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Interference effects for H --> WW/ZZ --> l anti-nu_l anti-l nu_l searches in gluon fusion at the LHC

Nikolas Kauer

TL;DR

This study quantitatively evaluates WW/ZZ interference in gluon-fusion Higgs processes leading to the same-flavour $\ell\bar{\nu}_\ell\bar{\ell}\nu_\ell$ final state at the LHC, across light and heavy Higgs masses, using LO loop-induced calculations with the gg2VV framework. It shows that interference is modest (~5%) for a SM-like light Higgs and negligible for heavier Higgs or the gluon-induced continuum unless kinematic constraints force one boson off-shell. The work also analyzes how standard and Higgs-search selection cuts modulate interference, finding that many cuts suppress interference to the percent level, while subdominant vector-boson contributions can still impact the signal-background interference by a few percent. For heavy-Higgs searches, upper bounds on transverse mass help mitigate potential interference-driven signal loss, and the results underscore the importance of including interference effects in precision Higgs analyses. The publicly available gg2VV tool enables reproducible evaluation of these effects in both SM and BSM contexts.

Abstract

WW/ZZ interference for Higgs signal and continuum background as well as signal-background interference is studied for same-flavour l anti-nu_l anti-l nu_l final states produced in gluon-gluon scattering at the LHC for light and heavy Higgs masses with minimal and realistic experimental selection cuts. For the signal cross section, we find WW/ZZ interference effects of O(5%) at M_H = 126 GeV. For M_H >= 200 GeV, we find that WW/ZZ interference is negligible. For the gg continuum background, we also find that WW/ZZ interference is negligible. As general rule, we conclude that non-negligible WW/ZZ interference effects occur only if at least one weak boson of the pair is dominantly off-shell due to kinematic constraints. The subdominant weak boson pair contribution induces a correction to the signal-background interference, which is at the few percentage point level before search selection cuts. Optimised selection cuts for M_H >~ 600 GeV are suggested.

Interference effects for H --> WW/ZZ --> l anti-nu_l anti-l nu_l searches in gluon fusion at the LHC

TL;DR

This study quantitatively evaluates WW/ZZ interference in gluon-fusion Higgs processes leading to the same-flavour final state at the LHC, across light and heavy Higgs masses, using LO loop-induced calculations with the gg2VV framework. It shows that interference is modest (~5%) for a SM-like light Higgs and negligible for heavier Higgs or the gluon-induced continuum unless kinematic constraints force one boson off-shell. The work also analyzes how standard and Higgs-search selection cuts modulate interference, finding that many cuts suppress interference to the percent level, while subdominant vector-boson contributions can still impact the signal-background interference by a few percent. For heavy-Higgs searches, upper bounds on transverse mass help mitigate potential interference-driven signal loss, and the results underscore the importance of including interference effects in precision Higgs analyses. The publicly available gg2VV tool enables reproducible evaluation of these effects in both SM and BSM contexts.

Abstract

WW/ZZ interference for Higgs signal and continuum background as well as signal-background interference is studied for same-flavour l anti-nu_l anti-l nu_l final states produced in gluon-gluon scattering at the LHC for light and heavy Higgs masses with minimal and realistic experimental selection cuts. For the signal cross section, we find WW/ZZ interference effects of O(5%) at M_H = 126 GeV. For M_H >= 200 GeV, we find that WW/ZZ interference is negligible. For the gg continuum background, we also find that WW/ZZ interference is negligible. As general rule, we conclude that non-negligible WW/ZZ interference effects occur only if at least one weak boson of the pair is dominantly off-shell due to kinematic constraints. The subdominant weak boson pair contribution induces a correction to the signal-background interference, which is at the few percentage point level before search selection cuts. Optimised selection cuts for M_H >~ 600 GeV are suggested.

Paper Structure

This paper contains 12 sections, 12 equations, 2 figures, 9 tables.

Table of Contents

  1. Introduction
  2. Calculational details
  3. Amplitude
  4. Phase space
  5. Results
  6. Gluon-induced continuum background
  7. Light Higgs boson signal
  8. Heavy Higgs boson signal
  9. Minimal cuts
  10. $H\to ZZ$ search cuts
  11. $H\to WW$ search cuts
  12. Conclusions

Figures (2)

  • Figure 1: Representative Feynman graphs for the LO amplitude of $gg\to WW \to \ell\bar{\nu}_\ell\bar{\ell}\nu_\ell$ (Higgs signal (a) and continuum background (b) contributions) and $gg\to ZZ \to \ell\bar{\nu}_\ell\bar{\ell}\nu_\ell$ (Higgs signal (c) and continuum background (d) contributions).
  • Figure 2: Representative triangle graphs that formally contribute to $gg\to \ell\bar{\nu}_\ell\bar{\ell}\nu_\ell$.