Off-shell effects in Higgs decays to heavy gauge bosons and signal-background interference in Higgs decays to photons at a linear collider

TL;DR

This paper analyzes off-shell contributions in Higgs decays to heavy gauge bosons and the interference effects in Higgs to diphoton decays at a linear collider, highlighting their importance for understanding electroweak symmetry breaking.

Contribution

It provides a detailed study of off-shell effects and signal-background interference in Higgs processes at electron-positron colliders, including their impact on Higgs width measurements.

Findings

Off-shell effects are significant depending on the collider energy.

Interference effects cause shifts in the diphoton invariant mass peak.

Sensitivity to the Higgs total width is discussed.

Abstract

We discuss off-shell contributions in Higgs decays to heavy gauge bosons $H\rightarrow VV^{(*)}$ with $V\in\lbrace Z,W\rbrace$ for a standard model (SM) Higgs boson for both dominant production processes $e^+e^-\rightarrow ZH\rightarrow ZVV^{(*)}$ and $e^+e^-\rightarrow \nu\bar\nu H\rightarrow \nu\bar\nu VV^{(*)}$ at a (linear) $e^+e^-$ collider. Dependent on the centre-of-mass energy off-shell effects are sizable and important for the understanding of the electroweak symmetry breaking mechanism. Moreover we shortly investigate the effects of the signal-background interference in $H\rightarrow \gamma\gamma$ decays for the Higgsstrahlung initiated process $e^+e^-\rightarrow Z\gamma\gamma$, where we report a similar shift in the invariant mass peak of the two photons as found for the LHC. For both effects we discuss the sensitivity to the total Higgs width.