Gauge-invariant TMD factorization for Drell-Yan hadronic tensor at small x

I. Balitsky

doi:10.1007/jhep05(2021)046

Abstract

The Drell-Yan hadronic tensor for electromagnetic (EM) current is calculated in the Sudakov region sgg {Q}^2gg {q}_{perp}^2 with frac{1}{Q^2} accuracy, first at the tree level and then with the double-log accuracy. It is demonstrated that in the leading order in Nc the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting tensor for unpolarized hadrons is EM gauge-invariant and depends on two leading-twist TMDs: f1 responsible for total DY cross section, and Boer-Mulders function {h}_1^{perp } . The order-of-magnitude estimates of angular distributions for DY process seem to agree with LHC results at corresponding kinematics.

Highlights

The Drell-Yan (DY) process of production of lepton pairs with large invariant mass in hadronic collisions [1] is one of the most important tools to study QCD. It is a unique source of information about partonic structure of hadrons [2]. It serves as a testing ground for factorization approaches in various kinematics regions, like the classical collinear factorization [3,4,5,6,7,8], TMD factorization [9,10,11,12,13], and SCET [14,15,16,17]
The differential cross section of DY process is determined by the product of leptonic tensor and hadronic tensor
The hadronic tensor Wμν is parametrized by 4 functions, for example in Collins-Soper frame [18]

Summary

Introduction

The Drell-Yan (DY) process of production of lepton pairs with large invariant mass in hadronic collisions [1] is one of the most important tools to study QCD. From experimental viewpoint, it is a unique source of information about partonic structure of hadrons [2]. The hadronic tensor Wμν is defined as. Where pA, pB are hadron momenta, q is the momentum of DY pair, X denotes the sum over full set of “out” states and Jμ is either electromagnetic or Z-boson current. The hadronic tensor Wμν is parametrized by 4 functions, for example in Collins-Soper frame [18]

Objectives

Results

Conclusion