which comes from the interference of the Bethe Heitler process with the DeltaVCS. (author)
Kuric, Katelyn M; Harris, Bryan T; Morton, Dean; Azevedo, Bruno; Lin, Wei-Shao
2017-09-29
This clinical report describes a digital workflow using extraoral digital photographs and volumetric datasets from cone beam computed tomography (CBCT) imaging to create a 3-dimensional (3D), virtual patient with photorealistic appearance. In a patient with microstomia, hinge axis approximation, diagnostic casts simulating postextraction alveolar ridge profile, and facial simulation of prosthetic treatment outcome were completed in a 3D, virtual environment. The approach facilitated the diagnosis, communication, and patient acceptance of the treatment of maxillary and mandibular computer-aided design and computer-aided manufacturing (CAD-CAM) of immediate dentures at increased occlusal vertical dimension. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Potentials of the inverse scattering problem in the three-nucleon problem
International Nuclear Information System (INIS)
Pushkash, A.M.; Simenog, I.V.; Shapoval, D.V.
1993-01-01
Possibilities of using the method of the inverse scattering problem for describing simultaneously the two-nucleon and the low-energy three-nucleon data in the S-interaction approximation are examined. 20 refs., 3 figs., 1 tab
Energy Technology Data Exchange (ETDEWEB)
Guegan, Baptiste [Rensselaer Polytechnic Inst., Troy, NY (United States)
2012-11-01
The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.
Excitation of Nucleon Resonances
International Nuclear Information System (INIS)
Burkert, Volker D.
2001-01-01
I discuss developments in the area of nucleon resonance excitation, both necessary and feasible, that would put our understanding of nucleon structure in the regime of strong QCD on a qualitatively new level. They involve the collection of high quality data in various channels, a more rigorous approach in the search for ''missing'' resonances, an effort to compute some critical quantities in nucleon resonance excitations from first principles, i.e. QCD, and a proposal focused to obtain an understanding of a fundamental quantity in nucleon structure
Nucleon quark distributions in a covariant quark-diquark model
Energy Technology Data Exchange (ETDEWEB)
Cloet, I.C. [Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, University of Adelaide, SA 5005 (Australia) and Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)]. E-mail: icloet@physics.adelaide.edu.au; Bentz, W. [Department of Physics, School of Science, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan)]. E-mail: bentz@keyaki.cc.u-tokai.ac.jp; Thomas, A.W. [Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)]. E-mail: awthomas@jlab.org
2005-08-18
Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. We find excellent agreement between our model results and empirical data.
Banerjee, S. N.; Chakraborty, S. N.
1980-01-01
Presents the outline of an approach related to the teaching of the chapter on bound and scattering states in a short-range potential, which forms a standard part of an undergraduate quantum mechanics course or nuclear physics course. (HM)
Off-energy-shell variations of two-nucleon transition matrix and three-nucleon problem
International Nuclear Information System (INIS)
Stingl, M.; Sauer, P.U.
1975-01-01
For a schematic three-nucleon problem, approximate analytic expressions are derived for the functional derivatives of measurable three-particle quantities with respect to off-shell variations of the triplet-s two-nucleon transition matrix. Those quantities include neutron-deuteron scattering lengths, trinucleon binding energies, and the 3 He charge form-factor minimum; correlations between off-shell changes in the latter two are discussed. An indication is given how results of this kind may be to decide whether or not a given set of discrepancies between calculated and experimental three-nucleon observables can be reconciled in terms of off-shell variations of a nonretarded hermitean two-nucleon interaction. The treatment is not restricted to special classes of phase-shift equivalent potentials or phase-shift preserving transformations but instead makes use of a systematic parameterization of off-shell variations in terms of symmetric rational approximants of increasing order
Block, Martin M
2002-01-01
Using an eikonal structure for the scattering amplitude, factorization theorems for nucleon-nucleon, gamma p and gamma gamma scattering at high energies have been derived, using only some very general assumptions. Using a QCD-inspired eikonal analysis of nucleon-nucleon scattering, we present here experimental confirmation for factorization of cross sections, nuclear slope parameters B and rho -values (ratio of real to imaginary portion of forward scattering amplitudes), showing that: 1) the three factorization theorems of Block and Kaidalov [2000] hold, 2) the additive quark model holds to approximately=1%, and 3) vector dominance holds to better than approximately=4%. Predictions for the total cross section, elastic cross section and other forward scattering parameters at the LHC (14 TeV) are given. (12 refs).
Energy Technology Data Exchange (ETDEWEB)
Dobretsov, Yu; Dolgoshein, B; Kirillov-Ugryumov, V
1980-12-01
The properties and formation are described of ..mu..-nucleon atoms, the Larmor method of muon spin precession is discussed and the experimental confirmation of the existence of ..mu..-nucleon atoms is shown. The prospects of their use are indicated.
International Nuclear Information System (INIS)
Dobretsov, Yu.; Dolgoshejn, B.; Kirillov-Ugryumov, V.
1980-01-01
The properties and formation are described of μ-nucleon atoms, the Larmor method of muon spin precession is discussed and the experimental confirmation of the existence of μ-nucleon atoms is shown. The prospects of their use are indicated. (J.P.)
Nucleon-nucleon scattering phase shifts
International Nuclear Information System (INIS)
Bryan, R.
1978-01-01
Here are presented 0 to 800 MeV nucleon-nucleon elastic and inelastic phase parameters derived by several groups: Arndt and Roper; Hoshizaki; Bugg; Bystricky, Lechanoine, and Lehar; and Bryan, Clark, and VerWest. Resonant-like behavior appears in the 1 D 2 and 3 F 3 states above the inelastic threshold in Hoshizaki's analysis but not in Arndt and Roper's. The np data are inadequate to permit determination of the I = O phase parameters above 600 MeV. 27 references
Nucleon-nucleon scattering in the functional quantum theory of the nonlinear spinor field
International Nuclear Information System (INIS)
Haegele, G.
1979-01-01
The author calculates the S matrix for the elastic nucleon-nucleon scattering in the lowest approximation using the quantum theory of nonlinear spinor fields with special emphasis to the ghost configuration of this theory. Introducing a general scalar product a new functional channel calculus is considered. From the results the R and T matrix elements and the differential and integral cross sections are derived. (HSI)
Nucleon-nucleon interaction in the soliton bag model
International Nuclear Information System (INIS)
Schuh, A.
1985-01-01
In the framework of the Soliton Bag Model introduced by Friedberg and Lee we treat S-wave nucleon-nucleon scattering. Our system consists of six quarks and the nontopological soliton field which represents an average colorfree interaction between the quarks and yields their (relative) confinement. The dynamical problem is treated by means of the Generator coordinate Method (GCM) where the total wave function is the weighted sum over static configurations of prescribed bag deformation. The static configurations needed for the GCM ansatz are generated starting from a potential well of prescribed deformation wherein we solve the Dirac equation for the quarks. The single particle quark orbitals are properly coupled with respect to orbital, color, spin, and isospin quantum numbers to form a totally antisymmetric 6-quark state. A mean field solution for the soliton field is then calculated and turned into a quantum mechanical state by a coherent state approximation. Since these static configurations are only to be seen as wave function generators for the GCM no selfconsistency between quark and soliton solution is enforced. With these configurations we then evaluate the norm and Hamiltonian kernels appearing in the GCM treatment. The Hill-Wheeler integral equation for the weight functions is transformed into a Schroedinger-type differential equation by an expansion into symmetric moments of up to second order. This equation is brought into a form where we can identify the interaction potential unambiguously. We find an intermediate range attraction of about 120 MeV and no attraction in the vicinity of the spherically symmetric shape of the system, in contradiction to the naive adiabatic potentials widely used in quark models for the nucleon-nucleon interaction up to now. (orig./HSI) [de
Electromagnetic structure of a bound nucleon
International Nuclear Information System (INIS)
Nogami, Y.
1977-01-01
The effect of binding on the electromagnetic (e.m.) structure of a nucleon in a nucleus is examined by means of a model consisting of a single nucleon which is bound in a harmonic oscillator potential and also coupled to the pion field through the Chew-Low interaction. The 'two-pion contribution' to the e.m. structure is considered. This is the part which is probably most susceptible to the binding effect. By the binding effect it is meant the one which arises because the nucleon wave functions, in the intermediate state as well as in the initial and final states, are distorted by the potential in which the nucleon is bound. This may be compared to a similar correction to the impulse approximation for pion-nucleus scattering. Unlike the latter which is likely to be quite appreciable, the binding correction to the e.m. structure of the nucleon is found to be negligibly small. The so-called quenching effect due to the Pauli principle when there are other nucleons is also discussed [pt
Energy Technology Data Exchange (ETDEWEB)
Henley, E M [Washington Univ., Seattle (USA). Dept. of Physics; Wolfenstein, L [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics
1978-05-15
The low-energy scattering of nucleons by /sup 2/H, /sup 3/He and /sup 4/He is analyzed for parity nonconserving effects. The asymmetry in the total cross section of longitudinally polarized projectiles is formulated in terms of the optical theorem and a distorted-wave Born approximation. For two nucleons at low energies it is only necessary to consider l = 0 to l = 1 matrix elements of the weak nucleon-nucleon potential. The asymmetries in the scattering from nuclear targets are related to the parameters of an effective weak nucleon-nucleon potential, so that they may be used to help differentiate between various proposed theoretical potentials.
International Nuclear Information System (INIS)
Eletsky, V.L.
1991-01-01
The problem of temperature dependence of nucleon mass is addressed by considering a retarded correlator of two currents with quantum numbers of a nucleon at finite temperature T π in the chiral limit. It is shown that at Euclidean momenta the leading one-loop corrections arise from direct interaction of thermal pions with the currents. A dispersive representation for the correlator shows that this interaction smears the nucleon pole over frequency interval with width ∼ T. This interaction does not change the exponential fall-off of the correlator in Euclidean space but gives an O(T 2 /F π 2 ) contribution to the pre-exponential factor. 11 refs. (author)
Separable expansions for virtual states and resonances
International Nuclear Information System (INIS)
Adhikari, S.K.; Fonseca, A.C.; Tomio, L.
1983-01-01
Finite rank expansions for two- and three-body t matrices are analytically continued to the unphysical sheet of the complex energy plane associated with the lowest two-body scattering threshold in order to obtain the position and residue of the virtual state and resonance poles. The present method is applied to study the 1 S 0 virtual state of two nucleons, the Efimov virtual states of three identical bosons, and the doublet virtual state of three nucleons
International Nuclear Information System (INIS)
Scott, D.K.
1978-03-01
Some initial experiments in the intermediate energy region between 10 and 200 MeV/nucleon, which is largely unexplored and poorly understood is considered as regards some initial experiments in this energy region. Included are the emission of complex fragments, localization in heavy ion reactions, coincidence experiments between light and heavy fragments, and the emission of light particles in heavy ion collisions. Some initial results in the region between 20 and 100 MeV/nucleon are presented. 41 references
The nucleon-nucleon potential in the chromodielectric soliton model
International Nuclear Information System (INIS)
Koepf, W.; Wilets, L.; Pepin, S.; Stancu, F.
1993-01-01
The short- and medium-range parts of the nucleon-nucleon interaction are being studied in the framework of the chromodielectric soliton model. The model consists of current quarks, gluons in the abelian approximation, and a scalar σ field which simulates the nonabelian interactions of the gluons and governs the medium through the dielectric function κ(σ). Absolute color confinement is effected by the vanishing of the dielectric in vacuum; this also removes the troublesome van der Waals problem. The authors distinguish between spatial confinement, which arises from the self energy of the quarks in medium (excluding MFA contributions), and color confinement which is effected through OGE in the MFA (including the corresponding self energy contributions). The static (adiabatic) energies are computed as a function of deformation (generalized bag separation) in a constrained MFA. Six quark molecular-type wave functions in all important space-spin-isospin-color configurations are included. The gluon propagator is solved in the deformed dielectric medium. The resultant Hamiltonian matrix is diagonalized. Dynamics are handled in the Generator Coordinate Method, which leads to the Hill-Wheeler integral equation. In the present case, this yields a set of coupled equations corresponding to the various configurations. Although this can be approximated by a set of differential equations, they propose to solve the integral equations with some regularization scheme
International Nuclear Information System (INIS)
Abbas, Afsar
1992-01-01
The surprising answer to this question Is nucleon deformed? is : Yes. The evidence comes from a study of the quark model of the single nucleon and when it is found in a nucleus. It turns out that many of the long standing problems of the Naive Quark Model are taken care of if the nucleon is assumed to be deformed. Only one value of the parameter P D ∼1/4 (which specifies deformation) fits g A (the axial vector coupling constant) for all the semileptonic decay of baryons, the F/D ratio, the pion-nucleon-delta coupling constant fsub(πNΔ), the double delta coupling constant 1 fsub(πΔΔ), the Ml transition moment μΔN and g 1 p the spin structure function of proton 2 . All this gives strong hint that both neutron and proton are deformed. It is important to look for further signatures of this deformation. When this deformed nucleon finds itself in a nuclear medium its deformation decreases. So much that in a heavy nucleus the nucleons are actually spherical. We look into the Gamow-Teller strengths, magnetic moments and magnetic transition strengths in nuclei to study this property. (author). 15 refs
International Nuclear Information System (INIS)
Wells, T.B.
1978-01-01
The charge dependence and charge asymmetry of the nucleon-nucleon force arising from the exchange of a pion and a photon with the excitation of a nucleon resonance [Δ(1236)] is calculated. This charge dependence and asymmetry is studied through its effects on the 1 S nucleon-nucleon scattering lengths. The complexity of the calculation forces the use of approximations. The calculation is performed first with a pole approximation for the resonance and a second time with a Chew-Low description of the resonance. Both calculations neglect nuclear recoil. Estimates of this effect are made. The changes in the scattering lengths are small ( +- / 2 = 1.0225 G/sub π 0 / 2 will explain the proton-neutron scattering length
Nucleon-nucleon scattering and different meson exchanges
International Nuclear Information System (INIS)
Osman, A.
1985-10-01
The iterative and noniterative diagrams with different meson exchange are investigated. The α, πβ and πγ meson exchange, (where α=π, rho, σ, ω, eta and delta; β=π, rho, σ and ω; γ=π and rho), are considered. These diagrams are taken to involve the nucleon-nucleon, the nucleon-isobar and the isobar-isobar intermediate states. The diagrams are calculated in momentum space following the noncovariant perturbation theory. The role of each of these diagrams is examined by calculating its contribution to the nucleon-nucleon interaction. The potential model is taken to include one-boson-exchange terms in addition to these diagrams. The nucleon-nucleon scattering phase shifts are described successfully showing the importance of tensor force. The contributions of the different parts are studied in the nucleon-nucleon scattering. (author)
Effective lagrangian for Kaon-nucleon scattering
International Nuclear Information System (INIS)
Andrade, S.C.B. de; Ferreira, E.M.
1980-11-01
A model for the Kaon-nucleon interaction is investigated, based on a lagrangian which includes the Yukawa interactions of hyperons, kaons and nucleons plus contact terms representing short range interactions in each isospin state. All diagrams up to fourth order are evaluated and the partial wave S matrix elements are unitarized through diagonal Pade approximants. The results of the calculations with this model give a good description of all experimental data on both I = O and I = 1 states of the KN system at low and intermediate energies. (Author) [pt
The spin structure of the nucleon
International Nuclear Information System (INIS)
Deur, A.
2008-02-01
This document describes the recent experimental results on the spin structure of the nucleon obtained with the electron accelerator Thomas Jefferson National Facility (Jefferson Lab), Virginia. We first discuss the goal of studying the nucleon spin structure and give the basis and phenomenology of high energy lepton scattering. Then, we discuss with some details a few sum rules concerning the spin structure of the nucleon. Those are important tools for studying the nucleon spin structure at Jefferson Lab. We then describe the present experimental situation and analyze the results. We have been able to determine an effective coupling constant for the strong interaction for any regime of quantum chromodynamics which proves that QCD is an approximately conformal theory. We conclude on the perspectives for this field of research, in particular with the 12 GeV energy upgrade of Jefferson Lab. The top priority will be the measurement of generalised parton distributions. The only issue that will stay misunderstood is the role of the very low x domain on the spin structure of the nucleon
Pion-nucleon vertex function with one nucleon off shell
International Nuclear Information System (INIS)
Mizutani, T.; Rochus, P.
1979-01-01
The pion-nucleon vertex function with an off-mass-shell nucleon is obtained through sideways dispersion relations with the P 11 and S 11 pion-nucleon phase shifts as only input. Contrary to the recent calculation of Nutt and Shakin, we find that the proper and improper vertex functions behave quite differently, indicating the importance of the nucleon propagator dressing. In particular the proper vertex function is found to have two poles in the unphysical region
A new form for the nucleon-nucleon potential
International Nuclear Information System (INIS)
Agarwal, B.K.
1976-01-01
The form of the internucleon force is considered. It is assumed that the nucleon-nucleon potential depends, in general, both on the distance ν and the angle theta. It is also assumed that the potential V(ν,ω) admits an analytic continuation into the complex ω-plane so that when ω=costheta is real it denotes the direction in which the potential is being determined. The analysis leads to a new parametryzation of the nucleon-nucleon potential
Pauli blocking and medium effects in nucleon knockout reactions
International Nuclear Information System (INIS)
Bertulani, C. A.; De Conti, C.
2010-01-01
We study medium modifications of the nucleon-nucleon (NN) cross sections and their influence on the nucleon knockout reactions. Using the eikonal approximation, we compare the results obtained with free NN cross sections with those obtained with a purely geometrical treatment of Pauli blocking and with NN obtained with more elaborated Dirac-Bruecker methods. The medium effects are parametrized in terms of the baryon density. We focus on symmetric nuclear matter, although the geometrical Pauli blocking also allows for the treatment of asymmetric nuclear matter. It is shown that medium effects can change the nucleon knockout cross sections and momentum distributions up to 10% in the energy range E lab =50-300 MeV/nucleon. The effect is more evident in reactions involving halo nuclei.
Parity violation in the nucleon-nucleon interaction
International Nuclear Information System (INIS)
Haxton, W.C.
1989-01-01
I discuss the present status of our understanding of parity nonconservation (PNC) in the nucleon-nucleon interaction, and some of the difficulties inherent in nuclear tests of PNC. I also discuss the nucleon/nuclear anapole moment, the parity violating coupling of the photon, and its relation to the PNC NN interaction. 13 refs., 1 fig., 2 tabs
International Nuclear Information System (INIS)
Grange, P.; Mathiot, J.F.; Roy-Stephan, M.; Frascaria, R.; Gales, S.
1990-01-01
The topics presented at the 1989 Joliot-Curie Lectures are reported. Two main subjects were retained: a simplified description of the N-body motion of particles in the quasi-particle configuration; study of the dynamics of nuclear components which are not described by nucleons in their ground state. The following themes were presented: quasiparticles and the Green functions, relativistic aspects of the quasiparticle concept, the dimensions of nucleons in the nuclei and the EMC effect, quarks and gluons in the nuclei, the delta in the nuclei, the strangeness, quasiparticles far from the Fermi sea, diffusion of electrons, stellar evolution and nucleosynthesis [fr
International Nuclear Information System (INIS)
Virchaux, M.
1992-11-01
The present status of experimental measurements of the nucleon structure functions is reviewed. The results from nearly all deep inelastic experiments are in good mutual agreement. Principles of the analysis of these structure function data in the framework of QCD are described. The specific features of the perturbative QCD predictions are observed in the data. This provides quantitative tests of the validity of QCD as well as determinations of the various parton distributions in the nucleon and some of the most precise measurements of the strong coupling constant αs. The future of this field of experimental physics is sketched
Medium corrections to nucleon-nucleon interactions
International Nuclear Information System (INIS)
Dortmans, P.J.; Amos, K.
1990-01-01
The Bethe-Goldstone equations have been solved for both negative and positive energies to specify two nucleon G-matrices fully off of the energy shell. Medium correction effects of Pauli blocking and of the auxiliary potential are included in infinite matter systems characterized by fermi momenta in the range 0.5 fm -1 to 1.8 fm -1 . The Paris interaction is used as the starting potential in most calculations. Medium corrections are shown to be very significant over a large range of energies and densities. On the energy shell values of G-matrices vary markedly from those of free two nucleon (NN) t-matrices which have been solved by way of the Lippmann-Schwinger equation. Off of the energy shell, however, the free and medium corrected Kowalski-Noyes f-ratios rate are quite similar suggesting that a useful model of medium corrected G-matrices are appropriately scaled free NN t-matrices. The choice of auxiliary potential form is also shown to play a decisive role in the negative energy regime, especially when the saturation of nuclear matter is considered. 30 refs., 7 tabs., 7 figs
The nucleon- nucleon interaction and symmetries
International Nuclear Information System (INIS)
Van Oers, W.T.H.
1992-11-01
With the advent of the possibility to study nucleon-nucleon scattering at medium energies, its extension to investigate fundamental symmetries was recognized early on. It was precisely the introduction of rotational invariance, parity conservation, time reversal invariance, and isotopic spin conversation that led to the description of the N - N scattering matrix in terms of five complex amplitudes: one set of five for proton-proton scattering and one set of five for neutron-proton scattering, or alternatively, one set for the isotopic spin state ι=ο and the other for the isotopic spin state ι=1. Clearly, if one or more of the above constraints are removed, there are additional amplitudes that need to be considered. To be meaningful, experiment requires observables that are particularly sensitive to the violation of a conservation law or symmetry principle. During the last decade a series of precision experiments has been performed to measure charge- symmetry breaking in n - p elastic scattering (corresponding to isotopic spin non-conservation), and to measure parity violation in p-p scattering. For a particle-anti-particle system,like the pp or λλ system one can raise the question of CP violation in a system other than the neutral kaon system may become possible in the near future through pp →λλ and pp→ ≡ ≡. A description is given of the ongoing efforts to measure charge symmetry breaking, parity violation and CP violation.(author). 42 refs., 6 figs
Nucleon strangeness: present and future
Sapozhnikov, M G
2010-01-01
A review of experimental results for the measurement of the strange quark distributions in the nucleon, is given. Contributions of the strange quarks to the nucleon mass, electromagnetic form factors and spin, are discussed.
Quenching of weak interactions in nucleon matter
International Nuclear Information System (INIS)
Cowell, S.; Pandharipande, V.R.
2003-01-01
We have calculated the one-body Fermi and Gamow-Teller charge-current and vector and axial-vector neutral-current nuclear matrix elements in nucleon matter at densities of 0.08, 0.16, and 0.24 fm -3 and proton fractions ranging from 0.2 to 0.5. The correlated states for nucleon matter are obtained by operating on Fermi-gas states by a symmetrized product of pair correlation operators determined from variational calculations with the Argonne-v18 and Urbana-IX two- and three-nucleon interactions. The squares of the charge- current matrix elements are found to be quenched by 20-25 % by the short-range correlations in nucleon matter. Most of the quenching is due to spin-isospin correlations induced by the pion exchange interactions which change the isospins and spins of the nucleons. A large part of it can be related to the probability for a spin-up proton quasiparticle to be a bare spin-up/down proton/neutron. Within the interval considered, the charge-current matrix elements do not have significant dependence on the matter density, proton fraction, and magnitudes of nucleon momenta; however, they do depend on momentum transfer. The neutral-current matrix elements have a significant dependence on the proton fraction. We also calculate the matrix elements of the nuclear Hamiltonian in the same correlated basis. These provide relatively mild effective interactions that give the variational energies in the Hartree-Fock approximation. The calculated two-nucleon effective interaction describes the spin-isospin susceptibilities of nuclear and neutron matter fairly accurately. However terms greater than or equal to three-body terms are necessary to reproduce the compressibility. Realistic calculations of weak interaction rates in nucleon matter can presumably be carried out using the effective operators and interactions studied here. All presented results use the simple two-body cluster approximation to calculate the correlated basis matrix elements. This allows for a clear
Axial structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Nucleon Compton Scattering with Two Space-Like Photons
International Nuclear Information System (INIS)
Andrei Afanasev; I. Akushevich; N.P. Merenkov
2002-01-01
We calculate two-photon exchange effects for elastic electron-proton scattering at high momentum transfers. The corresponding nucleon Compton amplitude is defined by two space-like virtual photons that appear to have significant virtualities. We make predictions for (a) a single-spin beam asymmetry, and (b) a single-spin target asymmetry or recoil proton polarization caused by an unpolarized electron beam
International Nuclear Information System (INIS)
Windmolders, R.
1989-01-01
In this paper the following topics are reviewed: 1. the structure functions measured in deep inelastic e-N, μ-N and ν-N scattering; 2. nuclear effects on the structure functions; 3. nuclear effects on the fragmentation functions; 4. the spin dependent structure functions and their interpretation in terms of nucleon constituents. (orig./HSI)
Nowak, M A; Zahed, I
1989-01-01
The issue of the strangeness content of the proton in relation to a large σ π N term is examined using the instanton-antiinstanton description of the QCD ground state. Modulo plausible assumptions, our results indicate no strangeness admixture in the nucleon state at zero momentum transfer.
International Nuclear Information System (INIS)
Anon.
1978-01-01
The design and operation of a nucleonic weighing machine fabricated for continuous weighing of material over conveyor belt are described. The machine uses a 40 mCi cesium-137 line source and a 10 litre capacity ionization chamber. It is easy to maintain as there are no moving parts. It can also be easily removed and reinstalled. (M.G.B.)
Effective nucleon-nucleon interaction in the RPA
International Nuclear Information System (INIS)
Batista, E.F.; Carlson, B.V.; Conti, C. de; Frederico, T.
2001-01-01
The purpose of the present work is to study the properties of the effective nucleon-nucleon interaction, in a infinite system of mesons and baryons , using the relativistic Hartree-Fock-Bogoliubov approximation. To derive the RHFB equations in a systematic fashion, we use Dyson's equation to sum to all orders the self-consistent tadpole and exchange contributions to the extended baryon Green's function (the Gorkov propagator). The meson propagator is computed as a sum over ring diagrams which consist in repeated insertions of the lowest-order proper polarization graph. The sum is the diagrammatic equivalent of the relativistic random phase approximation (RPA) that describes the well-known collective modes. In the nuclear medium, the σ and ω propagators are linked because of scalar-vector mixing, a density-dependent effect that generates a coupling between the Dyson's equation for the meson propagators. We use the dressed meson propagator to obtain the effective interaction and investigate its effect on the 1 S 0 pairing in nuclear matter. The effective interaction has title effect on the self-energy mean field, since the latter is dominated by the Hartree contribution, which is determined by the free meson propagators. The pairing field, however, is obtained from an exchange term, in which the effective interaction can play an important role. As the polarization corrections to the meson propagators tend to increase the σ-meson mass and decrease the ω-meson mass, they result in an effective interaction which is more repulsive than the bare one. We would expect this to result in a decrease in the 1 S 0 pairing, similar to that seen in nonrelativistic calculations. (author)
Nucleon-nucleon correlations in dense nuclear matter
International Nuclear Information System (INIS)
Alm, T.
1993-02-01
In this thesis new results on the problematics of the formation of nucleon-nucleon correlations in nuclear matter could be presented. Starting from a general study of the two-particle problem in matter we studied the occurrence of a suprafluid phase (pair condensate of nucleons). The Gorkov decoupling by means of anomalous Green functions was generalized, so that also Cooper pairs with spin 1 (triplet pairing) can be described. A generalized gap equation resulted, which permits to determine the order parameters of the suprafluied phase in arbitrary channels of the nucleon-nucleon scattering states. This equation was solvd in the 1 S 0 -, in the 3 P 2 - 3 F 2 , and in the 3 S 1 - 3 D 1 channel under application of realistic nucleon-nucleon potentials. The behaviour of the resulting gap parameters in the single channels was studied as function of density and temperature. (orig.) [de
The nucleon- nucleon interaction and symmetries
Energy Technology Data Exchange (ETDEWEB)
Van Oers, W T.H.
1992-11-01
With the advent of the possibility to study nucleon-nucleon scattering at medium energies, its extension to investigate fundamental symmetries was recognized early on. It was precisely the introduction of rotational invariance, parity conservation, time reversal invariance, and isotopic spin conversation that led to the description of the N - N scattering matrix in terms of five complex amplitudes: one set of five for proton-proton scattering and one set of five for neutron-proton scattering, or alternatively, one set for the isotopic spin state {iota}={omicron} and the other for the isotopic spin state {iota}=1. Clearly, if one or more of the above constraints are removed, there are additional amplitudes that need to be considered. To be meaningful, experiment requires observables that are particularly sensitive to the violation of a conservation law or symmetry principle. During the last decade a series of precision experiments has been performed to measure charge- symmetry breaking in n - p elastic scattering (corresponding to isotopic spin non-conservation), and to measure parity violation in p-p scattering. For a particle-anti-particle system,like the pp or {lambda}{lambda} system one can raise the question of CP violation in a system other than the neutral kaon system may become possible in the near future through pp {yields}{lambda}{lambda} and pp{yields} {identical_to} {identical_to}. A description is given of the ongoing efforts to measure charge symmetry breaking, parity violation and CP violation.(author). 42 refs., 6 figs.
Effective nucleon-nucleon t matrix in the (p,2p) reaction
International Nuclear Information System (INIS)
Kudo, Y.; Kanayama, N.; Wakasugi, T.
1989-01-01
The cross sections and the analyzing powers for the /sup 40/Ca(p-arrow-right,2p) reactions at E/sub p/ = 76.1, 101.3, and 200 MeV are calculated in the distorted-wave impulse approximation using the Love-Franey effective nucleon-nucleon interaction. It is shown that the calculated individual contributions of the central, spin-orbit, and tensor parts in the Love-Franey interaction to the cross sections and the analyzing powers strongly depend on the incident proton energies. The spectroscopic factors extracted are consistent with the other reaction studies
Ciofi degli Atti, Claudio; Mezzetti, Chiara Benedetta; Morita, Hiko
2017-04-01
order of magnitude less than the effect of two-nucleon short-range correlations. Conclusions: The convolution model of the spectral function of the three-nucleon systems featuring both two- and three-nucleon short-range correlations and correctly depending upon the ab initio two-nucleon relative and center-of-mass momentum distributions provides in the correlation region a satisfactory approximation of the spectral function in a wide range of momentum and removal energy. The extension of the model to complex nuclei is expected to provide a realistic microscopic parameter-free model of the spectral function, whose properties are therefore governed by the features of realistic two-nucleon interactions and the momentum distributions in a given nucleus.
One-boson-exchange approach to dilepton production in nucleon-nucleon collisions
International Nuclear Information System (INIS)
Haglin, K.L.
1991-01-01
The author calculates energy-dependent nucleon-nucleon elastic cross sections and electron-positron pair production differential cross sections for the processes pp → pp, np → np, and pp → ppe + e - , np → npe + e - at laboratory kinetic energies in the 1-5 GeV range. These calculations will be based on a one-boson-exchange (π, ρ, ω, σ, δ, η) approximation to the nucleon-nucleon scattering problem. Strong form factors are included in a manner which preserves gauge invariance. He finds excellent results as compared with data for the total elastic cross sections. The calculate differential elastic cross sections show only qualitative agreement with data. For dilepton production in n-p scattering the model overestimates the number of pairs as compared with proton on beryllium data. For the p-p case he finds the tensor coupling of the ρ to the nucleons to be clearly dominant. Data do not yet exist for the p-p case at these energies: the author predicts them
Energy Technology Data Exchange (ETDEWEB)
Price, C E; Shepard, J R [Colorado Univ., Boulder (USA). Dept. of Physics
1991-04-18
We compute properties of the nucleon in a hybrid chiral model based on the linear {sigma}-model with quark degrees of freedom treated explicity. In contrast to previous calculations, we do not use the hedgehog ansatz. Instead we solve self-consistently for a state with well defined spin and isospin projections. We allow this state to be deformed and find that, although d- and g-state admixtures in the predominantly s-state single quark wave functions are not large, they have profound effects on many nucleon properties including magnetic moments and g{sub A}. Our best fit parameters provide excellent agreement with experiment but are much different from those determined in hedgehog calculations. (orig.).
The multidimensional nucleon structure
Directory of Open Access Journals (Sweden)
Pasquini Barbara
2016-01-01
Full Text Available We discuss different kinds of parton distributions, which allow one to obtain a multidimensional picture of the internal structure of the nucleon. We use the concept of generalized transverse momentum dependent parton distributions and Wigner distributions, which combine the features of transverse-momentum dependent parton distributions and generalized parton distributions. We show examples of these functions within a phenomenological quark model, with focus on the role of the spin-spin and spin-orbit correlations of quarks.
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.
Analysis of corrections to the eikonal approximation
Hebborn, C.; Capel, P.
2017-11-01
Various corrections to the eikonal approximations are studied for two- and three-body nuclear collisions with the goal to extend the range of validity of this approximation to beam energies of 10 MeV/nucleon. Wallace's correction does not improve much the elastic-scattering cross sections obtained at the usual eikonal approximation. On the contrary, a semiclassical approximation that substitutes the impact parameter by a complex distance of closest approach computed with the projectile-target optical potential efficiently corrects the eikonal approximation. This opens the possibility to analyze data measured down to 10 MeV/nucleon within eikonal-like reaction models.
International Nuclear Information System (INIS)
Teller, S.
1977-01-01
Nucleonic weighing systems utilize the principle of the absorption or the scattering of nuclear radiation for a contactless measurement of the weight of material per unit length, the loading, of a conveyor. The load signal is processed in an electronic unit with a tachometer signal for the conveyor velocity to indicate the flow rate and the integrated flow of material. The different sources of error in nucleonic weighing using transmitted and forward scattered radiation are discussed, and the design of two nucleonic weighing systems is described. One is a conventional transmission gauge particularly suited for measuring rapid variation in belt loading due to a fast detection and linearizing unit. The other system consists of a forward scattering gauge, particularly suitable for measuring light inhomogeneous materials due to the linear relationship between the weight per unit area and the gauge response. Results from on-line trials with different materials are presented, and experiences from more than one year of operation for a batch weighing system for quick lime and a continuous weighing system for mineral wool are reported. (author)
Quark bags, P-matrix and nucleon-nucleon scattering
International Nuclear Information System (INIS)
Narodetskij, I.M.
1984-01-01
This paper is an extended version of the talk given at IX European Conference on Few Body Problems in Physics, Tbilisi, 1984. It reviews recent developments of the quark compound bag (QCB) model including explicit examples of the QCB nucleon-nucleon potentials, description of the deuteron properties, calculation of the six quark admixture in the deuteron and applications to the three-nucleon system
Nucleon-nucleon momentum correlation function for light nuclei
International Nuclear Information System (INIS)
Ma, Y.G.; Cai, X.Z.; Chen, J.G.; Fang, D.Q.; Guo, W.; Liu, G.H.; Ma, C.W.; Ma, E.J.; Shen, W.Q.; Shi, Y.; Su, Q.M.; Tian, W.D.; Wang, H.W.; Wang, K.; Wei, Y.B.; Yan, T.Z.
2007-01-01
Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics
Nucleon quark structure and strong meson-nucleon form factors
International Nuclear Information System (INIS)
Efimov, G.V.; Ivanov, M.A.
1987-01-01
The nucleon is considered as a three-quark system in virton-quark model. The main statistic properties of proton and neutron are calculated: magnetic moments, electromagnetic radii, G A /G V ratio in weak neutron decay. Strong meson-nucleon form factors which determine nucleon-nucleon potential are obtained as a function of squared transfer momentum of mesons. The results are compared with phenomenological form factors used for description of phases of NN-scattering in the one-boson-, exchange model
Coupled channels Marchenko inversion for nucleon-nucleon potentials
International Nuclear Information System (INIS)
Kohlhoff, H.; Geramb, H.V. von
1994-01-01
Marchenko inversion is used to determine local energy independent but channel dependent potential matrices from optimum sets of experimental phase shifts. 3 SD 1 and 3 PF 2 channels of nucleon-nucleon systems contain in their off-diagonal potential matrices explicitly the tensor force for T = 0 and 1 isospin. We obtain, together with single channels, complete sets of quantitative nucleon-nucleon potential results which are ready for application in nuclear structure and reaction analyses. The historic coupled channels inversion result of Newton and Fulton is revisited. (orig.)
Semi-phenomenological model of the nucleon-nucleon interaction
International Nuclear Information System (INIS)
Houriet, A.; Bagnoud, Y.
