Implications of the LHC two-photon signal for two-Higgs-doublet models

TL;DR

This paper examines how recent LHC hints of a 125 GeV Higgs decaying into two photons constrain various two-Higgs-doublet models, analyzing their parameter spaces and decay predictions.

Contribution

It provides a detailed analysis of the parameter space of different two-Higgs-doublet models based on the LHC two-photon signal, highlighting their implications for other decay channels.

Findings

Allowed parameter regions are consistent with the Standard Model for most decay channels.

Decays to τ+τ− are highly sensitive in the Lepton Specific model across the allowed region.

Decays to WW, ZZ, and bb are not more than twice the Standard Model predictions.

Abstract

We study the implications for Two Higgs Doublet Models of the recent announcement at the LHC giving a tantalizing hint for a Higgs boson of mass 125 GeV decaying into two photons. We require that the experimental result be within a factor of two of the theoretical Standard Model prediction, and analyze the type I and type II models as well as the lepton-specific and flipped models, subject to this requirement. It is assumed that there is no new physics other than two Higgs doublets. In all of the models, we display the allowed region of parameter space taking the recent LHC announcement at face value, and we analyze the $W^+W^-$, $ZZ$, $\bar{b}b$ and $\tau^+\tau^-$ expectations in these allowed regions. Throughout the entire range of parameter space allowed by the $\gamma\gamma$ constraint, the number of events for Higgs decays into $WW$, $ZZ$ and $b \bar b$ are not changed from the Standard Model by more than a factor of two. In contrast, in the Lepton Specific model, decays to $\tau^+ \tau^- $ are very sensitive across the entire $\gamma \gamma$-allowed region.