Anatomy and phenomenology of μ–τ lepton flavour violation in the MSSM

We perform a detailed analysis of several μ–τ lepton flavour violating (LFV) processes, namely τ→μX (X=γ,e+e−,μ+μ−,ρ,π,η,η′), Z→μτ and Higgs boson decays into μτ. First we present a model independent operator analysis relevant to such decays, then we explicitly compute the LFV operator coefficients [and (gμ−2)] in a general unconstrained MSSM framework, allowing slepton mass matrices to have large μ–τ entries. We systematically study the role and the interplay of dipole and non-dipole operators, showing how the rates and the mutual correlations of those LFV decays change in different regions of the MSSM parameter space. Values of the LFV branching ratios in the experimentally interesting range 10−9–10−7 can be achieved. For at least two MSSM Higgs bosons, the branching ratio of the LFV decay into μτ can reach values of order 10−4.