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Register a new user$mu to e gamma$ and $tau to l gamma$ decays in the fermion triplet seesaw model
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In the framework of the seesaw models with triplets of fermions, we evaluate the decay rates of $mu to e gamma$ and $tau to l gamma$ transitions. We show that although, due to neutrino mass constraints, those rates are in general expected to be well under the present experimental limits, this is not necessarily always the case. Interestingly enough, the observation of one of those decays in planned experiments would nevertheless contradict bounds stemming from present experimental limits on the $mu to eee$ and $tau to 3 l$ decay rates. Such detection of radiative decays would therefore imply that there exist sources of lepton flavour violation not associated to triplet fermions.
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The size of the branching ratios for the $tau to mu gamma$ and $tau to mu gamma gamma$ decays induced by a lepton flavor violating Higgs interaction $Htau mu$ is studied in the frame of effective field theories. The best constraint on the $Htau mu$ vertex, derived from the know measurement on the muon anomalous magnetic moment, is used to impose the upper bounds $Br(tau to mu gamma)<2.5times 10^{-10}$ and $Br(tau to mu gamma gamma)<2.3times 10^{-12}$, which are more stringent than current experimental limits on this class of transitions.
We report on a search for the lepton flavor violating tau- -> mu- gamma and tau- -> e- gamma decays based on 535/fb of data accumulated at the Belle experiment. No signal is found and we set 90% confidence level upper limits on the branching ratios Br(tau- -> mu- gamma) < 4.5x10^-8 and Br(tau- -> e- gamma) < 1.2x10^-7.
We study the anomalous magnetic moment of the muon, a_mu, and lepton flavor violating decay mu -> e gamma in TeV scale B-L extension of the Standard Model (SM) with inverse seesaw mechanism. We show that the B-L contributions to a_mu are severely constrained, therefore the SM contribution remains intact. We also emphasize that the current experimental limit of BR(mu -> e gamma) can be satisfied for a wide range of parameter space and it can be within the reach of MEG experiment.
We compute the non-perturbative contribution of semileptonic tensor operators $(bar q sigma^{mu u} q)(bar ell sigma_{mu u} ell)$ to the purely leptonic process $mu to e gamma$ and to the electric and magnetic dipole moments of charged leptons by matching onto chiral perturbation theory at low energies. This matching procedure has been used extensively to study semileptonic and leptonic weak decays of hadrons. In this paper, we apply it to observables that contain no strongly interacting external particles. The non-perturbative contribution to $mu to e $ processes is used to extract the best current bound on lepton-flavor-violating semileptonic tensor operators, $Lambda_text{BSM} gtrsim 450$ TeV. We briefly discuss how the same method applies to dark-matter interactions.
In this present paper, we investigate the muon pairs production in the interaction between two quasireal photons in $e^+e^-$ collision. The total and differential cross section of the process $gamma gamma to mu^+mu^-$ at a beam energy of photons from 3 GeV to 40 GeV in the center-of-mass and for different values of muon transverse momentum and the muon rapidity and the muon angle are calculated. We also study the total cross section, as a function of the $e^+ e^-$ center-of-mass energy $sqrt {s}$ in the region 5 GeV $leq sqrt {s} leq$ 209 GeV process of the $e^+ +e^- to e^+ + e^- +mu^+ + mu^-$ by the two-photon mechanism. The obtained our results are in satisfactory agreement with the experimental data.
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