Background to Higgs-boson searches from internal conversions of off-shell photons associated with $Z/\gamma ^*$-boson production at the LHC

TL;DR

This study investigates the impact of off-shell photon emissions and their conversions into lepton pairs on the background for Higgs boson searches at the LHC, extending previous analyses by including parton-shower effects.

Contribution

It introduces a detailed analysis of off-shell photon emissions in background processes, highlighting their significance at lower lepton transverse momenta and proposing a measurement method for these effects.

Findings

Including off-shell photon emissions does not significantly alter background estimates for pT > 7 GeV.

Parton-shower contributions become important at lower lepton transverse momenta.

A new measurement method is proposed to quantify parton-shower effects.

Abstract

This paper presents the studies of the background contribution to the $H \rightarrow 4l$ searches originating from the processes of off-shell (virtual) photon emissions and their conversions into lepton pairs accompanying the production of $Z/ \gamma ^*$-bosons at the LHC. They extend the analyses of the irreducible background presented in the ATLAS and CMS Higgs papers by taking into account the emissions of off-shell photons by parton showers. Including these effects does not change significantly the Higgs-searches background level, provided that the transverse momentum of each of the final-state leptons is restricted to the range of $p_{T, l} > 7$ GeV. In the kinematical region extended towards lower lepton transverse momenta the parton-shower contribution becomes important. A measurement method for pinning down the parton-shower effects is proposed.