scholarly journals Shadowing Aspects of Nuclear Parton Distributions

1997 ◽  
Vol 50 (1) ◽  
pp. 45
Author(s):  
S. Kumano
Keyword(s):  
Valence Quark ◽  
Parton Model ◽  
Symmetric Case ◽  
Dependent Data ◽  
Model Framework ◽  
Higher Twist Effects ◽  
Parton Distributions ◽  
Nuclear Dependence ◽  
Nuclear Interactions

Various shadowing aspects of nuclear parton distributions are discussed in a parton-model framework. We explain existing x dependent data of F2A /F2D, then the model is applied to a flavour asymmetry – d in a nucleus, to shadowing in valence-quark distributions, and to nuclear dependence of Q2 evolution. First, we find that a finite nuclear ū – đ distribution could be possible due to nuclear interactions even in the flavour symmetric case in the nucleon ( ū – đ = 0). Second, it is indicated that valence-quark shadowing could be used for discriminating among various shadowing models. Third, we find that nuclear dependence of Q2 evolution ∂ [F2Sn/F2C]/∂[ln Q2], which was found by the New Muon Collaboration (NMC), is essentially understood by modification of parton distributions in nuclei. However, higher-twist effects in nuclear interactions could be tested by studying the details of the nuclear Q2 evolution.

PARTON DISTRIBUTION FUNCTIONS AND THE QCD-IMPROVED PARTON MODEL — AN OVERVIEW

1987 ◽  
Vol 02 (04) ◽  
pp. 1369-1387 ◽  
Author(s):  
Wu-Ki Tung
Keyword(s):  
Parton Distribution ◽  
Particle Production ◽  
Heavy Particle ◽  
Parton Model ◽  
Distribution Functions ◽  
Collider Physics ◽  
Parton Distribution Functions ◽  
Parton Distributions ◽  
First Order ◽  
Small X

Some non-trivial features of the QCD-improved parton model relevant to applications on heavy particle production and semi-hard (small-x) processes of interest to collider physics are reviewed. The underlying ideas are illustrated by a simple example. Limitations of the naive parton formula as well as first order corrections and subtractions to it are dis-cussed in a quantitative way. The behavior of parton distribution functions at small x and for heavy quarks are discussed. Recent work on possible impact of unconventional small-x behavior of the parton distributions on small-x physics at SSC and Tevatron are summarized. The Drell-Yan process is found to be particularly sensitive to the small x dependence of parton distributions. Measurements of this process at the Tevatron can provide powerful constraints on the expected rates of semi-hard processes at the SSC.

scholarly journals Parton Distributions,d/u, and Higher Twist Effects at Highx

1999 ◽  
Vol 82 (12) ◽  
pp. 2467-2470 ◽  
Author(s):  
U. K. Yang ◽  
A. Bodek
Keyword(s):  
Higher Twist Effects ◽  
Parton Distributions

scholarly journals Quark correlations in the ground and excited nucleon states via the photo-absorption sum rules

2019 ◽  
Vol 204 ◽  
pp. 01008
Author(s):  
Sergo Gerasimov
Keyword(s):  
Cross Sections ◽  
Sum Rules ◽  
Valence Quark ◽  
Visual Representation ◽  
Nucleon Resonances ◽  
Nuclear Interactions ◽  
The Cross ◽  
Quark Correlation

The account of the dynamical correlations of quarks composing the nucleons is necessary for relevant description of nucleon and nuclear interactions. The present work is devoted to the use of the technique of known integral sum rules for the cross-sections and amplitude of the photo-hadron processes. In particular, a kind of the visual representation and quantification of the valence quark correlation characteristics referring to the photo-excitation of the nucleon resonances can be presented.

scholarly journals NEUTRON SPIN STRUCTURE STUDY AT JEFFERSON LAB HALL A

2003 ◽  
Vol 18 (08) ◽  
pp. 1153-1160
Author(s):  
JIAN-PING CHEN
Keyword(s):  
Spin Structure ◽  
Spin Asymmetry ◽  
Valence Quark ◽  
Structure Study ◽  
Precision Measurements ◽  
Neutron Spin ◽  
Higher Twist Effects ◽  
Jefferson Lab ◽  
Neutron Spin Structure ◽  
Bjorken X

With a high-intensity highly-polarized 6 GeV electron beam, and a high-density polarized 3 He target, we have carried out a number of experiments to study the neutron spin structure at Hall A in Jefferson Lab. Taking advantage of the high luminosity of Jefferson Lab, we completed two inclusive deep-inelastic-scattering experiments this summer. In the first precision measurements were made of the spin asymmetry [Formula: see text] in the valence quark (high Bjorken x) region, and in the second higher-twist effects were studied via precision measurements of [Formula: see text]. Physics motivation and preliminary results from the first experiment will be presented and discussed. I will also present nearly final results from an earlier experiment, which measured the generalized GDH sum for the neutron in the Q 2 range of 0.1 to 1 GeV 2. Planned near-term experiments will be briefly discussed.

scholarly journals THE LOOP CORRECTIONS TO THE PARITY-VIOLATING ELASTIC ELECTRON-PROTON SCATTERING

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3645-3651
Author(s):  
YU CHUN CHEN ◽  
CHUNG WEN KAO
Keyword(s):  
Strange Quark ◽  
Parton Model ◽  
Elastic Electron ◽  
Proton Scattering ◽  
Weak Current ◽  
Parton Distributions ◽  
Generalized Parton Distributions ◽  
Boson Exchange ◽  
Neutral Weak Current ◽  
Hadronic Model

We calculate the two-boson-exchange (TBE) corrections to the parity-violating asymmetry of the elastic electron-proton scattering in a parton model using the formalism of generalized parton distributions (GPD's). We find that these effects can reach a few percent and are comparable in size with the current experimental measurements of strange-quark effects in the proton neutral weak current. Our result is also compared with the result of the hadronic model.

