The role of transverse momentum on the nuclear valence and sea quark distribution functions

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
H. Nematollahi
Keyword(s):  
Transverse Momentum ◽  
Quark Distribution ◽  
Parton Model ◽  
Distribution Functions ◽  
Momentum Dependence ◽  
Free Nucleon ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Nuclear Modifications

Abstract We investigate the transverse momentum dependence of valence and sea quark distribution functions of light asymmetric nuclei ($$^{3}He$$3He and $$^{7}Li$$7Li). To this end, we first calculate the valence and sea distributions of these nuclei applying a parametrization method in which the parton distribution functions (PDFs) of nucleus are related to those of free nucleon via a weight function that contains the nuclear modifications. Then we obtain the unpolarized transverse momentum dependent (TMD) PDFs of the nucleus using the covariant parton model (CPM) approach. We also compute the valence and sea quark distributions ratios of $$^{3}He$$3He and $$^{7}Li$$7Li to those of deuteron and present the results with respect to x (Bjorken variable) at fixed values of transverse momentum. It is found that these ratios shift to the larger values of x by increasing the transverse momentum value as expected and they are not transverse momentum dependent in large x region.

scholarly journals Polarized parton distribution functions: parametrization and transverse momentum dependence

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
H. Nematollahi ◽  
P. Abolhadi ◽  
S. Atashbar ◽  
A. Mirjalili ◽  
M. M. Yazdanpanah
Keyword(s):  
Data Analysis ◽  
Transverse Momentum ◽  
Parton Distribution ◽  
Jacobi Polynomials ◽  
Global Analysis ◽  
Distribution Functions ◽  
Momentum Dependence ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Transverse Momentum Dependence

AbstractWe extract the polarized parton distribution functions (PPDFs) of proton. To this end we do a global analysis on recent and up-to-dated experimental data of polarized nucleon and deuteron structure functions at the NLO accuracy of perturbative QCD. We use the Jacobi polynomials expansion technique to do the required analyses. To achieve a more realistic estimation of the PPDFs and observable uncertainties we employ the Hessian error propagation. Following that we apply a theoretical approach which is based on imposing Lorentz structure in the parton model to investigate the transverse momentum dependence of these PPDFs. In this approach, the transverse momentum dependent (TMD) polarized parton distributions, which are also called the helicity distributions, are related to the integrated ones. This relation is indicating the priority and importance of data analysis for PPDFs. The results show a convenient general treatment expected for TMD densities which are in fact resulted from data analysis and fitting processes of integrated PPDFs in an adequate and a proper way.

scholarly journals Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
S. Acharya ◽  
◽  
D. Adamová ◽  
A. Adler ◽  
J. Adolfsson ◽  
...  
Keyword(s):  
Z Boson ◽  
Decay Channel ◽  
Theoretical Calculations ◽  
Center Of Mass ◽  
Laboratory Frame ◽  
Distribution Functions ◽  
Boson Production ◽  
Free Nucleon ◽  
Parton Distribution Functions ◽  
Nuclear Modifications

Abstract Measurement of Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity −4 < ημ< −2.5 and transverse momentum $$ {p}_{\mathrm{T}}^{\mu } $$ p T μ > 20 GeV/c in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass 60 < mμμ< 120 GeV/c2 and rapidity 2.5 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < 4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward (−4.46 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < −2.96) and forward (2.03 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < 3.53) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a 3.4σ deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.

Color Entanglement in Hadronic Processes for Transverse Momentum Dependent Parton Distribution Functions

2015 ◽  
Vol 37 ◽  
pp. 1560022
Author(s):  
M. G. A. Buffing ◽  
P. J. Mulders
Keyword(s):  
Transverse Momentum ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Initial State ◽  
Color Flow ◽  
Transverse Momentum Dependent ◽  
Gauge Link ◽  
Azimuthal Asymmetries ◽  
Different Parts

In the description of protons, we go beyond the ordinary collinear parton distribution functions (PDFs), by including transverse momentum dependent PDFs (TMDs). As such, we become sensitive to polarization modes of the partons and protons that one cannot probe without accounting for transverse momenta of partons, in particular when looking at azimuthal asymmetries. Hadronic processes require the inclusion of gluon contributions forming the gauge links, which are path-ordered exponentials tracing the color flow. In processes with two hadrons in the initial state, such as Drell-Yan (DY), the gauge links from different parts of the process get entangled. We show that in color disentangling this gauge link structure, one becomes sensitive to this color flow. After disentanglement, particular combinations of TMDs will require a different numerical color factor than one naively might have expected. Such color factors will even play a role for azimuthal asymmetries in the simplest hadronic processes such as DY.

scholarly journals DEFINITION AND EVOLUTION OF TRANSVERSE MOMENTUM DISTRIBUTIONS

2012 ◽  
Vol 20 ◽  
pp. 92-108 ◽  
Author(s):  
MIGUEL G. ECHEVARRÍA ◽  
AHMAD IDILBI ◽  
IGNAZIO SCIMEMI
Keyword(s):  
Transverse Momentum ◽  
Evolution Equation ◽  
Gauge Invariance ◽  
Parton Distribution ◽  
Ultra Violet ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Momentum Distributions ◽  
Definition Of

We consider the definition of unpolarized transverse-momentum-dependent parton distribution functions while staying on-the-light-cone. By imposing a requirement of identical treatment of two collinear sectors, our approach, compatible with a generic factorization theorem with the soft function included, is valid for all non-ultra-violet regulators (as it should), an issue which causes much confusion in the whole field. We explain how large logarithms can be resummed in a way which can be considered as an alternative to the use of Collins-Soper evolution equation. The evolution properties are also discussed and the gauge-invariance, in both classes of gauges, regular and singular, is emphasized.

HADRON STRUCTURE STUDY IN FORTHCOMING DRELL–YAN EXPERIMENTS: COMPASS PROJECT AT CERN

2009 ◽  
Vol 24 (35n37) ◽  
pp. 3033-3044 ◽  
Author(s):  
◽  
OLEG DENISOV
Keyword(s):  
Transverse Momentum ◽  
Structure Study ◽  
Distribution Functions ◽  
Proton Target ◽  
Production Mechanism ◽  
Hadron Structure ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Hadron Beam

The study of Drell–Yan (DY) processes involving the collision of an (un)polarised hadron beam on an (un)polarised proton target can result in a fundamental improvement of our knowledge on the transverse momentum dependent (TMDs) parton distribution functions (PDFs) of hadrons. The production mechanism of J/ψ and J/ψ - DY duality can also be addressed. One of the forthcoming polarised DY experiments (COMPASS (SPS, CERN)) is discussed in this context. The most important features of this project are briefly reviewed, as well as its sensitivity to the various transverse momentum dependent spin asymmetries.

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