Short and long distance effects in the decay τ → πντ( γ)

Abstract

We calculate the radiative corrections to the decays τ → Mν τ and M → μν μ , where the meson M is M = π or K. We perform a complete calculation, which includes internal bremsstrahlung and structure dependent radiation in the radiative decays and point meson, hadronic structure dependent and short distance contributions in the virtual corrections. Our result for the radiative correction to the ratio Γ( τ → πν τ ( γ))/ Γ( π → μν μ ( γ)) is δR τ/ π = (0.16 ± 0.14)%. For the ratio Γ( τ → Kν τ ( γ))/ Γ( K → μν μ ( γ)), we obtain δR τ/ K = (0.90±0.22)%.