Testing supersymmetry with lepton flavor violating τ and μ decays -: art. no. 055003

In this work the following lepton flavor violating tau and mu decays are studied: tau(-)->mu(-)mu(-)mu(+), tau(-)-> e(-)e(-)e(+), mu(-)-> e(-)e(-)e(+), tau(-)->mu(-)gamma, tau(-)-> e(-)gamma, and mu(-)-> e(-)gamma. We work in a supersymmetric scenario consisting of the minimal supersymmetric standard model particle content, extended by the addition of three heavy right-handed Majorana neutrinos and their supersymmetric partners, and where the generation of neutrino masses is done via the seesaw mechanism. Within this context, a significant lepton flavor mixing is generated in the slepton sector due to the Yukawa neutrino couplings, which is transmitted from the high to the low energies via the renormalization group equations. This slepton mixing then generates via loops of supersymmetric particles significant contributions to the rates of l(j)-> 3l(i) and the correlated l(j)-> l(i)gamma decays. We analyze here in full detail these rates in terms of the relevant input parameters, which are the usual minimal supergravity parameters and the seesaw parameters. For the l(j)-> 3l(i) decays, a full one-loop analytical computation of all the contributing supersymmetric loops is presented. This completes and corrects previous computations in the literature. In the numerical analysis compatibility with the most recent experimental upper bounds on all these tau and mu decays, with the neutrino data, and with the present lower bounds on the supersymmetric particle masses are required. Two typical scenarios with degenerate and hierarchical heavy neutrinos are considered. We will show here that the minimal supergravity and seesaw parameters do get important restrictions from these tau and mu decays in the hierarchical neutrino case.