In this paper we consider a Higgs boson with mass and other properties compatible with those of the recently discovered Higgs particle at the LHC, and explore the possibility of new Higgs leptonic decays, beyond the standard model, with the singular feature of being lepton flavor violating (LFV). We study these LFV Higgs decays, H → l klm , within the context of the inverse seesaw model (ISS) and consider the most generic case where three additional pairs of massive right-handed singlet neutrinos are added to the standard model particle content. We require in addition that the input parameters of this ISS model are compatible with the present neutrino data and other constraints, like perturbativity of the neutrino Yukawa couplings. We present a full one-loop computation of the BRðH → l klm Þ rates for the three possible channels, l klm ¼ μτ, eτ, eμ, and analyze in full detail the predictions as functions of the various relevant ISS parameters. We study in parallel the correlated one-loop predictions for the radiative decays, l m → l k γ, within this same ISS context, and require full compatibility of our predictions with the present experimental bounds for the three radiative decays, μ → eγ, τ → μγ, and τ → eγ. After exploring the ISS parameter space we conclude on the maximum allowed LFV Higgs decay rates within the ISS.

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Reprinted with permission from the American Physical Society: Arganda, E., Herrero, M.J., Marcano, X. Weiland, C. (2016). Enhancement of the lepton avor violating Higgs boson decay rates from SUSY loops in the inverse seesaw model. Physical Review D 93(5): 055010 c (2017) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. In this article, we study the full one-loop SUSY contributions to the lepton flavor violating Higgs decay h → τμ, within the context of the supersymmetric inverse seesaw model. We assume that both the righthanded neutrino masses, M R , and their supersymmetric partner masses, m~ν R , are not far from the interesting OðTeVÞ energy scale, and we work with scenarios with large neutrino Yukawa couplings that transmit large lepton flavor violating effects. By exploring the behavior with the most relevant parameters, mainly M R , m~ν R and the trilinear sneutrino coupling A ν , we will look for regions of the parameter space where the enhancement of BRðh → τμÞ is large enough to reach values at the percent level, which could explain the excess recently reported by CMS and ATLAS at the CERN Large Hadron Collider.

Abstract:In the present work we study the production of vector resonances at the LHC by means of the vector boson scattering W Z → W Z and explore the sensitivities to these resonances for the expected future LHC luminosities. We are assuming that these vector resonances are generated dynamically from the self interactions of the longitudinal gauge bosons, W L and Z L , and work under the framework of the electroweak chiral Lagrangian to describe in a model independent way the supposedly strong dynamics of these modes. The properties of the vector resonances, mass, width and couplings to the W and Z gauge bosons are derived from the inverse amplitude method approach. We implement all these features into a single model, the IAM-MC, adapted for MonteCarlo, built in a Lagrangian language in terms of the electroweak chiral Lagrangian and a chiral Lagrangian for the vector resonances, which mimics the resonant behavior of the IAM and provides unitary amplitudes. The model has been implemented in MadGraph, allowing us to perform a realistic study of the signal versus background events at the LHC. In particular, we have focused our study on the pp → W Zjj type of events, discussing first on the potential of the hadronic and semileptonic channels of the final W Z, and next exploring in more detail the most clear signals. These are provided by the leptonic decays of the gauge bosons, leading to a final state with + 1 − 1 + 2 νjj, = e, µ, having a very distinctive signature, and showing clearly the emergence of the resonances with masses in the range of 1.5-2.5 TeV, which we have explored.

In this work we present a new computation of the lepton flavor violating Higgs boson decays that are generated radiatively to one-loop from heavy right-handed neutrinos. We work within the context of the inverse seesaw model with three ν R and three extra singlets X, but the results could be generalized to other low scale seesaw models. The novelty of our computation is that it uses a completely different method by means of the mass insertion approximation which works with the electroweak interaction states instead of the usual 9 physical neutrino mass eigenstates of the inverse seesaw model. This method also allows us to write the analytical results explicitly in terms of the most relevant model parameters, that are the neutrino Yukawa coupling matrix Y ν and the right-handed mass matrix M R , which is very convenient for a phenomenological analysis. This Y ν matrix, being generically nondiagonal in flavor space, is the only responsible for the induced charged lepton flavor violating processes of our interest. We perform the calculation of the decay amplitude up to order O(Y 2 ν + Y 4 ν ). We also study numerically the goodness of the mass insertion approximation results. In the last part we present the computation of the relevant one-loop effective vertex H i j for the lepton flavor violating Higgs decay which is derived from a large M R mass expansion of the form factors. We believe that our simple formula found for this effective vertex can be of interest for other researchers who wish to estimate the H → i¯ j rates in a fast way in terms of their own preferred input values for the relevant model parameters Y ν and M