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We compute the generalized parton distributions (GPDs) of valence quarks, sea quarks, and gluons in the proton using light-front wave functions obtained within the basis light-front quantization (BLFQ) framework, providing a realistic…

High Energy Physics - Phenomenology · Physics 2026-04-21 Yiping Liu , Siqi Xu , Chandan Mondal , Xingbo Zhao , James P. Vary

We report global analysis results for polarized parton distribution functions in the nucleon. The optimum distributions are determined by using spin asymmetry data on polarized lepton scattering on proton, neutron, and deuteron. Their…

High Energy Physics - Phenomenology · Physics 2009-11-11 M. Hirai , S. Kumano , N. Saito

The fact that the spins of the quarks in the proton, as measured in deep inelastic lepton scattering, only add up to about 30$\%$ of the spin of the proton is still not understood after 30 years. We show that our newly developed model for…

High Energy Physics - Phenomenology · Physics 2019-06-21 Andreas Ekstedt , Hazhar Ghaderi , Gunnar Ingelman , Stefan Leupold

We report on the first global analysis of transverse momentum dependent helicity distributions of the proton. The analysis is performed at next-to-leading order with the evolution factor at next-to-next-to-leading-logarithmic accuracy.…

High Energy Physics - Phenomenology · Physics 2025-04-01 Ke Yang , Tianbo Liu , Peng Sun , Yuxiang Zhao , Bo-Qiang Ma

Gravitational form factors (GFFs) of hadrons encode essential information about the internal distributions of mass, spin, pressure, and shear among their quark and gluon constituents. We compute the quark and gluon GFFs of the proton using…

High Energy Physics - Phenomenology · Physics 2025-06-10 Sreeraj Nair , Chandan Mondal , Siqi Xu , Xingbo Zhao , James P. Vary

The proton diffractive structure function $F_2^{D(3)}$ measured in the H1 and ZEUS experiments at HERA are analysed in terms of perturbative QCD in the perspective of the QCD extrapolation to the Tevatron and the LHC. It is shown that both…

High Energy Physics - Phenomenology · Physics 2010-03-25 C. Royon , L. Schoeffel , R. Peschanski , E. Sauvan

We present a next-to-next-to-leading order (NNLO) global QCD analysis of the proton's helicity parton distribution functions (PDFs), the first of its kind. To obtain the distributions, we use data for longitudinal spin asymmetries in…

High Energy Physics - Phenomenology · Physics 2025-03-31 Ignacio Borsa , Daniel de Florian , Rodolfo Sassot , Marco Stratmann , Werner Vogelsang

The leading-twist parton distribution functions of the pion and kaon are calculated for the first time using a rainbow-ladder truncation of QCD's Dyson-Schwinger equations (DSEs) that self-consistently sums all planar diagrams. The…

Nuclear Theory · Physics 2020-02-05 Kyle D. Bednar , Ian C. Cloët , Peter C. Tandy

At small x, the effects of finite transverse momenta of partons inside a hadron become increasingly important, especially in analyses of jets and heavy-quark production. These effects can be systematically accounted for in a formalism based…

High Energy Physics - Phenomenology · Physics 2014-11-17 Gosta Gustafson , Leif Lonnblad , Gabriela Miu

To obtain improved parton densities of the proton, we present a new global analysis of deep inelastic and related data including, in particular, the recent measurements of $F_2$ at HERA, of the asymmetry of the rapidity distributions of…

High Energy Physics - Phenomenology · Physics 2014-11-17 A. D. Martin , R. G. Roberts , W. J. Stirling

The recent high precision SMC data on polarized $\mu p$ scatterings have again confirmed that very little of the proton spin is carried by quarks. To unravel the mystery of the proton spin structure, it is quite important to know the…

High Energy Physics - Phenomenology · Physics 2009-10-28 T. Morii , S. Tanaka , T. Yamanishi

We show that the parton distribution functions (PDF) described by the statistical model have very interesting physical properties which help to understand the structure of partons. The role of the quark helicity components is emphasized as…

High Energy Physics - Phenomenology · Physics 2015-09-28 Claude Bourrely

The quasi-probabilistic Wigner distributions are the quantum mechanical analog of the classical phase-space distributions. We investigate quark Wigner distributions for a quark state dressed with a gluon, which can be thought of as a simple…

High Energy Physics - Phenomenology · Physics 2017-05-09 Jai More , Asmita Mukherjee , Sreeraj Nair

The recent progress in the investigations on the quark structure of the $\Lambda$ and $\Sigma$ baryons are reviewed. It is shown that the quark structure of $\Lambda$ and $\Sigma$ hyperons can provide a new domain to test various theories…

High Energy Physics - Phenomenology · Physics 2009-10-31 Bo-Qiang Ma

We recall our recent description of quark parton densities of the proton at $Q^2=4 GeV^2$ in terms of Fermi-Dirac distributions parametrized with very few free parameters. We have also proposed some simple assumptions to relate unpolarized…

High Energy Physics - Phenomenology · Physics 2016-09-01 Claude Bourrely , Jacques Soffer

How quarks and gluons conspire to provide the total spin of proton is a long-standing puzzle in quantum chromodynamics (QCD). The unique capability of RHIC, that can provide longitudinally polarized $p+p$ collisions at both $\sqrt{s} = 200$…

High Energy Physics - Experiment · Physics 2024-02-26 Ting Lin

The observation of the quark transversity distribution requires another soft object sensitive to the quark's transverse spin. Dihadron fragmentation functions represent a convenient tool to analyze partonic spin, which can influence the…

High Energy Physics - Phenomenology · Physics 2017-08-23 Alessandro Bacchetta , Marco Radici

We check the $u$ and $d$ quark contributions to the spin content of the $\Lambda$ by means of the $q\to\Lambda$ fragmentation and find that the $u$ and $d$ quarks of the $\Lambda$ are likely positively polarized. The parton distributions in…

High Energy Physics - Phenomenology · Physics 2011-02-01 Jian-Jun Yang

The production of heavy flavor quark pairs, including top-anti-top, at the LHC proceeds primarily through gluon fusion. The correlation between the gluon spins affects various spin correlations between the produced quark and anti-quark.…

High Energy Physics - Phenomenology · Physics 2017-10-05 Gary R. Goldstein , S. Liuti

We present the first simultaneous global QCD analysis of spin-dependent parton distribution functions alongside their spin-averaged counterparts and pion, kaon, and unidentified hadron fragmentation functions. This analysis includes all…

High Energy Physics - Phenomenology · Physics 2023-09-08 C. Cocuzza , W. Melnitchouk , A. Metz , N. Sato