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Novel corrections to the momentum sum rule for nuclear structure functions

PHYSICS LETTERS B 2022年 824卷

作者： Brodsky, Stanley J. Lyubovitskij, Valery E. Schmidt, Ivan Stanford Univ SLAC Natl Accelerator Lab Stanford CA 94309 USA Univ Tubingen Kepler Ctr Astro & Particle Phys Inst Theoret Phys Morgenstelle 14 D-72076 Tubingen Germany Univ Tecn Federico Santa Maria Dept Fis Casilla 110-V Valparaiso Chile Univ Tecn Federico Santa Maria Ctr Cient Tecnol Valparaiso CCTval Casilla 110 Valparaiso Chile High Energy Frontier SAPHIR ANID Millennium Inst Subat Phys Fernandez Concha 700 Santiago Chile

We address novel features of deep inelastic lepton scattering on nuclei at small Bjorken variable x(Bj). In this regime the lepton-nuclear cross section involves the interference between the standard leptonquark scattering amplitude for the deep inelastic scattering (DIS) process on a single nucleon and a two-step process where diffractive scattering on a first nucleon combines with the amplitude for DIS on a second nucleon. The phases associated with the t-channel exchanges to the diffractive amplitude can produce either a destructive or constructive quantum-mechanical interference of the one-step and two-step amplitudes. This provides a mechanism regulating the respective amounts of shadowing suppression and anti-shadowing enhancement at low x(Bj). Furthermore, the standard leading-twist operator product and handbag diagram analyses of the forward virtual Compton amplitude on the nucleus are inapplicable, barring a conventional probabilistic interpretation. A main observable consequence is the impossibility of extracting momentum and spin sum rules from nuclear structure functions. We present numerical predictions supporting this picture and test them against DIS neutrino-nucleus and charged-leptonnucleus scattering data. (C) 2021 The Author(s). Published by Elsevier B.V.

关键词： Deep inelastic scattering Diffractive deep inelastic scattering Parton distribution functions nuclear structure functions Momentum sum rules Operator expansion

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QCD Evolution of nuclear structure functions at Large X: EMC Effect and Cumulative Processes

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PHYSICS OF PARTICLES AND NUCLEI LETTERS 2018年第4期15卷 384-386页

作者： Kim, V. T. Petersburg Nucl Phys Inst NRC KI Gatchina 188300 Russia St Petersburg Polytech Univ St Petersburg 195251 Russia

QCD evolution of nuclear structure functions at large x is reviewed within the an approach based on QCD factorization for hard processes and multiquark flucton model. In this approach, x > 1 region of the nuclear structure functions is intimately related with x < 1 region due to manifestation of quark and gluon degrees of freedom in nuclei. Properties of QCD evolution and observed EMC-ratio for nuclear structure functions at x < 1 result in an admixture of hard extra sea quark distribution. This extra nuclear quark sea provides a bump above unity for EMC-ratio at small x and becomes dominant in the nuclear quark sea for cumulative region x > 1. It leads to a striking prediction, confirmed by data, for the same spectrum slopes of all cumulative hadrons in nuclear fragmentation region.

关键词： nuclear structure functions multiquark fluctons cumulative processes EMC-effect

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Effect of bound nucleon internal structure change on nuclear structure functions

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PHYSICS LETTERS B 2005年第1-2期612卷 5-12页

作者： Tsushima, K Saito, K Steffens, FM Univ Estadual Paulista Inst Fis Teor BR-01405900 Sao Paulo Brazil Mackenzie Presbiteriana Univ FCBEE BR-01302907 Sao Paulo Brazil Natl Ctr Theoret Sci Taipei Taipei 10617 Taiwan Tokyo Univ Sci Fac Sci & Technol Dept Phys Noda Chiba 2788510 Japan

Effect of bound nucleon internal structure change on nuclear structure functions is investigated based on local quark-hadron duality. The bound nucleon structure functions calculated for charged-lepton and (anti)neutrino scattering are all enhanced in symmetric nuclear matter at large Bjorken-x (x greater than or similar to 0.85) relative to those in a free nucleon. This implies that a part of the enhancement observed in the nuclear structure function F-2 (in the resonance region) at large Bjorken-x (the EMC effect) is due to the effect of the bound nucleon internal structure change. However, the x dependence for the charged-lepton and (anti)neutrino scattering is different. The former (latter) is enhanced (quenched) in the region 0.8 less than or similar to x less than or similar to 0.9 (0.7 less than or similar to x less than or similar to 0.85) due to the difference of the contribution from axial vector forrn factor. Because of these differences charge symmetry breaking in parton distributions will be enhanced in nuclei. (c) 2005 Elsevier B.V. All rights reserved.