UNPOLARIZED NUCLEON STRUCTURE FUNCTIONS IN THE NAMBU-JONA-LASINIO CHIRAL SOLITON MODEL

1996 ◽  
Vol 11 (38) ◽  
pp. 3021-3034 ◽  
Author(s):  
H. WEIGEL ◽  
L. GAMBERG ◽  
H. REINHARDT
Keyword(s):  
Constituent Quark ◽  
Valence Quark ◽  
Parton Model ◽  
Structure Functions ◽  
Nucleon Structure ◽  
Quark Masses ◽  
Model Interpretation ◽  
Chiral Soliton ◽  
Quark Level ◽  
Chiral Soliton Model

We study nucleon structure functions within the bosonized Nambu-Jona-Lasinio model where the nucleon emerges as a chiral soliton. As examples we present the unpolarized structure functions for the νp and [Formula: see text] scattering and discuss the Gottfried sum rule in the valence quark approximation. This approximation is justified for moderate constituent quark masses (~ 400 MeV) as the valence quark level dominates the predictions of nucleon properties. We find that these structure functions are well localized in the interval 0≤x Bj ≤1 permitting a parton model interpretation.

scholarly journals An analysis of parton distribution functions of the pion and the kaon with the maximum entropy input

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Chengdong Han ◽  
Gang Xie ◽  
Rong Wang ◽  
Xurong Chen
Keyword(s):  
Parton Distribution ◽  
Valence Quark ◽  
Quark Distribution ◽  
Parton Model ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Theoretical Predictions ◽  
Gluon Distributions ◽  
Qcd Analysis ◽  
Mass Dependent

AbstractWe present pion and kaon parton distribution functions from a global QCD analysis of the experimental data within the framework of dynamical parton model. We use the DGLAP equations with parton–parton recombination corrections and the valence input of uniform distribution which maximizes the information entropy. At our input scale $$Q_0^2$$ Q 0 2 , there are no sea quark and gluon distributions. All the sea quarks and gluons of the pion and the kaon are completely generated from the parton splitting processes. The mass-dependent parton splitting kernel is applied for the strange quark distribution in the kaon. The obtained valence quark and sea quark distributions at high $$Q^{2}$$ Q 2 ($$Q^2>5$$ Q 2 > 5 GeV$$^2$$ 2 ) are compatible with the existed experimental measurements. Furthermore, the asymptotic behaviours of parton distribution functions at small and large x have been studied for both the pion and the kaon. Lastly, the first three moments of parton distributions at high $$Q^{2}$$ Q 2 scale are calculated, which are consistent with other theoretical predictions.

scholarly journals Small x behavior of parton distributions: a study of higher twist effects

2008 ◽  
Vol 39 (3) ◽  
pp. 307-347 ◽  
Author(s):  
A. Yu. Illarionov ◽  
A. V. Kotikov ◽  
G. Parente
Keyword(s):  
Higher Twist Effects ◽  
Parton Distributions ◽  
Small X

CALCULATING SPIN-DEPENDENT PARTON DISTRIBUTIONS IN THE BAG MODEL

2003 ◽  
Vol 18 (08) ◽  
pp. 1391-1395 ◽  
Author(s):  
A. I. SIGNAL
Keyword(s):  
Experimental Data ◽  
Nuclear Physics ◽  
Lower Energy ◽  
Valence Quark ◽  
High Energy ◽  
Nucleon Structure ◽  
Pion Cloud ◽  
Model Calculations ◽  
Parton Distributions

Model calculations of parton distributions are an important way to connect our knowledge of physics at high energy scales with physics at lower energy scales typical of nuclear physics. Earlier work on the spin-independent valence quark distributions has shown that DIS data support a bag radius around 0.8 fm, and highlighted the importance of chiral symmetry and the role of the pion cloud in nucleon structure. Here, that work is extended to the spin-dependent parton distributions. We calculate these distributions in the model and compare with experimental data.

scholarly journals Quark Spin-Orbit Correlations

2015 ◽  
Vol 37 ◽  
pp. 1560036 ◽  
Author(s):  
Cédric Lorcé
Keyword(s):  
Angular Momentum ◽  
Phase Space ◽  
Orbital Angular Momentum ◽  
Valence Quark ◽  
Complete Characterization ◽  
Proton Spin ◽  
Spin Orbit ◽  
Parton Distributions ◽  
Transverse Momentum Dependent ◽  
Quark Spin

The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.

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