Indirect bounds on Z→μe, and lepton flavor violation at future colliders

Abstract

Motivated by the interest in lepton number violating processes, we study the\nconnection between the rate of Z -> mu e decay and those of the low-energy\nprocesses mu ->3 e, and mu -> e conversion in nuclear field. We show that if\nthe vector or axial Z form factors are dominant, Br(Z->mu e) is not observable,\nwhile if the Z dipole form factors are dominant, the relatively weak indirect\nbound Br(Z->mu e)<7 10^{-9} does not fully preclude a signal at future\ncolliders, as TESLA. We finally comment on the relation of Z->mu e with Z->tau\ne and Z->tau mu decays, and suggest a simple scaling law for these three\nprocesses.\n