Interference of Higgs diphoton signal and background in production with a jet at the LHC

TL;DR

This paper investigates how interference effects impact the Higgs diphoton mass measurement at the LHC, especially in processes with an additional jet, finding the mass shift to be minimal with certain jet cuts.

Contribution

It extends previous interference studies to include processes with an extra jet, showing the mass shift is negligible for specific jet transverse momentum cuts.

Findings

Mass shift due to interference is very small with jet pT cuts of 25 GeV or more.

Interference effects are reduced in processes with an additional jet compared to gluon fusion alone.

Cancellation occurs between different subprocesses, minimizing the overall mass shift.

Abstract

The Higgs mass determination from diphoton events at the LHC can be affected by interference between the Higgs resonant and continuum background amplitudes with the same initial and final states. For the leading order gluon fusion process, this shift was previously found to exceed 100 MeV, with some dependence on the diphoton mass resolution and the methods used to extract and fit the peak from data. In this paper, I consider the mass shift for the process pp --> j\gamma\gamma\ that includes an additional central jet in the final state. For cuts on the transverse momentum of the jet of 25 GeV or more, the diphoton Higgs peak mass shift due to interference is found to be very small, due in part to less interference for the gluon-gluon initiated subprocess, and in part to a cancellation between it and the quark-gluon initiated subprocess.