First constraints on the nonperturbative gluon Collins-Soper kernel

Abstract

The gluon Collins-Soper kernel, which encodes the rapidity evolution of transverse-momentum-dependent gluon distributions, is constrained for the first time in the nonperturbative regime, for transverse momentum scales $q_T\in [300\text{ MeV},1.3\text{ GeV}]$. The constraints are determined in lattice QCD at a close-to-physical pion mass $M_{\ddot{I}}€=172(3)\text{ MeV}$, a single lattice spacing $a=0.15\text{ fm}$, and next-to-next-to-leading logarithmic matching in Large-Momentum Effective Theory. These results represent the first step toward a controlled determination of the gluon Collins-Soper kernel in QCD, with eventual phenomenological import and relevance to present and future experiments sensitive to the gluon structure of hadronic matter.

24 pages, 16 figures