μ-e conversion with four generations

We study μ-e conversion with sequential four generations. A large mass for the fourth generation neutrino can enhance the conversion rate by orders of magnitude. We compare constraints obtained from μ-e conversion using experimental bounds on various nuclei with those from μ→eγ and μ→ee¯e. We find that the current bound from μ-e conversion with Au puts the most stringent constraint in this model. The relevant flavor changing parameter λμe=Vμ4⁎Ve4 is constrained to be less than 1.6×10−5 for the fourth generation neutrino mass larger than 100 GeV. Implications for future μ-e conversion, μ→eγ and μ→ee¯e experiments are discussed.