1977-01-01
A nucleon with isobars is used to elaborate a model of the nucleon-nucleon interaction at low energy (Esub(CM) 2 sub(r), the pion-nucleon renormalized coupling constant. The model establishes a very good coordination for deuteron and p-p scattering-polarization measurements ( 1 K 0 , 1 D 2 , 1 G 4 phase shifts), and permits the determination of f 2 sub(r) for every independent experimental value. For 21 such values, the mean value 2 sub(r)>=0.0785 with Δf 2 sub(r)=0.0024(3%) is obtained. (Auth.)
Technical data on nucleonic gauges
International Nuclear Information System (INIS)
2005-07-01
This nucleonic gauge manual and directory provides a reference database of nucleonic control systems available to potential users in the fields of exploration, exploitation and processing of natural resources and in the manufacturing industries. It starts with background information an the general principals of nucleonic gauges, followed by portable nuclear analysis systems (PNAS), computer tomography, cost-benefit on NCS (Nucleonic Control Systems) applications and trends and transfer of NCS technology. It continues with radiation protection and safety, discusses nucleonic gauges with low radioactivity sources and ends with typical models of nucleonic gauges. The basic principles of the most popular techniques are reviewed and reference data links to suppliers are provided. Information sheets on many typical commercial devices are also included. It will help end-users to select the most suitable alternative to solve a particular problem or to measure a certain parameter in a specific process
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
Relativistic Faddeev description of baryons and nucleon structure function in the NJL model
Energy Technology Data Exchange (ETDEWEB)
Bentz, W.; Mineo, H.; Asami, H.; Yazaki, K
2000-05-08
In this work we use the Nambu-Jona-Lasinio (NJL) model as an effective quark theory based on QCD to describe the structure of baryons. Based on the solutions of the relativistic 3-quark Faddeev equation in the ladder approximation, we discuss the masses of the nucleon and the delta, the static properties of the nucleon, and the quark light cone momentum distributions in the nucleon.
International Nuclear Information System (INIS)
Brown, V.R.
1990-01-01
Nucleon-nucleon bremsstrahlung, NNγ, is a fundamental process, which involves the strong and electromagnetic fields acting simultaneously. Since the electromagnetic interaction is well known, NNγ provides a calculable tool for comparing off-energy-shell effects from different two-nucleon potentials compared to experiment and also provides a simple testing ground, which is sensitive to meson-exchange-current contributions that are so important in electronuclear physics. Historically, experimental studies have focused on ppγ, with only a few measurements of npγ. The present workshop was organized primarily to investigate the interest in, the value of, and the feasibility of doing an npγ experiment using the neutron white source at LANL. An increasing amount of US nuclear physics dollars are being spent on electronuclear physics. npγ is a fundamental process with large meson-exchange currents. In the npγ calculations of Brown and Franklin, the meson-exchange contributions increase the cross section by a factor of roughly two and later the angular distribution of the emitted photon dramatically. The details of these calculated effects have never been verified experimentally, but the proper quantum-mechanical inclusion of meson-exchange contributions, using the methods of brown and Franklin, has proved to be essential in understanding the heavy-ion results. The understanding of the importance of such terms is extremely important inelectronuclear processes, such as are presently under investigation or being planned at Bates, SLAC, and CEBAF. Just one example is in the electrodisintegration of the deuteron, where meson-exchange contributions must be included properly before any conclusions about nuclear models, such as QCD versus meson-exchange potentials can be made
Chiral symmetry and the nucleon--nucleon interaction
International Nuclear Information System (INIS)
Brown, G.E.
1977-01-01
The nucleon--nucleon interaction is understood in terms of a dynamic model, the sigma model. The anti NN → ππ helicity amplitudes are assumed to be physical data, and the dynamical model must reproduce these data, more or less. 14 references
Solitary wave exchange potential and nucleon-nucleon interaction
International Nuclear Information System (INIS)
Prema, K.; Raghavan, S.S.; Sekhar Raghavan
1986-11-01
Nucleon-nucleon interaction is studied using a phenomenological potential model called solitary wave exchange potential model. It is shown that this simple model reproduces the singlet and triplet scattering data and the deuteron parameters reasonably well. (author). 6 refs, 2 figs, 1 tab
International Nuclear Information System (INIS)
Simon, G.G.
1978-01-01
In this thesis results of measurements of the differential cross sections of the elastic and inelastic electron deuteron scattering are presented. The data were taken at several scattering angles and in the electron energy range of 150 MeV up to 320 MeV. The extracted form factors and structure functions are compared with theoretical results which are sensitive to details of nucleon structure and of the nucleon-nucleon forces. (FKS)
Nucleon-nucleon forces in the quark compound bag model and few-nucleon systems
International Nuclear Information System (INIS)
Kalashnikova, Yu.S.; Narodetskij, I.M.
1984-01-01
Role of quark-gluon degrees of freedom is discussed in nucleon-nucleon scattering at low and intermediate energies. It is shown that the existence of six-quark hags fixes the form of NN potential at small distances, which leads to the P-matrix satisfying the criterion of Jaffe and Low. The dynamical model of three-nucleon system is discussed taking into accoint the contribution of six-quark bags
International Nuclear Information System (INIS)
McClelland, J.B.; Aas, B.; Azizi, A.
1982-01-01
A complete measurement of the polarization transfer observables has been made for the first time in the (p,p') reaction at intermediate energies. Measurements are reported for the 12 C(p,p') 12 C reaction to the 1 + , T = 0(12.71 MeV) and 1 + , T = 1(15.11 MeV) states at 500 MeV at laboratory scattering angles of 3.5 0 , 5.5 0 , 7.5 0 , and 12.0 0 . Linear combinations of these observables are shown to exhibit a very selective dependence on the isoscalar and isovector spin-dependent components of the nucleon-nucleon interaction. To the extent of the validity of the single collision approximation, these amplitudes are compared directly to the free nucleon-nucleon amplitudes at small momentum transfers
Isospin breaking in the pion-nucleon coupling constant and the nucleon-nucleon scattering length
Directory of Open Access Journals (Sweden)
V. A. Babenko
2016-08-01
Full Text Available Charge independence breaking (CIB in the pion-nucleon coupling constant and the nucleon-nucleon scattering length is considered on the basis of the Yukawa meson theory. CIB effect in these quantities is almost entirely explained by the mass difference between the charged and the neutral pions. Therewith charge splitting of the pion-nucleon coupling constant is almost the same as charge splitting of the pion mass. Calculated difference between the proton-proton and the neutron-proton scattering length in this case comprises ∼90% of the experimental value.
Nucleon-antinucleon interaction
International Nuclear Information System (INIS)
Dover, C.B.
1983-01-01
The current status of our understanding of the low energy nucleon-antinucleon (N anti N) interaction is reviewed. We compare several phenomenological models which fit the available N anti N cross section data. The more realistic of these models employ an annihilation potential W(r) which is spin, isospin and energy dependent. The microscopic origins for these dependences are discussed in terms of quark rearrangement and annihilation processes. It is argued that the study of N anti N annihilation offers a powerful means of studying quark dynamics at short distances. We also discuss how one may try to isolate coherent meson exchange contributions to the medium and long range part of the N anti N potential. These pieces of the N anti N interaction are calculable via the G-parity transformation from a model for the NN potential; their effects are predicted to be seen in N anti N spin observables, to be measured at LEAR. The possible existence of quasi-stable bound states or resonances of the anti N plus one or more nucleons is discussed, with emphasis on few-body systems. 42 references
International Nuclear Information System (INIS)
Schwamb, M.
2006-01-01
An overview over present achievements and future challenges in the field of few-nucleon systems is presented. Special emphasis is laid on the construction of a unified approach to hadronic and electromagnetic reactions on few-nucleon systems, necessary for studying the borderline between quark-gluon and effective descriptions. (orig.) (orig.)
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
Collective multipole excitations based on correlated realistic nucleon-nucleon interactions
International Nuclear Information System (INIS)
Paar, N.; Papakonstantinou, P.; Hergert, H.; Roth, R.
2006-01-01
We investigate collective multipole excitations for closed shell nuclei from 16 O to 208 Pb using correlated realistic nucleon-nucleon interactions in the framework of the random phase approximation (RPA). The dominant short-range central and tensor correlations a re treated explicitly within the Unitary Correlation Operator Method (UCOM), which provides a phase-shift equivalent correlated interaction VUCOM adapted to simple uncorrelated Hilbert spaces. The same unitary transformation that defines the correlated interaction is used to derive correlated transition operators. Using VUCOM we solve the Hartree-Fock problem and employ the single-particle states as starting point for the RPA. By construction, the UCOM-RPA is fully self-consistent, i.e. the same correlated nucleon-nucleon interact ion is used in calculations of the HF ground state and in the residual RPA interaction. Consequently, the spurious state associated with the center-of-mass motion is properly removed and the sum-rules are exhausted within ±3%. The UCOM-RPA scheme results in a collective character of giant monopole, dipole, and quadrupole resonances in closed-shell nuclei across the nuclear chart. For the isoscalar giant monopole resonance, the resonance energies are in agreement with experiment hinting at a reasonable compressibility. However, in the 1 - and 2 + channels the resonance energies are overestimated due to missing long-range correlations and three-body contributions. (orig.)
Resonance estimates for single spin asymmetries in elastic electron-nucleon scattering
International Nuclear Information System (INIS)
Barbara Pasquini; Marc Vanderhaeghen
2004-01-01
We discuss the target and beam normal spin asymmetries in elastic electron-nucleon scattering which depend on the imaginary part of two-photon exchange processes between electron and nucleon. We express this imaginary part as a phase space integral over the doubly virtual Compton scattering tensor on the nucleon. We use unitarity to model the doubly virtual Compton scattering tensor in the resonance region in terms of γ* N → π N electroabsorption amplitudes. Taking those amplitudes from a phenomenological analysis of pion electroproduction observables, we present results for beam and target normal single spin asymmetries for elastic electron-nucleon scattering for beam energies below 1 GeV and in the 1-3 GeV region, where several experiments are performed or are in progress
A chiral quark model of the nucleon
International Nuclear Information System (INIS)
Wakamatsu, M.; Yoshiki, H.
1991-01-01
The baryon-number-one extended solution of a chiral quark lagrangian is obtained in the stationary-phase approximation with full inclusion of the sea-quark degrees of freedom. The collective quantization method is then applied to this static solution to obtain the nucleon (and Δ) state with the definite spin and isospin. A fundamental quantity appearing in this quantization procedure is the moment of inertia of the soliton system. We evaluate this quantity without recourse to the derivative expansion, by performing the necessary double sum over all the positive- and negative-energy quark orbitals in the mean field potential. Closed formulas are-derived for the nucleon (and Δ) matrix elements of arbitrary quark bilinear operators. These formulas are then used for calculating various nucleon observables in a nonperturbative manner with inclusion of the sea-quark effects. An especially interesting observable is the spin expectation value of the proton related to the recent EMC experiment. We derive the proton spin sum rule, and then explicitly evaluate the detailed contents of this sum rule. The proton spin analysis is shown to be particularly useful for clarifying the underlying dynamical content of the Skyrme model at quark level, thereby providing us with valuable information about its utility and limitation. (orig.)
International Nuclear Information System (INIS)
Holben, B.C.; Bach, R.E.
1975-01-01
A nucleonic measuring instrument is described wherein a housing contains a radiation source and has an aperture controlled by a shutter which is spring loaded to a closed position for confining and shielding the radiation and is movable by a motor to an open position for releasing the radiation, the motor being supplied with power through a heat sensitive element so that it is deenergized and the shutter closes in response to a predetermined high ambient temperature such as may be caused by a fire, and including an explosive blank cartridge positioned in relation to the shutter guide which explodes in response to a still higher ambient temperature, deforming the guide and thereby locking the shutter in the closed position. (auth)
Nucleon Electromagnetic Form Factors
Energy Technology Data Exchange (ETDEWEB)
Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi
2007-10-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.
The Jlab Upgrade - Nucleon Studies with CLAS12
International Nuclear Information System (INIS)
Volker Burkert
2007-01-01
An overview is presented on the program to study the nucleon structure at the 12 GeV Jlab Upgrade using the CLAS12 detector. The focus is on deeply virtual exclusive processes to access the generalized parton distributions, semi-inclusive processes to study transveresx momentum-dependent distributions functions, and inclusive spin structure functions and resonance transition form factors at high Q 2 and with high precision
Diquarks and nucleon structure functions
International Nuclear Information System (INIS)
Linkevich, A.D.; Savrin, V.I.; Skachkov, N.B.
1982-01-01
Formulae for structure functions of the deep-inelastic lepton-nucleon scattering are obtained through relativistic wave functions of systems composed of particles with spins 0, 1/2 and 1, 1/2. These wave functions are solutions of covariant two-particle single-time equations describing the nucleon as a system formed out of a quark and a diquark. Diquark is considered as a boson with the spin 0 and 1. The expressions for the nucleon structure functions are obtained by using the matrix elements of the current operator corresponding to the elastic scattering of the photon on a quark and on a diquark [ru
International Nuclear Information System (INIS)
Close, F.E.
1993-06-01
When the new data on polarised lepton nucleon scattering are compared at the same value of Q 2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in O(α s ), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)
International Nuclear Information System (INIS)
Close, F.E.
1994-01-01
When the new data on polarised lepton nucleon scattering are compared at the same value of Q 2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in 0(α s ), higher twist effects, modern data on unpolarized structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)
Probing nuclear structure with nucleons
International Nuclear Information System (INIS)
Bauge, E.
2007-01-01
The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)
Nucleon-nucleon interaction with quark exchange and prediction of the color van der Waals potential
International Nuclear Information System (INIS)
Osman, A.
1988-01-01
The nucleon-nucleon interaction is considered by including the color nucleon clusters. The nucleon-nucleon system is treated as a six-quark system. The obtained local potentials reduce the short-range repulsion. The resulting nucleon-nucleon potential, using a quark-quark potential, agress well with the central-force potentials. The phase shifts calculated by using these local potentials are in good agreement with those obtained from other methods. Introducing the quark-quark potential in the nucleon-nucleon interaction leads to a color van der Waals potential much stronger than that implied by experiments
Nucleon-nucleon interaction with quark exchanges and prediction to colour van der Waals potential
International Nuclear Information System (INIS)
Osman, A.
1985-11-01
The nucleon-nucleon interaction is considered by including the colour nucleon clusters. The nucleon-nucleon system is treated as a six-quark system. The obtained local potentials reduce the short-range repulsion. The resulted nucleon-nucleon potential by using a quark-quark potential well agrees with the central-force potentials. The phase shifts calculated by using these local potentials are in good agreement with those obtained from other methods. Introducing the quark-quark potential in the nucleon-nucleon interaction, leads to a colour van der Waals potential very strong compared with that predicted by experiments. (author)
Nucleon-Nucleon Potentials and Computation of Scattering Phase Shifts
Directory of Open Access Journals (Sweden)
Jhasaketan Bhoi
2015-12-01
Full Text Available By judicious exploitation of supersymmetry formalism of quantum mechanics higher partial wave nucleon-nucleon potentials are generated from its ground state interactions. The nuclear Hulthen potential and the corresponding ground state wave function with the parameters of Arnold and MacKellar are used as the starting point of our calculation. We compute the scattering phase shifts for our constructed potentials through Phase Function Method to examine the merit of our approach to the problem.
International Nuclear Information System (INIS)
Goodman, M. C.
1999-01-01
The Soudan 2 detector is used to search for evidence of nucleon decay. Particular emphasis is put on searches for modes with multiple-charged particles in the final state, and for modes suggested by super-symmetric theories
Nucleon–nucleon scattering in the light of supersymmetric quantum ...
Indian Academy of Sciences (India)
2014-05-02
May 2, 2014 ... Abstract. By exploiting supersymmetry-inspired factorization method together with a judiciously chosen deuteron ground-state wave function, approximate higher partial wave nucleon–nucleon potentials are generated. In this context, a minor modification is also introduced to the gener- ated potentials.
NUCLEON POLARIZATION IN 3-BODY MODELS OF POLARIZED LI-6
SCHELLINGERHOUT, NW; KOK, LP; COON, SA; ADAM, RM
1993-01-01
Just as He-3 --> can be approximately characterized as a polarized neutron target, polarized Li-6D has been advocated as a good isoscalar nuclear target for the extraction of the polarized gluon content of the nucleon. The original argument rests upon a presumed ''alpha + deuteron'' picture of Li-6,
Inelastic electron scattering from a moving nucleon
Energy Technology Data Exchange (ETDEWEB)
Kuhn, S.E. [Old Dominion Univ., Norfolk, VA (United States); Griffioen, K. [College of William and Mary, Williamsburg, VA (United States)
1994-04-01
The authors propose to measure inelastically scattered electrons in coincidence with spectator protons emitted backwards relative to the virtual photon direction in the reaction d(e, e{prime}p{sub s})X. In a simple spectator model, the backward proton has equal and opposite momentum to the neutron before it is struck, allowing the authors to study the dependence on kinematics and off-shell behaviour of the electron-nucleon inelastic cross section. If the photon couples to a quark in a 6-quark bag, a different dependence of the cross section on the kinematic variables (x, Q{sup 2}, and p{sub s}) can be observed. This proposed experiment requires large acceptance and beam energies above 6 GeV. It is ideally suited for the CEBAF Large Acceptance Spectrometer (CLAS).
Theoretical interpretation of medium energy nucleon nucleus inelastic scattering
International Nuclear Information System (INIS)
Lagrange, Christian
1970-06-01
A theoretical study is made of the medium energy nucleon-nucleus inelastic scattering (direct interaction), by applying the distorted wave Born approximation such as can be deduced from the paired equation method. It is applied to the interpretation of the inelastic scattering of 12 MeV protons by 63 Cu; this leads us to make use of different sets of wave functions to describe the various states of the target nucleus. We analyze the nature of these states and the shape of the nucleon-nucleus interaction potential, and we compare the results with those obtained from other theoretical and experimental work. (author) [fr
Numerical Exact Ab Initio Four-Nucleon Scattering Calculations: from Dream to Reality
Fonseca, A. C.; Deltuva, A.
2017-03-01
In the present manuscript we review the work of the last ten years on the pursuit to obtain numerical exact solutions of the four-nucleon scattering problem using the most advanced force models that fit two nucleon data up to pion production threshold with a χ ^2 per data point approximately one, together with the Coulomb interaction between protons; three- and four-nucleon forces are also included in the framework of a meson exchange potential model where NN couples to NΔ. Failure to describe the world data on four-nucleon scattering observables in the framework of a non relativistic scattering approach falls necessarily on the force models one uses. Four-nucleon observables pose very clear challenges, particular in the low energy region where there are a number of resonances whose position and width needs to be dynamically generated by the nucleon-nucleon (NN) interactions one uses. In addition, our calculations constitute the most advance piece of work where observables for all four-nucleon reactions involving isospin I=0, I=0 coupled to I=1 and isospin I=1 initial states are calculated at energies both below and above breakup threshold. We also present a very extensive comparison between calculated results and data for cross sections and spin observables. Therefore the present work reveals both the shortcomings and successes of some of the present NN force models in describing four-nucleon data and serve as a benchmark for future developments.
Relations between the simultaneous and sequential transfer of two nucleons
International Nuclear Information System (INIS)
Satchler, G.R.
1982-01-01
The transfer of two nucleons between projectile and target in a direct or peripheral reaction such as (p,t) or ( 16 O, 14 C) may occur in one-step or two-steps. These we refer to as simultaneous and sequential transfers, respectively. In the former, the interaction acts once and both nucleons are transferred. In the latter, the interaction acts once to transfer one nucleon, the system then propagates in one or more intermediate states and is followed by a second action of the interaction to transfer the second nucleon. This process may be symbolized for the examples as (p,d; d,t) and ( 16 O, 15 N; 15 N, 14 C), implying the intermediate formation of a deuteron or the nucleus 15 N. In terms of a perturbation theory expansion, such as the distorted-wave Born series, simultaneous transfer is possible in first order while sequential transfer requires second order. The nuclear forces are predominantly two-body in character; hence, in first-order only one of the two nucleons experiences an interaction. The possibility of finding that the other nucleon has also transferred arises only because its state within the projectile is not orthogonal to the state in the target into which it transfers. In the two-step process each nucleon is transferred under the direct influence of an interaction with the target. The one-step and two-step amplitudes are frequently comparable in magnitude for light-ion reactions while the two-step may dominate in reactions with heavy ions. Our purpose here is to gain some insight into the relationship between the two amplitudes by using a simple approximate form of the theory. For simplicity, we shall discuss a light-ion reaction and, to be specific, we choose the (t,p) reaction (or the inverse (p,t) reaction)
Hard breakup of two nucleons from the 3He nucleus
International Nuclear Information System (INIS)
Sargsian, Misak M.; Granados, Carlos
2009-01-01
We investigate a large angle photodisintegration of two nucleons from the 3 He nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon breakup reaction through the convolution of photon-quark scattering, NN hard scattering amplitude, and nuclear spectral function, which can be calculated using a nonrelativistic 3 He wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for NN scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as s -11 . Second, the s 11 weighted cross section will have the shape of energy dependence similar to that of s 10 weighted NN elastic scattering cross section. Also one predicts an enhancement of the pp breakup relative to the pn breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn breakup cross sections. This is due to the fact that the same-helicity pp-component is strongly suppressed in the ground state wave function of 3 He. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer NN breakup reactions for circularly polarized photons. For the pp breakup this asymmetry is predicted to be zero while for the pn it is close to (2/3).
Chiral model for nucleon and delta
International Nuclear Information System (INIS)
Birse, M.C.; Banerjee, M.K.
1985-01-01
We propose a model of the nucleon and delta based on the idea that strong QCD forces on length scales approx.0.2--1 fm result in hidden chiral SU(2) x SU(2) symmetry and that there is a separation of roles between these forces which are also responsible for binding quarks in hadrons and the forces which produce absolute confinement. This leads us to study a linear sigma model describing the interactions of quarks, sigma mesons, and pions. We have solved this model in the semiclassical (mean-field) approximation for the hedgehog baryon state. We refer to this solution as a chiral soliton. In the semiclassical approximation the hedgehog state is a linear combination of N and Δ. We project this state onto states of good spin and isospin to calculate matrix elements of various operators in these states. Our results are in reasonable agreement with the observed properties of the nucleon. The mesonic contributions to g/sub A/ and sigma(πN) are about two to three times too large, suggesting the need for quantum corrections
Ciofi degli Atti, Claudio; Morita, Hiko
2017-12-01
Background: The nuclear spectral function is a fundamental quantity that describes the mean-field and short-range correlation dynamics of nucleons embedded in the nuclear medium; its knowledge is a prerequisite for the interpretation of various electroweak scattering processes off nuclear targets aimed at providing fundamental information on strong and weak interactions. Whereas in the case of the three-nucleon and, partly, the four-nucleon systems, the spectral function can be calculated ab initio within a nonrelativistic many-body Schroedinger approach, in the case of complex nuclei only models of the correlated, high-momentum part of the spectral function are available so far. Purpose: The purpose of this paper is to present a new approach such that the spectral function for a specific nucleus can be obtained from a reliable many-body calculation based upon realistic nucleon-nucleon interactions, thus avoiding approximations leading to adjustable parameters. Methods: The expectation value of the nuclear many-body Hamiltonian, containing realistic nucleon-nucleon interaction of the Argonne family, is evaluated variationally by a normalization-conserving linked-cluster expansion and the resulting many-body correlated wave functions are used to calculate the one-nucleon and the two-nucleon momentum distributions; by analyzing the high-momentum behavior of the latter, the spectral function can be expressed in terms of a transparent convolution formula involving the relative and center-of-mass (c.m.) momentum distributions in specific regions of removal energy E and momentum k . Results: It is found that as a consequence of the factorization of the many-body wave functions at short internucleon separations, the high-momentum behavior of the two-nucleon momentum distributions in A =3 ,4 ,12 ,16 ,40 nuclei factorizes, at proper values of the relative and c.m. momenta, into the c.m. and relative momentum distributions, with the latter exhibiting a universal A
p-wave pion production from nucleon-nucleon collisions
International Nuclear Information System (INIS)
Baru, V.; Epelbaum, E.; Haidenbauer, J.; Hanhart, C.; Kudryavtsev, A. E.; Lensky, V.; Meissner, U.-G.
2009-01-01
We investigate p-wave pion production in nucleon-nucleon collisions up to next-to-next-to-leading order in chiral effective field theory. In particular, we show that it is possible to describe simultaneously the p-wave amplitudes in the pn→ppπ - , pp→pnπ + , pp→dπ + channels by adjusting a single low-energy constant accompanying the short-range operator that is available at this order. This study provides a nontrivial test of the applicability of chiral effective field theory to reactions of the type NN→NNπ.
Inequalities and bounds for nucleon-nucleon scattering
International Nuclear Information System (INIS)
Ramandurai, K.S.
1979-08-01
The objective of this work is to derive model-independent inequalities and bounds for nucleon-nucleon elastic scattering amplitudes based on well-established theoretical principles and symmetries. Two classes of methods are used: algebraic and variational. In the algebraic part, the author derives inequalities and bounds for NN amplitudes and observables using their mutual relations and x symmetries. In the variational part, he employs Lagrange's method of undetermined multipliers to evaluate the bounds. He tests the predictions of a sample of proposed phase shifts at three different energies using the results obtained
Method to obtain resonances and virtual states
International Nuclear Information System (INIS)
Adhikari, S.K.; Fonseca, A.C.; Tomio, L.
1982-01-01
A naive method is proposed for the calculation of resonance position and-residue at low energies and of virtual states localized in the non-physical sheet associated to the lowest threshold of two body breaking. This method is applied to the study of some virtual states of the few nucleon system. (L.C.) [pt
Exact and approximate multiple diffraction calculations
International Nuclear Information System (INIS)
Alexander, Y.; Wallace, S.J.; Sparrow, D.A.
1976-08-01
A three-body potential scattering problem is solved in the fixed scatterer model exactly and approximately to test the validity of commonly used assumptions of multiple scattering calculations. The model problem involves two-body amplitudes that show diffraction-like differential scattering similar to high energy hadron-nucleon amplitudes. The exact fixed scatterer calculations are compared to Glauber approximation, eikonal-expansion results and a noneikonal approximation
One-Boson Approach to Dilepton Production in Nucleon-Nucleon Collisions.
Haglin, Kevin Lee
1990-01-01
We calculate energy dependent nucleon-nucleon total elastic cross sections and invariant mass dependent electron-positron pair production differential cross sections for the processes pp to pp, np to np and pp to ppe ^+e^-, pn to pne^+e ^- at laboratory kinetic energies in the 1-5 GeV range. These calculations will be based on relativistic quantum field theory in the one-boson-exchange (pi,rho,omega,sigma,delta, eta) approximation to the nucleon-nucleon scattering problem. There are several independent Feynman diagrams for each process--twenty-five for the case np to npe^+e^ - and forty-eight for the case pp to ppe^+e^- --which, for evaluation, require taking the trace of as many as ten gamma matrices and evaluating an angular integral of a quotient of polynomial functions of initial and final energies, particle masses, coupling constants and so on. These mathematical operations are carried out with the aid of the following algebraic manipulators: for the trace operations we use REDUCE 3.3 on the VAX at the ACS facility and for testing the angular integration algorithms we use MAPLE on the Cray-2 at the Minnesota Supercomputer Institute. Finally, we use Cray-2 Fortran for the resulting numerical substitutions. Gauge invariance is strictly observed while including strong and electromagnetic form factors. The numerical results for these calculations are compared with existing data from the Particle Data Group Booklet and compared with recently released data from the Dilepton Spectrometer (DLS) at the Bevalac of proton on Beryllium. For the latter comparison, the spectrometer's finite acceptance function is introduced before a rapidity and transverse momentum integration.
Energy Technology Data Exchange (ETDEWEB)
Close, F.E.
1993-06-01
When the new data on polarised lepton nucleon scattering are compared at the same value of Q{sup 2} and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in O({alpha}{sub s}), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author).
Weak Deeply Virtual Compton Scattering
International Nuclear Information System (INIS)
Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin
2006-01-01
We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities
Dispersion relations in real and virtual Compton scattering
International Nuclear Information System (INIS)
Drechsel, D.; Pasquini, B.; Vanderhaeghen, M.
2003-01-01
A unified presentation is given on the use of dispersion relations in the real and virtual Compton scattering processes off the nucleon. The way in which dispersion relations for Compton scattering amplitudes establish connections between low energy nucleon structure quantities, such as polarizabilities or anomalous magnetic moments, and the nucleon excitation spectrum is reviewed. We discuss various sum rules for forward real and virtual Compton scattering, such as the Gerasimov-Drell-Hearn sum rule and its generalizations, the Burkhardt-Cottingham sum rule, as well as sum rules for forward nucleon polarizabilities, and review their experimental status. Subsequently, we address the general case of real Compton scattering (RCS). Various types of dispersion relations for RCS are presented as tools for extracting nucleon polarizabilities from the RCS data. The information on nucleon polarizabilities gained in this way is reviewed and the nucleon structure information encoded in these quantities is discussed. The dispersion relation formalism is then extended to virtual Compton scattering (VCS). The information on generalized nucleon polarizabilities extracted from recent VCS experiments is described, along with its interpretation in nucleon structure models. As a summary, the physics content of the existing data is discussed and some perspectives for future theoretical and experimental activities in this field are presented
The hyperon-nucleon interaction
International Nuclear Information System (INIS)
Haidenbauer, J.
2007-01-01
Results of two recent hyperon-nucleon interaction potentials, both developed by the Bonn-Juelich group, are presented that are derived either in the conventional meson-exchange picture or within leading order chiral effective field theory. The chiral potential consists of one-pseudoscalar-meson exchanges and non-derivative four-baryon contact terms. The most salient feature of the new meson-exchange hyperon-nucleon model is that the contributions in the scalar-isoscalar (σ) and vector-isovector (ρ) exchange channels are constrained by a microscopic model of correlated ππ and KK-bar exchange
Nucleon transfer between heavy nuclei
International Nuclear Information System (INIS)
Von Oertzen, W.
1984-02-01
Nucleon transfer reactions between heavy nuclei are characterized by the classical behaviour of the scattering orbits. Thus semiclassical concepts are well suited for the description of these reactions. In the present contribution the characteristics of single and multinucleon transfer reactions at energies below and above the Coulomb barrier are shown for systems like Sn+Sn, Xe+U and Ni+Pb. The role of the pairing interaction in the transfer of nucleon pairs is illustrated. For strong transitions the coupling of channels and the absorption into more complicated channels is taken into account in a coupled channels calculation
Induced Hyperon-Nucleon-Nucleon Interactions and the Hyperon Puzzle.
Wirth, Roland; Roth, Robert
2016-10-28
We present the first ab initio calculations for p-shell hypernuclei including hyperon-nucleon-nucleon (YNN) contributions induced by a similarity renormalization group transformation of the initial hyperon-nucleon interaction. The transformation including the YNN terms conserves the spectrum of the Hamiltonian while drastically improving model-space convergence of the importance-truncated no-core model, allowing a precise extraction of binding and excitation energies. Results using a hyperon-nucleon interaction at leading order in chiral effective field theory for lower- to mid-p-shell hypernuclei show a good reproduction of experimental excitation energies while hyperon separation energies are typically overestimated. The induced YNN contributions are strongly repulsive and we show that they are related to a decoupling of the Σ hyperons from the hypernuclear system, i.e., a suppression of the Λ-Σ conversion terms in the Hamiltonian. This is linked to the so-called hyperon puzzle in neutron-star physics and provides a basic mechanism for the explanation of strong ΛNN three-baryon forces.
Structure functions of nucleons and nuclei
Energy Technology Data Exchange (ETDEWEB)
Bentz, Wolfgang; Ito, Takuya [Department of Physics, Tokai University, Kanagawa (Japan); Cloet, Ian [Department of Physics, University of Washington, Seattle (United States); Thomas, Anthony [Jefferson Lab., Newport News, VA (United States); Yazaki, Koichi [RIKEN, Wako-shi, Saitama (Japan)
2009-07-01
We use an effective chiral quark theory to calculate the quark distributions and structure functions of nucleons and nuclei. The description of the single nucleon is based on the Faddeev framework, and nuclear systems are described in the mean field approximation. Particular amphasis is put on the prediction of the polarized EMC effect in nuclei, and on applications to deep inelastic neutrino-nucleus scattering. Concerning the polarized EMC effect, we discuss the quenching of the quark spin sum in nuclei and its implications for the spin dependent nuclear structure functions, and present results for several nuclei where an experimental observation is feasible. Concerning the case of deep inelastic neutrino-nucleus scattering, we estimate the effect of medium modifications of the quark distribution functions on the measured cross sections, and discuss an interesting resolution of the so called NuTeV anomaly. Finally, we discuss extensions of our model to describe fragmentation functions for semi-inclusive processes. The connection between our effective quark model description and the jet model of Field and Feynman is discussed.
Color oscillations of nucleons in a nucleus
International Nuclear Information System (INIS)
Petrov, V.A.; Smirnov, A.Yu.
1987-01-01
Possibility of nucleus description as an object consisting of quarks and gluons is considered. A model of two-nucleon interaction in a nucleus is presented and analytical expressions for the nucleus nucleon ground state wave functions and also for nuclear nucleon structure functions are obtained. The carried out analysis shows that the suggested model permits to express the nucleus structure functions at quark level only by means of nucleon and Δ-isobaric degrees of freedom
Studies of the nucleon-nucleus and the nucleon-nucleon interactions using polarized neutron beams
International Nuclear Information System (INIS)
Walter, R.L.; Howell, C.R.; Tornow, W.
1988-01-01
The results o four scattering measurements using beams of polarized neutrons are described. Results for the analyzing power A y (θ) for elastic scattering of neutrons from protons and deuterons are compared to calculations based on the Paris and the Bonn nucleon-nucleon interactions. Deficiencies particularly in the Bonn model are indicated. A nucleon-nucleus potential is derived from σ(θ) and A y (θ) data for n + 28 Si and p + 28 Si and the Coulomb correction terms are derived according to two approaches. A Fourier-Bessel expansion is used to investigate the form factors of the terms of the n + 208 Pb potential which are necessary to describe σ(θ) and A y (θ) data from 6 to 10 MeV. The nature of the spin-orbit term is also presented. (author)
On the nucleon renormalization in many nucleon problems due to pionic degrees of freedom
International Nuclear Information System (INIS)
Sauer, P.U.; Sawicki, M.; Furui, Sadataka.
1985-01-01
Conceptual problems of unified two-nucleon force models are discussed. The force models are based on the pion-nucleon vertex and attempt a description of the nucleon-nucleon interaction below and above pion threshold. The conceptual problems arise from the nucleon renormalization due to pionic degrees of freedom. Keeping channels with a single pion only no renormalization procedure can be given which is consistent in the one-nucleon and in the many-nucleon systems. The medium dependence of the one-pion exchange potential is illustrated. (author)
Investigation of the nucleon-nucleon tensor force in three-nucleon system
Energy Technology Data Exchange (ETDEWEB)
Clajus, M.; Egun, P.M.; Gruebler, W.; Hautle, P. (Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Mittelenergiephysik); Slaus, I. (Institut Rudjer Boskovic, Zagreb (Yugoslavia)); Vuaridel, B. (Michigan Univ., Ann Arbor (USA) Brookhaven National Lab., Upton, NY (USA)); Sperisen, F. (Indiana Univ., Bloomington (USA). Cyclotron Facility); Kretschmer, W.; Rauscher, A.; Schuster, W.; Weidmann, R.; Haller, M. (Erlangen-Nuernberg Univ., Erlangen (Germany, F.R.)); Bruno, M.; Cannata, F.; D' Agostino, M. (Istituto Nazionale di Fisica Nucleare, Bologna (Italy)); Witala, H.; Cornelius, T.; Gloeckle, W. (Bochum Univ. (Germany, F.R.)); Schmelzbach, P.A. (Paul Scherrer Inst., Villigen (Switzerland))
1990-08-16
Proton-deuteron elastic scattering has been investigated at E{sub p}=22.7 MeV by comparison of rigorous Faddeev calculations with experimental results. The observable most sensitive to the tensor force is the nucleon-nucleon polarization transfer coefficient K{sub y}sup(y'). The new angular distribution of K{sub y}sup(y') clearly favours the tensor force of the Bonn A potential, which is weaker than the one of the Paris potential. (orig.).
A nucleon-pair and boson coexistent description of nuclei
Dai, Lianrong; Pan, Feng; Draayer, J. P.