关键词： local quark-hadron duality nuclear structure functions bound nucleon internal structure change

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Nucleon and hadron structure changes in the nuclear medium and the impact on observables

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PROGRESS IN PARTICLE AND nuclear PHYSICS, VOL 58, NO 1 2007年第1期58卷 1-167页

作者： Saito, K. Tsushima, K. Thomas, A. W. Natl Ctr Theoret Sci Div Phys Taipei 10617 Taiwan Tokyo Univ Sci Fac Sci & Technol Dept Phys Noda Chiba 2788510 Japan Thomas Jefferson Natl Accelerator Facil Newport News VA 23606 USA

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. In conventional nuclear physics, the Skyrme effective forces are very popular, but, there is no satisfactory interpretation of the parameters appearing in the Skyrme forces. Comparing a many-body Hamiltonian generated by the QMC model in the zero-range limit with that of the Skyrme effective forces, it is possible to obtain a remarkable agreement between the Skyrme force and the QMC effective interaction. One can also investigate the relationship between the QMC model and Quantum Hadrodynamics, by carrying out a re-definition of the scalar field in matter. Furthermore, by using naive dimensional analysis, it is possible to see that the QMC model can provide remarkably natural coupling constants and hence the model itself is regarded as a natural effective field theory for nuclei. The model is first applied to nuclear matter, where the coupling constants are determined so as to produce the saturation condition at normal nuclear matter density. We find a new, simple scaling relation for the changes of hadron masses in a nuclear medium, which can be described in terms of the number of light quarks in a hadron and the value of the scalar mean field in matter. Once the coupling constants are fixed, the model can be applied to various finite nuclei, including strange and exotic hypernuclei. In this article, we discuss in detail the properties of hypernucle

关键词： quarks in nuclei quark-meson coupling model relativistic nuclear model properties of finite nuclei a new scaling formula for hadron masses in matter nucleon form factors hypernuclei and exotic nuclei meson-nucleus bound states nuclear structure functions hadron reactions in matter

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nuclear shadowing and diffraction

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INTERNATIONAL JOURNAL OF MODERN PHYSICS A 2005年第19期20卷 4436-4441页

作者： Albacete, JL Armesto, N Salgado, CA Capella, A Kaidalov, AB Univ Cordoba Dept Fis E-14071 Cordoba Spain CERN Div Theory Dept Phys CH-1211 Geneva Switzerland Univ Paris 11 Phys Theor Lab F-91405 Orsay France Inst Theoret & Expt Phys Moscow 117259 Russia

The relation between diffraction in lepton-proton collisions and shadowing of nuclear structure functions which arises from Gribov inelastic shadowing, is described. A model realizing such relation, which produces a parameter-free description of experimental data on nuclear structure functions at small x, is presented. The application to the description of multiplicities in nuclear collisions is discussed and related to other approaches.

关键词： nuclear structure functions small x diffraction

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Do ordinary nuclei contain exotic states of matter?

Do ordinary nuclei contain exotic states of matter?

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19th Winter Workshop on nuclear Dynamics

作者： Arrington, J Argonne Natl Lab Argonne IL 60439 USA

The strongly repulsive core of the short-range nucleon-nucleon interaction leads to the existence of high-momentum nucleons in nuclei. Inclusive electron scattering can be used to probe these high-momentum nucleons and study the nature of the corresponding short-range correlations in nuclei. With recent data from Jefferson Lab we have begun to map out the strength of two-nucleon correlations in nuclei, while upcoming experiments should allow us to isolate the presence of multi-nucleon correlations. In addition to their importance in describing nuclear structure, these configurations of correlated nucleons represent high-density 'droplets' of hadronic matter. As the density of hadronic matter increases there should be a weakening of quark confinement, similar to the onset of deconfinement expected at extremely high temperatures. While there have been hints of non-hadronic structure in nuclei, future measurements will allow us to directly probe the quark distributions of high-density configurations in nuclei. A modified quark structure in these closely packed nucleons would provide a clear signature of exotic components to the structure of nuclei.

