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One-loop determination of τ → π(K)ντ [γ] branching ratios and new physics tests

2022; Springer Nature; Volume: 2022; Issue: 2 Linguagem: Inglês

10.1007/jhep02(2022)173

1127-2236

M. A. Arroyo-Ureña, G. Hernández-Tomé, G. López-Castro, Pablo Roig, Ignasi Rosell,

Black Holes and Theoretical Physics

A bstract We calculate the ratios R τ / P ≡ Γ ( τ → Pν τ [ γ ]) /Γ ( P → μν μ [ γ ]) ( P = π , K ) at one loop following a large- N C expansion where Chiral Perturbation Theory is enlarged by including the lightest resonances and respecting the short-distance behavior dictated by QCD. We find δR τ / π = (0 . 18 ± 0 . 57)% and δR τ / K = (0 . 97 ± 0 . 58)%, where the uncertainties are induced fundamentally by the counterterms. We test the lepton universality, obtaining | g τ / g μ | π = 0 . 9964 ± 0 . 0038 and | g τ / g μ | K = 0 . 9857 ± 0 . 0078, and analyze the CKM unitarity, getting results at 2 . 1 σ and 1 . 5 σ from unitarity via | V us / V ud | and | V us |, respectively. We also update the search for non-standard interactions in τ decays. As a by-product, we report the theoretical radiative corrections to the τ → Pν τ [ γ ] decay rates: δ τπ = − (0 . 24 ± 0 . 56)% and δ τK = − (0 . 15 ± 0 . 57)%.