2017-07-01
We study a mixture of s-bosons and like-nucleon pairs with the standard pairing interaction outside an inert core. Competition between the nucleon-pairs and s-bosons is investigated in this scenario. The robustness of the BCS-BEC coexistence and crossover phenomena are examined through an analysis of pf-shell nuclei with realistic single-particle energies, in which two configurations with Pauli blocking of nucleon-pair orbits due to the formation of the s-bosons is taken into account. When the nucleon-pair orbits are considered to be independent of the s-bosons, the BCS-BEC crossover becomes smooth, with the number of the s-bosons noticeably more than that of the nucleon-pairs near the half-shell point, a feature that is demonstrated in the pf-shell for several values of the standard pairing interaction strength. As a further test of the robustness of the BCS-BEC coexistence and crossover phenomena in nuclei, results are given for values of even-even 102-130Sn with 100Sn taken as a core and valence neutron pairs confined within the 1d 5/2, 0g 7/2, 1d 3/2, 2s 1/2, 1h 11/2 orbits in the nucleon-pair orbit and the s-boson independent approximation. The results indicate that the B(E2) values are reproduced well. Supported by National Natural Science Foundation of China (11375080, 11675071), the U.S. National Science Foundation (OCI-0904874 and ACI-1516338), U. S. Department of Energy (DE-SC0005248), the Southeastern Universities Research Association, the China-U. S. Theory Institute for Physics with Exotic Nuclei (CUSTIPEN) (DE-SC0009971), and the LSU-LNNU joint research program (9961) is acknowledged
Calculations of nucleon structure functions
International Nuclear Information System (INIS)
Signal, A.I.
1990-01-01
We present a method of calculating deep inelastic nucleon structure functions using bag model wavefunctions. Our method uses the Peierls - Yoccoz projection to form translation invariant bag states. We obtain the correct support for the structure functions and satisfy the positivity requirements for quark and anti-quark distribution functions. (orig.)
Chiral perturbation theory with nucleons
International Nuclear Information System (INIS)
Meissner, U.G.
1991-09-01
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, πN scattering and the σ-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon
Flavor asymmetry of the nucleon
International Nuclear Information System (INIS)
Bijker, R.; Santopinto, E.
2008-01-01
The flavor asymmetry of the nucleon sea is discussed in an unquenched quark model for baryons in which the effects of quark-antiquark pairs (uu, dd and ss) are taken into account in an explicit form. The inclusion of qq pairs leads automatically to an excess of d over u quarks in the proton, in agreement with experimental data. (Author)
Flavor asymmetry of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Bijker, R. [Instituto de Ciencias Nucleares, UNAM, Apartado Postal 70-543, 04510 Mexico D. F. (Mexico); Santopinto, E. [INFN and Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova (Italy)]. e-mail: bijker@nucleares.unam.mx
2008-12-15
The flavor asymmetry of the nucleon sea is discussed in an unquenched quark model for baryons in which the effects of quark-antiquark pairs (uu, dd and ss) are taken into account in an explicit form. The inclusion of qq pairs leads automatically to an excess of d over u quarks in the proton, in agreement with experimental data. (Author)
Soudan 2 nucleon decay experiment
International Nuclear Information System (INIS)
Thron, J.L.
1986-01-01
The Soudan 2 nucleon decay experiment consists of a 1.1 Kton fine grained iron tracking calorimeter. It has a very isotropic detection structure which along with its flexible trigger will allow detection of multiparticle and neutrino proton decay modes. The detector has now entered its construction stage
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
Nucleon structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Dinter, Simon
2012-11-13
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.
Nucleon structure from lattice QCD
International Nuclear Information System (INIS)
Dinter, Simon
2012-01-01
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a 2 ) discretization effects.
Fusion reactor nucleonics: status and needs
International Nuclear Information System (INIS)
Lee, J.D.; Engholm, B.A.; Dudziak, D.J.; Haight, R.C.
1980-01-01
The national fusion technology effort has made a good start at addressing the basic nucleonics issues, but only a start. No fundamental nucleonics issues are seen as insurmountable barriers to the development of commercial fusion power. To date the fusion nucleonics effort has relied almost exclusively on other programs for nuclear data and codes. But as we progress through and beyond ETF type design studies the fusion program will need to support a broad based nucleonics effort including code development, sensitivity studies, integral experiments, data acquisition etc. It is clear that nucleonics issues are extremely important to fusion development and that we have only scratched the surface
Why do nucleons cling. [Meson theory
Energy Technology Data Exchange (ETDEWEB)
Kumar, N [Hindu Coll., Delhi (India)
1976-10-01
The nature of the forces which bind nucleons together within the nucleus of an atom have been discussed in detail. The characteristic properties of the nucleons, such as spin, interaction range etc. and the meson theory of nuclear forces are described. The present researches indicate that the force between two nucleons in a many-nucleon system is not very different from the force between two free nucleons. Researches related to the origin of nuclear forces based on the meson theory are now mainly concerned with the role played by the heavier mesons and the two pion exchanges in the middle region around 0.7 fm. (10/sup -13/ cm).
Nucleon-nucleon correlations and the Coulomb Displacement Energy
International Nuclear Information System (INIS)
Van Neck, D.; Waroquier, M.; Heyde, K.
1997-01-01
Coulomb Displacement Energies (CDE) are accurately known for a wide range of nuclear masses. Assuming isospin independence in the nuclear Hamiltonian, the CDE can in first instance be interpreted as the Coulomb interaction energy between the density of the excess neutrons and the proton charge density in the parent nucleus. However, when using reasonable mean-field models for the proton and neutron density one underestimates the CDE by about 8% on average. This discrepancy is known as the Nolen-Schiffer anomaly, and various explanations have been put forward in the past. In this work the role of nucleon-nucleon correlations are re-examined. Calculations for the pair density functions in various nuclei are presented. Preliminary results suggest that the modifications to the mean-field pair density functions cause an enhancement of the CDE in the order of 4%, which is rather A-independent. (author)
Leading order relativistic chiral nucleon-nucleon interaction
Ren, Xiu-Lei; Li, Kai-Wen; Geng, Li-Sheng; Long, Bingwei; Ring, Peter; Meng, Jie
2018-01-01
Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the need for a relativistic chiral force in relativistic nuclear structure studies, we explore a new relativistic scheme to construct the nucleon-nucleon interaction in the framework of covariant chiral effective field theory. The chiral interaction is formulated up to leading order with covariant power counting and a Lorentz invariant chiral Lagrangian. We find that the relativistic scheme induces all six spin operators needed to describe the nuclear force. A detailed investigation of the partial wave potentials shows a better description of the {}1S0 and {}3P0 phase shifts than the leading order Weinberg approach, and similar to that of the next-to-leading order Weinberg approach. For the other partial waves with angular momenta J≥slant 1, the relativistic results are almost the same as their leading order non-relativistic counterparts. )
Coherent generation of mesons in nucleon-nucleon interactions
Takibaev, Z S; Zaitsev, K G
1974-01-01
The authors have at an experiment conducted at CERN searched for events of 0 four-prong type which satisfy coherent pion production. The 2-meter hydrogen bubble chamber at CERN was bombarded by 19.07 GeV protons. The cross-section for four final state particle events was 13.04 mb. the cross-section for the process pp to pp pi /sup +/ pi /sup -/ was 1.1 mb and the cross section for coherent pion production was found to vary according to the criteria used between 0.044 mb. and 0.2 mb. Some theoretical work is given using the Glauber formalism in which it is assumed that the nucleon behaves like a nucleus and contains sub-particles. From the theory and data an upper limit of 10 is put on the number of subparticles in the nucleon. (9 refs).
Two-body Dirac equations for nucleon-nucleon scattering
International Nuclear Information System (INIS)
Liu Bin; Crater, Horace
2003-01-01
We investigate the nucleon-nucleon interaction by using the meson exchange model and the two-body Dirac equations of constraint dynamics. This approach to the two-body problem has been successfully tested for QED and QCD relativistic bound states. An important question we wish to address is whether or not the two-body nucleon-nucleon scattering problem can be reasonably described in this approach as well. This test involves a number of related problems. First we must reduce our two-body Dirac equations exactly to a Schroedinger-like equation in such a way that allows us to use techniques to solve them already developed for Schroedinger-like systems in nonrelativistic quantum mechanics. Related to this, we present a new derivation of Calogero's variable phase shift differential equation for coupled Schroedinger-like equations. Then we determine if the use of nine meson exchanges in our equations gives a reasonable fit to the experimental scattering phase shifts for n-p scattering. The data involve seven angular momentum states including the singlet states 1 S 0 , 1 P 1 , 1 D 2 and the triplet states 3 P 0 , 3 P 1 , 3 S 1 , 3 D 1 . Two models that we have tested give us a fairly good fit. The parameters obtained by fitting the n-p experimental scattering phase shift give a fairly good prediction for most of the p-p experimental scattering phase shifts examined (for the singlet states 1 S 0 , 1 D 2 and triplet states 3 P 0 , 3 P 1 ). Thus the two-body Dirac equations of constraint dynamics present us with a fit that encourages the exploration of a more realistic model. We outline generalizations of the meson exchange model for invariant potentials that may possibly improve the fit
Heavy quark production in semihard interactions of nucleons
International Nuclear Information System (INIS)
Levin, E.M.; Ryskin, M.G.; Shabel'skij, Yu.M.; Shuvaev, A.G.
1991-01-01
Cross section of semihard process (heavy quark production) in the interactions of high-energy nucleons is calculated. The normalization of gluon structure function at small x and the role of absorption corrections are discussed in detail. The virtuality of interacting gluons as well as their transverse motion and possible various polarizations are accounted for in calculations. Comparatively large cross section of the high-energy inclusive b-quark production (σ(b-barb) is predicted, in particular, σ(p-barp→b-barb)=150-300 μb at √s=1.8 TeV
Nucleon structure functions from lattice operator product expansion
Energy Technology Data Exchange (ETDEWEB)
Chambers, A.J.; Somfleth, K.; Young, R.D.; Zanotti, J.M. [Adelaide Univ., SA (Australia). CSSM, Dept. of Physics; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe (Japan); Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2017-03-15
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Nucleon structure functions from lattice operator product expansion
International Nuclear Information System (INIS)
Chambers, A.J.; Somfleth, K.; Young, R.D.; Zanotti, J.M.; Perlt, H.; Schiller, A.
2017-03-01
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Nucleon Structure Functions from Operator Product Expansion on the Lattice.
Chambers, A J; Horsley, R; Nakamura, Y; Perlt, H; Rakow, P E L; Schierholz, G; Schiller, A; Somfleth, K; Young, R D; Zanotti, J M
2017-06-16
Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments.
Coloured quarks and the short range nucleon nucleon interaction
International Nuclear Information System (INIS)
Ribeiro, J.E.F.T.
1978-02-01
The strong repulsive core that exists in the scattering of two nucleons is studied with the help of the Resonating Group Method (R.G.M.), where the Pauli Principle of fermion antisymmetry is taken explicitly into account. The quark-quark potential is described in terms of colour (long range confining potential) and hyperfine interactions alone. The mass differences N*(1688) - N(938) and Δ(1236) = N(938) are used to fit the two free constants of the assumed quark potential. It is shown that although the Pauli Principle does not exclude ab initio a S state of two nucleons, a strong repulsive potential is, nevertheless, found. Two cases are studied in detail: The Isosinglet case (neutron proton scattering) and the Isotriplet one (identical nucleons). Phase shifts for each case are presented and the obtained relative wave functions are found consistent with the observed experimental features for the repulsive potential. Some formal results concerning an important class of operators characteristic of the present R.G.M. calculations are also presented. (author)
Induced hyperon-nucleon-nucleon interactions and the hyperon puzzle
Energy Technology Data Exchange (ETDEWEB)
Wirth, Roland; Roth, Robert [Institut fuer Kernphysik, TU Darmstadt (Germany)
2016-07-01
There is a strong experimental and theoretical interest in determining the structure of hypernuclei and the effect of strangeness in strongly interacting many-body systems. Recently, we presented the first calculations of hypernuclei in the p shell from first principles. However, these calculations showed either slow convergence with respect to model-space size or, when the hyperon-nucleon potential is transformed via the Similarity Renormalization Group, strong induced three-body terms. By including these induced hyperon-nucleon-nucleon (YNN) terms explicitly, we get precise binding and excitation energies. We present first results for p-shell hypernuclei and discuss the origin of the YNN terms, which are mainly driven by the evolution of the Λ-Σ conversion terms. We find that they are tightly connected to the hyperon puzzle, a long-standing issue where the appearance of hyperons in models of neutron star matter lowers the predicted maximum neutron star mass below the bound set by the heaviest observed objects.
Equation of state of nuclear matter of nucleons and dibaryons
International Nuclear Information System (INIS)
Mrowczynski, St.
1985-01-01
The nuclear matter is considered consisting of nucleons and dibaryons, i.e. elementary particles of double baryon charge. The equation of state of such matter at zero temperature is found. The ideal gas approximation is considered and then the role of interaction is discussed which is included by means of delta-like potential. The peculiarities and possible phisical consequences of the equation of state are considered
Two-current nucleon observables in Skyrme model
International Nuclear Information System (INIS)
Chemtob, M.
1987-01-01
Three independent two-current nucleon observables are studied within the two-flavor Skyrme model for the πρω system. The effecive lagrangian is that of the gauged chiral symmetry approach, consistent with the vector meson dominance, in the linear realization (for the vector mesons) of the global chiral symmetry. The first application deals with the nucleon electric polarizability and magnetic susceptibility. Both seagull and dispersive contributions appear and we evaluate the latter in terms of the sums over intermediate states. The results are compared with existing quark model results as well as with empirical determinations. The second application concerns the zero-point quantum correction to the skyrmion mass. We apply a chiral perturbation theory approach to evaluate the ion loop contribution to the nucleon mass. The comparison with the conventional Skyrme model result reveals an important sensitivity to the stabilization mechanism. The third application is to lepton-nucleon deep inelastic scattering in the Bjorken scaling limit. The structure tensor is calculated in terms of the representation as a commutator product of two currents. Numerical results are presented for the scaling function F 2 (x). An essential use is made of the large N c (number of colors) approximation in all these applications. In the numerical computations we ignore the distortion effects, relative to the free plane wave limit, on the pionic fluctuations. (orig.)
Radical conservatism and nucleon decay
International Nuclear Information System (INIS)
Wilczek, Frank
2000-01-01
Unification of couplings, observation of neutrino masses in the expected range, and several other considerations confirm central implications of straightforward gauge unification based on SO(10) or a close relative and incorporating low-energy supersymmetry. The remaining outstanding consequence of this circle of ideas, yet to be observed, is nucleon instability. Clearly, we should aspire to be as specific as possible regarding the rate and form of such instability. I argue that not only esthetics, but also the observed precision of unification of couplings, favors an economical symmetry-breaking (Higgs) structure. Assuming this, one can exploit its constraints to build reasonably economical, overconstrained yet phenomenologically viable models of quark and lepton masses. Putting it all together, one arrives at reasonably concrete, hopeful expectations regarding nucleon decay. These expectations are neither ruled out by existing experiments, nor hopelessly inaccessible. Furthermore, the branching fractions can discriminate among different possibilities for physics at the unification scale
Energy Technology Data Exchange (ETDEWEB)
Chand, Ramesh
1963-10-15
Total scattering and absorption cross sections for anti K-nucleon collisions in I = 1, p_{3/2} - channel are given as functions of the two sets of energy dependent anti KN scattering parameters solutions, called solution A' and solution B'. These scattering parameters are obtained by linear interpolations between Watson's amplitudes around 400 MeV/c and the amplitude at the position of the pole in the anti KN scattering amplitude corresponding to the p_{3/2}-wave 1385 MeV Y_{1}-resonance with 50 MeV width. The zero-range expansion for p-wave anti K-nucleon phase shift and the scattering parameters of Watson's solution B are found to be in violation of the requirements of causality and of positive definiteness of transition probabilities. (auth)
International Nuclear Information System (INIS)
Dueren, M.
2001-01-01
The spin and flavor structure of quarks and gluons in nucleons and nuclei is more complicated than expected in the original naive quark model. Recent results which show some of the key failures of the naive picture are summarized here with emphasis on recent results from the HERMES experiment. Some future options to study the quarks structure in exclusive processes in electroproduction, photoproduction and pp annihilation are presented. (orig.)
Antinucleon-nucleon annihilation dynamics
International Nuclear Information System (INIS)
Myhrer, F.; Massachusetts Inst. of Tech., Cambridge
1989-01-01
The antinucleon-nucleon annihilation is predominantly described by a hot-fireball process where the many final quantum numbers are distributed in a statistical fashion. It is argued that caution must be used in employing the long-range meson-exchange forces to describe the protonium atomic states. The simplest processes of two final mesons do show puzzling behavior which might be a reflection of quark dynamics, but no guiding principles for these quark calculations have been established yet. (orig.)
International Nuclear Information System (INIS)
Osman, A.; Ramadan, S.
1989-01-01
Faddeev equations of bound three-nucleon system are presented as a set of integral equations. To solve them, a sutable form of the nucleon-nucleon interactions is used: with the exchange of a scalar meson, a pseudoscalar meson and a massless vector meson. Higher orders of these different meson exchanges in the nucleon-nucleon interactions have been taken into account. With these nuclear forces and nucleon-nucleon interactions, the three-nucleon binding energy is calculated by solving the Faddeev integral equations. The obtained value of the three-nucleon binding energy is 8.441 MeV. The inclusion of the higher order terms of the different meson exchange in the nuclear nucleon-nucleon interaction is found to affect the three-nucleon binding by about 3.92%. 3 figs., 16 refs
Generalized polarizabilities of the nucleon in baryon chiral perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Lensky, Vadim [Johannes Gutenberg Universitaet Mainz, Institut fuer Kernphysik, Cluster of Excellence PRISMA, Mainz (Germany); Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Pascalutsa, Vladimir; Vanderhaeghen, Marc [Johannes Gutenberg Universitaet Mainz, Institut fuer Kernphysik, Cluster of Excellence PRISMA, Mainz (Germany)
2017-02-15
The nucleon generalized polarizabilities (GPs), probed in virtual Compton scattering (VCS), describe the spatial distribution of the polarization density in a nucleon. They are accessed experimentally via the process of electron-proton bremsstrahlung (ep → epγ) at electron-beam facilities, such as MIT-Bates, CEBAF (Jefferson Lab), and MAMI (Mainz). We present the calculation of the nucleon GPs and VCS observables at next-to-leading order in baryon chiral perturbation theory (BχPT), and confront the results with the empirical information. At this order our results are predictions, in the sense that all the parameters are well known from elsewhere. Within the relatively large uncertainties of our calculation we find good agreement with the experimental observations of VCS and the empirical extractions of the GPs. We find large discrepancies with previous chiral calculations - all done in heavy-baryon χPT (HBχPT) - and discuss the differences between BχPT and HBχPT responsible for these discrepancies. (orig.)
International Nuclear Information System (INIS)
Liu Jianye; Xing Yongzhong; Guo Wenjun
2003-01-01
We study the isospin effects of the mean field and two-body collision on the nucleon emissions at the intermediate energy heavy-ion collisions by using an isospin-dependent transport theory. The calculated results show that the nucleon emission number N n depends sensitively on the isospin effect of nucleon-nucleon cross section and weakly on the isospin-dependent mean field for neutron-poor system in higher beam energy region. In particular, the correlation between the medium correction of two-body collision and the momentum-dependent interaction enhances the dependence of nucleon emission number N n on the isospin effect of nucleon-nucleon cross section. On the contrary, the ratio of the neutron-proton ratio of the gas phase to the neutron-proton ratio of the liquid phase, i.e., the degree of isospin fractionation [(N/Z) gas ] b /[(N/Z) liq ] b depends sensitively on the isospin-dependent mean field and weakly on the isospin effect of two-body collision for neutron-rich system in the lower beam energy region. In this case, N n and [(N/Z) gas ] b /[(N/Z) liq ] b are the probes for extracting the information about the isospin-dependent nucleon-nucleon cross section in the medium and the isospin-dependent mean field, respectively
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.)
Spin observables in nucleon-nucleus scattering
International Nuclear Information System (INIS)
Moss, J.M.
1982-01-01
The curse of inelastic nucleon scattering and charge exchange has always been the enormous complexity of the nucleon-nucleon (N-N) interaction. This complexity, however, can also be viewed as the ultimate promise of nucleons as probes of nuclear structure. Given an adequate theoretical basis, inelastic nucleon scattering is capable of providing information not obtainable with other probes. Recently a revolution of experimental technique has taken place that makes it desirable to re-examine the question of what physics is ultimately obtainable from inelastic nucleon scattering. It is now feasible to perform complete polarization transfer (PT) experiments for inelastic proton scattering with high efficiency and excellent energy resolution. Programs to measure PT obsevables are underway at several laboratories, and results are beginning to appear. Objectives of this presentation are to examine how such experiments are done, and what physics is presently obtained and may ultimately be learned from them
On single nucleon wave functions in nuclei
International Nuclear Information System (INIS)
Talmi, Igal
2011-01-01
The strong and singular interaction between nucleons, makes the nuclear many body theory very complicated. Still, nuclei exhibit simple and regular features which are simply described by the shell model. Wave functions of individual nucleons may be considered just as model wave functions which bear little resemblance to the real ones. There is, however, experimental evidence for the reality of single nucleon wave functions. There is a simple method of constructing such wave functions for valence nucleons. It is shown that this method can be improved by considering the polarization of the core by the valence nucleon. This gives rise to some rearrangement energy which affects the single valence nucleon energy within the nucleus.
Semiclassical calculations of the imaginary part of the nucleon-nucleus optical potential
International Nuclear Information System (INIS)
Hasse, R.W.; Schuck, P.
1984-03-01
We calculate for finite nuclei the imaginary part of the nucleus-nucleon optical potential on and off shell by using the local Fermi gas approximation and a finite range two-body exchange force. Results are compared with those obtained by infinite nuclear matter calculations as well as using the local density or Glauber approximation
Database of Nucleon-Nucleon Scattering Cross Sections by Stochastic Simulation, Phase I
National Aeronautics and Space Administration — A database of nucleon-nucleon elastic differential and total cross sections will be generated by stochastic simulation of the quantum Liouville equation in the...
Theoretical aspects of the nucleon-nucleon workshop
International Nuclear Information System (INIS)
Silbar, R.R.
1984-01-01
This report concentrates on the inelastic NN system from 300 to 1500 MeV. Topics covered include the visibility of quark signals, dibaryons, the model dependence of predicted NN inelasticities, and a review of how well present conventional models compare with a rapidly expanding database. The general conclusion is that there is so far no clear evidence in the NN system at intermediate energies for unconventional dibaryon resonances. Short remarks are also made concerning one theoretical contribution on elastic scattering and on new experimental results for deuteron photo-disintegration and pion-nucleon charge exchange. 11 references
Chiral nucleon-nucleon forces in nuclear structure calculations
Directory of Open Access Journals (Sweden)
Coraggio L.
2016-01-01
Full Text Available Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.
Influence of nucleon density distribution in nucleon emission probability
International Nuclear Information System (INIS)
Paul, Sabyasachi; Nandy, Maitreyee; Mohanty, A.K.; Sarkar, P.K.; Gambhir, Y.K.
2014-01-01
Different decay modes are observed in heavy ion reactions at low to intermediate energies. It is interesting to study total neutron emission in these reactions which may be contributed by all/many of these decay modes. In an attempt to understand the importance of mean field and the entrance channel angular momentum, we study their influence on the emission probability of nucleons in heavy ion reactions in this work. This study owes its significance to the fact that once population of different states are determined, emission probability governs the double differential neutron yield
Low energy peripheral scaling in nucleon-nucleon scattering and uncertainty quantification
Ruiz Simo, I.; Amaro, J. E.; Ruiz Arriola, E.; Navarro Pérez, R.
2018-03-01
We analyze the peripheral structure of the nucleon-nucleon interaction for LAB energies below 350 MeV. To this end we transform the scattering matrix into the impact parameter representation by analyzing the scaled phase shifts (L + 1/2) δ JLS (p) and the scaled mixing parameters (L + 1/2)ɛ JLS (p) in terms of the impact parameter b = (L + 1/2)/p. According to the eikonal approximation, at large angular momentum L these functions should become an universal function of b, independent on L. This allows to discuss in a rather transparent way the role of statistical and systematic uncertainties in the different long range components of the two-body potential. Implications for peripheral waves obtained in chiral perturbation theory interactions to fifth order (N5LO) or from the large body of NN data considered in the SAID partial wave analysis are also drawn from comparing them with other phenomenological high-quality interactions, constructed to fit scattering data as well. We find that both N5LO and SAID peripheral waves disagree more than 5σ with the Granada-2013 statistical analysis, more than 2σ with the 6 statistically equivalent potentials fitting the Granada-2013 database and about 1σ with the historical set of 13 high-quality potentials developed since the 1993 Nijmegen analysis.
Studies of nucleon resonance structure in exclusive meson electroproduction
International Nuclear Information System (INIS)
Aznauryan, I.G.; Bashir, A.; Braun, V.M.
2013-01-01
Studies of the structure of excited baryons are key factors to the N* program at Jefferson Lab (JLab). Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q 2 . This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever achieved, with a kinematic reach up to Q 2 = 12 GeV 2 . This high-Q 2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off protons, along with Quantum Chromodynamics (QCD)-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the nonperturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD. (author)
Current status of nucleonic gauges in Portugal
International Nuclear Information System (INIS)
Salgado, J.; Carvalho, F.G.; Manteigas, J.; Oliveira, C.; Goncalves, I.F.; Neves, J.; Cruz, C.
2000-01-01
The nucleonic gauges are largely used in Portugal industry, despite the fact that design and manufacturing of prototypes of nucleonic gauges is rather limited. The modernization of some industrial sectors (cement, paper and civil engineering) has enhanced applications of nucleonic gauges and has created local capability but new legislation tends to restrict further spread of them. The Institute of Nuclear Technology is the only applied research institution developing nucleonic gauges for moisture, thickness and density, and elemental analysis, as well as providing assistance in calibration, safe operation and maintenance of them. (author)
Models of direct reactions and quantum pre-equilibrium for nucleon scattering on spherical nuclei
International Nuclear Information System (INIS)
Dupuis, M.
2006-01-01
When a nucleon collides with a target nucleus, several reactions may occur: elastic and inelastic scatterings, charge exchange... In order to describe these reactions, different models are involved: the direct reactions, pre-equilibrium and compound nucleus models. Our goal is to study, within a quantum framework and without any adjustable parameter, the direct and pre-equilibrium reactions for nucleons scatterings off double closed-shell nuclei. We first consider direct reactions: we are studying nucleon scattering with the Melbourne G-matrix, which represents the interaction between the projectile and one target nucleon, and with random phase approximation (RPA) wave functions which describe all target states. This is a fully microscopic approach since no adjustable parameters are involved. A second part is dedicated to the study of nucleon inelastic scattering for large energy transfer which necessarily involves the pre-equilibrium mechanism. Several models have been developed in the past to deal with pre-equilibrium. They start from the Born expansion of the transition amplitude which is associated to the inelastic process and they use several approximations which have not yet been tested. We have achieved some comparisons between second order cross sections which have been calculated with and without these approximations. Our results allow us to criticize some of these approximations and give several directions to improve the quantum pre-equilibrium models. (author)
CERN. Geneva
2015-01-01
Most physics results at the LHC end in a likelihood ratio test. This includes discovery and exclusion for searches as well as mass, cross-section, and coupling measurements. The use of Machine Learning (multivariate) algorithms in HEP is mainly restricted to searches, which can be reduced to classification between two fixed distributions: signal vs. background. I will show how we can extend the use of ML classifiers to distributions parameterized by physical quantities like masses and couplings as well as nuisance parameters associated to systematic uncertainties. This allows for one to approximate the likelihood ratio while still using a high dimensional feature vector for the data. Both the MEM and ABC approaches mentioned above aim to provide inference on model parameters (like cross-sections, masses, couplings, etc.). ABC is fundamentally tied Bayesian inference and focuses on the “likelihood free” setting where only a simulator is available and one cannot directly compute the likelihood for the dat...
Schmidt, Wolfgang M
1980-01-01
"In 1970, at the U. of Colorado, the author delivered a course of lectures on his famous generalization, then just established, relating to Roth's theorem on rational approxi- mations to algebraic numbers. The present volume is an ex- panded and up-dated version of the original mimeographed notes on the course. As an introduction to the author's own remarkable achievements relating to the Thue-Siegel-Roth theory, the text can hardly be bettered and the tract can already be regarded as a classic in its field."(Bull.LMS) "Schmidt's work on approximations by algebraic numbers belongs to the deepest and most satisfactory parts of number theory. These notes give the best accessible way to learn the subject. ... this book is highly recommended." (Mededelingen van het Wiskundig Genootschap)
Strange nucleon electromagnetic form factors from lattice QCD
Alexandrou, C.; Constantinou, M.; Hadjiyiannakou, K.; Jansen, K.; Kallidonis, C.; Koutsou, G.; Avilés-Casco, A. Vaquero
2018-05-01
We evaluate the strange nucleon electromagnetic form factors using an ensemble of gauge configurations generated with two degenerate maximally twisted mass clover-improved fermions with mass tuned to approximately reproduce the physical pion mass. In addition, we present results for the disconnected light quark contributions to the nucleon electromagnetic form factors. Improved stochastic methods are employed leading to high-precision results. The momentum dependence of the disconnected contributions is fitted using the model-independent z-expansion. We extract the magnetic moment and the electric and magnetic radii of the proton and neutron by including both connected and disconnected contributions. We find that the disconnected light quark contributions to both electric and magnetic form factors are nonzero and at the few percent level as compared to the connected. The strange form factors are also at the percent level but more noisy yielding statistical errors that are typically within one standard deviation from a zero value.
Hard probes of short-range nucleon-nucleon correlations
Energy Technology Data Exchange (ETDEWEB)
J. Arrington, D. W. Higinbotham, G. Rosner, M. Sargsian
2012-10-01
The strong interaction of nucleons at short distances leads to a high-momentum component to the nuclear wave function, associated with short-range correlations between nucleons. These short-range, high-momentum structures in nuclei are one of the least well understood aspects of nuclear matter, relating to strength outside of the typical mean-field approaches to calculating the structure of nuclei. While it is difficult to study these short-range components, significant progress has been made over the last decade in determining how to cleanly isolate short-range correlations in nuclei. We have moved from asking if such structures exist, to mapping out their strength in nuclei and studying their microscopic structure. A combination of several different measurements, made possible by high-luminosity and high-energy accelerators, coupled with an improved understanding of the reaction mechanism issues involved in studying these structures, has led to significant progress, and provided significant new information on the nature of these small, highly-excited structures in nuclei. We review the general issues related to short-range correlations, survey recent experiments aimed at probing these short-range structures, and lay out future possibilities to further these studies.
Counter terms for low momentum nucleon-nucleon interactions
International Nuclear Information System (INIS)
Holt, Jason D.; Kuo, T.T.S.; Brown, G.E.; Bogner, Scott K.
2004-01-01
There is much current interest in treating low energy nuclear physics using the renormalization group (RG) and effective field theory (EFT). Inspired by this RG-EFT approach, we study a low-momentum nucleon-nucleon (NN) interaction, V low-k , obtained by integrating out the fast modes down to the scale Λ∼2 fm -1 . Since NN experiments can only determine the effective interaction in this low momentum region, our chief purpose is to find such an interaction for complex nuclei whose typical momenta lie below this scale. In this paper we find that V low-k can be highly satisfactorily accounted for by the counter terms corresponding to a short range effective interaction. The coefficients C n of the power series expansion ΣC n q n for the counter terms have been accurately determined, and results derived from several meson-exchange NN interaction models are compared. The counter terms are found to be important only for the S, P and D partial waves. Scaling behavior of the counter terms is studied. Finally we discuss the use of these methods for computing shell model matrix elements
Nucleonic level control in industries
International Nuclear Information System (INIS)
Eapen, A.C.; Rao, S.S.; Nair, R.S.
1979-01-01
The paper elicits the particular advantages of nucleonic level control methods in certain applications. The technique used is described briefly. Normal radioactive sources used and their selection for any application based on their characteristic emissions is explained. Level controller developed by the Bhabha Atomic Research Centre, Bombay, is described including details regarding electronic circuitry and the radiation detector used. Its application in zinc powder plant to measure powder level in a hopper is described. Some of the typical applications of gamma-ray level controllers are mentioned. (auth.)
Nucleon deformation from lattice QCD
International Nuclear Information System (INIS)
Tsapalis, A.
2008-01-01
The issue of nucleon and Delta(1232) deformation is discussed through the evaluation of the N to Delta electromagnetic transition and Delta electromagnetic form factors in Lattice QCD. The momentum dependence of the form factors is studied using 2+1 staggered dynamical flavors at pion masses as low as 350 MeV and compared to results obtained in the Wilson quenched and two-flavor dynamical theory at similar pion masses. The measurement of small non-zero quadrupole amplitudes, in agreement to recent experiments, establishes the existence of deformation in the N and Delta states. (author)
Insight into nucleon structure from generalized parton distributions
International Nuclear Information System (INIS)
J.W. Negele; R.C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; Th. Lippert; A.V.Pochinsky; D.B. Renner; D. Richards; K. Schilling; W. Schroers
2004-01-01
The lowest three moments of generalized parton distributions are calculated in full QCD and provide new insight into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon
Spin of two-nucleon system and nucleon-antinucleon combination in the S-state
International Nuclear Information System (INIS)
Baranik, A.T.; El-Naghy, A.; Ramadan, S.
1988-08-01
The spin of the two nucleon combination was studied. It was found that the resultant combination could be treated as a boson with spin one or zero, and the spin one state is more stable than the spin zero state. In the case of nucleon-antinucleon combination the spin zero state is more stable than the spin one state. The approach succeeded in describing the general features of the nucleon-nucleon and nucleon antinucleon scattering and polarization. (author). 3 refs, 4 figs
On the nucleon-nucleon potential obtained from non-linear coupling
International Nuclear Information System (INIS)
El Ghabaty, S.S.
1975-07-01
The static limit of a pseudoscalar symmetric meson theory of nuclear forces is examined. The Born-Oppenheimer potential is determined for the case of two very heavy nucleons exchanging pseudoscalar isovector pions with non-linear coupling. It is found that the non-linear terms induced by the γ 5 coupling are cancelled by the additional pion-nucleon coupling of the non-linear sigma model. The nucleon-nucleon potential thus obtained is the same as the Yukava potential except for strength at different separations between the two nucleons
International Nuclear Information System (INIS)
Lyon, W.S.; Ross, H.H.
1980-01-01
Two hundred and thirty two references are cited in this review of activation analysis(AA) for the period November 1977-November 1979. A special note is included covering changes taking place in the use of certain radiation measurement units. More of the cited references deal with new or expanded applications of AA rather than new equipment or new techniques
International Nuclear Information System (INIS)
Lipkin, H.J.
1991-11-01
The title of this lecture series raises two questions: (1) what is the OZI rule? (2) what is a nucleon. In the lectures both questions were addressed in parallel and the material moved back and forth between them. In a written version it seems more appropriate to treat the two question separately, begining with trying to understand the structure of the nucleon. Experimental evidence for the symmetry and quark structure of hadrons is reviewed with a historical introduction and updated by presenting constituent quark model relation for hadron masses and magnetic moments.Three definitions of the OZI rule are presented, all which forbid decay like φ->ρπ but making different selection rules for more complicate reactions. All suffer from the higer order paradox that a forbidden process can take place via two-step transition in which each step is allowed; e.g. φ-> KK-bar -> ρπ. No prescription is given for estimating the strength of forbidden processes. The role of cancellations between different higer order diagrams is discussed. (author)
Charge-symmetry-breaking nucleon form factors
Energy Technology Data Exchange (ETDEWEB)
Kubis, Bastian, E-mail: kubis@hiskp.uni-bonn.de [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics (Germany)
2011-11-15
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for {sup 4}He.
The axial polarizability of nucleons and nuclei
International Nuclear Information System (INIS)
Ericson, M.; Figureau, A.
1981-02-01
The part of the static nuclear axial polarizability arising from the nucleonic excitations is derived from the low energy expansion of the πN amplitude. It is shown that the contribution of the Δ intermediate state, though dominant, does not saturate the nucleonic response. A similar effect, though more pronounced, is known to occur for the magnetic susceptibility
On the electromagnetic polarisabilities of the nucleon
International Nuclear Information System (INIS)
Harun ar Rashid, A.M.