关键词： QCD in nuclei nuclear structure functions short range correlations

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structure functions of unstable lithium isotopes

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nuclear PHYSICS A 2002年第1-2期705卷 119-152页

作者： Saito, K Ueda, M Tsushima, K Thomas, AW Tohoku Coll Pharmaceut Sci Sendai Miyagi 9818558 Japan Univ Tsukuba Inst Phys Tsukuba Ibaraki 3058571 Japan Univ Adelaide Dept Phys & Math Phys Adelaide SA 5005 Australia Univ Adelaide Special Res Ctr Subatom Struct Matter CSSM Adelaide SA 5005 Australia

We study the spin-average and spin-dependent structure functions of the lithium isotopes. It is found that the light-cone momentum distribution of the valence neutron in the halo of Li-11 is very sharp and symmetric around y = 1, because of the weak binding. This implies that such neutrons are in an environment very close to that of a free neutron. The EMC ratios for Li isotopes are then calculated. Furthermore, we investigate a new ratio, given by the difference between the Li structure functions of mass number A (F-2(A)) and A - 1 (F-2(A-1)) divided by the difference between the structure functions of the deuteron and free proton. We study the possibility of extracting the neutron structure function from data for the nuclear structure functions of the Li isotopes. In particular, the ratios for A = 9 and 11present an attractive possibility for extracting the free neutron structure function. Next, as an example, we calculate the spin-dependent structure function of Li-9 isotope, which has spin 3/2. The spin structure function is given in terms of the multipole spin structure functions;(3/2)(3)g(1), which is analogous to the usual spin structure function, g(1), for a target with spin 1/2, and a new one, (3/2)(3)g(1), which first arises for a target with spin 3/2. The effect of the nuclear binding and Fermi motion on (3/2)(1)g(1) is about 10% in the region x < 0. 7, but it becomes quite important at large x. The spin structure function, (3/2)(3)g(1), is negative at small x but it becomes positive in the region 0.2 < x < 0.5. However, the magnitude is very small. At large x it is again negative and its absolute value becomes large because of the Fermi motion. Finally, we discuss the modification of the Gottfried and Bjorken integrals in a nuclear medium and point out several candidates for a pair of mirror nuclei to study the flavor-nonsinglet quark distributions in nuclei. (C) 2002 Elsevier Science B.V All rights reserved.

关键词： nuclear structure functions neutron structure functions unstable nuclei

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The ratio of gluon distributions in Sn and C

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PHYSICS LETTERS B 1996年第1-4期375卷 349-354页

作者： Gousset, T Pirner, HJ Institut für Theoretische Physik Universität Heidelberg Philosophenweg 19 D-69120 Heidelberg Germany

We calculate the ratio of gluon densities, G(Sn)(x)/G(C)(x), for 0.01 < x < 0.1, from the new high statistics data on F-2(Sn)/F-2(C) taken by the NM Collaboration. For small x, the shadowing in the gluon distribution is about equal to the shadowing of quark distribution. The antishadowing in the gluon distribution, however, is roughly 10%. We also compare with the difference of ratios R = sigma(L)/sigma(T) from Sn and C.

关键词： gluon densities shadowing-antishadowing nuclear structure functions

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Progress in Understanding Short-Range structure in Nuclei: An Experimental Perspective

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nuclear and Particle Science 1000年第1期72卷 307-337页

作者： John Arrington Nadia Fomin Axel Schmidt 1Lawrence Berkeley National Laboratory Berkeley California USA email: jarrington@lbl.gov 2Department of Physics and Astronomy University of Tennessee Knoxville Tennessee USA 3Department of Physics The George Washington University Washington DC USA

High-energy electron scattering is a clean, precise probe for measurements of hadronic and nuclear structure and plays a key role in understanding the role of high-momentum nucleons (and quarks) in nuclei. Jefferson Lab has dramatically expanded our knowledge of the high-momentum nucleons generated by short-range correlations, providing sufficient insight to model much of their impact on nuclear structure in neutron stars and in low- to medium-energy scattering observables, including neutrino oscillation measurements. These short-range correlations also seem related to the modification of the quark distributions in nuclei, and efforts to improve our understanding of the internal structure of these short-distance and high-momentum configurations in nuclei will provide important input on a wide range of high-energy observables.

关键词： high-energy electron–nucleus scattering short-range nucleon–nucleon correlations deep inelastic electron scattering nuclear structure functions superfast quarks

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