M. J. Herrero

Flavor physics of leptons and dipole moments

This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

The Standard Model

These lectures provide an introduction to the basic aspects of the Standard Model, SU(3) c × SU(2) L × U(1)y.

Imprints of massive inverse seesaw model neutrinos in lepton flavor violating Higgs boson decays

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 k l ¯ m , 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 BR ( H → l k l ¯ m ) rates for the three possible channels, l k l ¯ m = μ τ ¯ , e τ ¯ , e μ ¯ , 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 → e γ , τ → μ γ , and τ → e γ . After exploring the ISS parameter space we conclude on the maximum allowed LFV Higgs decay rates within the ISS.

Impact of θ13 on lepton flavour violating processes within SUSY seesaw

We study the impact of neutrino masses and mixings on LFV processes within the context of the supersymmetric seesaw scenario, where the CMSSM is extended by three right-handed (s)neutrinos. A hierarchical spectrum is considered for both heavy and light neutrinos. We systematically analyse the interesting relation between the leptonic mixing angle �13 and LFV muon and tau decays, namely lj → li and lj → 3li, and discuss the interplay with the other relevant parameters. We require compatibility with low energy neutrino data, bounds on both LFV decays and charged lepton electric dipole moments, and impose a successful baryogenesis via thermal leptogenesis. Particular emphasis is given to the implications that a future �13 measurement can have on our knowledge of the heavy neutrino sector.

mu-e conversion in nuclei within the CMSSM seesaw: Universality versus non-universality

In this paper we study ??e conversion in nuclei within the context of the Constrained Minimal Supersymmetric Standard Model, enlarged by three right handed neutrinos and their supersymmetric partners, and where the neutrino masses are generated via a seesaw mechanism. Two different scenarios with either universal or non-universal soft supersymmetry breaking Higgs masses at the gauge coupling unification scale are considered. In the first part we present a complete one-loop computation of the conversion rate for this process that includes the photon-, Z-boson, and Higgs-boson penguins, as well as box diagrams, and compare their size in the two considered scenarios. Then, in these two scenarios we analyse the relevance of the various parameters on the conversion rates, particularly emphasising the role played by the heavy neutrino masses, tan ?, and especially ?13. In the case of hierachical heavy neutrinos, an extremely high sensitivity of the rates to ?13 is indeed found. The last part of this work is devoted to the study of the interesting loss of correlation between the ??e conversion and ??e? rates that occurs in the non-universal scenario. In the case of large tan ? and light H0 Higgs boson, an enhanced ratio of the ??e to ??e? rates, with respect to the universal case is found, and this could be tested with the future experimental sensitivities.

The Electroweak chiral Lagrangian for the Standard Model with a heavy Higgs

Abstract The most general chiral lagrangian for electroweak interactions with the complete set of SU (2)L × U (1)Y invariant operators up to dimension four is considered. The two-point and three-point functions with external gauge fields are derived from this effective chiral lagrangian to one-loop order in a generic Rξ-gauge. The same set of Green functions are simultaneously studied in the renormalizable standard model to one-loop order, in a Rξ-gauge and in the large Higgs mass limit. An appropriate set of matching conditions connecting the Green functions of the two theories allows us to derive, systematically, the values of the chiral lagrangian coefficients corresponding to the large Higgs mass limit of the standard model. These chiral parameters represent the non-decoupling effects of a heavy Higgs particle and incorporate both the leading logarithmic dependence on mH and the next to leading constant contributions. Some phenomenological implications are also discussed.

Enhancement of the lepton flavor violating Higgs boson decay rates from SUSY loops in the inverse seesaw model.

This work is supported by the European Union Grant No. FP7 ITN INVISIBLES (Marie Curie Actions, Grant No. PITN-GA-2011-289442), by the CICYT through Grant No. FPA2012-31880, by the Spanish Consolider-Ingenio 2010 Programme CPAN (Grant No. CSD2007-00042), and by the Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme under Grant No. SEV-2012-0249. E. A. is financially supported by the Spanish DGIIDDGA Grant No. 2013-E24/2 and the Spanish MICINN Grants No. FPA2012-35453 and No. CPAN-CSD2007- 00042. X. M. is supported through the FPU Grant No. AP- 2012-6708. C. W. received financial support as an International Research Fellow of the Japan Society for the Promotion of Science and from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant NuMass Agreement No. 617143 during different stages of this work.

Flavor changing neutral Higgs boson decays from squark Gluino loops

We study the flavour changing neutral Higgs boson decays that can be induced from genuine supersymmetric particles at the one-loop level and within the context of the Minimal Supersymmetric Standard Model. We consider all the possible flavour changing decay channels of the three neutral Higgs bosons into second and third generation quarks, and focus on the Supersymmetric-QCD corrections from squark-gluino loops which are expected to provide the dominant contributions. We assume here the more general hypothesis for flavour mixing, where there is misalignment between the quark and squark sectors, leading to a flavour non-diagonal squark mass matrix. The form factors involved, and the corresponding Higgs partial decay widths and branching ratios, are computed both analytically and numerically, and their behaviour with the parameters of the Minimal Supersymmetric Standard Model and with the squark mass mixing are analyzed in full detail. The large rates found, are explained in terms of the non-decoupling behaviour of these squark-gluino loop corrections in the scenario with very large supersymmetric mass parameters. Our results show that if these decays are seen in future colliders they could provide clear indirect signals of supersymmetry.

Supersymmetric QCD corrections to the minimal supersymmetric standard model h{sup 0}b{bar B} vertex in the decoupling limit

We analyze the supersymmetric (SUSY) QCD contribution to the

The Higgs sector of the MSSM in the decoupling limit

h^0 b \bar{b}