Enhancement of $h \to \gamma \gamma$ by seesaw-motivated exotic scalars

TL;DR

This paper investigates how seesaw-motivated exotic scalars can enhance the Higgs decay to two photons, focusing on a TeV-scale model with scalar quadruplets and fermionic quintuplets, leading to significant increases in the diphoton decay rate.

Contribution

It introduces a simple TeV-scale seesaw model with exotic scalars that can notably increase the Higgs to diphoton decay rate compared to the Standard Model.

Findings

Charged scalar components, especially doubly charged, significantly enhance $h o \gamma \\gamma$ decay.

The $h o Z \\gamma$ decay width is mildly suppressed in the parameter space with enhanced diphoton decay.

Enhancement factors of 1.25 to 2 in the $h o \\gamma \\gamma$ decay width are achievable.

Abstract

We examine the role of seesaw motivated exotic scalars in loop-mediated Higgs decays. We consider a simple TeV-scale seesaw model built upon the fermionic quintuplet mediator in conjunction with the scalar quadruplet, where we examine portions of the model parameter space for which the contributions of charged components of the scalar quadruplet significantly increase the $h \to \gamma \gamma$ decay rate. The most significant change in the diphoton width comes from a doubly charged scalar \Phi^{--} which should be the lightest component in the scalar quadruplet. There is a mild suppression of the $h \to Z \gamma$ decay width by a factor 0.9 -- 0.7 in the part of the parameter space where the $h \to \gamma \gamma$ decay width is enhanced by a factor 1.25 -- 2.