Angular Distributions of Drell-Yan Lepton Pairs at the Tevatron: Order $α_s^2$ Corrections and Monte Carlo Studies

TL;DR

The paper provides a complete ${\cal O}(\alpha_s^2)$ calculation of the angular distributions of leptons from high-$p_T$ Drell–Yan γ^* production at the Tevatron, complemented by an ${\cal O}(\alpha_s)$ Monte Carlo study with realistic lepton cuts and energy resolution. It formulates the angular distribution in terms of helicity cross sections and angular coefficients $A_i$, analyzes two reference frames (Collins–Soper and Gottfried–Jackson), and demonstrates that NLO corrections to the angular coefficients are modest due to cancellations among the helicity channels. The numerical results show that the observed lepton distributions are largely shaped by kinematic acceptance effects, with polarization effects surviving mainly under mild cuts and minimal smearing. The work supports perturbative QCD factorization in this process and provides strategies to isolate polarization signals in experimental data.

Abstract

We investigate the angular distribution of the lepton pair in the process $p \bar{p} \rightarrow γ^{\ast} + X \rightarrow \ell^+\ell^- + X$, where the virtual photon is produced at high transverse momentum. The angular distribution of the leptons is very sensitive to possible nonperturbative effects, such as a nontrivial vacuum structure of QCD, and offers a good chance to test such effects. We present complete ${\cal O}(α_s^2)$ calculations of the decay lepton distributions in the lepton pair rest frame. An order ${\cal O}(α_s)$ Monte Carlo study of the lepton angular distributions, with acceptance cuts and energy resolution smearing applied to the leptons, is also presented.