A Study of Hadronic Backgrounds to Isolated Hard Photon Production with L3

TL;DR

This paper investigates hadronic backgrounds to isolated photon production at LEP, revealing that Monte Carlo models underestimate neutral hadron production, which impacts background estimates for LHC Higgs searches.

Contribution

It introduces two methods for studying hadronic backgrounds and compares observed data with Monte Carlo models, highlighting discrepancies in neutral hadron production predictions.

Findings

Monte Carlo models underestimate neutral hadron production by a factor of 1.5-2.5.

Observed background rates are higher than predictions, affecting LHC Higgs search estimates.

Two methods for background study are proposed and validated.

Abstract

I describe two methods for studying hadronic backgrounds to prompt photon production with L3, and compare the observed background rates with Monte Carlo predictions. I find that the Monte Carlo models JETSET and HERWIG underestimate the production of isolated neutral hadrons in hadronic Z decays at LEP. By extrapolating results obtained with L3, I estimate that the rate of prompt-photon + jet background to a H -> gamma gamma search at the LHC will be larger than Monte Carlo predictions by a factor of 1.5-2.5.