Degenerate Higgs bosons decays to $\gamma \gamma$ and $Z\gamma$ in the type II seesaw model

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 (Higgs triplet models) are close to mass degenerate with a mass near 125 GeV. We analyze the effects of the Higgs potential parameters constrained by the full set of perturbative unitarity, boundedness from below 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 favors 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.

Figure 1

The $R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) ratios as a function of ${\lambda }_1$ for various values of $m_{H^{\pm \pm }}=\{100,125,175,215\}\mathrm{GeV}$ with $-5\le {\lambda }_2\le 5$ and ${\lambda }_3=2{\lambda }_2$.

Figure 2

Scatter plots showing the $R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) ratios in the $[{\lambda }_1,{\lambda }_4]$ with $-1\le {\lambda }_1\le 3$, $-5\le {\lambda }_2\le 5$, ${\lambda }_3=2{\lambda }_2$, and $-3\le {\lambda }_4\le 1$. The charged Higgs bosons masses vary as $110\mathrm{GeV}\le m_{H^{\pm }}\le 248\mathrm{GeV}$ and $92\mathrm{GeV}\le m_{H^{\pm \pm }}\le 328\mathrm{GeV}$.

Figure 3

Scatter plots showing the $R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) as a function of $\sin \alpha$ for various values of ${\lambda }_4$ with $-1\le {\lambda }_1\le 3$, $-5\le {\lambda }_2\le 5$, and ${\lambda }_3=2{\lambda }_2$.

Figure 4

The $R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) ratios as a function of $m_{H^{\pm \pm }}$ for various values of ${\lambda }_1$ with $v_t=1\mathrm{GeV}$ and $-5\le {\lambda }_2\le 5$, ${\lambda }_3=2{\lambda }_2$ and $-12\le {\lambda }_4\le 2$.

Figure 5

Scatter plots showing the $R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) ratios in the $[m_H,m_{H^{\pm \pm }}]$ with $-1\le {\lambda }_1\le 3$, $-5\le {\lambda }_2\le 5$, ${\lambda }_3=2{\lambda }_2$, and $-3\le {\lambda }_4\le 1$.

Figure 6

The $R_{\gamma \gamma }$ and $R_{Z\gamma }$ correlation with $\lambda =0.53$, $-2\le {\lambda }_1\le 12$, $-5\le {\lambda }_2\le 5$, ${\lambda }_3=2{\lambda }_2$, and $-12\le {\lambda }_4\le 2$.

Figure 7

$R_{\gamma \gamma }$ (left) and $R_{Z\gamma }$ (right) ratios as a function of ${\lambda }_1$ for various values of $v_t$ with $\lambda =0.530$, $-1\le {\lambda }_1\le 3$, $-5\le {\lambda }_2\le 5$, ${\lambda }_3=2{\lambda }_2$, and $-3\le {\lambda }_4\le 1$.