Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Backgrounds To Higgs Boson Searches from Asymmetric Internal Conversion

Richard C. Gray, Can Kilic, Michael Park, Sunil Somalwar, Scott Thomas

TL;DR

The paper investigates backgrounds to Higgs searches in the WW(*) channel arising from W gamma* production with asymmetric internal conversion (LAME FAIC). It develops a theoretical framework based on the optical theorem to compute gamma* -> ll conversion probabilities, including differential distributions in the lepton momentum fraction z and polarization effects. The authors show that internal conversions can produce all lepton species and that a non-negligible fraction are highly asymmetric, yielding fake leptons at rates comparable to the Higgs signal in standard phase-space regions. These results underscore the importance of data-driven strategies to characterize and mitigate asymmetric internal-conversion backgrounds, with implications for both Higgs analyses and same-sign di-lepton searches.

Abstract

A class of potential backgrounds for Higgs boson searches in the W W to di-lepton channel at both the Tevatron and Large Hadron Collider is presented. Backgrounds from W photon production with external conversion of the on-shell photon in detector material to an asymmetric electron-positron pair, with loss of the trailing electron or positron has been treated adequately in Higgs searches. Here we consider analogous backgrounds from the production of a W with an off-shell photon and with the internal conversion of the off-shell photon in vacuum to an asymmetric lepton-anti-lepton pair. While the former process yields almost entirely electrons or positrons, the latter can give electron, positron, muon, and anti-muon backgrounds in roughly equal amounts. We estimate that asymmetric internal conversion backgrounds are comparable to the Higgs boson signal in the standard signal region of phase space. These processes also represent potential backgrounds for new physics searches in same-sign di-lepton channels. Some data driven methods to characterize asymmetric internal conversion backgrounds are suggested.

Backgrounds To Higgs Boson Searches from Asymmetric Internal Conversion

TL;DR

The paper investigates backgrounds to Higgs searches in the WW(*) channel arising from W gamma* production with asymmetric internal conversion (LAME FAIC). It develops a theoretical framework based on the optical theorem to compute gamma* -> ll conversion probabilities, including differential distributions in the lepton momentum fraction z and polarization effects. The authors show that internal conversions can produce all lepton species and that a non-negligible fraction are highly asymmetric, yielding fake leptons at rates comparable to the Higgs signal in standard phase-space regions. These results underscore the importance of data-driven strategies to characterize and mitigate asymmetric internal-conversion backgrounds, with implications for both Higgs analyses and same-sign di-lepton searches.

Abstract

A class of potential backgrounds for Higgs boson searches in the W W to di-lepton channel at both the Tevatron and Large Hadron Collider is presented. Backgrounds from W photon production with external conversion of the on-shell photon in detector material to an asymmetric electron-positron pair, with loss of the trailing electron or positron has been treated adequately in Higgs searches. Here we consider analogous backgrounds from the production of a W with an off-shell photon and with the internal conversion of the off-shell photon in vacuum to an asymmetric lepton-anti-lepton pair. While the former process yields almost entirely electrons or positrons, the latter can give electron, positron, muon, and anti-muon backgrounds in roughly equal amounts. We estimate that asymmetric internal conversion backgrounds are comparable to the Higgs boson signal in the standard signal region of phase space. These processes also represent potential backgrounds for new physics searches in same-sign di-lepton channels. Some data driven methods to characterize asymmetric internal conversion backgrounds are suggested.

Paper Structure

This paper contains 2 sections, 6 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Asymmetric Internal Conversion

Figures (1)

  • Figure 1: Diagrams for production of a leptonically decaying on/off-shell $W$-boson at a hadron collider in association with an initial or final state virtual off-shell photon radiation that internally converts in vacuum to a lepton--anti-lepton pair. Parentheses indicate asymmetric internal conversion in which the trailing converted lepton is not reconstructed as an independent isolated object. Diagrams with an off-shell photon radiated from the intermediate $W$-boson near the production or decay vertex are not shown.