Collins-Soper kernel from lattice QCD at the physical pion mass
Artur Avkhadiev, Phiala E. Shanahan, Michael L. Wagman, Yong Zhao
Abstract
This work presents a determination of the quark Collins-Soper kernel, which relates transverse-momentum-dependent parton distributions at different rapidity scales, using lattice 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-to-leading logarithmic matching to transverse-momentum-dependent parton distributions 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 $240\text{ }\text{ }\mathrm{MeV}\ensuremath{\lesssim}{q}_{T}\ensuremath{\lesssim}1.6\text{ }\text{ }\mathrm{GeV}$ with a precision sufficient to begin to discriminate between different phenomenological models in the nonperturbative region.