Vacuum stability and naturalness in type-II seesaw

Abstract

We study the vacuum stability and perturbativity conditions in the minimal type-II seesaw model. These conditions give characteristic constraints to the model parameters. In the model, there is a $$SU(2)_L$$ triplet scalar field, which could cause a large Higgs mass correction. From the naturalness point of view, heavy Higgs masses should be lower than $$350\,\mathrm{GeV}$$ , which may be testable by the LHC Run-II results. Due to the effects of the triplet scalar field, the branching ratios of the Higgs decay ( $$h\rightarrow \gamma \gamma , Z\gamma $$ ) deviate from the standard model, and a large parameter region is excluded by the recent ATLAS and CMS combined analysis of $$h\rightarrow \gamma \gamma $$ . Our result of the signal strength for $$h\rightarrow \gamma \gamma $$ is $$R_{\gamma \gamma } \lesssim 1.1$$ , but its deviation is too small to observe at the LHC experiment.