Type-II seesaw model with two-Higgs doublets

A study of searching for doubly charged Higgs $(\delta^{\pm\pm})$ is performed in two-Higgs-doublet extension of the type-II seesaw model. We find that a significant mixing effect between singly charged Higgs of Higgs doublet and of triplet is arisen from the scalar potential. The mixing leads to new production processes and decay patterns of doubly charged Higgs. With luminosity of 40 fb$^{-1}$ and collision energy of 13 TeV at the LHC, we show that $\delta^{\pm\pm}$ with mass below $330$ GeV could be observed at the $5\sigma$ level. Moreover, for the luminosity of 300 fb$^{-1}$, the observed mass of $\delta^{\pm\pm}$ could reach up to 450 GeV.