In general, there can be mass differences among scalar bosons of the Higgs triplet field with the hypercharge of $Y=1$. In the Higgs triplet model, when the vacuum expectation value $v_{\Delta }$ of the triplet field is much smaller than that $v$ ($\simeq 246\mathrm{GeV}$) of the Higgs doublet field as required by the electroweak precision data, a characteristic mass spectrum $m_{H^{++}}^2-m_{H^{+}}^2\simeq m_{H^{+}}^2-m_{{\varphi }^0}^2(\equiv \xi )$ appears, where $m_{H^{++}}$, $m_{H^{+}}$, $m_{{\varphi }^0}$ are the masses of the doubly-charged ($H^{++}$), the singly-charged ($H^{+}$), and the neutral (${\varphi }^0=H^0$ or $A^0$) scalar bosons, respectively. It should be emphasized that phenomenology with $\xi \ne 0$ is drastically different from that in the case with $\xi =0$ where the doubly-charged scalar boson decays into the same-sign dilepton ${\ell }^{+}{\ell }^{+}$ or the diboson $W^{+}{W}^{+}$ depending on the size of $v_{\Delta }$. We find that, in the case of $\xi >0$, where $H^{++}$ is the heaviest, $H^{++}$ can be identified via the cascade decays such as $H^{++}\to H^{+}{W}^{+(*)}\to {\varphi }^0{W}^{+(*)}{W}^{+(*)}\to b\overline{b}{\ell }^{+}\nu {\ell }^{+}\nu$. We outline how the Higgs triplet model can be explored in such a case at the LHC. By the determination of the mass spectrum, the model can be tested and further distinguished from the other models with doubly-charged scalar bosons.

• Received 20 October 2011

DOI:https://doi.org/10.1103/PhysRevD.85.055007