A Novel Route to V Us

Already in the past, hadronic τ decays have served as an interesting source to obtain information on the parameters of the Standard Model, like the strong coupling αs or the strange quark mass. Below it will be shown that the approach to obtain the strange mass from the hadronic τ-decay width can be turned into a determination of the CKM matrix element Vus, once the strange mass is used as an input from other sources. At present, we obtain Vus = 0.2179 ± 0.0045, where the error is completely dominated by the experimental uncertainty, and can be improved through an improved measurement of the hadronic τ-decay rate into strange particles Rτ,S .