Implications of Br(μ-> e γ) and Δa_mu on Muonic Lepton Flavor Violating Processes

Abstract

We study the implications of the experimental results on the μ-> eγdecay rate and the muon anomalous magnetic moment, on muonic lepton flavor violating processes, such as μ-> 3 e and μN -> e N. We use a model independent approach in this analysis, where these processes are considered to be loop induced by exchanging spin 1/2 and spin 0 particles. We explore two complementary cases, which has no or has an internal (built-in) cancellation mechanism in amplitudes. Our main results are as following. (a) Bounds from rates are used to constrain parameters, such as coupling constants and masses. These constraints can be easily updated by simple scalings, if the experimental situations change. (b) The muon g-2 data favors non-chiral interactions. (c) In μ-> 3 e and μN -> e N processes, Z-penguin diagrams may play some role, while box diagrams contributions are usually highly constrained. (d) In the first case (without any built-in cancellation mechanism), using the recent μ-> eγbound, we find that μ-> 3e and μN -> e N rates are bounded below the present experimental limits by two to three orders of magnitudes in general. Furthermore, by comparing Δa_μand Br(μ->eγ) data, the couplings of μand e are found to be highly hierarchical. Additional suppression mechanism should be called for. (e) In the second case (with a built-in cancellation mechanism), mixing angles can provide additional suppression factors to satisfy the Δa_μand Br(μ-> eγ) bounds. While the μ-> 3 e rate remains suppressed, the bounds on μN -> e N rates, implicated from the latest μ-> eγbound, can be relaxed significantly and can be just below the present experimental limits.