LFV in semileptonic τ decays and μ−e conversion in nuclei in SUSY-seesaw

Abstract

Abstract. Here we review the main results of LFV in the semileptonic tau decays τ → µPP (PP = π + π − , π 0 π 0 , K + K − , K 0K0 ), τ → µP (P = π, η, η ′ ), and τ → µV (V = ρ, φ ) as well as in µ − e conversion in nuclei within SUSY-seesaw scenarios, and compare our predictions with the present experimental bounds 1 . FRAMEWORK FOR LFVWe work within the framework of the Minimal Supersymmetric Standard Model (MSSM) enlarged by three right handed neutrinos and their SUSY partners, where potentially observable LFV effects in the charged lepton sector are expected to occur. We further assume a seesaw mechanism for neutrino mass generation and use thethe three heavy ones. U MNS is given by the three (light) neutrino mixing angles θ 12 , θ 23 and θ 13 , and three phases, δ , φ 1 and φ 2 . With this parameterisation it is easy to accommodate the neutrino data, while leaving room for extra neutrino mixings (from the right handed sector). It further allows for large Yukawa couplings Y ν ∼ O(1) by choosing large entries in m diag N and/or θ i . Here we focus in the particular LFV proc-φ ) decays and 2) µ − e conversion in heavy nuclei. The predictions in the following are for two different constrained MSSM-seesaw scenarios, with universal and non-universal Higgs soft masses. The respective parameters (in addition to the previous neutrino sector parameters) are: 1) CMSSM-seesaw: M 0 , M 1/2 , A 0 tan β , and sign(µ), and 2) NUHM-seesaw:1 Talk given at the SUSY08 conference, Seoul, by M. Herrero.and M H 2 = M 0 (1 + δ 2 ) 1/2 . The predictions presented here for the µ − e conversion rates include the full set of SUSY one-loop contributing diagrams, mediated by γ, Z, and Higgs bosons, as well as boxes, and do not use the Leading Logarithmic (LLog) nor the mass insertion approximations. In the case of semileptonic tau decays we have not included the boxes which are clearly subdonimant. The hadronisation of quark bilinears is performed within the chiral framework, using Chiral Perturbation Theory and Resonance Chiral Theory. This is a very short summary of the works in [1] and [2] to which we refer the reader for more details. RESULTS AND DISCUSSIONHere we present the predictions for BR(τ → µPP)and CR(µ − e, Nuclei) within the previously described framework and compare them with the following experimental bounds:, CR(µ − e, Au) < 7 × 10 −13 and CR(µ − e, Ti) < 4.3 × 10 −12 .As a general result in LFV processes that can be mediated by Higgs bosons we have found that the H 0 and A 0 contributions are relevant at large tan β if the Higgs masses are light enough. It is in this aspect where the main difference between the two considered scenarios lies. Within the CMSSM, light Higgs H 0 and A 0 bosons are only possible for low M SUSY (here we take M SUSY = M 0 = M 1/2 to reduce the number of input parameters). In contrast, within the NUHM, light Higgs bosons can be

Phenomenology of the triplet seesaw mechanism with gauge and Yukawa mediation of SUSY breaking

“…Although the Higgs-exchange diagram contribution also benefits from a tan β enhancement, its numerical relevance requires the Higgs bosons A and H to be significantly lighter than the sleptons, charginos and neutralinos [57,58,56,59]. As already discussed in Section 7.1, in our scenario this does not occur, thus the Higgs-mediated contributions come out to be subleading.…”

“…Moreover, the authors of Ref. [59] have recently re-evaluated the contributions to A L,R and claimed to have found additional contributions disregarded in Ref. [11].…”

Lepton flavor violation in the inert scalar model with higher representations

“…Moreover, B 1 , C 0 and C 24 are the loop functions, adopted from [60,62,63], presented in the appendix B. As B 1 and C 24 arise from divergent loop integrals, for large M ,…”

“…For the doublet, the contribution is given by the neutral fermion. Following the formulas given in [60,62,63…”

Differentiating Neutrino Models on the Basis of θ[sub 13] and Lepton Flavor Violation

“…The ji-e conversion branching ratio is the conversion rate scaled by the capture rate for the process, ii + Ti ^ v^+ Sc. The one-loop diagrams involving 7, Z and Higgs penguins all contribute along with box diagrams, but in the CMSSM scenario the /penguin has been shown to dominate [31]. We show two such diagrams involving slepton-neutralino and sneutrino-chargino loops in Fig.…”