1982-10-01
The dynamic electric and magnetic polarisabilities of the nucleon are calculated taking the photon-nucleon resonance vertex-function ambiguity parameters into account. The annihilation channel in the Compton scattering amplitude is also evaluated from the chiral effective Lagrangian. It is found that the electric and magnetic polarisabilities of the proton are of the same order of magnitude. (author)
Nucleon-nucleon theory and phenomenology. Progress report and renewal proposal
International Nuclear Information System (INIS)
Signell, P.
1981-01-01
Progress is outlined on five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction with the new dramatically altered ππ s-wave interaction and using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the πN and ππ physical regions of the N anti N → ππ amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly, and determining which phases are given by theory at which energies; (4) the introduction of our K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated and verified permanent nucleon-nucleon data bank in the 0 to 1200 MeV range that can be used by all nucleon-nucleon researchers (or anyone else) via Telenet dial-in and by means of a published compendium
Low-energy pion double charge exchange and nucleon-nucleon correlations in nuclei
International Nuclear Information System (INIS)
Leitch, M.J.
1989-01-01
Recent measurements of pion double-charge exchange (DCX) at energies 20 to 70 MeV are providing a new means for studying nucleon-nucleon correlations in nuclei. At these energies the nucleus is relatively transparent, allowing simpler theoretical models to be used in interpreting the data and leading to a clearer picture. Also the contribution to DCX of sequential charge-exchange scattering through the intermediate analog state is suppressed near 50 MeV and transitions through non-analog intermediate states become very important. Recent theoretical studies by several groups have shown that while transitions through the analog route involve relatively long nucleon-nucleon distances, those through non-analog intermediate states obtain nearly half their strength from nucleon pairs with less than 1 fermi separation. Thus DCX near 50 MeV is an excellent way to study short-range nucleon-nucleon correlations. 31 refs., 29 figs., 4 tabs
Evaluation of the three-nucleon analyzing power puzzle
International Nuclear Information System (INIS)
Tornow, W.; Witala, H.
1998-01-01
The current status of the three-nucleon analyzing power puzzle is reviewed. Applying tight constraints on the allowed deviations between calculated predictions and accepted values for relevant nucleon-nucleon observables reveals that energy independent correction factors applied to the 3 P j nucleon-nucleon interactions can not solve the puzzle. Furthermore, using the same constraints, charge-independence breaking in the 3 P j nucleon-nucleon interactions can be ruled out as a possible tool to improve the agreement between three-nucleon calculations and data. The study of the energy dependence of the three-nucleon analyzing power puzzle gives clear evidence that the 3 P j nucleon-nucleon interaction obtained from phase-shift analyses and used in potential models are correct above about 25 MeV, i.e., the 3 P j nucleon-nucleon interactions have to be modified only at lower energies in order to solve the three-nucleon analyzing power puzzle, unless new three-nucleon forces can be found that account for the three-nucleon analyzing power puzzle without destroying the beautiful agreement between rigorous three-nucleon calculations and a large body of accurate three-nucleon data. (orig.)
Evaluation of the three-nucleon analyzing power puzzle
Energy Technology Data Exchange (ETDEWEB)
Tornow, W. [Duke Univ., Durham, NC (United States). Dept. of Physics]|[Triangle Univ. Nuclear Lab., Durham, NC (United States); Witala, H. [Uniwersytet Jagiellonski, Cracow (Poland). Inst. Fizyki
1998-07-20
The current status of the three-nucleon analyzing power puzzle is reviewed. Applying tight constraints on the allowed deviations between calculated predictions and accepted values for relevant nucleon-nucleon observables reveals that energy independent correction factors applied to the {sup 3}P{sub j} nucleon-nucleon interactions can not solve the puzzle. Furthermore, using the same constraints, charge-independence breaking in the {sup 3}P{sub j} nucleon-nucleon interactions can be ruled out as a possible tool to improve the agreement between three-nucleon calculations and data. The study of the energy dependence of the three-nucleon analyzing power puzzle gives clear evidence that the {sup 3}P{sub j} nucleon-nucleon interaction obtained from phase-shift analyses and used in potential models are correct above about 25 MeV, i.e., the {sup 3}P{sub j} nucleon-nucleon interactions have to be modified only at lower energies in order to solve the three-nucleon analyzing power puzzle, unless new three-nucleon forces can be found that account for the three-nucleon analyzing power puzzle without destroying the beautiful agreement between rigorous three-nucleon calculations and a large body of accurate three-nucleon data. (orig.) 18 refs.
Unitary three-body calculation of nucleon-nucleon scattering
International Nuclear Information System (INIS)
Tanabe, H.; Ohta, K.
1986-07-01
We calculate nucleon-nucleon elastic scattering phase parameters based on a unitary, relativistic, pion-exchange model. The results are highly dependent on the off-shell amplitudes of πN scattering. The isobar-dominated model for the P 33 interaction leads to too small pion production rates owing to its strong suppression of off-shell pions. We propose to expand the idea of the Δ-isobar model in such a manner as to incorporate a background (non-pole) interaction. The two-potential model, which was first applied to the P 11 partial wave by Mizutani and Koltun, is applied also to the P 33 wave. Our phenomenological model for πN interaction in the P 33 partial wave differs from the conventional model only in its off-shell extrapolation, and has two different variants for the πN → Δ vertex. The three-body approach of Kloet and Silbar is extended such that the background interactions can be included straightfowardly. We make detailed comparisons of the new model with the conventional one and find that our model adequately reproduces the 1 D 2 phase parameters as well as those of peripheral partial waves. We also find that the longitudinal total cross section difference Δσ L (pp → NNπ) comes closer to the data compared to Kloet and Silbar. We discuss about the backward pion propagation in the three-body calculation, and the Pauli-principle violating states for the background P 11 interaction. (author)
Nonresonant approximations to the optical potential
International Nuclear Information System (INIS)
Kowalski, K.L.
1982-01-01
A new class of approximations to the optical potential, which includes those of the multiple-scattering variety, is investigated. These approximations are constructed so that the optical potential maintains the correct unitarity properties along with a proper treatment of nucleon identity. The special case of nucleon-nucleus scattering with complete inclusion of Pauli effects is studied in detail. The treatment is such that the optical potential receives contributions only from subsystems embedded in their own physically correct antisymmetrized subspaces. It is found that a systematic development of even the lowest-order approximations requires the use of the off-shell extension due to Alt, Grassberger, and Sandhas along with a consistent set of dynamical equations for the optical potential. In nucleon-nucleus scattering a lowest-order optical potential is obtained as part of a systematic, exact, inclusive connectivity expansion which is expected to be useful at moderately high energies. This lowest-order potential consists of an energy-shifted (trho)-type term with three-body kinematics plus a heavy-particle exchange or pickup term. The natural appearance of the exchange term additivity in the optical potential clarifies the role of the elastic distortion in connection with the treatment of these processes. The relationship of the relevant aspects of the present analysis of the optical potential to conventional multiple scattering methods is discussed
Electromagnetic properties of the three-nucleon ground state
International Nuclear Information System (INIS)
Strueve, W.
1985-01-01
The electromagnetic form factors of the three-nucleon ground state are calculated on the base of an exact solution of the Faddeev equations. In a Hilbert space of nucleons and a possible Δ-isobar the effects of a non-perturbative description of the Δ-isobar on the magnetic form factors are studied. Pure nucleonic current operators with two- and three-particle character can be described in the extended Hilbert space by simpler one-body operators. Additionally nonrelativistic meson-exchange corrections due to π and ρ exchange are calculated consistently with the requirements of current conservation. Further relativistic corrections are estimated on selected examples. The calculations yield a total magnetic contribution of the Δ-isobar which is smaller than hitherto assumed, a static approximation of the Δ propagation is proved as inadmissible and must be rejected. Together with the meson-exchange corrections a well agreement with the experimental data at low momentum transfers results. Especially the magnetic moments and magnetization radii can be explained. For higher momentum transfers the results show the importance of further corrections. The regard of selected relativistic corrections leads to a good description of the experimental magnetic form factors. Also by this way the position of the minimum and the height of the second maximum in the 3 He charge form factor can be explained. The comparison with the latest experimental results reveals furthermore unresolved problems in the description of the 3 H charge form factor. (orig.) [de
Electromagnetic dissociation of relativistic [sup 28]Si by nucleon emission
Energy Technology Data Exchange (ETDEWEB)
Sonnadara, U.J.
1992-12-01
A detailed study of the electromagnetic dissociation of [sup 28]Si by nucleon emission at E[sub lab]/A = 14.6 (GeV/nucleon was carried out with [sup 28]Si beams interacting on [sup 208]Pb). [sup 120]Sn. [sup 64]C targets. The measurements apparatus consists of detectors in the target area which measure the energy and charged multiplicity, and a forward spectrometer which measures the position, momentum and energy of the reaction fragments. The exclusive electromagnetic dissociation cross sections for decay channels having multiple nucleons in the final state have been measured which enables the selection of events produced in pure electromagnetic interactions. The measured cross sections agree well with previous measurements obtained for the removal of a few nucleons as well as with measurements on total charge removal cross sections from other experiments. The dependence of the integrated cross sections on the target charge Z[sub T] and the target mass AT confirms that for higher Z targets the excitation is largely electromagnetic. Direct measurements of the excitation energy for the electromagnetic dissociation of [sup 28]Si [yields] p+[sup 27]Al and [sup 28]Si [yields] n+[sup 27]Si have been obtained through a calculation of the invariant mass in kinematically, reconstructed events. The excitation energy spectrum for all targets peak near the isovector giant dipole resonance in [sup 28]Si. These distributions are well reproduced by combining the photon spectrum calculated using the Weizsaecker-Williams approximation with the experimental data on the photonuclear [sup 28]Si([sub [gamma],p])[sup 27]Al and [sup 28]Si([sub [gamma],n])[sup 27]Si. The possibilities of observing double giant dipole resonance excitations in [sup 28]Si have been investigated with cross section measurements as well as with excitation energy reconstruction.
Approximated treatment of the Pauli principle effects in elastic collisons
International Nuclear Information System (INIS)
Schechter, H.
1984-08-01
Exact microscopic methods like the RGM (Resonanting Group Method) and the GCM (Generator Coordinate Method) and approximate methods like the OCM (Orthogonality Condition Model) are used to study the effects of Pauli Principle in α- 16 O elastic scattering. Using V2 and BL nucleon-nucleon interactions, nucleus-nucleus effective potentials are obtained from RGM 'exact' wave functions and also from an approximate method developed previoulsy. Using these potentials in the OCM Saito Equation phase-shifts are calculated for partial waves Λ = 0, 1, ... 11, in the energy range 0 [pt
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
International Nuclear Information System (INIS)
Desplanques, B.
1989-12-01
The concept of nucleon in nuclei has often been referred to in recent literature. What it is used for is rarely precised however. In this paper, it is shown (or reminded) that the nucleon in nuclei is a model dependent object. As an illustration, it is shown that nuclear matter in its ground state may be described to a good approximation, if not exactly, by an independent particle state and that the on-shell G-matrix used in calculating its binding energy gets its effective character from that of those particles. The expression of these particles in terms of free nucleon operators is given
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.
Virtually teaching virtual leadership
DEFF Research Database (Denmark)
Henriksen, Thomas Duus; Nielsen, Rikke Kristine; Børgesen, Kenneth
2017-01-01
This paper seeks to investigate the challenges to virtual collaboration and leadership on basis of findings from a virtual course on collaboration and leadership. The course used for this experiment was designed as a practical approach, which allowed participants to experience curriculum phenomena....... This experimental course provided insights into the challenges involved in virtual processes, and those experiences where used for addressing the challenges that virtual leadership is confronted with. Emphasis was placed on the reduction of undesired virtual distance and its consequences through affinity building....... We found that student scepticism appeared when a breakdown resulted in increasing virtual distance, and raises questions on how leaders might translate or upgrade their understandings of leadership to handling such increased distance through affinity building....
Study of the compressibility of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Morsch, P.H. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Kernphysik]|[Laboratoire National Saturne, Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)
1996-12-31
A brief discussion of the theoretical and experimental situation in baryon spectroscopy is given. Then, the radial structure is discussed, related to the ground state form factors and the compressibility. The compressibility derived from experimental data is compared with results from different nucleon models. From the study of the Roper resonance in nuclei information on the dynamical radius of the nucleon can be obtained. Experiments have been performed on deuteron and {sup 12}C which show no shift of the Roper resonance in these systems. This indicates no sizeable `swelling` or `shrinking` of the nucleon in the nuclear medium. (K.A.). 25 refs.
Computing nucleon EDM on a lattice
Abramczyk, Michael; Aoki, Sinya; Blum, Tom; Izubuchi, Taku; Ohki, Hiroshi; Syritsyn, Sergey
2018-03-01
I will discuss briefly recent changes in the methodology of computing the baryon EDM on a lattice. The associated correction substantially reduces presently existing lattice values for the proton and neutron theta-induced EDMs, so that even the most precise previous lattice results become consistent with zero. On one hand, this change removes previous disagreements between these lattice results and the phenomenological estimates of the nucleon EDM. On the other hand, the nucleon EDM becomes much harder to compute on a lattice. In addition, I will review the progress in computing quark chromo-EDM-induced nucleon EDM using chiral quark action.
Learning about nucleon resonances with pion photoproduction
International Nuclear Information System (INIS)
Walker, R.L.
1989-01-01
This chapter charts the discovery of nucleon resonances from pion-nucleon interactions. It was not until after the Albuquerque meeting in 1953 the experimentalists were able to persuade physicists about the existence of this phenomenon with the discovery of the P 33 resonance. The second and third resonances to be discovered, D 13 and F 15 , were seen as peaks in the total cross section for pion plus photoproduction, from 1956 onwards. Knowledge of pion-nucleon scattering has played an important role in the development of quark models. (UK)
In medium modification of nucleon electromagnetic properties
International Nuclear Information System (INIS)
Khanna, F.; Rakhimov, A.; Yakhsiev, U.
1997-01-01
Since nucleons are composite objects, their internal structure is expected to be changed by nuclear environment. A Skyrme like Lagrangian is proposed to consider such effects, namely the modification of electromagnetic (EM) properties of the nucleon. The static properties and EM form factors were obtained. It was shown that the charge radius of the nucleon increased in medium and the mass and axial coupling constant are reduced. The enhancement of magnetic moment of proton is smaller than that obtained in non-topological soliton model.Obtained results may be useful in electron nucleus scattering analysis.(A.A.D.)
Study of the compressibility of the nucleon
International Nuclear Information System (INIS)
Morsch, P.H.
1996-01-01
A brief discussion of the theoretical and experimental situation in baryon spectroscopy is given. Then, the radial structure is discussed, related to the ground state form factors and the compressibility. The compressibility derived from experimental data is compared with results from different nucleon models. From the study of the Roper resonance in nuclei information on the dynamical radius of the nucleon can be obtained. Experiments have been performed on deuteron and 12 C which show no shift of the Roper resonance in these systems. This indicates no sizeable 'swelling' or 'shrinking' of the nucleon in the nuclear medium. (K.A.)
Computing nucleon EDM on a lattice
Energy Technology Data Exchange (ETDEWEB)
Abramczyk, Michael; Izubuchi, Taku
2017-06-18
I will discuss briefly recent changes in the methodology of computing the baryon EDM on a lattice. The associated correction substantially reduces presently existing lattice values for the proton and neutron theta-induced EDMs, so that even the most precise previous lattice results become consistent with zero. On one hand, this change removes previous disagreements between these lattice results and the phenomenological estimates of the nucleon EDM. On the other hand, the nucleon EDM becomes much harder to compute on a lattice. In addition, I will review the progress in computing quark chromo-EDM-induced nucleon EDM using chiral quark action.
Medium modifications of nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Horikawa, T. [Department of Physics, School of Science, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Bentz, W. [Department of Physics, School of Science, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan)]. E-mail: bentz@keyaki.cc.u-tokai.ac.jp
2005-11-28
We use the Nambu-Jona-Lasinio model as an effective quark theory to investigate the medium modifications of the nucleon electromagnetic form factors. By using the equation of state of nuclear matter derived in this model, we discuss the results based on the naive quark-scalar diquark picture, the effects of finite diquark size, and the meson cloud around the constituent quarks. We apply this description to the longitudinal response function for quasielastic electron scattering. RPA correlations, based on the nucleon-nucleon interaction derived in the same model, are also taken into account in the calculation of the response function.
Nucleon wave function from lattice QCD
International Nuclear Information System (INIS)
Warkentin, Nikolaus
2008-04-01
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Nucleon wave function from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Warkentin, Nikolaus
2008-04-15
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Properties of simultaneous and sequential two-nucleon transfer
International Nuclear Information System (INIS)
Pinkston, W.T.; Satchler, G.R.
1982-01-01
Approximate forms of the first- and second-order distorted-wave Born amplitudes are used to study the overall structure, particularly the selection rules, of the amplitudes for simultaneous and sequential transfer of two nucleons. The role of the spin-state assumed for the intermediate deuterons in sequential (t, p) reactions is stressed. The similarity of one-step and two-step amplitudes for (α, d) reactions is exhibited, and the consequent absence of any obvious J-dependence in their interference is noted. (orig.)
Contribution to the study of the antinucleon-nucleon interactions
International Nuclear Information System (INIS)
Moussallam, B.
1985-01-01
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 j PC =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) [fr
International Nuclear Information System (INIS)
Gregersen, A.W.
1977-01-01
A comparison is made between matrix elements calculated using the uncoupled channel Sussex approach to second order in DWBA and matrix elements calculated using a square well potential. The square well potential illustrated the problem of the determining parameter independence balanced with the concept of phase shift difference. The super-soft core potential was used to discuss the systematics of the Sussex approach as a function of angular momentum as well as the relation between Sussex generated and effective interaction matrix elements. In the uncoupled channels the original Sussex method of extracting effective interaction matrix elements was found to be satisfactory. In the coupled channels emphasis was placed upon the 3 S 1 -- 3 D 1 coupled channel matrix elements. Comparison is made between exactly calculated matrix elements, and matrix elements derived using an extended formulation of the coupled channel Sussex method. For simplicity the potential used is a nonseparable cut-off oscillator. The eigenphases of this potential can be made to approximate the realistic nucleon--nucleon phase shifts at low energies. By using the cut-off oscillator test potential, the original coupled channel Sussex method of determining parameter independence was shown to be incapable of accurately reproducing the exact cut-off oscillator matrix elements. The extended Sussex method was found to be accurate to within 10 percent. The extended method is based upon more general coupled channel DWBA and a noninfinite oscillator wave function solution to the cut-off oscillator auxiliary potential. A comparison is made in the coupled channels between matrix elements generated using the original Sussex method and the extended method. Tables of matrix elements generated using the original uncoupled channel Sussex method and the extended coupled channel Sussex method are presented for all necessary angular momentum channels
Proton and neutron polarized targets for nucleon-nucleon experiments at SATURNE II
International Nuclear Information System (INIS)
Ball, J.; Combet, M.; Sans, J.L.; Benda, B.; Chaumette, P.; Deregel, J.; Durand, G.; Dzyubak, A.P.; Gaudron, C.; Lehar, F.; Janout, Z.; Khachaturov, B.A.
1996-01-01
A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. The polarized proton target is a 70 cm 3 cartridge loaded with Pentanol-2. For polarized neutron target, two cartridges loaded with 6 LiD and 6 LiH are set in the refrigerator and can be quickly inserted in the beam. First experiments using 6 Li products in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in a free nucleon-nucleon scattering using polarized proton targets. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. (author)
Double Polarized Neutron-Proton Scattering and Meson-Exchange Nucleon-Nucleon Potential Models
International Nuclear Information System (INIS)
Raichle, B.W.; Gould, C.R.; Haase, D.G.; Seely, M.L.; Walston, J.R.; Tornow, W.; Wilburn, W.S.; Raichle, B.W.; Gould, C.R.; Haase, D.G.; Seely, M.L.; Walston, J.R.; Tornow, W.; Wilburn, W.S.; Penttilae, S.I.; Hoffmann, G.W.
1999-01-01
We report on polarized beam - polarized target measurements of the spin-dependent neutron-proton total cross-section differences in longitudinal and transverse geometries (Δσ L and Δσ T , respectively) between E n =5 and 20MeV. Single-parameter phase-shift analyses were performed to extract the phase-shift mixing parameter var-epsilon 1 , which characterizes the strength of the nucleon-nucleon tensor interaction at low energies. Consistent with the trend of previous determinations at E n =25 and 50MeV, our values for var-epsilon 1 imply a stronger tensor force than predicted by meson-exchange nucleon-nucleon potential models and nucleon-nucleon phase-shift analyses. copyright 1999 The American Physical Society
International Nuclear Information System (INIS)
Knyaz'kov, O.M.; Kukhtina, I.N.
1989-01-01
The integral characteristics of the potential distribution in nuclei, namely the volume integrals, moments and mean square radii are studied in the framework of the semimicroscopic approach to the interaction of low energy nucleons with nuclei on the base of the exchange nucleon-nucleon correlations and the density dependence of effective forces. The ratio of the normalized multipole moments of potential and matter distributions is investigated. The energy dependence of the integral characteristics is analyzed. 15 refs.; 2 tabs
Nucleon-nucleon interaction and the quark model
International Nuclear Information System (INIS)
Faessler, A.
1985-01-01
The NN phase shifts are calculated using the quark model with a QCD inspired quark-quark force. The short range part of the NN force is given by quark and gluon exchange. The long range part is described by π and σ-meson exchange. The data fitted in the model are five values connected with three quarks only: the nucleon mass, the Δ mass, the root mean square radius of the charge distribution of the proton including the pion cloud, the π-N and the σ-N coupling constant at zero momentum transfer. The 1 S and 3 S phase shifts are nicely reproduced. The short range repulsion is decisively influenced by the node in the [42] r relative wave function. Very important is the colour magnetic quark-quark force which enlarges the [42] r admixture. In the OBEP's the short range repulsion is connected with the exchange of the ω-meson. But to reproduce the short range repulsion one had to blow up the ω-N coupling constant by a factor 2 to 3 compared to flavour SU 3 . With quark and gluon exchange the best fit to the ω-N coupling constant lies close to the SU 3 flavour value. This fact strongly supports the notion that the real nature of the short range repulsion of the NN interaction have been found
Calculation of the nucleon structure function from the nucleon wave function
Hussar, Paul E.
1993-01-01
Harmonic oscillator wave functions have played an historically important role in our understanding of the structure of the nucleon, most notably by providing insight into the mass spectra of the low-lying states. High energy scattering experiments are known to give us a picture of the nucleon wave function at high-momentum transfer and in a frame in which the nucleon is traveling fast. A simple model that crosses the twin bridges of momentum scale and Lorentz frame that separate the pictures of the nucleon wave function provided by the deep inelastic scattering data and by the oscillator model is presented.
Double polarized neutron-proton scattering and nucleon-nucleon tensor force: An alternative analysis
International Nuclear Information System (INIS)
Tornow, W.; Gould, C.R.; Haase, D.G.; Walston, J.R.; Raichle, B.W.
2002-01-01
Previous neutron-proton total cross-section difference measurements Δσ L and Δσ T between E n =7.43 and 17.1 MeV have been analyzed in a new way that reduces experimental systematic uncertainties. The results obtained for the 3 S 1 - 3 D 1 mixing parameter ε 1 are very similar to the published values, substantiating the previous conclusion that the nucleon-nucleon tensor force at low energies is stronger than predicted by the Nijmegen partial-wave analysis and, therefore, by all the recent high-precision nucleon-nucleon potential models as well
Pion photoproduction on the nucleon at threshold
International Nuclear Information System (INIS)
Cheon, I.T.; Jeong, M.T.
1989-08-01
Electric dipole amplitudes of pion photoproduction on the nucleon at threshold have been calculated in the framework of the chiral bag model. Our results are in good agreement with the existing experimental data
Polarized few-nucleon targets: new developments
Energy Technology Data Exchange (ETDEWEB)
Haeusser, O
1992-09-01
We discuss recent improvements in producing polarized few-nucleon targets for nuclear and particle physics experiments. The emphasis is on progress with polarized gas targets intended for experiments at electron and proton storage rings. (author) 54 refs., 1 tab.
Polarized few-nucleon targets: new developments
International Nuclear Information System (INIS)
Haeusser, O.
1992-09-01
We discuss recent improvements in producing polarized few-nucleon targets for nuclear and particle physics experiments. The emphasis is on progress with polarized gas targets intended for experiments at electron and proton storage rings. (author) 54 refs., 1 tab
Insights into nucleon structure from parton distributions
Energy Technology Data Exchange (ETDEWEB)
Melnitchouk, Wally [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
We review recent progress in understanding the substructure of the nucleon from global QCD analysis of parton distribution functions (PDFs). New high-precision data onW-boson production in p ¯ p collisions have significantly reduced the uncertainty on the d=u PDF ratio at large values of x, indirectly constraining models of the medium modification of bound nucleons. Drell-Yan data from pp and pd scattering reveal new information on the d¯-u¯ asymmetry, clarifying the role of chiral symmetry breaking in the nucleon. In the strange sector, a new chiral SU(3) analysis finds a valence-like component of the strange-quark PDF, giving rise to a nontrivial s- ¯ s asymmetry at moderate x values. We also review recent analyses of charm in the nucleon, which have found conflicting indications of the size of the nonperturbative charm component.
Nucleon parton distributions in chiral perturbation theory
International Nuclear Information System (INIS)
Moiseeva, Alena
2013-01-01
Properties of the chiral expansion of nucleon light-cone operators have been studied. In the framework of the chiral perturbation theory we have demonstrated that convergency of the chiral expansion of nucleon parton distributions strongly depends on the value of the variable x. Three regions in x with essentially different analytical properties of the resulting chiral expansion for parton distributions were found. For each of the regions we have elaborated special power counting rules corresponding to the partial resummation of the chiral series. The nonlocal effective operators for the vector and the axial nucleon parton distributions have been constructed at the zeroth and the first chiral order. Using the derived nonlocal operators and the derived power counting rules we have obtained the second order expressions for the nucleon GPDs H(x,ξ,Δ 2 ), H(x,ξ,Δ 2 ),E(x,ξ,Δ 2 ) valid in the region x>or similar a 2 χ .
Nucleon measurements at the precision frontier
Energy Technology Data Exchange (ETDEWEB)
Carlson, Carl E. [Physics Department, College of William and Mary, Williamsburg, VA 23187 (United States)
2013-11-07
We comment on nucleon measurements at the precision frontier. As examples of what can be learned, we concentrate on three topics, which are parity violating scattering experiments, the proton radius puzzle, and the symbiosis between nuclear and atomic physics.
Description of the nucleon wave function as a sum of well-chosen Gaussian functions
International Nuclear Information System (INIS)
Roux, C.; Silvestre-Brac, B.
1995-01-01
We study in detail the possibility of describing the nucleon (three quark-system) wave function as a superposition of Gaussian functions. A Faddeev treatment including 8 amplitudes is performed and taken as reference for the exact values. Several approximations are proposed and compared carefully to the exact solutions. Three different potentials have been tested and several observables are considered. (author)
The nucleon axial isoscalar coupling constant and the Bjorken sum rule
International Nuclear Information System (INIS)
Belyaev, V.M.; Ioffe, B.L.; Kogan, Ya.I.
1984-01-01
The nucleon coupling constant with the axial isoscalar current entering the Bjorken sum rule for the deep inelastic scattering of polarized electrons on a polarized target is calculated in nonperturbative QCD. The result, gsub(A)sup(s) approximately 0.5, is about a factor of two smaller as compared to that of the SU(6) symmetric quark model
Dilepton production in nucleon–nucleon collisions around 1 GeV ...
Indian Academy of Sciences (India)
We present a fully relativistic and gauge invariant framework for calculating the cross-sections of dilepton production in nucleon–nucleon ( ) collisions which is based on the meson-exchange approximation for the scattering amplitudes. Predictions of our model are compared with those of other covariant models that ...
Zero-point motion in the bag description of the nucleon
International Nuclear Information System (INIS)
Brown, G.E.; Durso, J.W.; Johnson, M.B.
1983-01-01
In the bag model, confinement of quarks is accomplished by introduction of a boundary condition at some definite radius R, where the energy of the total system is a minimum. This minimum is, however, relatively shallow and energies for substantially different bag radii are not much larger than this minimum value. This indicates that the zero-point motion of the bag surface may be important. In this paper, quantization of the bag surface motion is carried out in a somewhat ad hoc fashion, modelled after the generator coordinate theory in nuclear physics. This procedure unifies a number of ideas previously in the literature; it stresses the anharmonicity of the collective motion. As in earlier treatments, the Roper resonance emerges as a breathing-mode type of excitation of the nucleon. The one- and two-pion decays of the Roper resonance are calculated and the widths are found to fall short of the empirical ones. It is pointed out, however, that decays involving intermediate states containing virtual rho-mesons will enhance the widths. Pion-nucleon scattering in the P 11 channel is constructed in our model and found to agree roughly with experiment. A crucial term in the driving force involves the pion coupling to the nucleon through a virtual rho-meson. With introduction of zero-point motion of the bag surface, the motion of 'bag radius' becomes dependent on precisely which moment of the radius is measured. Our development gives a model for cutting off smoothly the pion-exchange term in the nucleon-nucleon interaction. (orig.)
Three nucleon interaction and nuclear composition
International Nuclear Information System (INIS)
Pandharipande, V.R.
1983-01-01
The author discusses results of some of the calculations carried out by J. Carlson, I. Lagaris, J. Lomnitz-Adler, R.A. Smith, R.B. Wiringa and himself to study the three nucleon interaction. The group has attempted to calculate the wavefunctions and binding energies of 3 H, 3 He, 4 He and nuclear matter, with the variational method, from a nonrelativistic Hamiltonian. Only nucleon degrees of freedom are retained in this Hamiltonian; the effects of other degrees of freedom are implicit in the two and three nucleon potentials. The author discusses further the calculations carried out, in collaboration with B. Friman, and R.B. Wiringa, to study the composition of nuclei. Nucleons interact by many processes including exchange of pions with or without excitation to isobar (Δ) states. Thus the nucleus contains pions being exchanged, and some nucleons in the Δ state. The group attempts to calculate the number and momentum distribution of these exchanged pions, and the fraction of time a nucleon in the nucleus is in the Δ state. 21 references, 4 figures
Effect of nucleon and hadron structure changes in-medium and its impact on observables
Energy Technology Data Exchange (ETDEWEB)
K. Saito; K. Tsushima; A.W. Thomas
2005-07-05
We study the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model. The QMC model is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels. The model is extended to investigate the properties of finite nuclei, in which, using the Born-Oppenheimer approximation to describe the interacting quark-meson system, one can derive the effective equation of motion for the nucleon (or baryon), as well as the self-consistent equations for the meson mean fields.
Temperature dependent relativistic microscopic optical potential and mean free paths of nucleons
International Nuclear Information System (INIS)
Han Yinlu; Shen Qingbiao; Zhuo Yizhong
1993-01-01
The relativistic microscopic optical potential, mean free paths and Schroedinger equivalent potential of nucleons at finite temperature in nuclear matter are studied based on Walecka's model and thermo field dynamics. We let only the Hartree-Fock self-energy of nucleon represent to be the real part of the microscopic optical potential and the fourth order of meson exchange diagrams, i.e. the core polarization represent the imaginary part of microscopic optical potential in nuclear matter. The microscopic optical potential of finite nuclei is obtained with the local density approximation
Nuclear disassembly of the (Pb+Au) system at Elab=29 MeV per nucleon
International Nuclear Information System (INIS)
Piasecki, E.; Kordyasz, A.; Bresson, S.; Crema, E.; Galin, J.; Guerreau, D.; Morjean, M.; Paulot, C.; Pouthas, J.; Jastrzebski, J.; Pienkowski, L.; Skulski, W.; Lott, B.; Quednau, B.; Schroder, W.U.; Toeke, J.
1990-01-01
Nuclei, with Z up to 82, emitted in the 208 Pb+ 197 Au reaction at E lab =29 MeV per nucleon, have been measured as a function of the associated neutron multiplicity. The data reveal the presence of strong correlations between character of a collision and neutron multiplicity. The trends suggest a disassembly of the nuclear system into a large number of nucleons and small fragments in the events with the highest neutron multiplicity. In such events, approximately one third of the neutrons are released from the system and fragments yields decrease in an exponential fashion with increasing mass
International Nuclear Information System (INIS)
Trefz, M.
1985-01-01
Starting from a realistic nucleon-nucleon interaction (Reid soft-core) in the model of two infinitely extended confusing nuclear matter complex energy densities are calculated by means of a G matrix. By means of a generalized local-density approximation the results are transferred to finite nuclei. In the framework of the frozen-density approximation in the energy-density formalism a complex potential between two nuclei is calculated. The potential calculated so contains not the contribution of 1-particle-1-hole states to the optical potential. The contribution of these states is therefore calculated in the Feshbach formalism, respectively these states are explicitely regarded in coupled-channel calculations. The model is applied to light (for instance 12 C+ 12 C), medium heavy (for instance 48 Ca+ 48 Ca), and heavy (for instance 40 Ar+ 208 Pb) systems. Potentials for incident energies of 5-84 MeV per projectile nucleon are calculated. By means of these potentials differential cross sections and reaction cross sections are determined and compared with the experimental data. The energy dependence of the reaction cross section is discussed. It is shown that at higher energies (40 MeV/N) the differential cross sections can be quantitatively reproduced. For the reaction cross section in the whole energy range good agreement with the experiment is obtained. Contrarily to current theoretical models it is proved that at low energies the excitation of collective states yields a large contribution to the reaction cross section and therefore must not be neglected. (orig.) [de
The nucleon-nucleon interaction in the framework of the boson exchange model
International Nuclear Information System (INIS)
Niephaus, G.H.
1984-01-01
The aim of this thesis was the description of the nucleon-nucleon interaction in a microscopically founded model. For this the description of the 2-nucleon problem by an interacting 2-nucleon-pion system was presented. The starting point of our description was a relativistic eigenvalue equation for the system of mesons and two baryons. The interaction of the baryons with the mesons was described by interaction Hamiltonians. By the elimination of antinucleon states by means of a unitary tansformation (Foldy-Wouthuysen transformation) the interaction Hamiltonians for nucleons could be generated for the field-theoretical Lagrangian densities. The Hamiltonians for resonant baryon states were obtained by means of a simplified procedure from the corresponding Lagrangian densities. Because the determination of Lagrangian densities is not unique, for the pion-nucleon coupling two alternative Lagrangian densities were allowed. For the interaction of positive-energy nucleonic states these two coupling yield nearly equal results; the production or annihilation of negative-energy nucleon states (antiparticles) the predictions however are very different. (orig./HSI) [de
Survey of structures revealed in nucleon-nucleon scattering experiments and dibaryon resonances
International Nuclear Information System (INIS)
Hidaka, K.; Yokosawa, A.
1979-01-01
Structures appearing in various experimental data (particularly those with polarized beams) in nucleon-nucleon systems are reviewed. Evidence is presented for the existence of dibaryon resonances with an emphasis on a diproton resonance in 3 F 3 (J/sup P/ = 3 - ) state. 38 references
Three-nucleon forces and their importance in three-nucleon sys- tems and heavier nuclei
Kalantar-Nayestanaki, N.
2014-01-01
Abstract In the past two decades, several laboratories have produced a large amount of data for cross sections, analyzing powers, and other spin observables from various reactions in the three-nucleon system. The experimental results are moderately described by only using the two-nucleon potentials
Experimental studies and microscopic analysis of the elastic scattering of low energy nucleons
International Nuclear Information System (INIS)
Tarrats-Saugnac, Annie.
