Probing lepton-number and lepton-flavor violation in semileptonic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>τ</mml:mi></mml:math>decays into two mesons

Abstract

The evaluation, systematic analysis, and numerical study of the semileptonic $\ensuremath{\tau}$-lepton decays with two mesons in the final state has been made in the frame of the standard model extended by right-handed neutrinos. In the analysis, heavy-neutrino nondecoupling effects, finite quark masses, quark and meson mixings, finite widths of vector mesons, chiral symmetry breakings in vector-meson-pseudoscalar-meson vertices, and effective Higgs-boson-pseudoscalar-meson couplings have been included. Numerical estimates reveal that the decays ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{K}^{\ensuremath{-}}{K}^{+}$, and ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{K}^{0}{\overline{K}}^{0}$ have branching ratios of the order of ${10}^{\ensuremath{-}6}$, close to present-day experimental sensitivities.