QCD parton showers and NLO EW corrections to Drell-Yan

TL;DR

This paper integrates NLO electroweak corrections into QCD parton shower simulations for Drell-Yan processes, highlighting differences in shower algorithms and their impact on muon transverse momentum distributions.

Contribution

It introduces an interface between the SANC framework with NLO EW corrections and QCD shower Monte Carlos, including handling of photon-in-a-proton initial states.

Findings

Residual differences of 2-3% in muon p_T distributions at high p_T.

NLO EW corrections are about 10% at p_T>50 GeV.

Implementation enables more precise Drell-Yan process simulations.

Abstract

We report on the implementation of an interface between the SANC generator framework for Drell-Yan hard processes, which includes next-to-leading order electroweak (NLO EW) corrections, and the Herwig++ and Pythia8 QCD parton shower Monte Carlos. A special aspect of this implementation is that the initial-state shower evolution in both shower generators has been augmented to handle the case of an incoming photon-in-a-proton, diagrams for which appear at the NLO EW level. The difference between shower algorithms leads to residual differences in the relative corrections of 2-3% in the p_T(mu) distributions at p_T(mu)>~50 GeV (where the NLO EW correction itself is of order 10%).