Right-handed electrons in radiative muon decay

摘要

Electrons emitted in the radiative decay mu(-) --> e(-)(v) over barv(mu)gamma have a significant probability of being right-handed, even in the limit m(e) --> 0. Such "wrong-helicity" electrons, arising from helicity-flip bremsstrahlung, contribute an amount alpha/4pi Gamma(0) to the muon decay width (Gamma(0) equivalent to G(F)(2)m(mu)(5)/(192pi(3))). We use the helicity-flip splitting function D-hf (z) of Falk and Sehgal [Phys. Lett. B 325 (1994) 509] to obtain the spectrum of the right-handed electrons and the photons that accompany them. For a minimum photon energy E-gamma = 10 MeV (20 MeV), approximately 4% (7%) of electrons in radiative mu-decay are right-handed. (C) 2003 Published by Elsevier B.V. [References: 13]