Collins-Soper kernel from lattice QCD at the physical pion mass

TL;DR

This paper reports the first lattice QCD calculation of the Collins-Soper kernel at near-physical pion mass, providing insights into TMD evolution and non-perturbative QCD effects.

Contribution

It introduces a novel lattice QCD determination of the Collins-Soper kernel at physical pion mass with systematic uncertainty analysis and high transverse momentum resolution.

Findings

Kernel determined at 240 MeV to 1.6 GeV transverse momentum

Results discriminate between phenomenological models in non-perturbative region

Systematic uncertainties from operator mixing thoroughly analyzed

Abstract

This work presents a determination of the quark Collins-Soper kernel, which relates transverse-momentum-dependent parton distributions (TMDs) at different rapidity scales, using lattice Quantum Chromodynamics (QCD). This is the first lattice QCD calculation of the kernel at quark masses corresponding to a close-to-physical value of the pion mass, with next-to-next-leading logarithmic matching to TMDs from the corresponding lattice-calculable distributions, and includes a complete analysis of systematic uncertainties arising from operator mixing. The kernel is extracted at transverse momentum scales $240\,\text{MeV}\lesssim q_{T}\lesssim 1.6\,\text{GeV}$ with a precision sufficient to begin to discriminate between different phenomenological models in the non-perturbative region.