Effect of Heavy Leptons on Charmed-Particle Decays

Abstract

The helicity argument applied to purely leptonic decays of heavy pseudoscalar mesons ($F, D$) gives a high branching ratio $\frac{\Gamma (F, D\to \nu +\mathrm{heavy}\mathrm{lepton} \mathrm{}(L\left)\right)}{\Gamma (F, D\to \mu +\nu )}$. The branching ratio $\frac{\Gamma (F\to L+\nu )}{\Gamma \left(F_{\mu 3} \mathrm{and} F_{e3\mathrm{}}\right)}$ is estimated to be 5-50% for the $F_{l3\mathrm{}}$ dominant $\eta$ decay mode, and $\frac{\Gamma (F\to L+\nu )}{\Gamma (F\to \mathrm{all})}$ is 0.3 to 1.5%.