Comparisons of the Monte Carlo programs HORACE and WINHAC for single-W-boson production at hadron colliders

TL;DR

This work benchmarks two independent Monte Carlo generators, HORACE and WINHAC, for single-W production with leptonic decays at hadron colliders, emphasizing higher-order QED corrections in W decays. It performs thorough parton-level and hadron-level comparisons and investigates non-zero quark-mass effects across multiple observables. The results show excellent agreement in total cross sections and most differential distributions, with residual differences attributed to subleading terms and muon-mass treatments. The findings support the reliability of HORACE and WINHAC for precision W-mass/width extractions and PDF studies, while outlining paths for incorporating full EW corrections and QCD effects in future work.

Abstract

We present the comparisons of two independent Monte Carlo event generators, HORACE and WINHAC, for single-W-boson production in hadronic collisions with multiphoton effects in leptonic W decays. These comparisons were performed first at the parton level with fixed quark-beams energy, and then at the hadron level for proton-proton collisions at the LHC. In general, a good agreement between the two programs has been found. Possible sources of differences in some of the presented results are discussed. We also present and discuss the effects of including non-zero quark masses for the main single-W-boson observables at the LHC.

Figures (40)

• Figure 1: Distributions of the electron energy at parton level for ${\cal O}(\alpha)$ and "Best" predictions from HORACE and WINHAC, as well as their differences. The results are shown for BARE (left) and CALO (right) event selections.
• Figure 2: Distributions of the muon energy at parton level for ${\cal O}(\alpha)$ and "Best" predictions from HORACE and WINHAC, as well as their differences. The results are shown for BARE (left) and CALO (right) event selections.
• Figure 3: Distributions of the electron polar angle at parton level for ${\cal O}(\alpha)$ and "Best" predictions from HORACE and WINHAC, as well as their differences. The results are shown for BARE (left) and CALO (right) event selections.
• Figure 4: Distributions of the muon polar angle at parton level for ${\cal O}(\alpha)$ and "Best" predictions from HORACE and WINHAC, as well as their differences. The results are shown for BARE (left) and CALO (right) event selections.
• Figure 5: Distributions of the hardest-photon energy at parton level in the electron channel for ${\cal O}(\alpha)$ and "Best" predictions from HORACE and WINHAC, as well as their differences. The results are shown for BARE (left) and CALO (right) event selections.