Abstract
In the inverse seesaw model (ISS), the smallness of the neutrino masses is related to the smallness of a lepton number violating mass term whilst the seesaw scale is naturally close to the TeV scale, which allows for large effects in lepton flavor and universality violating observables. With the ongoing and planned measurements of the Higgs boson properties at the LHC, we found timely to investigate the possibility of having large lepton flavor violating Higgs decay (LFVHD) rates within the context of the ISS, considering the most generic case where three additional pairs of massive right-handed singlet neutrinos are added to the Standard Model particle content. We present a full one-loop computation of the LFVHD rates and analyze in full detail the predictions as functions of the various relevant ISS parameters, which are required to be compatible with the present neutrino data and the present experimental bounds for the three LFV radiative decays, and also consistent with other constraints, like perturbativity of the neutrino Yukawa couplings. At the end, we conclude on the maximum allowed LFVHD rates within the ISS, which may reach maximal values of order 10−5 for the H→eτ‾ and H→μτ‾ channels, close to the expected future LHC sensitivities.
Highlights
The fact of considering the discovered scalar particle at the CERN-LHC as the Higgs particle of the Standard Model (SM), with very similar properties and a measured mass of mAhTLAS = 125.5 ± 0.6 GeV [1] and mCh MS = 125.7 ± 0.4 GeV [2], has at present reached a broad consensus.On the other hand, there is a major consensus about the fact that the SM must be modified to include the neutrino masses and oscillations in agreement with present data [3], which are nowadays quite impressive and call for an explanation from a theoretical framework beyond the SM
The seesaw mechanism that produces the small light physical neutrino masses in the Inverse Seesaw Model (ISS) is associated to the smallness of the Majorana mass model parameters and it allows for large Yukawa neutrino couplings while having at the same time moderately heavy RH neutrino masses at the O(TeV) energies which are reachable at the present colliders, like the LHC
These RH neutrinos can produce non-negligible contributions to processes with Lepton Flavor Violation (LFV) via radiative corrections that are mediated by the sizable neutrino Yukawa couplings, leading to some hint of these rare processes, which are totally absent in the SM
Summary
The fact of considering the discovered scalar particle at the CERN-LHC as the Higgs particle of the Standard Model (SM), with very similar properties and a measured mass of mAhTLAS = 125.5 ± 0.6 GeV [1] and mCh MS = 125.7 ± 0.4 GeV [2], has at present reached a broad consensus. There is a major consensus about the fact that the SM must be modified to include the neutrino masses and oscillations in agreement with present data [3], which are nowadays quite impressive and call for an explanation from a theoretical framework. / Nuclear Physics B Proceedings Supplement 00 (2021) 1–7 the ISS context with three extra pairs of RH neutrinos, the Higgs decays into lepton-antilepton pairs H → lklm with k m (LFVHD), which are being currently explored at the LHC [7]. We refer the reader to our main article [8] for more information and details about the full one-loop computation of the LFV partial decay widths, the complete set of references and our full numerical results
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