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Register a new userRadiative seesaw corrections and charged-lepton decays in a model with soft flavour violation
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We consider the one-loop radiative corrections to the light-neutrino mass matrix and their consequences for the predicted branching ratios of the five lepton-flavour-violating decays $ell_1^- to ell_2^- ell_3^+ ell_3^-$ in a two-Higgs-doublet model furnished with the type-I seesaw mechanism and soft lepton-flavour violation. We find that the radiative corrections are very significant; they may alter the predicted branching ratios by several orders of magnitude and, in particular, they may help explain why $mbox{BR}(mu^- to e^- e^+ e^-)$ is strongly suppressed relative to the branching ratios of the decays of the $tau^-$. We conclude that, in any serious numerical assessment of the predictions of this model, it is absolutely necessary to take into account the one-loop radiative corrections to the light-neutrino mass matrix.
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We consider a two-Higgs-doublet extension of the Standard Model, with three right-handed neutrino singlets and the seesaw mechanism, wherein all the Yukawa-coupling matrices are lepton flavour-diagonal and lepton flavour violation is soft, originating solely in the non-flavour-diagonal Majorana mass matrix of the right-handed neutrinos. We consider the limit $m_R to infty$ of this model, where $m_R$ is the seesaw scale. We demonstrate that there is a region in parameter space where the branching ratios of all five charged-lepton decays $ell_1^- to ell_2^- ell_3^+ ell_3^-$ are close to their experimental upper bounds, while the radiative decays $ell_1^- to ell_2^- gamma$ are invisible because their branching ratios are suppressed by $m_R^{-4}$. We also consider the anomalous magnetic moment of the muon and show that in our model the contributions from the extra scalars, both charged and neutral, can remove the discrepancy between its experimental and theoretical values.
The Little Higgs model with T-parity (LHT) belongs to the non-minimal flavour violating model. This model has new sources of flavour and CP violation both in quark and leptonic sectors. These new sources of flavour violation originates by the interaction of Standard Model (SM) fermions with heavy gauge bosons and heavy (or mirror) fermions. In this work we will present the impact of the new flavour structure of T-parity models on flavour violations in leptonic sector.
Here we update the predictions for lepton flavour violating tau and muon decays, $l_j to l_i gamma$, $l_j to 3 l_i$, and $mu-e$ conversion in nuclei. We work within a SUSY-seesaw context where the particle content of the Minimal Supersymmetric Standard Model is extended by three right handed neutrinos plus their corresponding SUSY partners, and where a seesaw mechanism for neutrino mass generation is implemented. Two different scenarios with either universal or non-universal soft supersymmetry breaking Higgs masses at the gauge coupling unification scale are considered. After comparing the predictions with present experimental bounds and future sensitivities, the most promising processes are particularly emphasised.
We calculate the predictions for lepton flavour violating (LFV) tau and muon decays, $l_j to l_i gamma$, $l_j to 3 l_i$, $mu-e$ conversion in nuclei and LFV semileptonic tau decays $tau to mu PP$ with $PP= pi^+pi^-, pi^0pi^0, K^+K^-, K^0 {bar K}^0$ $tau to mu P$ with $P=pi^0, eta, eta$ and $tau to mu V$ with $V = rho^0, phi$, performing the hadronisation of quark bilinears within the chiral framework. We work within a SUSY-seesaw context where the particle content of the Minimal Supersymmetric Standard Model is extended by three right-handed neutrinos plus their corresponding SUSY partners, and where a seesaw mechanism for neutrino mass generation is implemented. Two different scenarios with either universal or non-universal soft supersymmetry breaking Higgs masses at the gauge coupling unification scale are considered. After comparing the predictions with present experimental bounds and future sensitivities, the most promising processes are particularly emphasised.
We address the constraints on the SUSY seesaw parameters arising from Lepton Flavour Violation observables. Working in the Constrained Minimal Supersymmetric Standard Model extended by three right-handed (s)neutrinos, we study the predictions for the branching ratios of $l_j to l_i gamma$ and $l_j to 3 l_i$ channels. We impose compatibility with neutrino data, electric dipole moment bounds, and further require a successful baryon asymmetry of the Universe (via thermal leptogenesis). We emphasise the interesting interplay between $theta_{13}$ and the LFV muon decays, pointing out the hints on the SUSY seesaw parameters that can arise from measurements of $theta_{13}$ and LFV branching ratios. This is a brief summary of the work of Ref. cite{Antusch:2006vw}.
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