Degenerate Higgs bosons decays to ${\gamma\gamma}$ and ${Z\gamma}$ in the type II Seesaw Model

Abstract

Using the most recent results of CMS and ATLAS, we study the Higgs decays to $\gamma\gamma$ and $Z\gamma$ in the scenario where the two CP even Higgs predicted by the type II seesaw model (HTM) are close to mass degenerate with a mass near $125$ GeV. We analyse the effects of the Higgs potential parameters constrained by the full set of perturbative unitarity, boundedness from below (BFB) as well as from precision electroweak measurements on these decay modes. Our analysis demonstrates that the observed excess in the diphoton Higgs decay channel can be interpreted in our scenario within a delineated region controlled by $\lambda_{1}$ and $\lambda_{4}$ coupling. We also find a deviation in the Higgs decay to $Z\gamma$ with respect to the Standard Model prediction and the largest enhancement is found for a ratio $R_{Z\gamma}$ of the order $1.6$. Furthermore we show that consistency with current ATLAS data on the diphoton decay channel favours a light doubly charged Higgs with mass in the range $92 - 180$~GeV. Finally, we find that the $\gamma\gamma$ and $Z \gamma$ Higgs decay modes are generally correlated and the magnitude of correlation is sensitive to the sign of the $\lambda_{1}$ parameter.