Drell-Yan lepton angular distributions in perturbative QCD

TL;DR

This paper compares experimental measurements of Drell-Yan lepton angular distributions with perturbative QCD calculations at leading and next-to-leading order, showing good overall agreement and limited evidence for effects beyond fixed-order theory.

Contribution

It provides a detailed comparison of experimental data with NLO perturbative QCD calculations for Drell-Yan angular coefficients using publicly available numerical codes.

Findings

Perturbative QCD describes data well at colliders and fixed-target regimes.

No strong evidence found for effects beyond fixed-order collinear factorization.

Next-to-leading order corrections improve the agreement with experimental data.

Abstract

We present a comprehensive comparison of the available experimental data for the Drell-Yan lepton angular coefficients $\lambda$ and $\nu$ to calculations at leading and next-to-leading order of perturbative QCD. To obtain the next-to-leading order corrections, we make use of publicly available numerical codes that allow us to compute the Drell-Yan cross section at second order in perturbation theory and from which the contributions we need can be extracted. Our comparisons reveal that perturbative QCD is able to describe the experimental data overall rather well, especially at colliders, but also in the fixed-target regime. On the basis of the angular coefficients alone, there appears to be little (if any) convincing evidence for effects that go beyond fixed-order collinear factorized perturbation theory, although the presence of such effects is not ruled out.