Implications of a very light pseudoscalar boson on lepton flavor violation

Abstract

A long-lived very light pseudoscalar boson would favor lepton flavor violating transitions of charged leptons. Its implications on the l_i --> l_j γγ, and l_i --> l_j e^+ e^- transitions are investigated. Assuming 2 m_e < m_ϕ<m_μ, it is found that the inequality B(l_i --> l_j γγ)<B(l_i --> l_j e^+ e^-) is hold. The experimental constraints on the decays l_i --> l_j γ, l_i --> l_j l_k l_k, and l_i --> l_j γγare used to bound the ϕl_i l_j couplings.