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) Ltriplet scalar field, which could cause a large Higgs mass correction. From the naturalness point of view, heavy Higgs masses should be lower than 350GeV, 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→ γγ, Zγ) deviate from the standard model, and a large parameter region is excluded by the recent ATLAS and CMS combined analysis of h→ γγ. Our result of the signal strength for h→ γγ is Rγγ≲ 1.1 , but its deviation is too small to observe at the LHC experiment.