1982-05-01
Data on the elastic scattering of low energy nucleons (between 20 and 40 MeV) by nuclei distributed throughout the entire mass table are examined in the framework of a microscopic approach. Two major problems occur at these low energies which do not occur at higher energies: the Pauli principle limits the interaction possibilities of projectiles with bound nucleons in the nucleus; it is not possible to neglect the antisymmetrization between projectiles and nucleon targets resulting in the addition of a nonlocal term to the potential. A quadratic moment approximation is used. As regards the inhibition of reactions inside the nucleus by the Pauli principle, an effective interaction with a relatively simple analytical form and easy to use for systematic analyses was determined [fr
Axial vector diquark correlations in the nucleon: structure functions and static properties
Energy Technology Data Exchange (ETDEWEB)
Mineo, H. E-mail: mineo@nt.phys.s.u-tokyo.ac.jp; Bentz, W.; Ishii, N.; Yazaki, K
2002-06-03
In order to extract information on the strength of quark-quark correlations in the axial vector (a.v.) diquark channel (J{sup P}=1{sup +},T=1), we analyze the quark light cone momentum distributions in the nucleon, in particular their flavor dependencies, and the static properties of the nucleon. To construct the nucleon as a relativistic 3-quark bound state, we use a simple 'static' approximation to the full Faddeev equation in the Nambu-Jona-Lasinio model, including correlations in the scalar (J{sup P}=0{sup +},T=0) and a.v. diquark channels. It is shown that the a.v. diquark correlations should be rather weak compared to the scalar ones. From our analysis we extract information on the strength of the correlations as well as on the probability of the a.v. diquark channel.
Pre-equilibrium emission of nucleons from reactions induced by medium-energy heavy ions
International Nuclear Information System (INIS)
Korolija, M.; Holuh, E.; Cindro, N.; Hilscher, D.
1984-01-01
Recent data on fast-nucleon emission in heavy-ion-induced reactions are analysed successfully in terms of pre-equilibrium models; it is shown that the relevant parameters of those models preserve the physical meaning they have in light-ion-induced reactions. The initial exciton number obtained from a Griffin-plot analysis and the initial number of degrees of freedom, which is the relevant parameter of the modified HMB model, appear to be approximately equal for a given reaction at a given energy. It is inferred that, for heavy-ion reactions, the determination of such a parameter is substantially dominated by the centre-of-mass energy per nucleon above the Coulomb barrier, in contrast with the results of nucleon-induced reactions
Isospin Mixing in the Nucleon and 4He and the Nucleon Strange Electric Form Factor
International Nuclear Information System (INIS)
Viviani, M.; Girlanda, L.; Kievsky, A.; Marcucci, L. E.; Rosati, S.; Schiavilla, R.; Kubis, B.; Lewis, R.
2007-01-01
In order to isolate the contribution of the nucleon strange electric form factor to the parity-violating asymmetry measured in 4 He(e-vector,e ' ) 4 He experiments, it is crucial to have a reliable estimate of the magnitude of isospin-symmetry-breaking (ISB) corrections in both the nucleon and 4 He. We examine this issue in the present Letter. Isospin admixtures in the nucleon are determined in chiral perturbation theory, while those in 4 He are derived from nuclear interactions, including explicit ISB terms. A careful analysis of the model dependence in the resulting predictions for the nucleon and nuclear ISB contributions to the asymmetry is carried out. We conclude that, at the low momentum transfers of interest in recent measurements reported by the HAPPEX Collaboration at Jefferson Lab, these contributions are of comparable magnitude to those associated with strangeness components in the nucleon electric form factor
Isospin mixing in the nucleon and He-4 and the nucleon strange electric form-factor
International Nuclear Information System (INIS)
M. Viviani; R. Schiavilla; B. Kubis; R. Lewis; L. Girlanda; A. Kievsky; L.E. Marcucci; S. Rosati
2007-01-01
In order to isolate the contribution of the nucleon strange electric form factor to the parity-violating asymmetry measured in 4 He((rvec e),e(prime)) 4 He experiments, it is crucial to have a reliable estimate of the magnitude of isospin-symmetry-breaking (ISB) corrections in both the nucleon and 4 He. We examine this issue in the present letter. Isospin admixtures in the nucleon are determined in chiral perturbation theory, while those in 4 He are derived from nuclear interactions, including explicit ISB terms. A careful analysis of the model dependence in the resulting predictions for the nucleon and nuclear ISB contributions to the asymmetry is carried out. We conclude that, at the low momentum transfers of interest in recent measurements reported by the HAPPEX collaboration at Jefferson Lab, these contributions are of comparable magnitude to those associated with strangeness components in the nucleon electric form factor
Parity violation in nuclei: studies of the weak nucleon-nucleon interaction
International Nuclear Information System (INIS)
Mcdonald, A.B.
1980-03-01
The Weinberg-Salam Unified Model of weak and electromagnetic interactions has been very successful in explaining parity violation and neutral current effects in neutrino-nucleon, electron-nucleon and neutrino-electron interactions. A wide variety of nuclear physics parity violation experiments are in progress to measure effects of the weak nucleon-nucleon interaction in few nucleon systems and certain heavier nuclei where enhancements are expected. The current status of these experiments will be reviewed, including details of an experiment at Chalk River to search for parity violation in the photodisintegration of deuterium and an extension of our previous measurements of parity mixing in 21 Ne. The interpretation of results in terms of basic models of the weak interaction will be discussed. (Auth)
Colonoscopy - virtual; CT colonography; Computed tomographic colonography; Colography - virtual ... Differences between virtual and conventional colonoscopy include: VC can view the colon from many different angles. This is not as easy ...
Light hypernuclei and hyperon-nucleon interaction
International Nuclear Information System (INIS)
Carlson, J.; Gibson, B.F.
1990-01-01
Light Hypernuclei are a vital testing ground for our understanding of the Hyperon-Nucleon interaction. We have performed microscopic calculations of four and five-body hypernuclei using the Nijmegen nucleon-nucleon and hyperon-nucleon interactions. Our calculations include explicit Sigma degrees of freedom. These degrees of freedom are quite important since, in contrast to the Δ - N mass difference of ∼ 300 MeV, the Σ resonance is only about 80 MeV above the Λ. In addition, although there is no one-pion-exchange in the ΛN diagonal channel, this longest-range term does contribute to the transition ΛN - ΣN interaction. Our variational calculations show that the A=4 spin 0 ground state binding energy is well reproduced by the Nijmegen HN integration, a one-boson exchange model fit to the available scattering data. The spin 1 excited state and the A=5 ground state are strongly underbound, however. We demonstrate the importance of the strong tensor terms of the Nijmegen model, particularly those in the transition channel, in obtaining this result. The limited data currently available for hyperon-nucleon scattering must be greatly improved in order to place reasonable constraints on the interaction. 12 refs., 3 figs., 3 tabs
Light hypernuclei and hyperon-nucleon interaction
Energy Technology Data Exchange (ETDEWEB)
Carlson, J.; Gibson, B.F.
1990-01-01
Light Hypernuclei are a vital testing ground for our understanding of the Hyperon-Nucleon interaction. We have performed microscopic calculations of four and five-body hypernuclei using the Nijmegen nucleon-nucleon and hyperon-nucleon interactions. Our calculations include explicit Sigma degrees of freedom. These degrees of freedom are quite important since, in contrast to the {Delta} {minus} N mass difference of {approx} 300 MeV, the {Sigma} resonance is only about 80 MeV above the {Lambda}. In addition, although there is no one-pion-exchange in the {Lambda}N diagonal channel, this longest-range term does contribute to the transition {Lambda}N {minus} {Sigma}N interaction. Our variational calculations show that the A=4 spin 0 ground state binding energy is well reproduced by the Nijmegen HN integration, a one-boson exchange model fit to the available scattering data. The spin 1 excited state and the A=5 ground state are strongly underbound, however. We demonstrate the importance of the strong tensor terms of the Nijmegen model, particularly those in the transition channel, in obtaining this result. The limited data currently available for hyperon-nucleon scattering must be greatly improved in order to place reasonable constraints on the interaction. 12 refs., 3 figs., 3 tabs.
Neutrino-nucleus cross section in the impulse approximation regime
International Nuclear Information System (INIS)
Benhar, Omar; Farina, Nicola
2005-01-01
In the impulse approximation regime the nuclear response to a weakly interacting probe can be written in terms of the measured nucleon structure functions and the target spectral function, yielding the energy and momentum distribution of the constituent nucleons. We discuss a calculation of charged current neutrino-oxygen interactions in the quasielastic channel, carried out within nuclear many body theory. The proposed approach, extensively and successfully employed in the analysis of electron-nucleus scattering data, allows for a parameter free prediction of the neutrino-nucleus cross section, whose quantitative understanding will be critical to the analysis of the next generation of high precision neutrino oscillation experiments
International Nuclear Information System (INIS)
Tornow, W.; Howell, C.R.; Walter, R.L.; Slaus, I.
1992-01-01
Comparison of data for neutron-deuteron and proton-deuteron analyzing power A y for elastic scattering has become crucial for investigating charge-symmetry breaking in the 3 P nucleon-nucleon interactions. We extended this comparison down to 5 MeV and find that the relative difference between n-d and p-d scattering at the A y maximum near 120 degree increases with decreasing energy. By applying a straightforward Coulomb ''correction'' to the p-d data, we account for most of the difference, suggesting that the Coulomb force, rather than charge-symmetry breaking, is responsible for most of the observed difference
Lensky, Vadim; Hagelstein, Franziska; Pascalutsa, Vladimir; Vanderhaeghen, Marc
2018-04-01
We derive two new sum rules for the unpolarized doubly virtual Compton scattering process on a nucleon, which establish novel low-Q2 relations involving the nucleon's generalized polarizabilities and moments of the nucleon's unpolarized structure functions F1(x ,Q2) and F2(x ,Q2). These relations facilitate the determination of some structure constants which can only be accessed in off-forward doubly virtual Compton scattering, not experimentally accessible at present. We perform an empirical determination for the proton and compare our results with a next-to-leading-order chiral perturbation theory prediction. We also show how these relations may be useful for a model-independent determination of the low-Q2 subtraction function in the Compton amplitude, which enters the two-photon-exchange contribution to the Lamb shift of (muonic) hydrogen. An explicit calculation of the Δ (1232 )-resonance contribution to the muonic-hydrogen 2 P -2 S Lamb shift yields -1 ±1 μ eV , confirming the previously conjectured smallness of this effect.
Diophantine approximation and badly approximable sets
DEFF Research Database (Denmark)
Kristensen, S.; Thorn, R.; Velani, S.
2006-01-01
. The classical set Bad of `badly approximable' numbers in the theory of Diophantine approximation falls within our framework as do the sets Bad(i,j) of simultaneously badly approximable numbers. Under various natural conditions we prove that the badly approximable subsets of Omega have full Hausdorff dimension...
Symmetry energy of nucleonic matter with tensor correlations
Hen, Or; Li, Bao-An; Guo, Wen-Jun; Weinstein, L. B.; Piasetzky, Eli
2015-02-01
The nuclear symmetry energy (Esym(ρ ) ) is a vital ingredient of our understanding of many processes, from heavy-ion collisions to neutron stars structure. While the total nuclear symmetry energy at nuclear saturation density (ρ0) is relatively well determined, its value at supranuclear densities is not. The latter can be better constrained by separately examining its kinetic and potential terms and their density dependencies. The kinetic term of the symmetry energy, Esymkin(ρ0) , equals the difference in the per-nucleon kinetic energy between pure neutron matter (PNM) and symmetric nuclear matter (SNM), often calculated using a simple Fermi gas model. However, experiments show that tensor force induced short-range correlations (SRC) between proton-neutron pairs shift nucleons to high momentum in SNM, where there are equal numbers of neutrons and protons, but have almost no effect in PNM. We present an approximate analytical expression for Esymkin(ρ0) of correlated nucleonic matter. In our model, Esymkin(ρ0) =-10 MeV, which differs significantly from +12.5 MeV for the widely-used free Fermi gas model. This result is consistent with our analysis of recent data on the free proton-to-neutron ratios measured in intermediate energy nucleus-nucleus collisions as well as with microscopic many-body calculations, and previous phenomenological extractions. We then use our calculated Esymkin(ρ ) in combination with the known total symmetry energy and its density dependence at saturation density to constrain the value and density dependence of the potential part and to extrapolate the total symmetry energy to supranuclear densities.
Lattice QCD Calculation of Nucleon Structure
International Nuclear Information System (INIS)
Liu, Keh-Fei; Draper, Terrence
2016-01-01
It is emphasized in the 2015 NSAC Long Range Plan that 'understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics.' Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, ?NN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the 'quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the D_s meson decay constant f_D__s, the strangeness and charmness, the meson mass decomposition and the strange quark spin from the
Lattice QCD Calculation of Nucleon Structure
Energy Technology Data Exchange (ETDEWEB)
Liu, Keh-Fei [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy; Draper, Terrence [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy
2016-08-30
It is emphasized in the 2015 NSAC Long Range Plan that "understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, πNN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the D_{s} meson decay constant f_{Ds}, the strangeness and charmness, the meson mass
Alpha-clustering in dilute nucleonic sea
International Nuclear Information System (INIS)
Tohsaki, Akihiro
1999-01-01
α-clusters are expected to come out here and there in nucleonic sea owing to energetic benefit as its density is diluted. We propose a precise treatment to elucidate α-clusterized process in nucleonic sea after the breakdown of the uniformness. In order to do this, an infinite number of nucleons are considered by taking account of both the Pauli exclusion principle and effective internucleon forces. This method is called a microscopic approach, which has been successful in an α-cluster structure in light nuclei. In particular, we shed light on overcoming difficulties in a static model within the microscopic framework. This improvement is verified by using the empirical value in Weizaecker's mass formula. (author)
Phenomenological two-nucleon interaction operator
International Nuclear Information System (INIS)
Lagaris, I.E.; Pandharipande, V.R.
1981-01-01
We report a phenomenological two-nucleon interaction operator obtained by fitting the nucleon-nucleon phase shifts up to 425 MeV in S, P, D and F waves, and the deuteron properties. The operator has the standard eight potentials associated with the two-body operators 1, sigma 1 x sigma 2 , tau 1 x tau 2 , sigma 1 x sigma 2 tau 1 x tau 2 , S 12 , S 12 tau 1 x tau 2 , L x S and L x Stau 2 ; and six phenomenological potentials associated with operators L 2 , L 2 sigma 1 x sigma 2 , L 2 tau 1 x tau 2 , L 2 sigma 1 x sigma 2 tau 1 xtau 2 (L x S) 2 tau 1 x tau 2 . The six quadratic L terms are relatively weak, and are chosen in order to make many-body calculations with this operator simpler. (orig.)
Internal spin structure of the nucleon
International Nuclear Information System (INIS)
Hughes, V.W.; Kuti, J.
1983-01-01
The study of the structure of the proton and neutron through deep inelastic scattering, initially with electrons but subsequently with muons and neutrinos as well, has played a central role in establishing the quark-parton theory of the composition of hadrons and of quantum chromodynamics (QCD). One important aspect of these theoretical and experimental developments is the two spin-dependent structure functions, which are independent of the two spin-averaged structure functions and define the internal spin structure of the nucleon. Since both quarks and gluons possess spin and the forces between them are spin dependent, we can expect important information on these forces and on nucleon structure to be obtained through the study of the spindependent aspects of the nucleon wave function, as has been the case before in atomic and nuclear physics
Composite nucleon approach to the deuteron problem
International Nuclear Information System (INIS)
Agarwal, B.K.
1975-01-01
A composite model is suggested for the nucleons by assuming a long-range strong gluon force between a diquark boson B and a quark A. In the proton, A is trapped inside B in an oscillator potential; and in the neutron, A is on the surface of B in a hydrogenlike state. Nucleon form factors are obtained in agreement with experiments. The model contains a mechanism for a large effective mass of the quark A. When B is identified with π and A with μ, one can fix the gluon charge value and obtain the magnetic moments of the proton and neutron. The (μπ) atomic model for the nucleon can be used to construct the deuteron on a hydrogen molecule model. It leads to values for the binding energy, electric quadrupole moment, and form factors of the deuteron that are in agreement with experiments
The quark model and the nature of the repulsive core of the nucleon-nucleon interaction
International Nuclear Information System (INIS)
Faessler, A.; Fernandez, F.; Luebeck, G.; Shimizu, K.
1982-01-01
The nature of the repulsive core of the nucleon-nucleon is studied in the quark model. The resonating group equation for nucleon-nucleon scattering is solved with the colour Fermi-Breit interaction including further a linear or quadratic confinement potential. It is shown that the colour magnetic interaction which is adjusted to the Δ-nucleon mass splitting favours the orbital symmetry and disfavours the completely symmetric orbital state. For the important orbital symmetry the relative S wave function between the two nucleons has to have a node. In the framework of the resonating group including the NN, ΔΔ and the hidden colour (CC) channels it is shown that this node produces a 3 S and 1 S phase shift which is identical to a hard core phase shift with a hard core radius γ 0 between 0.3 and 0.6 fm depending on the assumed root mean square radius of the quark part of the nucleon. (orig./HSI)
Description of a nucleon in nuclear matter
International Nuclear Information System (INIS)
Bunatian, G.G.
1992-01-01
The nonlinear cloudy bag model, CBM, is generalized to describe a nucleon in nuclear matter at various densities ρ and temperatures T. The influence of the nuclear medium on the bag-nucleon in the framework of CBM is due to the modification of the equation describing the CBM pion field π. These changes are accounted for in the CBM by including in the CBM lagrangian the pion polarization operator π(ρ,T). The free pion propagator D is replaced in a nuclear medium by D(ρ,T). The changing of the pion field π and propagator D leads via the CBM equations to the modification of the bag size R and quark momentum p, determined simultaneously from these equations, and then to modifications of other bag-nucleon characteristics: the total energy E, r.m.s. radii, magnetic moment μ, polarizability α and so on, which all are expressed as the expectation values of the corresponding operators in the bag-nucleon state. The quantity π(ρ,T) was studied in the works whose results are used in this investigation. The nucleon size R in the nuclear matter at normal density ρ o and zero temperature decreases by 5% and the quarks momentum p also decreases, however, insignificantly, by 1-2%. On the other hand, the values of the r.m.s. radii increases by 15% for a proton and by 100% for a neutron. The author has also found that the polarizability of a nucleon in nuclear matter is roughly two times as much as in free space
Once more on the radiative corrections to the nucleon structure functions in QCD
International Nuclear Information System (INIS)
Stamenov, D.B.
1994-09-01
A new representation of the next to leading QCD corrections to the nucleon structure functions is given in terms of parton distributions. All O(α s ) corrections to the leading logarithmic approximation (LLA) are included. In contrast to the similar representations in the literature terms of order O(α 2 s ) do not attend in our expressions for the nucleon structure functions taken in the next to leading logarithmic approximation. This result is generalized for any order in α s beyond the LLA. Terms of order O(α n s ) which belong only tot he approximation in consideration are present in such a representation for the structure functions. (author). 11 refs
Evidence for pion absorption on four nucleons
International Nuclear Information System (INIS)
Rzehorz, B.; Backenstoss, G.; Dzemidzic, M.; Zagreb Univ.; Furic, M.; Zagreb Univ.; Hoffart, A.; Petkovic, T.; Zagreb Univ.; Ullrich, H.; Weyer, H.J.; Weiser, D.; Wildi, M.
1996-01-01
Experimental spectra from the coincident detection of three nucleons after the pion absorption in 4 He are displayed. The presence of a mechanism with four nucleons participating in the absorption process is made obvious. The total cross-sections for this absorption mode are: σ 4NA abs =(1.0±0.2)mb at T π =120 MeV and σ 4NA abs =(2.18± 0.65) mb at T π =210 MeV. (orig.)
Recent Studies of Nucleon Electromagnetic Form Factors
International Nuclear Information System (INIS)
Gilad, Shalev
2010-01-01
The electromagnetic form factors of nucleons are fundamental quantities in nucleon structure. As such, they have been studied extensively both theoretically and experimentally. Significant progress has been made with new measurements at Jlab, MAMI and MIT-Bates, with emphases on expanding the momentum-transfer range and on higher precision. In this paper, we describe the status of this field and present new results from measurements at both low and high momentum transfers. We also compare the experimental data to model predictions, and mention possible implications of the new results to other fields.
Nuclear medium effects on the nucleon properties
International Nuclear Information System (INIS)
Gerard, A.
1986-06-01
The idea that the nuclear medium may modify the properties of the nucleon is not really a new one. But until these last few years the intrinsic properties of the nucleon such as its mass, baryonic or electromagnetic size, magnetic moments, were hardly suspected to be substantially modified by the nuclear environment. The question raised essentially from two categories of experimental investigations, in quite different kinematical regimes and it remains at the present time a controversal subject. In this paper I try to review the present status of experimental investigations and some of the recent theoretical developments relevant to this topic
Diquark correlations from nucleon charge radii
International Nuclear Information System (INIS)
Carlson, Carl E.; Carone, Christopher D.; Kwee, Herry J.; Lebed, Richard F.
2006-01-01
We argue that precise measurements of charge and magnetic radii can meaningfully constrain diquark models of the nucleon. We construct properly symmetrized, nonrelativistic three-quark wave functions that interpolate between the limits of a pointlike diquark pair and no diquark correlation. We find that good fits to the data can be obtained for a wide range of diquark sizes, provided that the diquark wave functions are close to those that reduce to a purely scalar state in the pointlike limit. A modest improvement in the experimental uncertainties will render a fit to the charge radii a more telling diagnostic for the presence of spatially correlated quark pairs within the nucleon
Axial nucleon form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Constantinou, M.; Guichon, P.; Jansen, K.; Korzec, T.
2011-01-01
We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.
Probing nuclear structure with nucleons; Sonder la structure nucleaire avec des nucleons
Energy Technology Data Exchange (ETDEWEB)
Bauge, E. [CEA Bruyeres-le-Chatel, Service de Physique Nucl aire, 91 (France)
2007-07-01
The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)
The nucleon-nucleon spin-orbit interaction in the Skyrme model
International Nuclear Information System (INIS)
Riska, D.O.; Dannbom, K.
1987-01-01
The spin-orbit and quadratic spin-orbit components of the nucleon-nucleon interaction are derived in the Skyrme model at the classical level. These interaction components arise from the orbital and rotational motion of the soliton fields that form the nucleons. The isospin dependent part of the spin-orbit interaction is similar to the corresponding component obtained from boson exchange mechanisms at long distances although at short distances it is weaker. The isospin independent spin-orbit component is however different from the prediction of boson exchange mechanisms and has the opposite sign. The quadratic spin-orbit interaction is weak and has only an isospin dependent component
The Glauber approach in perturbative QCD: nucleon case
International Nuclear Information System (INIS)
Ayala Filho, A.L.; Pelotas Univ., RS; Ducaty, M.B. Gay; Levin, E.M.; Petersburg Nuclear Physics Inst.,
1997-01-01
We investigate the shadowing corrections for the nucleon gluon distribution predicted from Glauber (Mueller) approach in perturbative QCD. This work is a digest for the nucleon case of the extended work prior presented by the authors
Nucleon Form Factors Using Spin Degrees of Freedom
International Nuclear Information System (INIS)
Jones, Mark
2002-01-01
An overview of recent measurements of the neutron and proton electromagnetic form factors from double polarization experiments. Spin observables are sensitive to the product of nucleon form factor which allows access to the small nucleon electric form factors
Electron scattering from nucleons and deuterons at intermediate energies
International Nuclear Information System (INIS)
Burkert, V.
1985-04-01
Recent results from electron scattering of nucleons and deuterons are discussed. A tentative physics program for ELSA employing the polarized electron beams as well as the polarized nucleon and deuteron target facilities is outlined. (orig.)
Three-body approach to the nucleon-nucleus optical potential
International Nuclear Information System (INIS)
Tandy, P.C.; Redish, E.F.; Bolle, D.
1976-01-01
In the Watson single scattering theory of the optical potential it is customary to approximate the propagation by two-body Green functions in order to simplify calculations. The reaction mechanism being described, however, is decidedly three-body in character. The central difficulty in building three-body models for nucleon-nucleus elastic scattering is to find the proper way of imbedding the superposed three-body reaction mechanism in the many-body problem without introducing serious overcounting effects. One would also like an explicit description of the intermediate state processes responsible for absorption. In this paper a three-body approximation to the optical potential theory is presented which overcomes the overcounting problem and is capable of including the following effects: (1) the proper kinematics of the struck nucleon, (2) its binding potential, (3) the identity of target nucleons, and (4) realistic wave functions and spectroscopic factors. The three-body model for the optical potential can be extended using unitarity methods to yield a unified three-body-like model of elastic scattering, pickup, and single nucleon knockout. (Auth.)
Calculations of electromagnetic nucleon form factors and electroexcitation amplitudes of isobars
International Nuclear Information System (INIS)
Warns, M.; Schroeder, H.; Pfeil, W.; Rollnik, H.
1989-03-01
In this paper, we present numerical results for electroproduction amplitudes of proton resonances and electromagnetic nucleon form factors calculated in a relativized quark model. Interactions with both transversely and longitudinally polarized virtual photons were considered. Contributions of the different effects included in our approach have been analysed through a sample comparison with the available data. We also discuss the validity of the usual single-quark transition ansatz and possible parametrizations of the potential acting between the constituent quarks of the baryon. Impressive agreement is obtained with the nucleon form factor data up to squared momentum transfers of 2.5 GeV 2 , but still some problems remain with the Δ(1232) and higher resonances. (orig.)
Modeling a nucleon system: static and dynamical properties - density fluctuations
International Nuclear Information System (INIS)
Idier, D.
1997-01-01
This thesis sets forth a quasi-particle model for the static and dynamical properties of nuclear matter. This model is based on a scale ratio of quasi-particle to nucleons and the projection of the semi-classical distribution on a coherent Gaussian state basis. The first chapter is dealing with the transport equations, particularly with the Vlasov equation for Wigner distribution function. The second one is devoted to the statics of nuclear matter. Here, the sampling effect upon the nuclear density is treated and the state equation of the Gaussian fluid is compared with that given by Hartree-Fock approximation. We define state equation as the relationship between the nucleon binding energy and density, for a given temperature. The curvature around the state equation minimum of the quasi-particle system is shown to be related to the speed of propagation of density perturbation. The volume energy and the surface properties of a (semi-)infinite nucleon system are derived. For the resultant saturated auto-coherent semi-infinite system of quasi-particles the surface coefficient appearing in the mass formula is extracted as well as the system density profile. The third chapter treats the dynamics of the two-particle residual interactions. The effect of different parameters on relaxation of a nucleon system without a mean field is studied by means of a Eulerian and Lagrangian modeling. The fourth chapter treats the volume instabilities (spinodal decomposition) in nuclear matter. The quasi-particle systems, initially prepared in the spinodal region of the utilized interaction, are set to evolve. It is shown then that the scale ratio acts upon the amount of fluctuations injected in the system. The inhomogeneity degree and a proper time are defined and the role of collisions in the spinodal decomposition as well as that of the initial temperature and density, are investigated. Assuming different effective macroscopic interactions, the influence of quantities as
First results of the cosmic ray NUCLEON experiment
Energy Technology Data Exchange (ETDEWEB)
Atkin, E.; Shumikhin, V. [National Research Nuclear University ' MEPhI' , Kashirskoe highway 31, Moscow, 115409 (Russian Federation); Bulatov, V., E-mail: evatkin@mephi.ru, E-mail: shuma.v.v@mail.ru, E-mail: bulat@horizont.e-burg.ru [SDB Automatika, Mamin-Sibiryak str. 145, Ekaterinburg, 620075 (Russian Federation); and others
2017-07-01
The NUCLEON experiment was designed to study the chemical composition and energy spectra of galactic cosmic ray nuclei from protons to zinc at energies of ∼ 10{sup 11}–10{sup 15} eV per particle. The research was carried out with the NUCLEON scientific equipment installed on the Russian satellite 'Resource-P' No. 2 as an additional payload. This article presents the results for the measured nuclei spectra related to the first approximately 250 days of the scientific data collection during 2015 and 2016. The all-particle spectrum and the spectra of p, He, C, O, Ne, Mg, Si and Fe are presented. Some interesting ratios of the spectra are also presented and discussed. The experiment is now in its beginning stage and the data still have a preliminary character, but they already give numerous indications of the existence of various non-canonical phenomena in the physics of cosmic rays, which are expressed in the violation of a simple universal power law of the energy spectra. These features of the data are briefly discussed.
The nucleon spin and momentum decomposition using lattice QCD simulations
International Nuclear Information System (INIS)
Alexandrou, C.; Cyprus Univ., Nicosia; Constantinou, M.; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G.; Jansen, K.; Wiese, K.; Vaquero Aviles-Casco, A.
2017-11-01
We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is J u+d+s =0.408(61) stat. (48) syst. and the gluon contribution is J g =0.133(11) stat. (14) syst. giving a total of J N =0.54(6) stat. (5) syst. consistent with the spin sum. For the quark intrinsic spin contribution we obtain (1)/(2)ΔΣ u+d+s =0.201(17) stat. (5) syst. All quantities are given in the MS scheme at 2 GeV. The quark and gluon momentum fractions are also computed and add up to left angle x right angle u+d+s + left angle x right angle g =0.804(121) stat. (95) syst. +0.267(12) stat. (10) syst. =1.07(12) stat. (10) syst. satisfying the momentum sum.
Two-nucleon bound states in quenched lattice QCD
International Nuclear Information System (INIS)
Yamazaki, T.; Kuramashi, Y.; Ukawa, A.
2011-01-01
We address the issue of bound state in the two-nucleon system in lattice QCD. Our study is made in the quenched approximation at the lattice spacing of a=0.128 fm with a heavy quark mass corresponding to m π =0.8 GeV. To distinguish a bound state from an attractive scattering state, we investigate the volume dependence of the energy difference between the ground state and the free two-nucleon state by changing the spatial extent of the lattice from 3.1 fm to 12.3 fm. A finite energy difference left in the infinite spatial volume limit leads us to the conclusion that the measured ground states for not only spin triplet but also singlet channels are bounded. Furthermore the existence of the bound state is confirmed by investigating the properties of the energy for the first excited state obtained by a 2x2 diagonalization method. The scattering lengths for both channels are evaluated by applying the finite volume formula derived by Luescher to the energy of the first excited states.
The nucleon spin and momentum decomposition using lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Constantinou, M. [Temple Univ., Philadelphia, PA (United States). Dept. of Physics; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Jansen, K.; Wiese, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Vaquero Aviles-Casco, A. [Utah Univ., Salt Lake City, UT (United States). Dept. of Physics and Astronomy
2017-11-15
We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is J{sub u+d+s}=0.408(61){sub stat.}(48){sub syst.} and the gluon contribution is J{sub g}=0.133(11){sub stat.}(14){sub syst.} giving a total of J{sub N}=0.54(6){sub stat.}(5){sub syst.} consistent with the spin sum. For the quark intrinsic spin contribution we obtain (1)/(2)ΔΣ{sub u+d+s}=0.201(17){sub stat.}(5){sub syst.} All quantities are given in the MS scheme at 2 GeV. The quark and gluon momentum fractions are also computed and add up to left angle x right angle {sub u+d+s}+ left angle x right angle {sub g}=0.804(121){sub stat.}(95){sub syst.}+0.267(12){sub stat.}(10){sub syst.}=1.07(12) {sub stat.}(10){sub syst.} satisfying the momentum sum.
First results of the cosmic ray NUCLEON experiment
International Nuclear Information System (INIS)
Atkin, E.; Shumikhin, V.; Bulatov, V.
2017-01-01
The NUCLEON experiment was designed to study the chemical composition and energy spectra of galactic cosmic ray nuclei from protons to zinc at energies of ∼ 10 11 –10 15 eV per particle. The research was carried out with the NUCLEON scientific equipment installed on the Russian satellite 'Resource-P' No. 2 as an additional payload. This article presents the results for the measured nuclei spectra related to the first approximately 250 days of the scientific data collection during 2015 and 2016. The all-particle spectrum and the spectra of p, He, C, O, Ne, Mg, Si and Fe are presented. Some interesting ratios of the spectra are also presented and discussed. The experiment is now in its beginning stage and the data still have a preliminary character, but they already give numerous indications of the existence of various non-canonical phenomena in the physics of cosmic rays, which are expressed in the violation of a simple universal power law of the energy spectra. These features of the data are briefly discussed.
Roy-Steiner equations for pion-nucleon scattering
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.
2012-06-01
Starting from hyperbolic dispersion relations, we derive a closed system of Roy-Steiner equations for pion-nucleon scattering that respects analyticity, unitarity, and crossing symmetry. We work out analytically all kernel functions and unitarity relations required for the lowest partial waves. In order to suppress the dependence on the high energy regime we also consider once- and twice-subtracted versions of the equations, where we identify the subtraction constants with subthreshold parameters. Assuming Mandelstam analyticity we determine the maximal range of validity of these equations. As a first step towards the solution of the full system we cast the equations for the π π to overline N N partial waves into the form of a Muskhelishvili-Omnès problem with finite matching point, which we solve numerically in the single-channel approximation. We investigate in detail the role of individual contributions to our solutions and discuss some consequences for the spectral functions of the nucleon electromagnetic form factors.
The interaction of LAMBDA and nucleon in the LAMBDA hypernuclei
International Nuclear Information System (INIS)
Jin Xingnan
1988-01-01
The interaction of lambda particle and nucleon is discussed from phenomenological point of view. The effective interactions between the lambda particle and the nucleon in the hypernuclei are also presented in this paper. The structure effect of the hypernuclei will make influence to the effective interaction between the lambda particle and the nucleon in the hypernucei. The spin-orbital coupling of lambda particle in the lambda hypernucleus is much smaller than the spin-orbital coupling of nucleon in nucleus
The adiabatic approximation in multichannel scattering
International Nuclear Information System (INIS)
Schulte, A.M.
1978-01-01
Using two-dimensional models, an attempt has been made to get an impression of the conditions of validity of the adiabatic approximation. For a nucleon bound to a rotating nucleus the Coriolis coupling is neglected and the relation between this nuclear Coriolis coupling and the classical Coriolis force has been examined. The approximation for particle scattering from an axially symmetric rotating nucleus based on a short duration of the collision, has been combined with an approximation based on the limitation of angular momentum transfer between particle and nucleus. Numerical calculations demonstrate the validity of the new combined method. The concept of time duration for quantum mechanical collisions has also been studied, as has the collective description of permanently deformed nuclei. (C.F.)
Boson-exchange nucleon-nucleon potential and nuclear structure
International Nuclear Information System (INIS)
Grange, Pierre.
1976-01-01
A fully momentum-dependent one-boson-exchange potential is derived which takes into account the mesons, π, eta, sigma, rho, ω and phi. Scattering bound states and nuclear matter properties are studied in momentum space. The use of such potential is shown to be as easy as the use of more simple phenomenological interactions. In nuclear matter the formalism of Bethe-Goldstone is chosen to compute the binding energy versus density in the approximation of two-body and three-body correlations. The three-body correlated wave function obtained is then used [fr
Chiral symmetry and nucleon structure: Low energy aspects
International Nuclear Information System (INIS)
Weise, W.
1989-01-01
The symmetries and currents of QCD at low energy and long wavelength are realized in the form of mesons, rather than quarks and gluons. In this talk I summarize the merits, but also the limits, of chiral non-linear meson theories and their soliton solutions, in descriptions of nucleon structure and the nucleon-nucleon interaction. (orig.)
Three-nucleon scattering by using chiral perturbation theory potential
International Nuclear Information System (INIS)
Kamata, Hiroyuki
2003-01-01
Three-nucleon scattering problems are studied by using two-nucleon and three-nucleon potentials derived from chiral perturbation theory. The three-nucleon term is shown to appear in the effective potential of the rank of next-to-next-to-leading order (NNLO). New three-nucleon forces are taken into consideration in addition to the conventional Fujita-Miyazawa (FM) type three-nucleon potential. Two-nucleon potential of the chiral perturbation theory is as precise as the conventional ones in low energy region. The FM type three-nucleon force which explains Sagara discrepancy in high energy region is introduced automatically. Concerning the Ay puzzle, the results seems to behave as if the puzzle has been solved at the level of NLO, but at the NNLO (without three-nucleon force) level the result is similar to the cases of conventional potential indicating the need of three-nucleon force. In contrast to the FM type three-nucleon force, five free parameters exist in the new D and E type three-nucleon forces introduced by the NNLO, but they are reduced to two independent parameters by antisymmetrization, which are found to be sensitive to the coupling energy of tritons and to the nd scattering length (spin doublet state). Parameters determined from them cannot give satisfactory answer to the A y puzzle. It seems, however, too hasty to conclude that A y puzzle cannot be solved by the chiral perturbation theory. (S. Funahashi)
Microscopic nuclear structure with sub-nucleonic degrees of freedom
International Nuclear Information System (INIS)
Sauer, P.U.
1986-01-01
The paper reviews microscopic theories of nuclear structure. The subject is discussed under the topic headings: microscopic nuclear structure with nucleons only; microscopic nuclear structure with nucleons, isobars and mesons; and microscopic nuclear structure with nucleons, mesons and dibaryons. (U.K.)
