Reevaluation of Higgs-mediated μ-e transition in the MSSM

In this Letter, we reevaluated the Higgs-mediated contribution to μ→eγ, μ→3e, and μ-e conversion in nuclei in the MSSM, assuming left-handed sleptons have flavor-mixing mass terms. Contrary to previous works, it is found that Barr-Zee diagrams including top quark give dominant contribution to μ→eγ, and those including bottom quark and tau lepton are also non-negligible only when tanβ is large. As a result, the Higgs-mediated contribution dominates over the gaugino-mediated contribution at one-loop level in μ→eγ when MSUSY/mA0≳50, irrespectively of tanβ as far as tanβ is not large. Here, MSUSY and mA0 are a typical mass scale of the SUSY particles and the CP-odd Higgs boson mass, respectively. Ratio of branching ratios for μ→eγ and μ-e conversion in nuclei is also evaluated by including both the gaugino- and Higgs-mediated contributions to the processes. It is found that the ratio is sensitive to tanβ and MSUSY/mA0 when MSUSY/mA0∼(10-50) and tanβ≳10.