IFI and ISR Effects for Z/$gamma^*$ Drell-Yan Observables using ${cal KK}$MC-hh

Continuing with our investigations of the expected sizes of multiple photon radiative effects in heavy gauge boson production with decay to charged lepton pairs in the context of the precision physics of the LHC, using KK{MC}-hh 4.22 we consider IFI and ISR effects for specific Z/$gamma^*$ Drell-Yan observables measured by the ATLAS and CMS Collaborations. With this version of KK{MC}-hh, we have coherent exclusive exponentiation (CEEX) electroweak (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. Specifically, we illustrate the interplay between cuts of the type used in the measurement of $A_{FB}$ and $A_4$ 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 are applicable to current LHC experimental data analyses.