First Extraction of Transverse Momentum Dependent Helicity Distributions

TL;DR

This paper presents the first global analysis of transverse momentum dependent helicity distributions in protons, revealing flavor-specific polarization behaviors at different transverse momenta and momentum fractions.

Contribution

It introduces a novel global analysis at next-to-leading order with advanced evolution accuracy, providing new insights into TMD helicity distributions.

Findings

Nonzero signals for up and down quarks' polarization.

Large $x$ quarks become less polarized at higher transverse momentum.

Small $x$ quarks become more polarized with increasing transverse momentum.

Abstract

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. Nonzero signals are determined for up and down quarks and their $k_T$-integrated polarization are consistent with analyses in collinear factorization, while the distributions of other flavors are loosely constrained by existing data. With increasing transverse momentum, quarks at large $x$ become less polarized while those at small $x$ become more polarized.