Higgs boson decay into 2 photons in the type~II Seesaw Model

TL;DR

This paper investigates how the type II Seesaw Model affects the Higgs boson's decay into two photons, revealing parameter-dependent enhancements or suppressions that could explain experimental excesses or exclusions.

Contribution

It provides a detailed analysis of the diphoton decay channel in the type II Seesaw Model, highlighting the role of charged Higgs bosons and their interference effects, which are novel insights.

Findings

Enhanced diphoton decay in certain parameter regions due to charged Higgs contributions

Destructive interference leading to suppressed diphoton branching ratios

Constraints on charged Higgs masses from experimental limits

Abstract

We study the two photon decay channel of the Standard Model-like component of the CP-even Higgs bosons present in the type II Seesaw Model. The corresponding cross-section is found to be significantly enhanced in parts of the parameter space, due to the (doubly-)charged Higgs bosons' $(H^{\pm \pm})H^\pm$ virtual contributions, while all the other Higgs decay channels remain Standard Model(SM)-like. In other parts of the parameter space $H^{\pm \pm}$ (and $H^{\pm}$) interfere destructively, reducing the two photon branching ratio tremendously below the SM prediction. Such properties allow to account for any excess such as the one reported by ATLAS/CMS at $\approx 125$ GeV if confirmed by future data; if not, for the fact that a SM-like Higgs exclusion in the diphoton channel around 114-115 GeV as reported by ATLAS, does not contradict a SM-like Higgs at LEP(!), and at any rate, for the fact that ATLAS/CMS exclusion limits put stringent lower bounds on the $H^{\pm \pm}$ mass, particularly in the parameter space regions where the direct limits from same-sign leptonic decays of $H^{\pm \pm}$ do not apply.