Systematic studies of exact O(α2L) CEEX EW corrections in a hadronic MC for precision Z/γ* physics at LHC energies

S Jadach,B F L Ward,Z Wąs,S A Yost

doi:10.1103/physrevd.99.076016

Abstract

With an eye toward the precision physics of the LHC, such as the recent measurement of $M_W$ by the ATLAS Collaboration, we present here systematic studies relevant to the assessment of the expected size of multiple photon radiative effects in heavy gauge boson production with decay to charged lepton pairs. We use the new version 4.22 of ${\cal KK}$MC-hh so that we have CEEX EW exact ${\cal O}(\alpha^2 L)$ corrections in a hadronic MC and control over the corresponding EW initial-final interference (IFI) effects as well. In this way, we illustrate the interplay between cuts of the type used in the measurement of $M_W$ at the LHC and the sizes of the expected responses of the attendant higher order corrections. We find that there are per cent to per mille level effects in the initial-state radiation, fractional per mille level effects in the IFI and per mille level effects in the over-all ${\cal O}(\alpha^2 L)$ corrections that any treatment of EW corrections at the per mille level should consider. Our results have direct applicability to current LHC experimental data analyses.

Highlights

With large data samples already at 7 TeV and even larger ones at 8 and 13 TeV, the LHC experiments are well into the era of precision QCD ⊗ EW physics for processes such as single heavy gauge boson production with decay to lepton pairs
We explore the possible role of the new exact1 Oðα2LÞ coherent exclusive exponentiation (CEEX) EW corrections in KKMC-hh [4] in this context
KKMC-hh is the union of two developments in the Monte Carlo event generator approach to precision theoretical physics for high energy colliding beam devices: The exact amplitude-based CEEX/EEX Yennie-FrautschiSuura (YFS) monte carlo (MC) approach to EW higher order corrections pioneered in Refs. [5,6,55,56] and the QCD parton shower hadron MC approach pioneered in Refs. [37,57]

Summary

INTRODUCTION

With large data samples already at 7 TeV and even larger ones at 8 and 13 TeV, the LHC experiments are well into the era of precision QCD ⊗ EW physics for processes such as single heavy gauge boson production with decay to lepton pairs. [29], the same approach is used for the FSR correction again with the result that 0.3% FSR errors are obtained in differential spectra in some regions of phase space These are again cases where the effects of other EW corrections that enter at the per mille level could be significant, as we will illustrate with KKMC-hh in what follows. IV, we summarize our findings in view of our discussion in this Introduction

RECAPITULATION OF THE PHYSICS IN KKMC-hh

SUMMARY