Comparative study of various methods of primary energy estimation in nucleon-nucleon interactions
International Nuclear Information System (INIS)
Goyal, D.P.; Yugindro Singh, K.; Singh, S.
1986-01-01
The various available methods for the estimation of primary energy in nucleon-nucleon interactions have been examined by using the experimental data on angular distributions of shower particles from p-N interactions at two accelerator energies, 67 and 400 GeV. Three different groups of shower particle multiplicities have been considered for interactions at both energies. It is found that the different methods give quite different estimates of primary energy. Moreover, each method is found to give different values of energy according to the choice of multiplicity groups. It is concluded that the E ch method is relatively the better method among all the methods available, and that within this method, the consideration of the group of small multiplicities gives a much better result. The method also yields plausible estimates of inelasticity in high energy nucleon-nucleon interactions. (orig.)
The charge form factor of three-nucleon systems and the polarization of the bound nucleon
International Nuclear Information System (INIS)
Giannini, M.M.; Drechsel, D.; Arenhoevel, H.; Tornow, V.
1979-01-01
The discrepancy between theoretical calculations of the 3 He charge density and the results derived from elastic electron scattering may be due to the analysis of the experimental data in terms of spherical nucleons. A classical model with deformed nucleons gives qualitive agreement with experiment for an oblate quadrupole moment of -1.8 mb. Such a deformation of the bound nucleon can be described by the admixture of Δ(1232) and higher isobar components with spin >= 3/2. Since the admixture probabilities are small the dominant contributions stem from the transition quadrupole moments between free nucleon and isobar components. Taking into account the leading Δ(1232) components one can explain about half of the discrepancy. As this transition operator is isovector, the effects are opposite for 3 He and 3 H. (orig.)
Lepton-nucleon scattering at high energies
International Nuclear Information System (INIS)
Buchmueller, W.
1993-12-01
Recent theoretical developments in the field of inelastic lepton-nucleon scattering are reviewed with emphasis on physics at HERA. Structure functions at small Bjorken-x are discussed in detail. Further topics are photoproduction of jets, the gluon densities in proton and photon, charm physics, electroweak processes and the search for new particles and interactions. (orig.)
Spin structure of the nucleon and polarization
International Nuclear Information System (INIS)
Prescott, C.Y.
1994-09-01
Recent experiments at CERN and SLAC have added new knowledge about the spin structure of the proton and the deuteron. A brief historical background is presented, the status of experiments is discussed, and progress in the understanding of the spin of the nucleon in the context of the quark parton model is summarized
Scattering of vector mesons off nucleons
International Nuclear Information System (INIS)
Lutz, M.F.M.; Friman, B.; Wolf, G.
2001-12-01
We construct a relativistic and unitary approach to 'high' energy pion- and photon-nucleon reactions taking the πN, πΔ, ρN, ωN, ηN, K Λ, KΣ final states into account. Our scheme dynamically generates the s- and d-wave nucleon resonances N(1535), N(1650) and N(1520) and isobar resonances Δ(1620) and δ(1700) in terms of quasi-local interaction vertices. The description of photon-induced processes is based on a generalized vector-meson dominance assumption which directly relates the electromagnetic quasi-local 4-point interaction vertices to the corresponding vertices involving the ρ and ω fields. We obtain a satisfactory description of the elastic and inelastic pion- and photon-nucleon scattering data in the channels considered. The resulting s-wave ρ- and ω-nucleon scattering amplitudes are presented. Using these amplitudes we compute the leading density modification of the ρ and ω mass distributions in nuclear matter. We find a repulsive mass shift for the ω meson at small nuclear density but predict considerable strength in resonance-hole like ω-meson modes. Compared to previous calculations our result for the ρ-meson spectral function shows a significantly smaller in-medium effect. This reflects a not too large coupling strength of the N(1520) resonance to the ρN channel. (orig.)
Nuclear data requirements for fusion reactor nucleonics
International Nuclear Information System (INIS)
Bhat, M.R.; Abdou, M.A.
1980-01-01
Nuclear data requirements for fusion reactor nucleonics are reviewed and the present status of data are assessed. The discussion is divided into broad categories dealing with data for Fusion Materials Irradiation Test Facility (FMIT), D-T Fusion Reactors, Alternate Fuel Cycles and the Evaluated Data Files that are available or would be available in the near future
Nucleonic guages in Philippine industry: current applications
International Nuclear Information System (INIS)
Pedregosa, R.V.; Cayabo, L.B.; Leopando, L.L.
1996-01-01
Nucleonic gauges have been used in Philippine industries for more than thirty years. There are now close to 500 units being used to determine and/or control level, density, concentration, weight and other parameters. Gauges are found in the food, cement, mineral processing, steel, paper, cigarette, plastic and construction industries. (author)
Simple parametrization of nucleon form factors
International Nuclear Information System (INIS)
Kelly, J.J.
2004-01-01
This Brief Report provides simple parametrizations of the nucleon electromagnetic form factors using functions of Q 2 that are consistent with dimensional scaling at high Q 2 . Good fits require only four parameters each for G Ep , G Mp , and G Mn and only two for G En
Charge-symmetry-breaking nucleon form factors
International Nuclear Information System (INIS)
Kubis, Bastian
2011-01-01
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon’s strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for 4 He.
Nucleons II: cryopreservation and metabolic activity.
Reyes, R; Flores-Alonso, J C; Rodríguez-Hernández, H M; Merchant-Larios, H M; Delgado, N M
2001-01-01
The establishment of intracytoplasmatic sperm injection (ICSI) as a routine procedure in assisted fertilization has been used in the treatment of male infertility. The major technical problem that has arisen with the use of immotile sperm for ICSI has been differentiating between live and dead cells. Nucleons from human, pig, hamster, mouse, rat, and bull have been able to induce their chromatin decondensation by the action of heparin/GSH. Cryopreservation is deleterious to sperm function, killing more than 50% of the spermatozoa during the process. Nucleon cryostorage was performed at 5 and -5 degrees C and analyzed for total area (mu2), perimeter (mu), width (mu), and length (mu), using Metamorph Imaging System software. On the other hand, fluorescein diacetate (FDA) is hydrolyzed by intracellular estereases to produce fluorescein, which exhibits green fluorescence when excited by blue light. This fact is a striking result since the presence of this metabolic activity opens the possibility to select the nucleons for ICSI. In the present study, the authors decided to search for a suitable metabolic test, which might reflect the metabolism and viability of these chromatin structures. This is a simple cryostorage technique that after months of cryopreservation, allow the use of nucleons for ICSI with suitable fertilization and pregnancies rates.
Photonuclear studies in the few nucleon system
International Nuclear Information System (INIS)
Weiss, M.S.
1975-02-01
A brief review of photonuclear reactions in few nucleon systems is presented with comparison of theory with experiment. Discrepancies are examined and recent and current research aimed at resolving these problems are discussed. Emphasis is placed on two and three body photodisintegration. (33 figures) (U.S.)
Intermediate energy nucleon-deuteron scattering theory.
Wilson, J. W.
1973-01-01
Sloan's conclusion (1969) that terms of the multiple-scattering series beyond single scattering contribute only to S- and P-wave amplitudes in an S-wave separable model is examined. A comparison of experiments with the calculation at 146 MeV shows that the conclusion is valid in nucleon-deuteron scattering applications.
Pion photoproduction in nucleons at low energies
International Nuclear Information System (INIS)
Carvalho, F.A.B.R. de.
1983-01-01
A new semiphenomenological analysis of the multipoles for pion photoproduction from nucleons, in the region of the first π-N resonance is presented. Through an energy dependent model, multipoles with isospin 1/2 and 3/2 and total angular momentum J [pt
Nucleon Spin Structure: Longitudinal and Transverse
International Nuclear Information System (INIS)
Chen, Jian-Ping
2011-01-01
Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.
Calculation of nucleon electromagnetic form factors
International Nuclear Information System (INIS)
Renner, D.B.; Brower, R.; Dolgov, D.; Eicker, N.; Lippert, Th.; Negele, J.W.; Pochinsky, A.; Schilling, K.
2003-01-01
The formalism is developed to express nucleon matrix elements of the electromagnetic current in terms of form factors consistent with the translational, rotational, and parity symmetries of a cubic lattice. We calculate the number of these form factors and show how appropriate linear combinations approach the continuum limit
Aoki, Sinya
2013-07-01
We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for nucleon-nucleon potentials.
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
International Nuclear Information System (INIS)
Ono, A.; Horiuchi, H.
1996-01-01
Statistical properties of antisymmetrized molecular dynamics (AMD) are classical in the case of nucleon-emission processes, while they are quantum mechanical for the processes without nucleon emission. In order to understand this situation, we first clarify that there coexist mutually opposite two statistics in the AMD framework: One is the classical statistics of the motion of wave packet centroids and the other is the quantum statistics of the motion of wave packets which is described by the AMD wave function. We prove the classical statistics of wave packet centroids by using the framework of the microcanonical ensemble of the nuclear system with a realistic effective two-nucleon interaction. We show that the relation between the classical statistics of wave packet centroids and the quantum statistics of wave packets can be obtained by taking into account the effects of the wave packet spread. This relation clarifies how the quantum statistics of wave packets emerges from the classical statistics of wave packet centroids. It is emphasized that the temperature of the classical statistics of wave packet centroids is different from the temperature of the quantum statistics of wave packets. We then explain that the statistical properties of AMD for nucleon-emission processes are classical because nucleon-emission processes in AMD are described by the motion of wave packet centroids. We further show that when we improve the description of the nucleon-emission process so as to take into account the momentum fluctuation due to the wave packet spread, the AMD statistical properties for nucleon-emission processes change drastically into quantum statistics. Our study of nucleon-emission processes can be conversely regarded as giving another kind of proof of the fact that the statistics of wave packets is quantum mechanical while that of wave packet centroids is classical. copyright 1996 The American Physical Society
Effect of two-pion exchange in nucleon-nucleon scattering in high partial waves
International Nuclear Information System (INIS)
Harun ar Rashid, A.M.; Chaudhury, T.K.
1983-01-01
The work of Brown and Durso (Phys. Lett. 35B, 120 (1971)) on the soft-pion determination of the intermediate range nucleon-nucleon interaction is extended by using the most general form of the ΔNπ interaction which involves an arbitrary parameter Z. It is shown that both the annihilation channel helicity amplitude fsub(+)sup((O))(t) as well as peripheral proton-proton scattering phase shifts seem to favour Z=1/2. (author)
Pion-nucleon vertex function with an off-shell nucleon
International Nuclear Information System (INIS)
Nutt, W.T.; Shakin, C.M.
1977-01-01
A model calculation for the π-N vertex function is presented in the case in which there is a single off-mass-shell nucleon and a (nearly) on-mass-shell pion. Very strong effects due to the P 11 resonance at 1470 MeV are found. A simple parametrization of the vertex function is prvided in the case that at least one nucleon is on its mass shell. (Auth.)
International Nuclear Information System (INIS)
Schwarz, K.; Froehlich, J.; Zingl, H.F.K.
1980-01-01
The Bethe-Salpeter equation is solved in closed form with the help of a four dimensional separable 'potential'. For possible applications to three-nucleon investigations the authors have fitted all nucleon-nucleon S-wave phase shifts in a sufficient way by this method; in addition they also present an example for a P-wave. (Auth.)
Soliton bag model of the nucleon and delta dressed by a quark-antiquark pion
International Nuclear Information System (INIS)
Dethier, J.L.L.
1985-01-01
The Friedberg-Lee soliton bag model is used to describe the nucleon, delta and pion. The author builds upon the mean-field solutions to the model taking into account the one-gluon-exchange interaction by the use of a free gluon propagator in the Coulomb gauge and allowing the nucleon or delta to consist of a bare three quark bag and a three quark bag dressed by one quark-antiquark pion. This way of treating the pion cloud differs from most other works on the subject by the fact that he takes the quark substructure of the pion into account. The generator coordinate method enables him to find an approximate solution to the ground state of the nucleon and the delta from which static physical properties can be calculated. The soliton field part of the ground state is treated in a coherent state approximation (similar to the mean-field approximation, but remaining a true quantum state). The generator coordinate or Hill-Wheeler integral equations are solved numerically with the help of the Tikhonov regularization. Detailed numerical results are given for different sets of parameters. The agreement with experiment is as good as in the mean-field approximation but new quantities are now accessible to computation (e.g., the neutron charge radius and the NN[ and NΔπ coupling constants
The nucleon-nucleon interaction from a realistic pseudoscalar-vector chiral lagrangian
International Nuclear Information System (INIS)
Kaiser, N.; Meissner, U.G.; Massachusetts Inst. of Tech., Cambridge
1990-01-01
We investigate the static nucleon-nucleon potential in the framework of a non-linear chiral meson theory. The model includes pions as well as the vector mesons ρ and ω. All parameters are fixed in the meson sector and predictions about the nucleon-nucleon interaction follow without adjusting any parameters. We use an S-matrix approach to calculate correlated two-pion exchange between two solitons. The most prominent feature of this two-pion exchange is that it leads very natural to attraction in the scalar-isoscalar channel. We also discuss the effect of πp correlations on the central potential, and present the spectral function related to the correlated two-pion exchange. Furthermore, we study the form factors of the nucleon sources related to the two-pion exchange and find that they are of dipole type with typical cutoff scales Λ D ≅ 700 MeV. We also discuss the destructive interference of π- and ρ-exchange in the isovector tensor potential. Altogether, we present a unified treatment of meson exchange phenomenology based on a serious model of the nucleon. Finally, we point out the limitations of the model and discuss some further applications. (orig.)
Search for basic properties of the nucleon-nucleon interaction
International Nuclear Information System (INIS)
Gersten, A.
1981-01-01
Extraction of N-N amplitudes directly from phase-shift analysis is described and the results are compared to those obtained via potential or pseudopotential models at low and intermediate energies and through Regge trajectory exchanges and diffraction models at high energies. While potential models fit the experimental data up to about 400 MeV lab energy, the information obtained directly by phase-shift analysis of N-N amplitudes is obtained from experiments in the 400-800 MeV range. At higher energies the real part of the amplitudes becomes better approximated by the first Born term. In this way one can get an insight into the meson exchange structure of the N-N amplitudes. (O.T.)
The current status of nucleonic gauge activity in China
International Nuclear Information System (INIS)
Liye Zhou
2000-01-01
The nucleonic gauge technology in China is in full development. The nucleonic gauges are widely used, mainly in metallurgy, coal, cement and rubber industries. The simple first generation of nucleonic gauge is locally designed and manufactured in industrial scale by many institutions and enterprises. The local market is large and far from being saturated. The quality and reliability of nucleonic gauges and their integration into the control system are still concern. Research and development is going on to improve the quality and to design and produce second generation of multibeam and multienergy nucleonic gauges. (author)
Four-nucleon system with Δ-isobar excitation
International Nuclear Information System (INIS)
Deltuva, A.; Fonseca, A.C.; Sauer, P.U.
2008-01-01
The four-nucleon bound state and scattering below three-body breakup threshold are described based on the realistic coupled-channel potential CD Bonn+Δ which allows the excitation of a single nucleon to a Δ isobar. The Coulomb repulsion between protons is included. In the four-nucleon system the two-baryon coupled-channel potential yields effective two-, three- and four-nucleon forces, mediated by the Δ isobar and consistent with each other and with the underlying two-nucleon force. The effect of the four-nucleon force on the studied observables is much smaller than the effect of the three-nucleon force. The inclusion of the Δ isobar is unable to resolve the existing discrepancies with the experimental data
Muoproduction of J/ψ and the gluon distribution of the nucleon
International Nuclear Information System (INIS)
Ashman, J.; Combley, F.; Salmon, D.; Wheeler, S.; Bee, C.P.; Brown, S.C.; Court, G.; Francis, D.; Gabathuler, E.; Gamet, R.; Hayman, P.; Holt, J.R.; Jones, T.; Matthews, M.; Wimpenny, S.J.; Coignet, G.; Toth, J.; Urban, L.; Drees, J.; Edwards, A.W.; Hamacher, K.; Korzen, B.; Kruener, U.; Moenig, K.; Pavel, N.; Peschel, H.; Nassalski, J.; Sandacz, A.; Windmolders, R.; Ernst, T.; Landgraf, U.; Schroeder, T.; Stier, H.E.; Stock, J.; Wallucks, W.
1992-01-01
Measurements are presented of the inclusive distributions of the J/ψ meson produced by muons of energy 200 GeV from an ammonia target. The gluon distribution of the nucleon has been derived from the data in the range 0.04< x<0.36 using a technique based on the colour singlet model. An arbitrary normalisation factor is required to obtain a reasonable integral of the gluon distribution. Some comments are made on the use of J/ψ production by virtual photons to extract the gluon distribution at HERA. (orig.)
New QCD sum rules for nucleon axial-vector coupling constants
International Nuclear Information System (INIS)
Lee, F.X.; Leinweber, D.B.; Jin, X.
1997-01-01
Two new sets of QCD sum rules for the nucleon axial-vector coupling constants are derived using the external-field technique and generalized interpolating fields. An in-depth study of the predicative ability of these sum rules is carried out using a Monte Carlo based uncertainty analysis. The results show that the standard implementation of the QCD sum rule method has only marginal predicative power for the nucleon axial-vector coupling constants, as the relative errors are large. The errors range from approximately 50% to 100% compared to the nucleon mass obtained from the same method, which has only a 10%- 25% error. The origin of the large errors is examined. Previous analyses of these coupling constants are based on sum rules that have poor operator product expansion convergence and large continuum contributions. Preferred sum rules are identified and their predictions are obtained. We also investigate the new sum rules with an alternative treatment of the problematic transitions which are not exponentially suppressed in the standard treatment. The alternative treatment provides exponential suppression of their contributions relative to the ground state. Implications for other nucleon current matrix elements are also discussed. copyright 1997 The American Physical Society
Ambiguities in the description of nucleon transfer in deep inelastic scattering
International Nuclear Information System (INIS)
Dworzecka, M.; Zielinska-Pfabe, M.; Griffin, J.J.
1986-01-01
Here the authors discuss certain ambiguities which are in the description of (N,Z) evolution in heavy ion collisions by means of nucleon exchange models. Such descriptions have been formulated either in terms of Markovian Master (MM) equations (or its approximate version in the form of Fokker-Planck equation) in terms of transition rates per unit time, or in terms of Random Walk (RW) on the energy surface in terms of transition probabilities per nucleon exchanged. In a series of papers they have shown that the RW is the useful tool in studying probability distributions of particle numbers (protons and neutrons) as a function of energy loss. The authors purpose was to compare the implications of different (often competing) physical mechanisms for specific features of the (N-Z) distribution. One result of that analysis was that not all of the kinetic energy loss could be attributed to the nucleon transfer process assumed; rather, an additional step had to be allowed in the random walk in which no nucleon is transferred, but kinetic energy is lost nonetheless. Only then could the total width, σ/sub A/ 2 , of the (N-Z) distribution (as a function of energy loss) be made to conform with the experimental data. Conversely requiring this conformance yielded a specific value of the average relative probability for this additional non-transfer step
International Nuclear Information System (INIS)
Signell, P.
1981-01-01
This project has involved five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the πN and ππ physical regions of the N anti N → ππ amplitude (with signifantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 meV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 1-1200 MeV range that can be used by all nucleon-nucleon researchers
A pion and gluon exchange model of the non-annihilation part of the nucleon-antinucleon interaction
International Nuclear Information System (INIS)
Fernandez, F.
1988-01-01
The effect of quark antisymmetrization on the one-pion and one-gluon exchange between nucleons and antinucleons is explicitly calculated within the framework of the Born-Oppenheimer approximation. We found an effective short range part of the N-anti N interaction which is repulsive in all the spin-isospin channels. (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
1993-04-01
until exhausted. SECURITY CLASSIFICATION OF THIS PAGE All other editions are obsolete. UNCLASSIFIED " VIRTUAL REALITY JAMES F. DAILEY, LIEUTENANT COLONEL...US" This paper reviews the exciting field of virtual reality . The author describes the basic concepts of virtual reality and finds that its numerous...potential benefits to society could revolutionize everyday life. The various components that make up a virtual reality system are described in detail
From nucleons to quarks in nuclei
International Nuclear Information System (INIS)
Laget, J.M.
1984-07-01
Nuclear Physics has now evolved from the study of the many nucleon problem, to the study of the interplay of the degrees of freedom of such a complex system and the internal degrees of freedom of each of its hadronic constituents. Extensive studies of electronuclear reactions have allowed us to disentangle the basic mechanisms of the interaction between two baryons in a nucleus. The pion exchange mechanism, which dominates at large distance has been singled out. The NΔ interaction, which enter the description of the intermediate range part, has been studied. Evidences for effects due to the quark structure of the nucleon have been found. They involve the short distance structure of the nucleus
Low-energy pion-nucleon scattering
International Nuclear Information System (INIS)
Gibbs, W.R.; Ai, L.; Kaufmann, W.B.
1998-01-01
An analysis of low-energy charged pion-nucleon data from recent π ± p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f 2 =0.0756±0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P 31 and P 13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided. copyright 1998 The American Physical Society
Lectures on the soliton theory of nucleons
International Nuclear Information System (INIS)
Ripka, G.
1984-04-01
In these lectures we describe models in which the pion field or, more precisely, the chiral fields, are responsible for the binding of quarks in the nucleon. Such bound states in which the quarks constitute a source for the chiral fields, which, in turn, bind the quarks to each other, are called solitons. The starting point for such theories or models are chiral invariant lagrangians. They are not derived from QCD. The Skyrme lagrangian is simpler in that it involves only chiral fields and no quarks. However it may be understood as an effective lagrangian from which the quark degrees of freedom have been integrated out. It is not yet clear to what extent various models are equivalent. The description of the nucleon in these lectures may be viewed as an extension of the T.D. Lee solitons so as to include the pionic degree of freedom
DEFF Research Database (Denmark)
Davis, Hilary; Skov, Mikael B.; Stougaard, Malthe
2007-01-01
. This paper reports on the design, implementation and initial evaluation of Virtual Box. Virtual Box attempts to create a physical and engaging context in order to support reciprocal interactions with expressive content. An implemented version of Virtual Box is evaluated in a location-aware environment...
Personal history of nucleon polarization experiments
International Nuclear Information System (INIS)
Chamberlain, O.
1984-09-01
The history of nucleon scattering experiments is reviewed, starting with the observation of large proton polarizations in scattering from light elements such as carbon, and ending with the acceleration of polarized proton beams in high-energy synchrotrons. Special mention is made about significant contributions made by C.L. Oxley, L. Wolfenstein, R.D. Tripp, T. Ypsilantis, A. Abragam, M. Borghini, T. Niinikoski, Froissart, Stora, A.D. Krisch, and L.G. Ratner
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
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
Electromagnetic interactions with nuclei and nucleons
International Nuclear Information System (INIS)
Thornton, S.T.; Sealock, R.M.
1990-01-01
This report discusses the following topics: general LEGS work; photodisintegration of the deuteron; progress towards other experiments; LEGS instrumentation; major LEGS software projects; NaI detector system; nucleon detector system; waveshifting fibers; EGN prototype detector for CEBAF; photon beam facility at CEBAF; delta electroproduction in nuclei; quasielastic scattering and excitation of the Delta by 4 He(e,e'); and quasielastic scattering at high Q 2
Nucleon-deuteron low energy parameters
International Nuclear Information System (INIS)
Zankel, H.; Mathelitsch, L.
1983-01-01
Momentum space Fadeev equations are solved for nucleon-deuteron scattering and effective range parameters are calculated. A reverse trend is found in the two spin states by 4 asub(nd) 4 asub(pd) and 2 asub(pd) 2 asub(nd) which is in agreement with a configuration space calculation, but in conflict with all existing experiments. The Coulomb contributions to the effective range are small in quartet but sizeable in doublet scattering. (Author)
Nucleon electromagnetic form factors with Wilson fermions
International Nuclear Information System (INIS)
Goeckeler, M.; Haegler, P.; Horsley, R.
2007-10-01
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Nucleon electromagnetic form factors with Wilson fermions
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-10-15
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Parity violation in two-nucleon systems
Energy Technology Data Exchange (ETDEWEB)
Liu, C.-P., E-mail: cpliu@mail.ndhu.edu.tw [National Dong Hwa University, Department of Physics (China)
2013-03-15
Nuclear few-body systems become attractive avenues for the study of low-energy parity violation because experiments start to meet the precision requirements and theoretical calculations can be performed reliably. In this talk, an attempt of parametrizing low-energy parity-violating observables by the Danilov parameters will be introduced. Analyses of two-nucleon observables, based on the modern phenomenological potentials or the one of effective field theory, will be discussed.
Use of a finite range nucleon-nucleon interaction in the continuum shell model
International Nuclear Information System (INIS)
Faes, Jean-Baptiste
2007-01-01
The unification of nuclear structure and nuclear reactions was always a great challenge of nuclear physics. The extreme complexity of finite quantum systems lead in the past to a separate development of the nuclear structure and the nuclear reactions. A unified description of structure and reactions is possible within the continuum shell model. All previous applications of this model used the zero-range residual interaction and the finite depth local potential to generate the single-particle basis. In the thesis, we have presented an extension of the continuum shell model for finite-range nucleon-nucleon interaction and an arbitrary number of nucleons in the scattering continuum. The great advantage of the present formulation is the same two-body interaction used both to generate the single-particle basis and to describe couplings to the continuum states. This formulation opens a possibility for an ab initio continuum shell model studies with the same nucleon-nucleon interaction generating the nuclear mean field, the configuration mixing and the coupling to the scattering continuum. First realistic applications of the above model has been shown for spectra of "1"7F and "1"7O, and elastic phase-shifts in the reaction "1"6O(p, p)"1"6O. (author)
Few-Nucleon Research at TUNL: Probing Two- and Three-Nucleon Interactions with Neutrons
Howell, C. R.; Tornow, W.; Witała, H.
2016-03-01
The central goal of few-nucleon research at the Triangle Universities Nuclear Laboratory (TUNL) is to perform measurements that contribute to advancing ab-initio calculations of nuclear structure and reactions. The program aims include evaluating theoretical treatments of few-nucleon reaction dynamics through strategically comparing theory predictions to data, determining properties of the neutron-neutron interaction that are not accessible in two-nucleon reactions, and searching for evidence of longrange features of three-nucleon interactions, e.g., spin and isospin dependence. This paper will review studies of three- and four-nucleon systems at TUNL conducted using unpolarized and polarized neutron beams. Measurements of neutron-induced reactions performed by groups at TUNL over the last six years are described in comparison with theory predictions. The results are discussed in the context of the program goals stated above. Measurements of vector analyzing powers for elastic scattering in A=3 and A=4 systems, differential cross sections for neutron-deuteron elastic scattering and neutrondeuteron breakup in several final-state configurations are described. The findings from these studies and plans for the coming three years are presented in the context of worldwide activities in this front, in particular, research presented in this session.
Few-Nucleon Research at TUNL: Probing Two- and Three-Nucleon Interactions with Neutrons
Directory of Open Access Journals (Sweden)
Howell C.R.
2016-01-01
Full Text Available The central goal of few-nucleon research at the Triangle Universities Nuclear Laboratory (TUNL is to perform measurements that contribute to advancing ab-initio calculations of nuclear structure and reactions. The program aims include evaluating theoretical treatments of few-nucleon reaction dynamics through strategically comparing theory predictions to data, determining properties of the neutron-neutron interaction that are not accessible in two-nucleon reactions, and searching for evidence of longrange features of three-nucleon interactions, e.g., spin and isospin dependence. This paper will review studies of three- and four-nucleon systems at TUNL conducted using unpolarized and polarized neutron beams. Measurements of neutron-induced reactions performed by groups at TUNL over the last six years are described in comparison with theory predictions. The results are discussed in the context of the program goals stated above. Measurements of vector analyzing powers for elastic scattering in A=3 and A=4 systems, differential cross sections for neutron-deuteron elastic scattering and neutrondeuteron breakup in several final-state configurations are described. The findings from these studies and plans for the coming three years are presented in the context of worldwide activities in this front, in particular, research presented in this session.
Constructional requirements and classification of nucleonic gauges
Energy Technology Data Exchange (ETDEWEB)
Gomes, J.D.R.L.; Costa, M.L.L.; Gomes, R.S.; Costa, E.L.C.; Caldas, G.H.F., E-mail: rogeriog@cnen.gov.br, E-mail: jlopes@cnen.gov.br, E-mail: mara@cnen.gov.br, E-mail: evaldo@cnen.gov.br, E-mail: gcaldas@cnen.gov.br [Comissão Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). Diretoria de Radioproteção e Segurança Nuclear; Thomé, Z.D., E-mail: zielithome@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Seção de Engenharia Nuclear
2017-07-01
There are several hundred of nucleonic gauges installed in at least 500 industrial facilities in Brazil. In recent years, several standards have been issued by different international committees in order to specify requirements for the design of nucleonic gauges taking into account issues related to radiological protection. The aspects of design and manufacturing of these devices using radioactive sources should be treated as an important feature to an adequate safety approach during the whole operational life, mainly taking into account the extreme conditions of the places where the devices are installed. Thus, the agreement with these standards should be included as part of the equipment specification to the licensing process, however, most nucleonic gauges were installed in the period prior to the issuance of these international standards. In this work was studied the performance of shielding design taking into account international standards concerning the constructional requirements and classification of gauges. In view of the specific operational conditions found at reference facilities, the measurements obtained will be used for validation of a Monte Carlo code based on GEANT4 to allow extrapolations for other operational conditions. The results obtained in this study can enable the establishment of a safety indicator tool to industrial facilities, taking into account different designs, so that this additional parameter can be used to determine and to optimize the frequency of regulatory inspections. (author)
Constructional requirements and classification of nucleonic gauges
International Nuclear Information System (INIS)
Gomes, J.D.R.L.; Costa, M.L.L.; Gomes, R.S.; Costa, E.L.C.; Caldas, G.H.F.; Thomé, Z.D.
2017-01-01
There are several hundred of nucleonic gauges installed in at least 500 industrial facilities in Brazil. In recent years, several standards have been issued by different international committees in order to specify requirements for the design of nucleonic gauges taking into account issues related to radiological protection. The aspects of design and manufacturing of these devices using radioactive sources should be treated as an important feature to an adequate safety approach during the whole operational life, mainly taking into account the extreme conditions of the places where the devices are installed. Thus, the agreement with these standards should be included as part of the equipment specification to the licensing process, however, most nucleonic gauges were installed in the period prior to the issuance of these international standards. In this work was studied the performance of shielding design taking into account international standards concerning the constructional requirements and classification of gauges. In view of the specific operational conditions found at reference facilities, the measurements obtained will be used for validation of a Monte Carlo code based on GEANT4 to allow extrapolations for other operational conditions. The results obtained in this study can enable the establishment of a safety indicator tool to industrial facilities, taking into account different designs, so that this additional parameter can be used to determine and to optimize the frequency of regulatory inspections. (author)
International Nuclear Information System (INIS)
Tornow, W.; Witala, H.; Kievsky, A.
1998-01-01
The 4 P J waves in nucleon-deuteron scattering were analyzed using proton-deuteron and neutron-deuteron data at E N =3 MeV. New sets of nucleon-nucleon 3 P j phase shifts were obtained that may lead to a better understanding of the long-standing A y (θ) puzzle in nucleon-deuteron elastic scattering. However, these sets of 3 P j phase shifts are quite different from the ones determined from both global phase-shift analyses of nucleon-nucleon data and nucleon-nucleon potential models. copyright 1998 The American Physical Society
Wen, Heming; Le-Ngoc, Tho
2013-01-01
This SpringerBriefs is an overview of the emerging field of wireless access and mobile network virtualization. It provides a clear and relevant picture of the current virtualization trends in wireless technologies by summarizing and comparing different architectures, techniques and technologies applicable to a future virtualized wireless network infrastructure. The readers are exposed to a short walkthrough of the future Internet initiative and network virtualization technologies in order to understand the potential role of wireless virtualization in the broader context of next-generation ubiq
Virtual marketing in virtual enterprises
Ale Ebrahim, Nader; Fattahi, Hamaid Ali; Golnam, Arash
2008-01-01
Virtualization caused tremendous evolution in the economics of marketing channels, patterns of physical distribution and the structure of distributors and developed a new concept that is known as virtual marketing (VM). VM combines the powerful technologies of interactive marketing and virtual reality. Virtual enterprise (VE) refers to an organization not having a clear physical locus. In other words, VE is an organization distributed geographically and whose work is coordinated through e...
International Nuclear Information System (INIS)
Han Yinlu; Shen Qingbiao; Zhuo Yizhong
1994-01-01
The relativistic microscopic optical potential, the Schroedinger equivalent potential, and mean free paths of a nucleon at finite temperature in nuclear matter and finite nuclei are studied based on Walecka's model and thermo-field dynamics. We let only the Hartree-Fock self-energy of a nucleon represent the real part of the microscopic optical potential and the fourth order of meson exchange diagrams, i.e. the polarization diagrams represent the imaginary part of the microscopic optical potential in nuclear matter. The microscopic optical potential of finite nuclei is obtained by means of the local density approximation. (orig.)
Skyrme-model πNN form factor and nucleon-nucleon interaction
International Nuclear Information System (INIS)
Holzwarth, G.; Machleidt, R.
1997-01-01
We apply the strong πNN form factor, which emerges from the Skyrme model, in the two-nucleon system using a one-boson-exchange (OBE) model for the nucleon-nucleon (NN) interaction. Deuteron properties and phase parameters of NN scattering are reproduced well. In contrast to the form factor of monopole shape that is traditionally used in OBE models, the Skyrme form factor leaves low-momentum transfers essentially unaffected while it suppresses the high-momentum region strongly. It turns out that this behavior is very appropriate for models of the NN interaction and makes it possible to use a soft pion form factor in the NN system. As a consequence, the πN and the NN systems can be described using the same πNN form factor, which is impossible with the monopole. copyright 1997 The American Physical Society
Three-nucleon force contribution in the distorted-wave theory of (d ,p ) reactions
Timofeyuk, N. K.
2018-05-01
The distorted-wave theory of A (d ,p )B reactions, widely used to analyze experimental data, is based on a Hamiltonian that includes only two-nucleon interactions. However, numerous studies of few-nucleon systems and many modern developments in nuclear structure theory show the importance of the three-nucleon (3 N ) force. The purpose of this paper is to study the contribution of the 3 N force of the simplest possible form to the A (d ,p )B reaction amplitude. This contribution is given by a new term that accounts for the interaction of the neutron and proton in the incoming deuteron with one of the target nucleons. This term involves a new type of nuclear matrix elements containing an infinite number of target excitations in addition to the main part associated with the traditional overlap function between A and B . The nuclear matrix elements are calculated for double-closed shell targets within a mean field theory where target excitations are shown to be equivalent to exchanges between valence and core nucleons. These matrix elements can be readily incorporated into available reaction codes if the 3 N interaction has a spin-independent zero-range form. Distorted-wave calculations are presented for a contact 3 N force with the volume integral fixed by the chiral effective field theory at the next-to-next-to-leading order. For this particular choice, the 3 N contribution is noticeable, especially at high deuteron incident energies. No 3 N effects are seen for incident energies below the Coulomb barrier. The finite range can significantly affect the 3 N contribution to the (d ,p ) cross sections. Finite-range studies require new formal developments and, therefore, their contribution is preliminarily assessed within the plane-wave Born approximation, together with sensitivity to the choice of the deuteron model.
Two-nucleon emitters within a pseudostate method: The case of 6Be and 16Be
Casal, J.
2018-03-01
Background: Since the first experimental observation, two-nucleon radioactivity has gained renewed attention since the early 2000s. The 6Be system is the lightest two-proton ground-state emitter, while 16Be was recently proposed to be the first two-neutron ground-state emitter ever observed. A proper understanding of their properties and decay modes requires a reasonable description of the three-body continuum. Purpose: Study the ground-state properties of 6Be and 16Be within a general three-body model and investigate their nucleon-nucleon correlations in the continuum. Method: The pseudostate (PS) method in hyperspherical coordinates, using the analytical transformed harmonic oscillator (THO) basis for three-body systems, is used to construct the 6Be and 16Be ground-state wave functions. These resonances are approximated as a stable PS around the known two-nucleon separation energy. Effective core-N potentials, constrained by the available experimental information on the binary subsystems 5Li and 15Be, are employed in the calculations. Results: The ground state of 16Be is found to present a strong dineutron configuration, with the valence neutrons occupying mostly an l =2 state relative to the core. The results are consistent with previous R -matrix calculations for the actual continuum. The case of 6Be shows a clear symmetry with respect to its mirror partner, the two-neutron halo 6He: The diproton configuration is dominant, and the valence protons occupy an l =1 orbit. Conclusions: The PS method is found to be a suitable tool in describing the properties of unbound core+N +N ground states. For both 16Be and 6Be, the results are consistent with previous theoretical studies and confirm the dominant dinucleon configuration. This favors the picture of a correlated two-nucleon emission.
