Muon decays revisited: Effects of massive neutrinos, their mixings, and grand unification

Abstract

We have calculated the effects of massive Dirac and Majorana neutrinos and their mixings in the ${e}^{+}$ spectrum in ${\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}({\ensuremath{\nu}}_{\ensuremath{\mu}}^{c})$ decays. Particular attention was paid to the three-neutrinos world with the mass of ${\ensuremath{\nu}}_{\ensuremath{\tau}}$ in the ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ range. We also obtained electron-neutrinos correlations and indicated their use as a signature of Majorana neutrinos.