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Related papers: Single-Logarithmic Corrections to Small-$x$ Helici…

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We calculate single-logarithmic corrections to the small-$x$ flavor-singlet helicity evolution equations derived recently in the double-logarithmic approximation. The new single-logarithmic part of the evolution kernel sums up powers of…

High Energy Physics - Phenomenology · Physics 2022-04-08 Yuri V. Kovchegov , Andrey Tarasov , Yossathorn Tawabutr

We present a numerical solution of the revised version of the small-$x$ helicity evolution equations at large $N_c$ and $N_f$. (Here $N_c$ and $N_f$ are the numbers of quark colors and flavors, respectively.) The evolution equations are…

High Energy Physics - Phenomenology · Physics 2023-09-13 Daniel Adamiak , Yuri V. Kovchegov , Yossathorn Tawabutr

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

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 2016-07-15 Yuri V. Kovchegov , Daniel Pitonyak , Matthew D. Sievert

The proton spin puzzle is a longstanding problem in high-energy nuclear physics: how the proton spin distributes among the spin and orbital angular momenta of the quarks and gluons inside. Two of the unresolved pieces of the puzzle are the…

High Energy Physics - Phenomenology · Physics 2023-06-29 Yossathorn Tawabutr

We include the quark to gluon and gluon to quark shock-wave transition operators into the small Bjorken-$x$ evolution equations for helicity in the flavor-singlet channel derived earlier. While such transitions do not affect the large-$N_c$…

High Energy Physics - Phenomenology · Physics 2024-06-18 Jeremy Borden , Yuri V. Kovchegov , Ming Li

The proton spin puzzle denotes the challenge of describing the proton's spin in terms of the angular momenta of the quarks and gluons which comprise it. These quarks and gluons carry a fraction $x$ of the proton's momentum. Contributions…

High Energy Physics - Phenomenology · Physics 2026-03-24 Jeremy Borden

We construct an exact analytic solution of the revised small-$x$ helicity evolution equations, where the contributions of the quark-to-gluon and gluon-to-quark transition operators were newly included. These evolution equations are written…

High Energy Physics - Phenomenology · Physics 2025-08-04 Jeremy Borden , Yuri V. Kovchegov

We construct a numerical solution of the recently-derived large-$N_c \& N_f$ small-$x$ helicity evolution equations with the aim to establish the small-$x$ asymptotics of the quark helicity distribution beyond the large-$N_c$ limit explored…

High Energy Physics - Phenomenology · Physics 2020-08-26 Yuri V. Kovchegov , Yossathorn Tawabutr

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

We construct an exact analytic solution of the revised small-$x$ helicity evolution equations derived recently. The equations we solve are obtained in the large-$N_c$ limit (with $N_c$ the number of quark colors) and are double-logarithmic…

High Energy Physics - Phenomenology · Physics 2023-07-25 Jeremy Borden

We construct an exact analytic solution of the revised small-$x$ helicity evolution equations derived recently. The equations we solve are obtained in the large-$N_c$ limit (with $N_c$ the number of quark colors) and are double-logarithmic…

High Energy Physics - Phenomenology · Physics 2023-07-19 Jeremy Borden , Yuri V. Kovchegov

Helicity of quarks and gluons inside the proton at small Bjorken $x$ is one of the missing pieces of the proton spin puzzle, with limited experimental results due to various challenges. To address the problem, we derive under the framework…

High Energy Physics - Phenomenology · Physics 2023-12-01 Yossathorn Tawabutr

We construct a numerical solution of the small-$x$ evolution equations recently derived in \cite{Kovchegov:2015pbl} for the (anti)quark helicity TMDs and PDFs as well as the $g_1$ structure function. We focus on the case of large $N_c$…

High Energy Physics - Phenomenology · Physics 2017-02-08 Yuri V. Kovchegov , Daniel Pitonyak , Matthew D. Sievert

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

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

This dissertation highlights the contributions I have made to the field of theoretical nuclear physics, specifically in high-energy Quantum Chromodynamics (QCD). High-energy QCD is a robust subject and my research is refined to the…

High Energy Physics - Phenomenology · Physics 2025-04-24 Nicholas Baldonado

We revisit the problem of small Bjorken-$x$ evolution of the gluon and flavor-singlet quark helicity distributions in the shock wave ($s$-channel) formalism. Earlier works on the subject in the same framework resulted in an evolution…

High Energy Physics - Phenomenology · Physics 2024-08-23 Florian Cougoulic , Yuri V. Kovchegov , Andrey Tarasov , Yossathorn Tawabutr

Proton is a composite particle, so its spin S_P is made from the spins of the partons which the proton consists of. The discrepancy between S_P = 1/2 and the experimentally detected sum of the parton spins was named Proton Spin Puzzle.…

High Energy Physics - Phenomenology · Physics 2025-03-14 B. I. Ermolaev
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