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.
A Bayesian analysis of the nucleon QCD sum rules
International Nuclear Information System (INIS)
Ohtani, Keisuke; Gubler, Philipp; Oka, Makoto
2011-01-01
QCD sum rules of the nucleon channel are reanalyzed, using the maximum-entropy method (MEM). This new approach, based on the Bayesian probability theory, does not restrict the spectral function to the usual ''pole + continuum'' form, allowing a more flexible investigation of the nucleon spectral function. Making use of this flexibility, we are able to investigate the spectral functions of various interpolating fields, finding that the nucleon ground state mainly couples to an operator containing a scalar diquark. Moreover, we formulate the Gaussian sum rule for the nucleon channel and find that it is more suitable for the MEM analysis to extract the nucleon pole in the region of its experimental value, while the Borel sum rule does not contain enough information to clearly separate the nucleon pole from the continuum. (orig.)
K-nucleon scattering and the cloudy bag model
International Nuclear Information System (INIS)
Jennings, B.K.
1986-01-01
The cloudy bag model (CBM) has been applied with considerable success to low energy meson-nucleon scattering. In this talk I will describe in particular calculations for kaon-nucleon and antikaon-nucleon scattering. The main emphasis will be on s-waves with special attention paid to the antikaon-nucleon system in the isospin zero channel where the Λ(1405) is important. In the CBM the Λ(1405) is an antikaon-nucleon bound state and I show that this interpretation is consistent with the antikaon-nucleon scattering in the region of the Λ(1670) and Λ(1800) although ambiguities in the phase shift analysis prevent a definite conclusion
K-nucleon scattering and the cloudy bag model
Jennings, B. K.
1986-10-01
The cloudy bag model (CBM) has been applied with considerable success to low energy meson-nucleon scattering. In this talk I will describe in particular calculations for kaon-nucleon and antikaon-nucleon scattering. The main emphasis will be on s-waves with special attention paid to the antikaon-nucleon system in the isospin zero channel where the Λ(1405) is important. In the CBM the Λ(1405) is an antikaon-nucleon bound state and I show that this interpretation is consistent with the antikaon-nucleon scattering in the region of the Λ(1670) and Λ(1800) although ambiguities in the phase shift analysis prevent a definite conclusion.
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
Spin symmetry in the Dirac sea derived from the bare nucleon-nucleon interaction
Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan
2018-06-01
The spin symmetry in the Dirac sea has been investigated with relativistic Brueckner-Hartree-Fock theory using the bare nucleon-nucleon interaction. Taking the nucleus 16O as an example and comparing the theoretical results with the data, the definition of the single-particle potential in the Dirac sea is studied in detail. It is found that if the single-particle states in the Dirac sea are treated as occupied states, the ground state properties are in better agreement with experimental data. Moreover, in this case, the spin symmetry in the Dirac sea is better conserved and it is more consistent with the findings using phenomenological relativistic density functionals.
NN → NN π: the new frontier in nucleon-nucleon interactions
International Nuclear Information System (INIS)
Silbar, R.R.
1986-01-01
The torch in nucleon-nucleon scattering has been passed to experimental and theoretical studies of pion production. Comparing two unitary models shows that most of the structures predicted for spin observables in NN → NNπ are model independent and roughly in agreement with the data. The contribution of rho- exchange is small, indicating the reaction is largely ''peripheral''. The energy dependence of these isobar models is smooth. The largely unstudied reactions producing neutral and negatively-charged pions show richer structure than positively-charged pion production. 6 refs
QCD sum rule for nucleon in nuclear matter
International Nuclear Information System (INIS)
Mallik, S.; Sarkar, Sourav
2010-01-01
We consider the two-point function of nucleon current in nuclear matter and write a QCD sum rule to analyse the residue of the nucleon pole as a function of nuclear density. The nucleon self-energy needed for the sum rule is taken as input from calculations using phenomenological N N potential. Our result shows a decrease in the residue with increasing nuclear density, as is known to be the case with similar quantities. (orig.)
Comments on electromagnetic form factors of the nucleon
International Nuclear Information System (INIS)
Sachs, R.G.; Wali, K.C.
1989-01-01
This paper draws the concept of nucleon form factors further to consider the electromagnetic aspect based on the magnetic moment of the nucleon. These are seen as valid physical interpretations of form factors in electron-nucleon interactions. A linear combination of two functions, associated with charge radius, is derived, which agreed well with experimental results. The paper also expands the specific form to include relativistic cases and consider appropriate frames of reference. (UK)
Portable nucleonics instrument design: The PortaCAT example
International Nuclear Information System (INIS)
Wallace, G.; Pohl, P.; Hutchinson, E.
2000-01-01
Portable nucleonic gauges prototypes are designed and manufactured in New Zealand for niche applications. Considerable development in hardware and software provide new opportunity in design of relatively low cost portable nucleonic gauges. In this paper are illustrated principles, and specific factors to be consider when designing portable nucleonic instrumentation, using an example called PortaCAT, which is a portable computed tomography scanner designed for imaging wooden power poles. (author)
Conflicting coupling of unpaired nucleons in odd-odd nuclei
International Nuclear Information System (INIS)
Volkov, D.A.; Levon, A.I.
1990-01-01
Phenomenological approach is described, using it, energy spectra of odd-odd nucleus collective bands based on conflicting state of unpaired nucleons can be calculated. It is ascertained that in a conflicting bond unpaired nucleon acts as a spectator, i.e. energy spectra of collective bands in odd-odd nuclei are similar to the spectra of collective bands in heighbouring odd nuclei, which are based on the state of a strongly bound nucleon is included in the conflicting configuration
Three-nucleon problem with phase equivalent potentials
International Nuclear Information System (INIS)
Pushkash, O.M.; Shapoval, D.V.; Simenog, I.V.
1991-01-01
The effect of the t-matrix off-shell variations with nonlocal phase equivalent N-N potentials on the three-nucleon parameters is studied. The variations, which lower or increase the tritium binding energy, are revealed. We show that under certain conditions, the three-nucleon low-energy observables are almost insensitive to the high energy behaviour of the negative parts of the scattering phase shifts. The inverse problem method is applied to reconstruct simple S-wave potentials which to provide a unified description of the two-nucleon and low-energy three-nucleon data. 22 refs.; 6 figs. (author)
Equidistant structure and effective nucleon mass in nuclear matter
International Nuclear Information System (INIS)
Tezuka, Hirokazu.
1981-11-01
The effective nucleon mass of the Equidistant Multi-Layer Structure (EMULS) is discussed self-consistently. In the density region where the Fermi gas state in nuclear matter is unstable against the density fluctuation, the EMULS gives lower binding energy. It is, however, shown that such a structure with an ordinary nucleon mass collapses due to too strong attraction. We point out that such a collapse can be avoided by taking account of an effective nucleon mass affected by the localization of nucleons. (author)
Forward pion-nucleon charge exchange reaction and Regge constraints
International Nuclear Information System (INIS)
Huang Fei; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meibner, U.-G.
2009-01-01
We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude. (authors)
A survey of the alpha-nucleon interaction
International Nuclear Information System (INIS)
Ali, S.; Ahmad, A.A.Z.; Ferdous, N.
1984-10-01
A survey of the alpha-nucleon interaction is made. The experimental work on angular distributions of differential scattering cross-sections and polarizations in proton-alpha and neutron-alpha scattering is described. The phenomenological approach which includes the study of both local and non-local potentials reproducing the experimental alpha-nucleon scattering data, is discussed. Basic studies of the alpha-nucleon interaction attempting to build an interaction between an alpha particle and a nucleon from first principles are then described. A critical discussion of the results with some concluding remarks suggesting the direction for further investigation is made. (author)
Hyperon-nucleon interaction in the quark cluster model
International Nuclear Information System (INIS)
Straub, U.; Zhang Zongye; Braeuer, K.; Faessler, A.; Khadkikar, S.B.; Luebeck, G.
1988-01-01
The lambda-nucleon and sigma-nucleon interaction is described in the nonrelativistic quark cluster model. The SU(3) flavor symmetry breaking due to the different quark masses is taken into account, i.e. different wavefunctions for the light (up, down) and heavy (strange) quarks are used in flavor and orbital space. The six-quark wavefunction is fully antisymmetrized. The model hamiltonian contains gluon exchange, pseudoscalar meson exchange and a phenomenological σ-meson exchange. The six-quark scattering problem is solved within the resonating group method. The experimental lambda-nucleon and sigma-nucleon cross sections are well reproduced. (orig.)
Comparison of approximate methods for multiple scattering in high-energy collisions. II
International Nuclear Information System (INIS)
Nolan, A.M.; Tobocman, W.; Werby, M.F.
1976-01-01
The scattering in one dimension of a particle by a target of N like particles in a bound state has been studied. The exact result for the transmission probability has been compared with the predictions of the Glauber theory, the Watson optical potential model, and the adiabatic (or fixed scatterer) approximation. The approximate methods optical potential model is second best. The Watson method is found to work better when the kinematics suggested by Foldy and Walecka are used rather than that suggested by Watson, that is to say, when the two-body of the nucleon-nucleon reduced mass
Directory of Open Access Journals (Sweden)
Shimizu Y.
2010-04-01
Full Text Available Measurements of a complete set of deuteron analyzing powers (iT11, T20, T21, T22 for elastic deuteron–proton scattering at 250 MeV/nucleon have been performed with polarized deuteron beams at RIKEN RI Beam Factory. The obtained data are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson-Melbourne’99, and UrbanaIX three nucleon forces.
DEFF Research Database (Denmark)
Jensen, Sisse Siggaard
2006-01-01
-systems, the paper introduces the designing strategy referred to as virtual exploratories. Some of the advanced virtual worlds may inspire the design of such provoking and challenging virtual exploratories, and especially the Massively Multi-User Online Role-Playing Games (MMORPGS). However, if we have to learn from...... the design and activity of the advanced virtual worlds and role-playing games, then the empirical research on the actors’ activity, while they are acting, is an important precondition to it. A step towards the conception of such a designing strategy for virtual exploratories is currently pursued....... [1] The research project: Actors and Avatars Communicating in Virtual Worlds – an Empirical Analysis of Actors’ Sense-making Strategies When Based on a Communication Theoretical Approach’ (2006-2007) is supported...
Energy-dependent microscopic optical potential for scattering of nucleons on light nuclei
Energy Technology Data Exchange (ETDEWEB)
Farag, M.Y.H.; Esmael, E.H. [Cairo University, Physics Department, Faculty of Science, Giza (Egypt); Maridi, H.M. [Cairo University, Physics Department, Faculty of Science, Giza (Egypt); Taiz University, Physics Department, Faculty of Applied Science, Taiz (Yemen)
2014-06-15
We present an energy-dependent microscopic optical model potential for elastic scattering of nucleons on light nuclei. The single-folding model is used for the real part of the optical potential (OP), while the imaginary part is derived within the high-energy approximation theory. The energy dependence of the OP is determined from the parameterization of the volume integrals those calculated from the best-fit OP that fit the experimental data of the cross sections and analyzing powers. This energy-dependent OP is successfully applied to analyze the proton elastic scattering of {sup 4,6,i8}He, {sup 6,7}Li, and {sup 9,10}Be nuclei at low and intermediate incident energies up to 200MeV/nucleon. (orig.)
Systematics of intermediate-energy single-nucleon removal cross sections
Tostevin, J. A.; Gade, A.
2014-11-01
There is now a large and increasing body of experimental data and theoretical analyses for reactions that remove a single nucleon from an intermediate-energy beam of neutron- or proton-rich nuclei. In each such measurement, one obtains the inclusive cross section for the population of all bound final states of the mass A -1 reaction residue. These data, from different regions of the nuclear chart, and that involve weakly and strongly bound nucleons, are compared with theoretical expectations. These calculations include an approximate treatment of the reaction dynamics and shell-model descriptions of the projectile initial state, the bound final states of the residues, and the single-particle strengths computed from their overlap functions. The results are discussed in the light of recent data, more exclusive tests of the eikonal dynamical description, and calculations that take input from more microscopic nuclear structure models.
Relativistic one-boson-exchange model for the nucleon-nucleon interaction
International Nuclear Information System (INIS)
Gross, F.; Van Orden, J.W.; Holinde, K.
1992-01-01
Nucleon-nucleon data below 300-MeV laboratory energy are described by a manifestly covariant wave equation in which one of the intermediate nucleons is restricted to its mass shell. Antisymmetrization of the kernel yields an equation in which the two nucleons are treated in an exactly symmetric manner, and in which all amplitudes satisfy the Pauli principle exactly. The kernel is modeled by the sum of one boson exchanges, and four models, all of which fit the data very well (χ 2 congruent 3 per data point) are discussed. Two models require the exchange of only the π, σ, ρ, and ω, but also require an admixture of γ 5 coupling for the pion, while two other models restrict the pion coupling to pure γ 5 γ μ , but require the exchange of six mesons, including the η, and a light scalar-isovector meson referred to as σ 1 . Deuteron wave functions resulting from these models are obtained. The singularities and relativistic effects which are a part of this approach are discussed, and a complete development of the theory is presented
Phase variation of nucleon-nucleon amplitude for proton-12C elastic scattering
International Nuclear Information System (INIS)
Deng Yibing; Wang Shilai; Yin Gaofang
2006-01-01
Franco and Yin studied for α- 4 He, 3 He, 2 He, 1 He elastic-scattering by using the phase of the nucleon-nucleon elastic-scattering amplitude varies with momentum transfer in the framework of Glauber multiple scattering theory at intermediate energy. The phase variation leads to large changes in the differential cross sections, and brings the Glauber theory into agreement with experimental data. Later Lombard and Maillet is based on the suggestion by Franco and Yin studied for the p- 4 He elastic-scattering in the framework of Glauber theory, and found this phase to be actually important for the description of spin observables. Recently Wang Shilai and Deng Yibing et al studied for the p- 4 He elastic-scattering in the framework of KMT multiple scattering theory at intermediate energy, and found this phase lead to differential cross sections and polarization, which are in better agreement with experimental data. This paper is based on the suggestion by Franco and Yin that the phase of the nucleon-nucleon scattering amplitude should vary with momentum transfer. The proton elastic scattering on 12 C is studied in the KMT multiple scattering theory with microscopic momentum space first term optical potential. The Coulomb interactions are taken into account in our calculation. The theoretical calculation results show that the phase leads to differential cross section and polarization are in better agreement with experimental data. In conclusion this phase is actually important in the framework of KMT theory. (authors)
Jonker, Catholijn; Broekens, Joost; Plaat, Aske
2014-01-01
Virtual Reality is used successfully to treat people for regular phobias. A new challenge is to develop Virtual Reality Exposure Training for social skills. Virtual actors in such systems have to show appropriate social behavior including emotions, gaze, and keeping distance. The behavior must be realistic and real-time. Current approaches consist of four steps: 1) trainee social signal detection, 2) cognitive-affective interpretation, 3) determination of the appropriate bodily responses, and...
Silva, A. Christian; Prange, Richard E.
2007-03-01
We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation strategy.
Three-Body Antikaon-Nucleon Systems
Czech Academy of Sciences Publication Activity Database
Shevchenko, Nina V.
2017-01-01
Roč. 58, č. 1 (2017), č. článku UNSP 6. ISSN 0177-7963 R&D Projects: GA ČR(CZ) GA15-04301S Institutional support: RVO:61389005 Keywords : three-body * antikaon-nucleon * K p interactions Subject RIV: BE - Theoretical Physics OBOR OECD: Atom ic, molecular and chemical physics (physics of atom s and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 0.877, year: 2016
Electron scattering and few nucleon systems
International Nuclear Information System (INIS)
Frois, B.
1983-08-01
Recent result obtained by electron scattering in the few-nucleon systems (A 3 He charge and magnetic form factors are discussed. New theoretical results indicate that three body forces improve considerably the saturation properties of 3 He, 4 He and nuclear matter, but are not able to reconcile experiment and theory for the charge form factors of 3 He and 4 He. Calculations of meson exchange effects with different theoretical approaches bring the theory into reasonable agreement with the experimental charge and magnetic form factor fo 3 He. Recent results of the measurements of the two and three body break-up of 3 He are discussed
Perspectives of lepton-nucleon scattering
International Nuclear Information System (INIS)
Eisele, F.
1987-01-01
Present day lepton-nucleon scattering experiments will find a continuation at the HERA e-p collider in the near future. HERA experiments will be complementary and in concurrence to other colliders (e/sup +/e/sup -/, p-barp) which will work in a similar energy range at a similar time. HERA has a rewarding unique program of ''standard'' physics. If new physics should show up in the new energy domain, HERA will be an excellent machine to help reveiling its structure. Depending on luck and time scale, HERA offers also the chance of original discoveries in fields where it is unique
Experimental study of the nucleon spin structure
Energy Technology Data Exchange (ETDEWEB)
Litmaath, M.F.
1996-05-07
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.).
Experimental study of the nucleon spin structure
International Nuclear Information System (INIS)
Litmaath, M.F.
1996-01-01
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.)
Nucleon structure and properties of dense matter
International Nuclear Information System (INIS)
Kutschera, M.; Pethick, C.J.; Illinois Univ., Urbana, IL
1988-01-01
We consider the properties of dense matter in a framework of the Skyrme soliton model and the chiral bag model. The influence of the nucleon structure on the equation of state of dense matter is emphasized. We find that in both models the energy per unit volume is proportional to n 4/3 , n being the baryon number density. We discuss the properties of neutron stars with a derived equation of state. The role of many-body effects is investigated. The effect of including higher order terms in the chiral lagrangian is examined. The phase transition to quark matter is studied. 29 refs., 6 figs. (author)
Relativistic origin of three-nucleon force
International Nuclear Information System (INIS)
Haberzettl, H.; Parke, W.C.
1995-01-01
Based on the manifestly covariant cluster-dynamical formalism recently proposed by Haberzettl, the three-body forces entering three-nucleon equations are discussed. It is shown that there exist additional contributions to the (nonrelativistic) three-body force, not taken into account in the usual treatments, arising from the proper nonrelativistic limits of higher-order meson-exchange Feynman diagrams. Using the Paris potential, a five-channel triton bound-state calculation results in additional binding of about 0.6 MeV due to this new mechanism. copyright 1995 American Institute of Physics
International Nuclear Information System (INIS)
Tornow, T.; Tornow, W.
1999-01-01
It Is shown that the 3 P j neutron-proton (proton-proton) phase shifts cannot be determined to less than ± 100 % (± 20 %) uncertainty at low energies (∼ 10 MeV), even if high-accuracy nucleon-nucleon data were to become available for currently inaccessible observables. For a more accurate determination, appropriate theoretical constraints have to be invoked, but their accuracy can be judged only from the comparison of rigorous three-nucleon continuum calculations with particular three-nucleon observables. (author)
International Nuclear Information System (INIS)
Ginsburg, C.A.
1980-01-01
In many problems, a desired property A of a function f(x) is determined by the behaviour of f(x) approximately equal to g(x,A) as x→xsup(*). In this letter, a method for resuming the power series in x of f(x) and approximating A (modulated Pade approximant) is presented. This new approximant is an extension of a resumation method for f(x) in terms of rational functions. (author)
International Nuclear Information System (INIS)
Rogalla, P.; Meiri, N.; Hamm, B.; Rueckert, J.C.; Schmidt, B.; Witt, C.
2001-01-01
Flexible bronchoscopy represents a clinically well-established invasive diagnostic tool. Virtual bronchoscopies, calculated from thin-slice CT sections, allow astonishing immitations of reality although principal differences exist between both technologies: the Fact that colour representation is artificial and concommitant interventions are impossible limits the clinical use of virtual bronchoscopy. However, its value increases when calculations can be attained within minutes due to technological advancements, and when virtually any chest CT is suitable for further postprocessing. Indications, findings and the clinical role of virtual bronchoscopy are discussed. (orig.) [de
DEFF Research Database (Denmark)
Svejvig, Per; Commisso, Trine Hald
2012-01-01
that the best practice knowledge has not permeated sufficiently to the practice. Furthermore, the appropriate application of information and communication technology (ICT) remains a big challenge, and finally project managers are not sufficiently trained in organizing and conducting virtual projects....... The overall implications for research and practice are to acknowledge virtual project management as very different to traditional project management and to address this difference.......Virtual projects are common with global competition, market development, and not least the financial crisis forcing organizations to reduce their costs drastically. Organizations therefore have to place high importance on ways to carry out virtual projects and consider appropriate practices...
Sparse approximation with bases
2015-01-01
This book systematically presents recent fundamental results on greedy approximation with respect to bases. Motivated by numerous applications, the last decade has seen great successes in studying nonlinear sparse approximation. Recent findings have established that greedy-type algorithms are suitable methods of nonlinear approximation in both sparse approximation with respect to bases and sparse approximation with respect to redundant systems. These insights, combined with some previous fundamental results, form the basis for constructing the theory of greedy approximation. Taking into account the theoretical and practical demand for this kind of theory, the book systematically elaborates a theoretical framework for greedy approximation and its applications. The book addresses the needs of researchers working in numerical mathematics, harmonic analysis, and functional analysis. It quickly takes the reader from classical results to the latest frontier, but is written at the level of a graduate course and do...
Nucleon resonance production in electromagnetic interactions
International Nuclear Information System (INIS)
Mukhtarov, A.I.; Sadykhov, F.S.; Vasil'ev, O.A.; Abdullaev, S.K.; Mustafaev, V.Z.
1977-01-01
The results of investigation into nucleon resonance production (NR) in the ep → eNsup(*)(eNsup(*)γ) and eantie → antipNsup(*)(antipNsup(*)γ) processes, where Nsup(*) is a nucleon resonance of the 3/2 or 5/2 spin are presented. The calculation of the NR structure functions with the mass M and 3/2 or 5/2 spin is carried out. The Δ(1236), N(1688) and Δ(2160) NR production was observed in the ep → eNsup(*) and eantie → antipNsup(*) processes. For the ep-interaction the energy dependence of the NR production differential cross section at the electron scattering angle THETA = 6 dea and the angular dependence of the longitudinal polarization degree of the scattered electrons at the electron energy of 6 GeV are presented. The energy dependence of the total cross section of the NR production for eantie → antipNsup(*) is obtained. The ep → eNsup(*)γ radiative electron scattering on a proton is investigated only in case of the Δ(1236)NR production. The dependence of the effective cross section of the Δ(1236) radiative production process on THETA for the energies of an incident and scattered electron of 6 and 2.5 GeV, respectively, and the dependence of the cross section on the scattered electron energy at the initial energy of 6 GeV and THETA = 15 deg are presented
The spin structure of the nucleon
International Nuclear Information System (INIS)
Le Goff, J.M.
2005-02-01
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*ΔΣ + Δg + L q + L g where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and L q and L g are the orbital momentum of the quark and the gluon respectively. The ΔΣ contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization Δg/g and the so-called transversity. (A.C.)
Hypernuclei and hyperon-nucleon interactions
International Nuclear Information System (INIS)
Yamamoto, Yasuo
1994-01-01
The properties of baryon many-body systems which contain nucleons and hyperons with strangeness link closely to the underlying hyperon(Y)-nucleon(N) and YY interactions. It is very convenient to derive effective interactions in nuclear media from those in free space. The G-matrix gives a good starting point for such approach. It is possible and important to explore the properties of YN and YY interactions, and test their theoretical models by analyzing hypernuclear phenomena. In this work, the G-matrix interaction of the baryon pair in a nuclear matter was derived. The coupling effect between different baryon channels is renormalized into the G-matrix. The density dependence of the resultant G-matrix originates from the repulsive core singularity, the tensor force and also the coupling between different baryon channels. For the application to various hypernuclear problems, it is convenient to construct effective local potentials which simulate the G-matrices. Those are parameterized in a three-range Gaussian form. The parameters are determined so as to simulate the calculated G-matrices. The effective interactions are called YNG-ND, NF, NS, JA and JB. The data on ΛN, ΣN, ΛΛ and ΣN interactions are given. (K.I.)
Toward a consistent random phase approximation based on the relativistic Hartree approximation
International Nuclear Information System (INIS)
Price, C.E.; Rost, E.; Shepard, J.R.; McNeil, J.A.
1992-01-01
We examine the random phase approximation (RPA) based on a relativistic Hartree approximation description for nuclear ground states. This model includes contributions from the negative energy sea at the one-loop level. We emphasize consistency between the treatment of the ground state and the RPA. This consistency is important in the description of low-lying collective levels but less important for the longitudinal (e,e') quasielastic response. We also study the effect of imposing a three-momentum cutoff on negative energy sea contributions. A cutoff of twice the nucleon mass improves agreement with observed spin-orbit splittings in nuclei compared to the standard infinite cutoff results, an effect traceable to the fact that imposing the cutoff reduces m * /m. Consistency is much more important than the cutoff in the description of low-lying collective levels. The cutoff model also provides excellent agreement with quasielastic (e,e') data
Interacting boson model with surface delta interaction between nucleons
International Nuclear Information System (INIS)
Druce, C.; Moszkowski, S.A.
1984-01-01
The surface delta interaction is used as an effective nucleon-nucleon interaction to investigate the structure and interaction of the bosons in the interacting boson model. The authors have obtained analytical expressions for the coefficients of a multipole expansion of the neutron-boson proton-boson interaction for the case of degenerate orbits
Nucleon self-energy in the relativistic Brueckner theory
Energy Technology Data Exchange (ETDEWEB)
Waindzoch, T; Fuchs, C; Faessler, A [Inst. fuer Theoretische Physik, Univ. Tuebingen (Germany)
1998-06-01
The self-energy of the nucleon in nuclear matter is calculated in the relativistic Brueckner theory. We solve the Thompson equation for the two nucleon scattering in the medium using different Bonn potentials. The self-energy has a rather strong momentum dependence while the equation of state compares well with previous calculations. (orig.)
Contribution of nucleonic degrees of freedom to the EMC effect
International Nuclear Information System (INIS)
Anisovich, V.V.; Sarantsev, A.V.; Starodubskii, V.E.
1987-01-01
The dispersion-integration method has been used to calculate the contribution of nucleonic degrees of freedom to the EMC effect. The structure of the amplitude of deep inelastic scattering is discussed for a nucleus with spin one half. The question of the functional form of the structure function of a nucleon off the mass shell is discussed
Examination of the strangeness contribution to the nucleon magnetic moment
Chen, XS; Timmermans, RGE; Sun, WM; Zong, HS; Wang, F
We examine the nucleon strangeness magnetic moment mu(s) with a lowest order meson cloud model. We observe that (1) strangeness in the nucleon is a natural requirement of the empirical relation mu(p)/mu(n)similar or equal to-3/2, which favors an SU(3) octet meson cloud instead of merely the SU(2)
Three-nucleon forces and the trinucleon bound states
International Nuclear Information System (INIS)
Friar, J.L.; Frois, B.
1986-04-01
A summary of the bound-state working group session of the ''International Symposium on the Three-Body Force in the Three-Nucleon System'' is presented. The experimental evidence for three-nucleon forces has centered on two ground state properties: the tritium binding energy and the trinucleon form factors. Both are discussed
On contribution of instantons to nucleon sum rules
International Nuclear Information System (INIS)
Dorokhov, A.E.; Kochelev, N.I.
1989-01-01
The contribution of instantons to nucleon QCD sum rules is obtained. It is shown that this contribution does provide stabilization of the sum rules and leads to formation of a nucleon as a bound state of quarks in the instanton field. 17 refs.; 3 figs
Nucleon color oscillations in nuclei and the EMC-effect
International Nuclear Information System (INIS)
Smirnov, A.Yu.
1984-01-01
The problem of the EMC-effect is discussed. It is shown that the existence of long-range six-quark clusters in nuclei allows to understand why the nucleon structure function in a nucleus differs from that of a free nucleon
An approach to the structure function for nucleon
International Nuclear Information System (INIS)
Long Ming
1986-01-01
The structure function for nucleon is discussed by using the method given in a previous paper. The formula are compared with the experimental data from low Q 2 to high Q 2 . The results show that the way that the structure function for nucleon can be obtained from the hadronic wavefunction is a possible approach of investigating structure functions for hadron
Nucleon self-energy in the relativistic Brueckner theory
International Nuclear Information System (INIS)
Waindzoch, T.; Fuchs, C.; Faessler, A.
1998-01-01
The self-energy of the nucleon in nuclear matter is calculated in the relativistic Brueckner theory. We solve the Thompson equation for the two nucleon scattering in the medium using different Bonn potentials. The self-energy has a rather strong momentum dependence while the equation of state compares well with previous calculations. (orig.)
DEFF Research Database (Denmark)
Buus, Lillian; Bygholm, Ann
In relation to the Tutor course in the Mediterranean Virtual University (MVU) project, a virtual workshop “Getting experiences with different synchronous communication media, collaboration, and group work” was held with all partner institutions in January 2006. More than 25 key-tutors within MVU...
Approximate symmetries of Hamiltonians
Chubb, Christopher T.; Flammia, Steven T.
2017-08-01
We explore the relationship between approximate symmetries of a gapped Hamiltonian and the structure of its ground space. We start by considering approximate symmetry operators, defined as unitary operators whose commutators with the Hamiltonian have norms that are sufficiently small. We show that when approximate symmetry operators can be restricted to the ground space while approximately preserving certain mutual commutation relations. We generalize the Stone-von Neumann theorem to matrices that approximately satisfy the canonical (Heisenberg-Weyl-type) commutation relations and use this to show that approximate symmetry operators can certify the degeneracy of the ground space even though they only approximately form a group. Importantly, the notions of "approximate" and "small" are all independent of the dimension of the ambient Hilbert space and depend only on the degeneracy in the ground space. Our analysis additionally holds for any gapped band of sufficiently small width in the excited spectrum of the Hamiltonian, and we discuss applications of these ideas to topological quantum phases of matter and topological quantum error correcting codes. Finally, in our analysis, we also provide an exponential improvement upon bounds concerning the existence of shared approximate eigenvectors of approximately commuting operators under an added normality constraint, which may be of independent interest.
Nucleon electric dipole moments in high-scale supersymmetric models
International Nuclear Information System (INIS)
Hisano, Junji; Kobayashi, Daiki; Kuramoto, Wataru; Kuwahara, Takumi
2015-01-01
The electric dipole moments (EDMs) of electron and nucleons are promising probes of the new physics. In generic high-scale supersymmetric (SUSY) scenarios such as models based on mixture of the anomaly and gauge mediations, gluino has an additional contribution to the nucleon EDMs. In this paper, we studied the effect of the CP-violating gluon Weinberg operator induced by the gluino chromoelectric dipole moment in the high-scale SUSY scenarios, and we evaluated the nucleon and electron EDMs in the scenarios. We found that in the generic high-scale SUSY models, the nucleon EDMs may receive the sizable contribution from the Weinberg operator. Thus, it is important to compare the nucleon EDMs with the electron one in order to discriminate among the high-scale SUSY models.
Elastic nucleon-deuteron scattering and breakup with chiral forces
Directory of Open Access Journals (Sweden)
Witała Henryk
2016-01-01
Full Text Available Results on three-nucleon (3N elastic scattering and breakup below the pion production threshold are discussed. The large discrepancies found between a theory based on numerical solutions of 3N Faddeev equations with standard nucleon-nucleon (NN potentials only and data point to the need for three-nucleon forces (3NF’s. This notion is supported by the fact that another possible reason for the discrepancies in elastic nucleon-deuteron (Nd scattering, relativistic effects, turned out to be small. Results for a new generation of chiral NN forces (up to N4LO together with theoretical truncation errors are shown. They support conclusions obtained with standard NN potentials
Superfluidity of nuclei and the nucleon--phonon interaction
International Nuclear Information System (INIS)
Kadmenskii, S.G.; Luk'yanovich, P.A.
1989-01-01
The Lehmann expansion for the exact one-particle Green function in a system with superfluidity is obtained. Expressions for the correlation function and mass operator are derived with allowance for a retarded nucleon--phonon interaction. Within the scope of the formalism developed, equations for the superfluidity of nuclei allowing for quasiparticle fragmentation effects are derived. It is concluded that the retarded nucleon--phonon interaction in the particle--particle channel causes a decrease of the fragmentation of the one-particle force in the vicinity of the Fermi surface. It is shown that inclusion of a nonretarded vacuum interaction of two nucleons and of a retarded interaction due to the exchange between two nucleons of low-lying highly collectivized quadrupole phonons is sufficient to provide the necessary scale of attraction in the description of pair correlations of nucleons in nuclei with developed superfluidity
Roy–Steiner-equation analysis of pion–nucleon scattering
Directory of Open Access Journals (Sweden)
Meißner U.-G.
2017-01-01
Full Text Available 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.c
Roy-Steiner-equation analysis of pion-nucleon scattering
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.
Quark cluster model in the three-nucleon system
International Nuclear Information System (INIS)
Osman, A.
1986-11-01
The quark cluster model is used to investigate the structure of the three-nucleon systems. The nucleon-nucleon interaction is proposed considering the colour-nucleon clusters and incorporating the quark degrees of freedom. The quark-quark potential in the quark compound bag model agrees with the central force potentials. The confinement potential reduces the short-range repulsion. The colour van der Waals force is determined. Then, the probability of quark clusters in the three-nucleon bound state systems are numerically calculated using realistic nuclear wave functions. The results of the present calculations show that quarks cluster themselves in three-quark systems building the quark cluster model for the trinucleon system. (author)
Nucleon electric dipole moments in high-scale supersymmetric models
Energy Technology Data Exchange (ETDEWEB)
Hisano, Junji [Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI),Nagoya University,Nagoya 464-8602 (Japan); Department of Physics, Nagoya University,Nagoya 464-8602 (Japan); Kavli IPMU (WPI), UTIAS, University of Tokyo,Kashiwa, Chiba 277-8584 (Japan); Kobayashi, Daiki; Kuramoto, Wataru; Kuwahara, Takumi [Department of Physics, Nagoya University,Nagoya 464-8602 (Japan)
2015-11-12
The electric dipole moments (EDMs) of electron and nucleons are promising probes of the new physics. In generic high-scale supersymmetric (SUSY) scenarios such as models based on mixture of the anomaly and gauge mediations, gluino has an additional contribution to the nucleon EDMs. In this paper, we studied the effect of the CP-violating gluon Weinberg operator induced by the gluino chromoelectric dipole moment in the high-scale SUSY scenarios, and we evaluated the nucleon and electron EDMs in the scenarios. We found that in the generic high-scale SUSY models, the nucleon EDMs may receive the sizable contribution from the Weinberg operator. Thus, it is important to compare the nucleon EDMs with the electron one in order to discriminate among the high-scale SUSY models.
Strong interactions and quantum chromodynamics at the leading logarithm approximation
International Nuclear Information System (INIS)
Mantrach, A.
1982-11-01
This thesis is a contribution to the study of Quantum Chromodynamics (QCD) at the leading logarithm approximation (LLA). We have used the interpretation of the LLA in terms of the generalized parton model to propose tests of elementary processes of QCD in large transverse momentum photoproduction reactions. We have used the LLA to sum gluon radiation effects induced in high energy hadronic reactions. We have obtained this way a rise of the nucleon-nucleon total cross section of 15 mb from 60 GeV to 540 GeV. We have exploited the existence of a preconfinement transition in the LLA to study scaling violations in the framework of the dual parton model [fr
Structure functions of longitudinal virtual photons at low virtualities
International Nuclear Information System (INIS)
Ioffe, B.L.; Shushpanov, I.A.
1996-01-01
The structure functions F L 1 and F L 2 of longitudinal virtual photons at low virtualities are calculated in the framework of chiral perturbation theory (ChPT) in the zero and first order of ChPT. It is assumed that the virtuality of a target longitudinal photon p 2 is much less than the virtuality of the hard projectile photon Q 2 and both are less than the characteristic ChPT scale. In this approximation the structure functions are determined by the production of two pions in γγ collisions. The numerical results for F L 2 and F L 1 are presented (the upper index refers to the longitudinal polarization of the virtual target photon). The possibilities of measurements of these structure functions are briefly discussed. copyright 1996 The American Physical Society
Approximating distributions from moments
Pawula, R. F.
