The puzzle of the $>3\sigma$ low (c.f. three-family-unitarity expections) determination of $V_{us}$ from the conventional implementation of flavor-breaking (FB) finite-energy sum rules (FESRs) employing inclusive hadronic $\tau$ decay data is revisited, problems with this implementation
identified, and an alternative implementation which cures them described. Applying this new implementation using preliminary BaBar results for the exclusive $\tau\rightarrow K^-\pi^0\nu_\tau$ branching fraction, we find $\vert V_{us}\vert=0.2229(22)_{exp}(4)_{th}$, in good agreement with results from other sources. Limitations on near-term possibilities for reducing experimental errors are discussed, and a new approach to improving this situation via dispersive analyses of strange hadronic $\tau$ data using lattice input described.
$|V_{us}|$ from $\tau$ decays in theory
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Pre-published on:
June 05, 2017
Published on:
June 13, 2017
Abstract
DOI: https://doi.org/10.22323/1.291.0030
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Copyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.