This work presents a lattice quantum chromodynamics (QCD) calculation of the nonperturbative Collins-Soper kernel, which describes the rapidity evolution of quark transverse-momentum-dependent parton distribution functions. The kernel is extracted at transverse momentum scales in the range 400 MeV <qT<1.7 GeV in a calculation with dynamical fermions and quark masses corresponding to a larger-than-physical pion mass, mπ=538(1) MeV. It is found that different approaches to extract the Collins-Soper kernel from the same underlying lattice QCD matrix elements yield significantly different results and uncertainty estimates, revealing that power corrections, such as those associated with higher-twist effects, and perturbative matching between quasi and light-cone beam functions, cannot be neglected.
@article{arxiv.2107.11930,
title = {Lattice QCD calculation of the Collins-Soper kernel from quasi TMDPDFs},
author = {Phiala Shanahan and Michael Wagman and Yong Zhao},
journal= {arXiv preprint arXiv:2107.11930},
year = {2021}
}