Miguel Garcia-Echevarria, Ahmad Idilbi, Ignazio Scimemi
We derive a factorization theorem for Drell-Yan process at low q_T using effective field theory methods. In this theorem all the obtained quantities are gauge invariant and the special role of the soft function--and its subtraction thereof--is emphasized. We define transverse-momentum dependent parton distribution functions (TMDPDFs) which are free from light-cone singularities and of mixed divergences, while all the Wilson lines are defined on-the-light-cone. We show explicitly to first order in \alpha_s that the partonic Feynman PDF is obtained from the newly defined partonic TMDPDF by integrating over the transverse momentum of the parton inside the hadron. We obtain a resummed expression for the TMDPDF, and hence for the cross section, in impact parameter space. The universality of the newly defined non-perturbative hadronic matrix elements is established. The factorization theorem is validated to first order in \alpha_s and also the gauge invariance between Feynman and light-cone gauges.
View original:
http://arxiv.org/abs/1111.4996
No comments:
Post a Comment