Determination of the Collins-Soper Kernel from Lattice QCD

TL;DR

This paper reports non-perturbative lattice QCD calculations of the Collins-Soper kernel, crucial for understanding the energy dependence of TMDs, showing good agreement with experimental data and prior studies.

Contribution

First non-perturbative lattice QCD determination of the Collins-Soper kernel using dynamical fermions and Mellin moments of quasi-TMDs.

Findings

CS kernel agrees with experimental extractions.

Results are consistent with previous lattice studies.

Analysis uses dynamical $N_f=2+1$ clover fermions.

Abstract

We present lattice results for the non-perturbative Collins-Soper (CS) kernel, which describes the energy-dependence of transverse momentum-dependent parton distributions (TMDs). The CS kernel is extracted from the ratios of first Mellin moments of quasi-TMDs evaluated at different nucleon momenta.The analysis is done with dynamical $N_f=2+1$ clover fermions for the CLS ensemble H101 ($a=0.0854\,\mathrm{fm}$, $m_{\pi}=m_K=422\,\mathrm{MeV}$). The computed CS kernel is in good agreement with experimental extractions and previous lattice studies.