Effects of anomalous couplings of the tau lepton

Abstract

The dimension-six CP-conserving $SU_L(2)\times U_Y(1)$ invariant operators involving the tau lepton are studied. It leads to the new physics effects to the lepton flavor violation (LFV) and lepton flavor-changing neutral current(FCNC). With the available experimental data on the decays $Z \to \tau^+ + \tau^- $, $Z\to \mu^+ + \mu^- $ and $\mu^- \to e^- +\gamma$, the constraints on parameters of the effective lagrangian can be given. According to such constraints, the branching ratio of the decay $Z\to \mu^\pm + \tau^\mp $ could reach to $10^{-6}-10^{-7}$. The size of the LFV effects depends crucially on the dynamics of the lepton mass generation. Assuming the lepton mass matrices in the form of a Fritzsch ansatz, we point out that the experiment on $\mu\to e \gamma$ will put stronger limits on the anomalous magnitic and electric dipole moments of the tau lepton than obtained by Escribano and Mass\'{o}.