Vus determination from KLOE

Abstract

KLOE recent experimental results on KL, Ks and K± decays relevant for the extraction of the CKM matrix element Vus are reported, including the preliminary measurement of BR(Kπ2+) presented at this conference. From a global fit using only KLOE results a value of |Vus|f+(0) = 0.21556 ± 0.00059 is obtained, where f+(0) is the form factor parametrizing the hadronic matrix element evaluated at zero momentum transfer. From the ratio of the radiative inclusive decay rates of K± → μ±ν(γ) and π± → μ±ν(γ), combined with the KLOE measurement of BR(K± → μ±ν) and the lattice calculation of the ratio of decay constants fK/fπ = 1.189(7), the value Vus/Vud = 0.2323(15) has been obtained. These results, together with Vus = 0.97372(26), are compatible at 1.5σ level with CKM matrix unitarity.