Global effective-field-theory analysis of new-physics effects in (semi)leptonic kaon decays

Abstract

We analyze the decays K → πℓν and P → ℓν (P = K, π, ℓ = e, μ) using a low-energy Effective-Field-Theory approach to parametrize New Physics and study the complementarity with baryon β decays. We then provide a road map for a global analysis of the experimental data, with all the Wilson coefficients simultaneously, and perform a fit leading to numerical bounds for them and for Vus. A prominent result of our analysis is a reinterpretation of the well-known Vud − Vus diagram as a strong constraint on new physics. Finally, we reinterpret our bounds in terms of the SU(2)L × U(1)Y -invariant operators, provide bounds to the corresponding Wilson coefficients at the TeV scale and compare our results with collider searches at the LHC.