Drell-Yan angular lepton distributions at small x from TMD factorization.

Abstract

Abstract The Drell-Yan process is studied in the framework of TMD factorization in the Sudakov region s » Q 2 » q ⊥ 2 $$ {q}_{\perp}^2 $$ corresponding to recent LHC experiments with Q 2 of order of mass of Z-boson and transverse momentum of DY pair ∼ few tens GeV. The DY hadronic tensors are expressed in terms of quark and quark-gluon TMDs with 1 Q 2 $$ \frac{1}{Q^2} $$ and 1 N c 2 $$ \frac{1}{N_c^2} $$ accuracy. It is demonstrated that in the leading order in N c the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting hadronic tensors depend on two leading-twist TMDs: f 1 responsible for total DY cross section, and Boer-Mulders function h 1 ⊥ $$ {h}_1^{\perp } $$ . The corresponding qualitative and semi-quantitative predictions seem to agree with LHC data on five angular coefficients A 0 − A 4 of DY pair production. The remaining three coefficients A 5 − A 7 are determined by quark-quark-gluon TMDs multiplied by extra 1 N c $$ \frac{1}{N_c} $$ so they appear to be relatively small in accordance with LHC results.

Keywords

• Perturbative QCD
• Nonperturbative Effects