Two-Higgs-doublet type-II seesaw model

Motivated by the new observed scalar boson of 126 GeV at ATLAS and CMS, various phenomena in the two-Higgs-doublet model are investigated broadly in the literature. For considering the model that possesses a solution to the massive neutrinos, we study the simplest extension of conventional type-II seesaw model to two Higgs doublets. We find that the new interactions in the scalar potential cause the sizable mixture of charged Higgses in a triplet and doublets. As a result, we have a completely different decay pattern for doubly charged Higgs (${\delta }^{\pm \pm }$); even the vacuum expectation value of a Higgs triplet is at GeV level, which is limited by the precision measurement for the $\rho$ parameter. For illustrating the new characters of the model, we study the influence of new interactions on the new open channels ${\delta }^{++}\to (H_1^{+}{W}^{{+}^{(*)}},H_1^{+}{H}_1^{+})$ with $H_1^{+}$ being the lightest charged Higgs. Additionally, due to the new mixing effect, the triplet charged Higgs could couple to quarks in the model; therefore, the search for ${\delta }^{++}$ via ${\delta }^{++}\to tb{W}^{+}\to b\overline{b}{W}^{+}{W}^{+}$ by mediated $H_1^{+}$ becomes significant.

Figure 1

The mixing effect $|\sin {\theta }_{\pm }|$ of $H^{\pm }$ and ${\delta }^{\pm }$ as a function of $\mu$ with $m_{H^{\pm }}=100\mathrm{GeV}$ and $m_{{\delta }^{\pm }}=250\mathrm{GeV}$. The left panel is for scheme I, while the right panel is for scheme II. The dotted, dashed, and dotted-dashed lines stand for $\tan \beta =1$, 10, and 30, respectively.

Figure 2

BRs for ${\delta }^{++}$ decays. The (a)–(f) plots, respectively, stand for BP1–6, defined in Tables 2 and 3.