The transverse-momentum-dependent (TMD) soft function is a key ingredient in QCD factorization of Drell-Yan and other processes with relatively small transverse momentum. We present a lattice QCD study of this function at moderately large rapidity on a 2+1 flavor CLS dynamic ensemble with a = 0.098 fm. We extract the rapidity-independent part of the soft function through a large-momentum-transfer pseudo-scalar meson form factor and its quasi-TMD wave function using leading-order factorization in large-momentum effective theory. We also investigate the rapidity-dependent part of the soft function—the Collins-Soper evolution kernel—based on the large-momentum evolution of the quasi-TMD wave function.

Dr. Qi-An Zhang received his PhD at Institute of High Energy Physics, Chinese Academy of Science. And now he is a postdoc of T.D.Lee institute. His main research interests include the large momentum effective theory and lattice QCD simulations of parton physics.