Abstract
We analyze the vacuum stability in the inert Higgs doublet extension of the Standard Model (SM), augmented by right-handed neutrinos (RHNs) to explain neutrino masses at tree level by the seesaw mechanism. We make a comparative study of the high- and low-scale seesaw scenarios and the effect of the Dirac neutrino Yukawa couplings on the stability of the Higgs potential. Bounds on the scalar quartic couplings and Dirac Yukawa couplings are obtained from vacuum stability and perturbativity considerations. These bounds are found to be relevant only for low-scale seesaw scenarios with relatively large Yukawa couplings. The regions corresponding to stability, metastability and instability of the electroweak vacuum are identified. These theoretical constraints give a very predictive parameter space for the couplings and masses of the new scalars and RHNs which can be tested at the LHC and future colliders. The lightest non-SM neutral CP-even/odd scalar can be a good dark matter candidate and the corresponding collider signatures are also predicted for the model.
Highlights
As alluded to above, nonzero neutrino masses provide a strong motivation for beyond the Standard Model (SM) physics
To see the individual effects of the scalar quartic couplings λ2,3,4,5 on the stability scale, we show in figure 10 the three-dimensional correlation plots for λ3 versus λ4 with energy scale μ for different values of YN and MR with a fixed λ2 = λ5 = 0.01
We have considered a simple extension of the SM with a Z2-odd inert Higgs doublet, supplemented by right-handed neutrinos with potentially large Dirac Yukawa couplings
Summary
We extend the SM by adding another SU(2)L-doublet scalar field and three RHNs which are singlets under the SM gauge group. We consider the SM gauge-singlet RHNs which are even under Z2 symmetry and generate small neutrino masses via type-I seesaw mechanism, while the lightest component of the Z2-odd inert doublet is the DM candidate.
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