1987-11-01
A method based upon Pearson-type approximations from statistics is developed for approximating a symmetric probability density function from its moments. The extended Fokker-Planck equation for non-Markov processes is shown to be the underlying foundation for the approximations. The approximation is shown to be exact for the beta probability density function. The applicability of the general method is illustrated by numerous pithy examples from linear and nonlinear filtering of both Markov and non-Markov dichotomous noise. New approximations are given for the probability density function in two cases in which exact solutions are unavailable, those of (i) the filter-limiter-filter problem and (ii) second-order Butterworth filtering of the random telegraph signal. The approximate results are compared with previously published Monte Carlo simulations in these two cases.
CONTRIBUTIONS TO RATIONAL APPROXIMATION,
Some of the key results of linear Chebyshev approximation theory are extended to generalized rational functions. Prominent among these is Haar’s...linear theorem which yields necessary and sufficient conditions for uniqueness. Some new results in the classic field of rational function Chebyshev...Furthermore a Weierstrass type theorem is proven for rational Chebyshev approximation. A characterization theorem for rational trigonometric Chebyshev approximation in terms of sign alternation is developed. (Author)
Lytton, William W; Neymotin, Samuel A; Hines, Michael L
2008-06-30
In an effort to design a simulation environment that is more similar to that of neurophysiology, we introduce a virtual slice setup in the NEURON simulator. The virtual slice setup runs continuously and permits parameter changes, including changes to synaptic weights and time course and to intrinsic cell properties. The virtual slice setup permits shocks to be applied at chosen locations and activity to be sampled intra- or extracellularly from chosen locations. By default, a summed population display is shown during a run to indicate the level of activity and no states are saved. Simulations can run for hours of model time, therefore it is not practical to save all of the state variables. These, in any case, are primarily of interest at discrete times when experiments are being run: the simulation can be stopped momentarily at such times to save activity patterns. The virtual slice setup maintains an automated notebook showing shocks and parameter changes as well as user comments. We demonstrate how interaction with a continuously running simulation encourages experimental prototyping and can suggest additional dynamical features such as ligand wash-in and wash-out-alternatives to typical instantaneous parameter change. The virtual slice setup currently uses event-driven cells and runs at approximately 2 min/h on a laptop.
International Nuclear Information System (INIS)
Smotritskij, L.M.
2001-01-01
Application of resonance phase for two quasi-stationary states with similar spin and unlike parity is shown to enable to coordinate the experimentally observed signed dependence of P-odd effects in neutron reactions with the theory. The developed approach enables to obtain information on isospin structure of a weak nucleon-nucleon interaction [ru
International Nuclear Information System (INIS)
Yakosawa, A.
1977-01-01
Results of various asymmetry measurements in nucleon-nucleon scattering with polarized beams and targets at ZGS energies are presented. A possible direct-channel resonance in the pp system is discussed. Most of the discussion above ZGS energies are aimed at future measurements
Approximation techniques for engineers
Komzsik, Louis
2006-01-01
Presenting numerous examples, algorithms, and industrial applications, Approximation Techniques for Engineers is your complete guide to the major techniques used in modern engineering practice. Whether you need approximations for discrete data of continuous functions, or you''re looking for approximate solutions to engineering problems, everything you need is nestled between the covers of this book. Now you can benefit from Louis Komzsik''s years of industrial experience to gain a working knowledge of a vast array of approximation techniques through this complete and self-contained resource.
International Nuclear Information System (INIS)
Misono, S.; Imanishi, B.
1997-02-01
We have investigated recoil effects in heavy-ion reactions for the nucleon transfers, and the validity of the spatially local approximation for the non-local transfer interaction defined by the orthogonalized coupled-reaction-channel (OCRC) theory. This approximation makes it easier to treat multi-step transfer processes with the coupled channel method and makes it possible to define the nucleon molecular orbitals with the inclusion of the recoil effects. The transfer interaction is expanded in a power series of the momentum operator, and is approximated by the first order term, i.e., the spatially local term. The numerical calculation for the core-symmetric systems 12 C+ 13 C and 16 O+ 17 O with this approximation shows that the recoil effects are well included in the results at energies lower than a few MeV/nucleon. Furthermore, the OCRC formalism allows us even to employ the complete no-recoil approximation for the calculation of cross sections, even though it is not adequate to use this approximation in the distorted wave Born approximation (DWBA) method. As to polarization, however, the no-recoil approximation is not good even in the OCRC formalism. We discuss the recoil effects on nucleon molecular-orbital states. It is shown that states of the covalent molecular orbitals of the valence (transferred) nucleon are little affected by the recoil effects, as already suggested by Korotky et al. in the full finite-range DWBA analysis of the transfer reaction, 13 C( 13 C, 12 C) 14 C. (author). 59 refs
ρ, ω, and φ meson-nucleon scattering lengths from QCD sum rules
International Nuclear Information System (INIS)
Koike, Y.
1995-01-01
The QCD sum rule method is applied to derive a formula for the ρ, ω, and φ meson-nucleon spin-isospin--averaged scattering lengths a ρ,ω,φ . We found that the crucial matrix elements are left-angle bar qγ μ D ν q right-angle N (q=ud) (twist-2 nucleon matrix element) for a ρ,ω and m s left-angle bar ss right-angle N for a φ , and obtained a ρ =0.14±0.07 fm, a ω =0.11±0.06 fm, and a φ =0.035±0.020 fm. These small numbers originate from a common factor 1/(m N +m ρ,ω,φ ). Our result suggests a slight increase (<60 MeV for ρ and ω, and <15 MeV for φ) of the effective mass of these vector mesons in nuclear matter (in the dilute nucleon-gas approximation). The origin of the discrepancy with Hatsuda-Lee was clarified
Advances in Nucleon-Nucleon Scattering Experiments and Their Theoretical Consequences
International Nuclear Information System (INIS)
Bekteshi, Sadik; Kabashi, Skender; Kamishi, Burim
2007-01-01
An overview of critical analysis of the experimental data obtained from nucleon-nucleon scattering is given and investigated in this work. Comparison of the experimental data with results of recent partial wave analysis of Nijmegen group, VPI/GWU and Saclay is given. Potentials of Nijmegen, Bonn and Argonne group are discussed. Experimental data which lead to the break of charge symmetry, to the break of the charge independence and to the determination of the off-shell tensor force, are particularly emphasized. Disagreements which exist between theoretical calculations related to the contribution of particular mechanism in different reactions are pointed out. In this relation, still open problems to be solved and measurement that should be undertaken in the future are identified, as well
Picture book of nucleon--nucleon scattering: amplitudes, models, double- and triple-spin observables
International Nuclear Information System (INIS)
Field, R.D.; Stevens, P.R.
1975-01-01
A comprehensive study of nucleon-nucleon scattering is presented with particular emphasis on the underlying amplitude structure. The five complex NN amplitudes are determined as a function of energy and momentum transfer from existing pp, anti pp, and np elastic scattering data and np and anti pp CHEX data. Some constraints determined from meson-baryon fits are imposed. The resulting amplitudes are used to make predictions of forthcoming double- and triple-spin measurements, and are also compared with the model amplitudes of Kane and Seidl. In addition, the usefulness of transversity amplitudes in NN scattering is discussed, the status of our present knowledge concerning them is examined, and model predictions of these amplitudes are displayed. The paper is presented in a ''picture book'' form so that the reader can get a good overview of NN scattering by studying the figures and reading the tables and figure captions
New large-Nc relations among the nucleon and nucleon-to-Delta GPDs
International Nuclear Information System (INIS)
Marc Vanderhaeghen; Vladimir Pascalutsa
2006-01-01
We establish relations which express the generalized parton distributions (GPDs) describing the N → Δ transition in terms of the nucleon GPDs. These relations are based on the known large-N c relation between the N → Δ electric quadrupole moment and the neutron charge radius, and a newly derived large-N c relation between the electric quadrupole (E2) and Coulomb quadrupole (C2) transitions. Namely, in the large-N c limit we find C2=E2. The resulting relations among the nucleon and N → Δ GPDs provide predictions for the N → Δ electromagnetic form factors which are found to be in very good agreement with experiment for moderate momentum transfers
Flavor asymmetry of the nucleon sea and the five-quark components of the nucleons.
Chang, Wen-Chen; Peng, Jen-Chieh
2011-06-24
The existence of the five-quark Fock states for the intrinsic charm quark in the nucleons was suggested some time ago, but conclusive evidence is still lacking. We generalize the previous theoretical approach to the light-quark sector and study possible experimental signatures for such five-quark states. In particular, we compare the d-ū and ū + d-s-s data with the calculations based on the five-quark Fock states. The qualitative agreement between the data and the calculations is interpreted as evidence for the existence of the intrinsic light-quark sea in the nucleons. The probabilities for the |uuduū and |uuddd Fock states are also extracted.
Compound-nuclear tests of time reversal invariance in the nucleon-nucleon interaction
International Nuclear Information System (INIS)
French, J.B.; Pandey, A.; Smith, J.
1987-01-01
The theory for the effects of time-reversal noninvariance (TRNI) in complex systems is reviewed. Applied to the compound-nuclear data for energy-level, width and cross-section fluctuations (the latter for detailed-balance pairs of reactions proceeding through the compound nucleus) this gives bounds on multiparticle TRNI Hamiltonian matrix elements. Using a fluctuation-free form of statistical spectroscopy the results are reduced to bounds on α, the relative magnitude of the TRNI nucleon-nucleon interaction. The level and width analyses for heavy nuclei gave α ≤ 2 x 10 -3 at high (∼99%) statistical confidence; preliminary calculations for detailed balance with 24 Mg(α,p) 27 Al and its inverse gives α ≤ 4 x 10 -3 at the same high confidence, but ≤0.2 x 10 -3 at 80% confidence. Suggestions are made about experiments which should yield sharper bounds. 28 refs., 1 tab
Expectation Consistent Approximate Inference
DEFF Research Database (Denmark)
Opper, Manfred; Winther, Ole
2005-01-01
We propose a novel framework for approximations to intractable probabilistic models which is based on a free energy formulation. The approximation can be understood from replacing an average over the original intractable distribution with a tractable one. It requires two tractable probability dis...
International Nuclear Information System (INIS)
Burleson, G.R.
1987-01-01
We are applying for a three-year grant from the US Department of Energy to New Mexico State University to continue its support of our work on experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies, which has been carried out in collaboration with groups from various laboratories and universities. The nucleon-nucleon work is aimed at making measurements that will contribute to a determination of the isospin-zero amplitudes, as well as continuing our investigations of evidence for dibaryon resonances. It is based at the LAMPF accelerator in Los Alamos, New Mexico. Current and planned experiments include measurements of total cross-section differences in pure spin states and of spin parameters in neutron-proton scattering. The pion-nucleus work is aimed at improving our understanding both of the nature of the pion-nucleus interaction and of nuclear structure. It consists of two programs, one based at LAMPF and one based principally at the SIN laboratory in Switzerland. The LAMPF-based work involves studies of large-angle scattering, double-charge-exchange scattering, including measurements at a new energy range above 300 MeV, and a new program of experiments with polarized nuclear targets. The SIN-based work involves studies of quasielastic scattering and absorption, including experiments with a new large-acceptance detector system planned for construction there. We are requesting support to continue the LAMPF-based work at its current level and to expand the SIN-based work to allow for increased involvement in experiments with the new detector system. 57 refs
Production of wrong sign muons in neutrino-nucleon and antineutrino-nucleon collisions
International Nuclear Information System (INIS)
Onipchuk, A.B.
1988-01-01
The contribution is considered introduced by the quasipartonic mechanism to production of muons with a wrong sign in ν μ (ν-bar μ )N collisions. The ratios of muon production cross sections in the processes ν μ (ν-bar μ )N → μ + (μ - ) + ... to the inclusive cross sections have been calculated. Comparison to neutrino-nucleon data is made. The x and y distributions and mean kinematical characteristics of the scattered neutrinos are found
Ordered cones and approximation
Keimel, Klaus
1992-01-01
This book presents a unified approach to Korovkin-type approximation theorems. It includes classical material on the approximation of real-valuedfunctions as well as recent and new results on set-valued functions and stochastic processes, and on weighted approximation. The results are notonly of qualitative nature, but include quantitative bounds on the order of approximation. The book is addressed to researchers in functional analysis and approximation theory as well as to those that want to applythese methods in other fields. It is largely self- contained, but the readershould have a solid background in abstract functional analysis. The unified approach is based on a new notion of locally convex ordered cones that are not embeddable in vector spaces but allow Hahn-Banach type separation and extension theorems. This concept seems to be of independent interest.
Structure and spin of the nucleon
Directory of Open Access Journals (Sweden)
Avakian H.
2014-03-01
Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL. TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC, FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
Nucleon electromagnetic form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Koutsou, G.; Negele, J. W.; Tsapalis, A.
2006-01-01
We evaluate the isovector nucleon electromagnetic form factors in quenched and unquenched QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at β=6.0 enabling us to reach low momentum transfers and a lowest pion mass of about 400 MeV. In the unquenched theory we use two degenerate flavors of dynamical Wilson fermions on a lattice of spatial size 1.9 fm at β=5.6 and lowest pion mass of about 380 MeV enabling comparison with the results obtained in the quenched theory. that unquenching effects are small for the pion masses considered in this work. We compare our lattice results to the isovector part of the experimentally measured form factors
Parity nonconservation in two-nucleon systems
International Nuclear Information System (INIS)
Nagle, D.E.
1975-01-01
The observation of a violation of the parity symmetry in two-nucleon systems implies the presence of a weak hadronic force. The positive effect reported by Lobashov et al. in the reaction np → dγ, for the circular polarization of the gamma ray, would imply a large value for the parity nonconserving (PNC) amplitude. A transmission experiment has been undertaken for 15-MeV longitudinally polarized protons on hydrogen. A transmission experiment for 6-GeV polarized protons on Be and on H 2 O is in progress at the ZGS at Argonne National Laboratory. The current results of the latter two experiments are summarized, and the relation to theoretical calculations is discussed. (2 figures, 1 table) (U.S.)
Nucleon form factors. Probing the chiral limit
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Dept.; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2006-10-15
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Jet structure in lepton-nucleon scattering
International Nuclear Information System (INIS)
Kitazoe, T.; Morii, T.
1980-01-01
Materialization processes are studied in lepton-nucleon scattering on the assumption that all incoming and outgoing hadrons have a localized space-time structure described in terms of the Bethe-Salpeter (BS) amplitude. It is shown on the basis of loop diagrams that a coordination of strongly Lorentz contracted BS amplitudes has a key role in deriving two-jet structure. The formalism manifests two distinct models, depending on the parameters which represent the ranges of a BS amplitude. One is a strongly ordered cascade model which is in accordance with a naive quark cascade model. The other is an uncorrelated jet model which corresponds to an uncorrelated Monte Carlo calculation and it fails to be described as a cascade process. The former model predicts an equal spacing momentum distribution in rapidity space. The latter predicts symmetrical distributions in Feynman x-space. Several observable quantities are presented to discriminate between these two models. (orig.)
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
sdg Interacting boson model: two nucleon transfer
International Nuclear Information System (INIS)
Devi, Y.D.; Kota, V.K.B.
1996-01-01
A brief overview of the sdg interacting boson model (sdg IBM) is given. The two examples: (i) spectroscopic properties (spectra, B(E2)s, B(E4)s etc) of the rotor-γ unstable transitional Os-Pt isotopes and (ii) the analytical formulation of two nucleon transfer spectroscopic factors and sum-rule quantities are described in detail. They demonstrate that sdg IBM can be employed for systematic description of spectroscopic properties of nuclei and that large number of analytical formulas, which facilitate rapid analysis of data and provide a clear insight into the underlying structures, can be derived using sdg IBM dynamical symmetries respectively. (author). 24 refs., 5 figs., 3 tabs
Nucleon form factors. Probing the chiral limit
International Nuclear Information System (INIS)
Goeckeler, M.; Haegler, P.; Horsley, R.
2006-10-01
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
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
Nucleon-nucleon optical model for energies to 3 GeV
International Nuclear Information System (INIS)
Funk, A.; Von Geramb, H.V.; University of Melbourne, VIC; Amos, K.A.
2001-01-01
Several nucleon-nucleon potentials, Paris, Nijmegen, Argonne, and those derived by quantum inversion, which describe the NN interaction for T Lab ≤ 300 MeV are extended in their range of application as NN optical models. Extensions are made in r-space using complex separable potentials definable with a wide range of form factor options including those of boundary condition models. We use the latest phase shift analyses SP00 (FA00, WI00) of Arndt et al. from 300 MeV to 3 GeV to determine these extensions. The imaginary parts of the optical model interactions account for loss of flux into direct or resonant production processes. The optical potential approach is of particular value as it permits one to visualize fusion, and subsequent fission, of nucleons when T Lab > 2 GeV. We do so by calculating the scattering wave functions to specify the energy and radial dependences of flux losses and of probability distributions. Furthermore, half-off the energy shell t-matrices are presented as they are readily deduced with this approach. Such t-matrices are required for studies of few- and many-body nuclear reactions
The spin structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Le Goff, J.M
2005-02-15
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*{delta}{sigma} + {delta}g + L{sub q} + L{sub g} where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and L{sub q} and L{sub g} are the orbital momentum of the quark and the gluon respectively. The {delta}{sigma} contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization {delta}g/g and the so-called transversity. (A.C.)
Nucleon Polarisabilities and Effective Field Theories
Griesshammer, Harald W.
2017-09-01
Low-energy Compton scattering probes the nucleon's two-photon response to electric and magnetic fields at fixed photon frequency and multipolarity. It tests the symmetries and strengths of the interactions between constituents, and with photons. For convenience, this energy-dependent information is often compressed into the two scalar dipole polarisabilities αE 1 and βM 1 at zero photon energy. These are fundamental quantities, and important for the proton charge radius puzzle and the Lamb shift of muonic hydrogen. Combined with emerging lattice QCD computations, they provide stringent tests for our understanding of hadron structure. Extractions of the proton and neutron polarisabilities from all published elastic data below 300 MeV in Chiral Effective Field Theory with explicit Δ (1232) are now available. This talk emphasises χEFT as natural bridge between lattice QCD and ongoing or approved efforts at HI γS, MAMI and MAX-lab. Chiral lattice extrapolations from mπ > 200 MeV to the physical point compare well to lattice computations. Combining χEFT with high-intensity experiments with polarised targets and polarised beams will extract not only scalar polarisabilities, but in particular the four so-far poorly explored spin-polarisabilities. These parametrise the stiffness of the spin in external electro-magnetic fields (nucleonic bi-refringence/Faraday effect). New chiral predictions for proton, deuteron and 3He observables show intriguing sensitivities on spin and neutron polarisabilities. Data consistency and a model-independent quantification of residual theory uncertainties by Bayesian analysis are also discussed. Proton-neutron differences explore the interplay between chiral symmetry breaking and short-distance Physics. Finally, I address their impact on the neutron-proton mass difference, big-bang nucleosynthesis, and their relevance for anthropic arguments. Supported in part by DOE DE-SC0015393 and George Washington University.
The interacting boson approximation and the spectroscopy of the even Cadmium and Tin isotopes
International Nuclear Information System (INIS)
Morrison, I.; Smith, R.
1981-01-01
Within the framework of the Interacting Boson Approximation (IBA), the authors investigate, using the even-mass isotopes Cd 108 to Cd 116 and Sn 116 to Sn 124 , whether a single two-boson interaction can describe the energy, B(E2), quadrupole moment and some inelastic nucleon scattering systematics of these nuclei
The reactive content of the proton-nucleus impulse - approximation Dirac optical potential
International Nuclear Information System (INIS)
Carlson, B.V.; Isidro Filho, M.P.; Hussein, M.S.
1984-01-01
The total reaction cross sections for intermediate energy proton scattering on 40 Ca and 208 Pb are calculated within the Dirac-Eikonal formalism. Comparison with data indicate that the recently proposed impulse-approximation Dirac optical potential for nucleon-nucleus scattering, is not absorptive enough. (Author) [pt
Proceedings of the workshop on two-nucleon system
International Nuclear Information System (INIS)
Kawaguchi, Masaaki; Namiki, Mikio; Fukawa, Mineo; Masaike, Akira
1980-08-01
The workshop on two nucleon system started its works four years ago to promote the experiment project on nucleon-nucleon system in the National Laboratory for High Energy Physics by the close cooperation of experimenters and theorists. In particular, several proposals have been made about the experiments using the polarized targets of hydrogen and deuterium, the spectrometers of large solid angle and others, and the investigation into them have been forwarded. It was decided to publish the results of the fourth meeting held in the National Laboratory for High Energy Physics on October 19 and 20, 1979, as the interim report, summarizing the contents. Some of the initial objectives have not been realized yet, but the data have been produced gradually from the experiments in the National Laboratory for High Energy Physics, and are contributing to various analyses. This report is composed of the physics of nucleon-nucleon systems and anti-nucleon-nucleon systems, the results of experiments and the projects corresponding to them, and the hypothetic round-table talk on the points which this workshop considers as problematic and the views of outside researchers on the National Laboratory for High Energy Physics. Finally, the materials distributed at the time of the meeting are added for reference as the appendix. Some numerical values are mutually different, but adjustment was not made. (Kako, I.)
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.)
Nucleon decay in a realistic SO(10) SUSY GUT
International Nuclear Information System (INIS)
Lucas, V.; Raby, S.
1997-01-01
In this paper, we calculate neutron and proton decay rates and branching ratios in a predictive SO(10) SUSY GUT which agrees well with low energy data. We show that the nucleon lifetimes are consistent with the experimental bounds. The nucleon decay rates are calculated using all one-loop chargino and gluino-dressed diagrams regardless of their chiral structure. We show that the four-fermion operator C jk (u R d jR )(d kL ν τL ), commonly neglected in previous nucleon decay calculations, not only contributes significantly to nucleon decay, but, for many values of the initial GUT parameters and for large tanβ, actually dominates the decay rate. As a consequence, we find that τ p /τ n is often substantially larger than the prediction obtained in small tanβ models. We also find that gluino-dressed diagrams, often neglected in nucleon decay calculations, contribute significantly to nucleon decay. In addition we find that the branching ratios obtained from this realistic SO(10) SUSY GUT differ significantly from the predictions obtained from open-quotes genericclose quotes SU(5) SUSY GUT close-quote s. Thus, nucleon decay branching ratios, when observed, can be used to test theories of fermion masses. copyright 1997 The American Physical Society
Geber, Beverly
1995-01-01
Virtual work teams scattered around the globe are becoming a feature of corporate workplaces. Although most people prefer face-to-face meetings and interactions, reality often requires telecommuting. (JOW)
International Nuclear Information System (INIS)
Bjorklund, E.
1993-01-01
In the 1970's, when computers were memory limited, operating system designers created the concept of ''virtual memory'' which gave users the ability to address more memory than physically existed. In the 1990s, many large control systems have the potential for becoming data limited. We propose that many of the principles behind virtual memory systems (working sets, locality, caching, and clustering) can also be applied to data-limited systems - creating, in effect, ''virtual data systems.'' At the Los Alamos National Laboratory's Clinton P. Anderson Meson Physics Facility (LAMPF), we have applied these principles to a moderately sized (10,000 data points) data acquisition and control system. To test the principles, we measured the system's performance during tune-up, production, and maintenance periods. In this paper, we present a general discussion of the principles of a virtual data system along with some discussion of our own implementation and the results of our performance measurements
Virtual Worlds for Virtual Organizing
Rhoten, Diana; Lutters, Wayne
The members and resources of a virtual organization are dispersed across time and space, yet they function as a coherent entity through the use of technologies, networks, and alliances. As virtual organizations proliferate and become increasingly important in society, many may exploit the technical architecture s of virtual worlds, which are the confluence of computer-mediated communication, telepresence, and virtual reality originally created for gaming. A brief socio-technical history describes their early origins and the waves of progress followed by stasis that brought us to the current period of renewed enthusiasm. Examination of contemporary examples demonstrates how three genres of virtual worlds have enabled new arenas for virtual organizing: developer-defined closed worlds, user-modifiable quasi-open worlds, and user-generated open worlds. Among expected future trends are an increase in collaboration born virtually rather than imported from existing organizations, a tension between high-fidelity recreations of the physical world and hyper-stylized imaginations of fantasy worlds, and the growth of specialized worlds optimized for particular sectors, companies, or cultures.
Approximate and renormgroup symmetries
Energy Technology Data Exchange (ETDEWEB)
Ibragimov, Nail H. [Blekinge Institute of Technology, Karlskrona (Sweden). Dept. of Mathematics Science; Kovalev, Vladimir F. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Mathematical Modeling
2009-07-01
''Approximate and Renormgroup Symmetries'' deals with approximate transformation groups, symmetries of integro-differential equations and renormgroup symmetries. It includes a concise and self-contained introduction to basic concepts and methods of Lie group analysis, and provides an easy-to-follow introduction to the theory of approximate transformation groups and symmetries of integro-differential equations. The book is designed for specialists in nonlinear physics - mathematicians and non-mathematicians - interested in methods of applied group analysis for investigating nonlinear problems in physical science and engineering. (orig.)
Approximate and renormgroup symmetries
International Nuclear Information System (INIS)
Ibragimov, Nail H.; Kovalev, Vladimir F.
2009-01-01
''Approximate and Renormgroup Symmetries'' deals with approximate transformation groups, symmetries of integro-differential equations and renormgroup symmetries. It includes a concise and self-contained introduction to basic concepts and methods of Lie group analysis, and provides an easy-to-follow introduction to the theory of approximate transformation groups and symmetries of integro-differential equations. The book is designed for specialists in nonlinear physics - mathematicians and non-mathematicians - interested in methods of applied group analysis for investigating nonlinear problems in physical science and engineering. (orig.)
Approximations of Fuzzy Systems
Directory of Open Access Journals (Sweden)
Vinai K. Singh
2013-03-01
Full Text Available A fuzzy system can uniformly approximate any real continuous function on a compact domain to any degree of accuracy. Such results can be viewed as an existence of optimal fuzzy systems. Li-Xin Wang discussed a similar problem using Gaussian membership function and Stone-Weierstrass Theorem. He established that fuzzy systems, with product inference, centroid defuzzification and Gaussian functions are capable of approximating any real continuous function on a compact set to arbitrary accuracy. In this paper we study a similar approximation problem by using exponential membership functions
Potvin, Guy
2015-10-01
We examine how the Rytov approximation describing log-amplitude and phase fluctuations of a wave propagating through weak uniform turbulence can be generalized to the case of turbulence with a large-scale nonuniform component. We show how the large-scale refractive index field creates Fermat rays using the path integral formulation for paraxial propagation. We then show how the second-order derivatives of the Fermat ray action affect the Rytov approximation, and we discuss how a numerical algorithm would model the general Rytov approximation.
Internal Spin Structure of the Nucleon in Polarized Deep Inelastic Muon-Nucleon Scattering
International Nuclear Information System (INIS)
Wislicki, W.
1998-01-01
We present the study of the internal spin structure of the nucleon in spin-dependent deep inelastic scattering of muons on nucleons. The data were taken by the NA47 experiment of the Spin Muon Collaboration (SMC) on the high energy muon beam at CERN. The experiment used the polarized proton and deuteron targets. The structure function g 1 p (x) and g 1 d (x) were determined from the asymmetries of the spin-dependent event rates in the range of 0.003 2 >=10 GeV 2 . Using the first moments of these structure functions an agreement with the Bjorken sum rule prediction was found within one standard deviation. The first moments of g 1 (x), for both proton and deuteron, are smaller than the Ellis-Jaffe sum rule prediction. This disagreement can be interpreted in terms of negative polarization of the strange sea in the nucleon. The singlet part of the axial current matrix element can be interpreted as an overall spin carried by quarks in the nucleon. Its value is significantly smaller than nucleon spin. Semi-inclusive asymmetries of yields of positive and negative hadrons produced on both targets were also measured and analysed in term of quark-parton model, together with inclusive asymmetries. From this analysis the quark spin distributions were determined, separately for valence u and d quarks and for non-strange sea quarks. Valence u quarks are positively polarized and their polarization increases with x. Valence d quarks are negatively polarized and their polarization does not exhibit any x-dependence. The non-strange sea is unpolarized in the whole measured range of x. The first moments of the valance quark spin distributions were found consistent with the values obtained from weak decay constants F and D and their second moments are consistent with lattice QCD calculations. In the QCD analysis of the world data the first moment of the gluon spin distribution was found with a large error. Also, a search for a non-perturbative anomaly at high x was done on the world
Some new applications of nucleonic gauges in Russia
International Nuclear Information System (INIS)
Fedorkov, V.G.
2000-01-01
Russia has been a big producer of nucleonic gauges for many years. There are still some institutions that design and manufacture nucleonic gauges for industry, like level gauges, density gauges and thickness gauges. Industrial demands for NCS (especially after the Chernobyl accident) have been decreasing. Examples of recent development are given in this paper. Substantial improvements in the hardware, source and detectors system, are being undertaken. The potential for new applications is large, also, there is a good capability of local researchers for increasing the quality and quantity of nucleonic gauges in industry to meet local needs and to compete better in the international scale and market. (author)
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.)
Pseudoscalar form factors in tau-neutrino nucleon scattering
International Nuclear Information System (INIS)
Hagiwara, K.; Mawatari, K.; Yokoya, H.
2004-01-01
We investigate the pseudoscalar transition form factors of nucleon for quasi-elastic scattering and Δ resonance production in tau-neutrino nucleon scattering via the charged current interactions. Although the pseudoscalar form factors play an important role for the τ production in neutrino-nucleon scattering, these are not known well. In this Letter, we examine their effects in quasi-elastic scattering and Δ resonance production and find that the cross section, Q 2 distribution, and spin polarization of the produced τ ± leptons are quite sensitive to the pseudoscalar form factors
Remarks on the pion–nucleon σ-term
Energy Technology Data Exchange (ETDEWEB)
Hoferichter, Martin, E-mail: mhofer@uw.edu [Institute for Nuclear Theory, University of Washington, Seattle, WA 98195-1550 (United States); Ruiz de Elvira, Jacobo; Kubis, Bastian [Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn (Germany); Meißner, Ulf-G. [Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn (Germany); Institut für Kernphysik, Institute for Advanced Simulation, Jülich Center for Hadron Physics, JARA-HPC, and JARA-FAME, Forschungszentrum Jülich, D-52425 Jülich (Germany)
2016-09-10
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.
Remarks on the pion–nucleon σ-term
Directory of Open Access Journals (Sweden)
Martin Hoferichter
2016-09-01
Full Text Available 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.
Remarks on the pion-nucleon σ-term
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.
Spin-dependent parton distributions in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Cloet, I.C. [Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, University of Adelaide, SA 5005 (Australia); Bentz, W. [Department of Physics, School of Science, Tokai University Hiratsuka-shi, Kanagawa 259-1292 (Japan); Thomas, A.W. [Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)
2005-04-15
Spin-dependent quark light-cone momentum distributions are calculated for a nucleon in the nuclear medium. We utilize a modified NJL model where the nucleon is described as a composite quark-diquark state. Scalar and vector mean fields are incorporated in the nuclear medium and these fields couple to the confined quarks in the nucleon. The effect of these fields on the spin-dependent distributions and consequently the axial charges is investigated. Our results for the 'spin-dependent EMC effect' are also discussed.
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.)
Results on nucleon structure functions in quantum chromodynamics
International Nuclear Information System (INIS)
Martin, F.
1979-01-01
Gluon bremsstrahlung processes inside the nucleon are investigated using the standard renormalization-group analysis. A new method of inverting the moments is applied which leads to analytic results for the parton distributions near x = 1 and x = 0. The nucleon is considered as a bound state of three quarks subsequently ''renormalized'' by gluon bremsstrahlung and quark-antiquark pair production. An ''unrenormalized'' valance quark distribution peaked at x = 1/3, with a width related to the nucleon radius, leads to good agreement with deep-inelastic data. However, the gluon distribution obtained seems too steep near x = 0
On the Faddeev-Yacubovsky model of four nucleon scattering problem with account of spin and isospin
International Nuclear Information System (INIS)
Sharma, V.K.
1976-01-01
The Faddeev-Yacubovsky model of four nucleons taking into account their spin and isospin with the two-channel resonating group approximation, is considered. In this approximation, one employs a completely antisymmetric wave function which can be written as the clustering of d + d and n+He 3 (or p+H 3 ) systems with antisymmetric spin isospin states. The two-nucleon interactions used are of the separable Yamaguchi form in Ssub(1)sup(3) and Ssub(0)sup(3) states. The equations for the states with quantum numbers S=0,1,2 T=0 are obtained. It is shown that with subsequent separable representation of two-particle t-matrix reduces the equations to a set of one-dimensional coupled integral equations. (author)
Electron-nucleon scattering experiments in the GeV range
International Nuclear Information System (INIS)
Glawe, U.B.
1980-01-01
In the framework of this thesis a computer code systems was developed which describes the inclusive electron scattering on bound nucleons in the impact approximation. It could be shown that the structure functions for the quasi-free scattering can be represented as an incoherent superposition of the structure functions of the free processes. The structure functions of the free processes were determined from experimental cross sections. From the comparison of the calculations with electron scattering experiments on the nuclei 6 Li, 9 Be, 12 C, 27 Al, and 28 Si in the kinematic range 0.0 2 2 and W [de
Geometric approximation algorithms
Har-Peled, Sariel
2011-01-01
Exact algorithms for dealing with geometric objects are complicated, hard to implement in practice, and slow. Over the last 20 years a theory of geometric approximation algorithms has emerged. These algorithms tend to be simple, fast, and more robust than their exact counterparts. This book is the first to cover geometric approximation algorithms in detail. In addition, more traditional computational geometry techniques that are widely used in developing such algorithms, like sampling, linear programming, etc., are also surveyed. Other topics covered include approximate nearest-neighbor search, shape approximation, coresets, dimension reduction, and embeddings. The topics covered are relatively independent and are supplemented by exercises. Close to 200 color figures are included in the text to illustrate proofs and ideas.
International Nuclear Information System (INIS)
Knobloch, A.F.
1980-01-01
A simplified cost approximation for INTOR parameter sets in a narrow parameter range is shown. Plausible constraints permit the evaluation of the consequences of parameter variations on overall cost. (orig.) [de
Energy Technology Data Exchange (ETDEWEB)
Guillon, B
2005-10-15
In the framework of the Quantum Chromodynamics (QCD), the nucleon is described as being composed of three valence quarks surrounded by a sea of virtual quark-antiquark pairs and gluons. If the role of this virtual sea in the nucleon properties is inferred to be important, this contribution is still poorly understood. In this context, we study the role of the strange quarks in the nucleon since this is the lightest quark flavor of the sea with no valence contribution. We are determining its contribution to the charge and magnetization distributions in the nucleon via parity violation experiments. The measurement is performed by elastically scattering polarized electrons from nucleon target. A world wide program in which the G0 experiment takes place has been performing for a decade. The G0 experiment and the analysis of the results from its forward angles phase are the topics of this thesis. This document presents the physics case of the strangeness content of the nucleon (mass, spin, impulsion). It describes also the formalism related to the electroweak probe and the form factors, and then the principle of parity violating asymmetry measurement. The G0 experimental setup, which was built and installed in the Hall C of the Jefferson Laboratory (Usa), is detailed. This set-up was designed for the measurement of asymmetries of the order of 10{sup -6} with an overall relative uncertainty better than 10 %, over a momentum transfer range 0.1-1 (GeV/c){sup 2}. The various steps of the data analysis are exposed. They have allowed us to start from measured counting rates to reach parity violating physics asymmetries. This required a careful treatment of the various sources of systematical errors which is discussed extensively. Finally the results from the G0 forward angle measurement, its comparison with others experiments and with theoretical models, are presented. They support a non null strange quark contribution. (author)
Gautschi, Walter; Rassias, Themistocles M
2011-01-01
Approximation theory and numerical analysis are central to the creation of accurate computer simulations and mathematical models. Research in these areas can influence the computational techniques used in a variety of mathematical and computational sciences. This collection of contributed chapters, dedicated to renowned mathematician Gradimir V. Milovanovia, represent the recent work of experts in the fields of approximation theory and numerical analysis. These invited contributions describe new trends in these important areas of research including theoretic developments, new computational alg