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We analyze the world polarized deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data at low values of $x < 0.1$, using small-$x$ evolution equations for the flavor singlet and nonsinglet helicity parton distribution functions…

We present the first-ever description the world data on the $g_1^{p,n}$ structure function at small Bjorken $x$ using evolution equations in $x$ derived from first principles QCD. This is a Monte-Carlo analysis within the JAM global…

High Energy Physics - Phenomenology · Physics 2021-08-10 Daniel Adamiak

We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-$x$ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton…

We apply the valence quark model recently calculated for polarized proton to constrain the non-perturbative initial condition for the small-$x$ helicity evolution. The remaining free parameters are constrained by performing a global…

High Energy Physics - Phenomenology · Physics 2025-11-04 Daniel Adamiak , Heikki Mäntysaari , Yossathorn Tawabutr

The contribution to proton helicity from the spins of quarks and gluons at small Bjorken $x$ can be conveniently studied through the small-$x$ helicity evolution. Recently, it has been employed in a global analysis that includes polarized…

High Energy Physics - Phenomenology · Physics 2024-07-16 Yossathorn Tawabutr

A small-$x$ helicity evolution has been derived in 2016-18 and received an important modification in 2022. This article discusses its general framework and summarizes the recent theoretical developments, including the asymptotic behaviors…

High Energy Physics - Phenomenology · Physics 2023-09-14 Yossathorn Tawabutr

A QCD analysis of the world data on inclusive polarized deep inelastic scattering of leptons on nucleons is presented in leading and next-to-leading order. New parameterizations are derived for the quark and gluon distributions and the…

High Energy Physics - Phenomenology · Physics 2009-11-07 J. Blümlein , H. Böttcher

We perform the first global QCD analysis of polarized inclusive and semi-inclusive deep-inelastic scattering and single-inclusive $e^+e^-$ annihilation data, fitting simultaneously the parton distribution and fragmentation functions using…

High Energy Physics - Phenomenology · Physics 2017-10-04 J. J. Ethier , N. Sato , W. Melnitchouk

We present a new next-to-leading order QCD analysis of the world data on inclusive polarized deep inelastic lepton-nucleon scattering adding to the old set of data the final SMC results, the HERMES proton and very recent SLAC/E155 deuteron…

High Energy Physics - Phenomenology · Physics 2009-10-31 Elliot Leader , Alexsander V. Sidorov , Dimiter B. Stamenov

Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized hydrogen and 3He targets, in the kinematic…

High Energy Physics - Experiment · Physics 2008-11-26 K. Ackerstaff , The HERMES Collaboration

Global analysis has been performed within the next-to-leading order in Quantum Chromodynamics (QCD) to determine polarized parton distributions with new experimental data in spin asymmetries. The new data set includes JLab, HERMES, and…

High Energy Physics - Phenomenology · Physics 2008-11-26 M. Hirai , S. Kumano , N. Saito

We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the…

High Energy Physics - Phenomenology · Physics 2014-03-05 P. Jimenez-Delgado , A. Accardi , W. Melnitchouk

In this thesis we consider the polarized deep inelastic scattering in the region of low values of Bjorken variable, $x$. We formulate the evolution equations for the unintegrated parton distributions which include a complete resummation of…

High Energy Physics - Phenomenology · Physics 2007-05-23 B. Ziaja

We construct small-$x$ evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the $g_1$ structure function. These evolution equations resum powers of $\alpha_s \, \ln^2 (1/x)$ in the…

High Energy Physics - Phenomenology · Physics 2016-12-23 Yuri V. Kovchegov , Daniel Pitonyak , Matthew D. Sievert

I review recent theoretical results on polarized deep inelastic lepton nucleon scattering. Some specific issues, like $Q^2$ evolution of structure functions, the small $x$ behaviour, and the determination of polarized parton densities, are…

High Energy Physics - Phenomenology · Physics 2007-05-23 Giovanni Ridolfi

The recently revised small-$x$ helicity evolution, resumming the double-logarithmic factor, $\alpha_s\ln^2(1/x)$, allows for the study of helicity distributions of quarks and gluons at small Bjorken $x$, corresponding to high center-of-mass…

High Energy Physics - Phenomenology · Physics 2024-07-15 Adrian Dumitru , Heikki Mäntysaari , Yossathorn Tawabutr

An updated next-to-leading order (NLO) QCD analysis of the spin asymmetries A_1^N(x,Q^2) and parton distributions delta f(x,Q^2) in longitudinally polarized deep-inelastic lepton-nucleon scattering is presented within the framework of the…

High Energy Physics - Phenomenology · Physics 2007-05-23 M. Stratmann

We rederive the small-$x$ evolution equations governing quark helicity distribution in a proton using solely an operator-based approach. In our previous works on the subject, the evolution equations were derived using a mix of diagrammatic…

High Energy Physics - Phenomenology · Physics 2019-04-03 Yuri V. Kovchegov , Matthew D. Sievert

Our present information on the gluon polarisation Delta g/g is reviewed. The data from fixed-target lepton-nucleon experiments are in context with the recent data from the RHIC polarised pp collider. The main tools to study Delta g/g in…

High Energy Physics - Experiment · Physics 2008-11-26 G. K. Mallot

We have used QCD and polarized deep-inelastic scattering data to construct x-dependent polarized parton distributions. These flavor dependent distributions evolve under the NLO DGLAP equations, satisfy positivity constraints and agree well…

High Energy Physics - Phenomenology · Physics 2007-05-23 Gordon P. Ramsey
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