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Register a new userModel-independent Analysis of Lepton Flavour Violating Tau Decays
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Many models for physics beyond the Standard Model predict lepton-flavour violating decays of charged leptons at a level which may become observable very soon. In the present paper we investigate the decays of a Tau into three charged leptons in a generic way, based on effective-field-theory methods, where the relevant operators are classified according to their chirality structure. We work out the decay distributions and discuss phenomenological implications.
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In this work we study the Lepton Flavour Violating semileptonic $tau$ decays: 1) $tau to mu PP$ with $PP= pi^+pi^-, pi^0pi^0, K^+K^-, K^0 {bar K}^0$; 2) $tau to mu P$ with $P=pi^0, eta, eta$ and 3) $tau to mu V$ with $V = rho^0, phi$. We work within the context of two constrained MSSM scenarios: the CMSSM and NUHM. A full one-(SUSY)loop computation is presented and the importance of the various contributions, the $gamma$-, $Z$-, and Higgs bosons mediated ones are analysed. The hadronization of quark bilinears is performed within the chiral framework. Some discrepancies in the predicted rates for BR($tau to mu eta$), BR($tau to mu eta$) and BR($tau to mu K^+K^-$) are found with respect to previous estimates, which will be commented here. These three channels will be shown to be the most competitive ones to test simultaneously the Lepton Flavour Violation and the Higgs sector. We further present here a set of approximate formulas for all the semileptonic channels which we believe can be useful for further comparison with present and future data.
We study Lepton Flavour Violating hadron decays of the tau lepton within the Simplest Little Higgs model. Namely we consider $tau rightarrow mu (P, V, PP)$ where $P$ and $V$ are short for a pseudoscalar and a vector meson. We find that, in the most positive scenarios, branching ratios for these processes are predicted to be, at least, four orders of magnitude smaller than present experimental bounds.
We study lepton flavor violating (LFV) tau and B decays in models with heavy neutrinos to constrain the mixing matrix parameters U_{tau N}. We find that the best current constraints when the heavy neutrinos are purely left-handed come from LFV radiative tau decay modes. To obtain competitive constraints in LFV B decay it is necessary to probe b -> X_{s} tau^{pm} e^{mp} at the 10^{-7} level. When the heavy neutrinos have both left and right-handed couplings, the mixing parameters can be constrained by studying LFV B decay modes and LFV tau decay into three charged leptons. We find that the branching ratios B(tau^{pm} -> l_1^{pm} l_2^{pm} l_3^{mp}), B(B_{s} -> tau^{pm} e^{mp}) and B(b -> X_{s} l_1^{pm} l_2^{mp}) need to be probed at the 10^{-8} level in order to constrain the mixing parameters beyond what is known from unitarity.
Supposing only Lorentz and the gauge invariances of the Lagrangian, we derive energy and angular distributions for $tau^pm to mu^pm mu^pm mu^mp$ lepton flavor violating decay process. Using these results, we discuss methods to determine the parameters associated with the lepton flavor violating interactions.
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/$c^2$ decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV, collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb$^{-1}$. The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/$c^2$ to 4 pb for a mass of 195 GeV/$c^2$.
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