Two-Higgs-Doublet Models and Enhanced Rates for a 125 GeV Higgs

TL;DR

This paper investigates the potential for enhanced Higgs decay signals in two-Higgs-doublet models near 125 GeV, considering various experimental and theoretical constraints, and finds specific scenarios where such enhancements are possible.

Contribution

It provides a detailed analysis of the enhancement possibilities for Higgs decay channels in two-Higgs-doublet models under current constraints, highlighting differences between Type I and Type II models.

Findings

Significant gamma gamma enhancement in Type I models is possible with certain parameters.

Type II models require even greater ZZ mode enhancement for gamma gamma signal increase, which current data disfavors.

Maximum gamma gamma to SM ratio found is approximately 1.3 for specific tanβ values and minimal charged Higgs mass.

Abstract

We examine the level of enhancement that can be achieved in the ZZ and \gamma\gamma channels for a two-Higgs-doublet model Higgs boson (either the light h or the heavy H) with mass near 125 GeV after imposing all constraints from LEP data, B physics, precision electroweak data, vacuum stability, unitarity and perturbativity. The latter constraints restrict substantially the possibilities for enhancing the gg -> h -> \gamma\gamma or gg -> H -> \gamma\gamma signal relative to that for the SM Higgs, hSM. Further, we find that a significant enhancement of the gg -> h -> \gamma\gamma or gg -> H -> \gamma\gamma signal in Type II models is possible only if the gg -> h -> ZZ or gg -> H -> ZZ mode is even more enhanced, a situation disfavored by current data. In contrast, in the Type I model one can achieve enhanced rates in the \gamma\gamma final state for the h while having the ZZ mode at or below the SM rate - the largest [gg -> h -> \gamma\gamma]/[gg -> hSM -> \gamma\gamma] ratio found is of order ~1.3 when the two Higgs doublet vacuum expectation ratio is tan\beta = 4 or 20 and the charged Higgs boson has its minimal LEP-allowed value of m_{H^\pm} = 90 GeV.