Precision studies for Drell-Yan processes at NNLO

TL;DR

This paper compares four computational codes for Drell-Yan processes at NNLO, revealing discrepancies at NNLO accuracy due to neglected power corrections, which depend on the observable and experimental cuts.

Contribution

It provides a detailed comparison of NNLO predictions from different codes and identifies the impact of power corrections on their agreement.

Findings

Predictions agree at NLO but differ at NNLO.

Differences can be larger than NNLO corrections.

Neglected power corrections influence the discrepancies.

Abstract

We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell-Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.