Abstract
We review the status of the determination of \vert V_{us}\vert|Vus| from both flavor-breaking finite-energy sum rules based on inclusive non-strange and strange hadronic \tauτ decay data and the recent lattice-based analysis of inclusive strange hadronic \tauτ decay data. In particular, we update the results from these analysis frameworks taking into account recent improvements to a number of strange branching fractions reported by HFLAV at CKM2018 and this meeting. We find that inclusive \tauτ decay data yields results for \vert V_{us}\vert|Vus| compatible within errors with the expectations of three-family unitarity.
Highlights
As is well known, the conventional implementation of the flavor-breaking (FB) finite-energy sum rule (FESR) determination of |Vus|, employing (i) inclusive non-strange and strange branching fractions (BFs) and (ii) certain assumptions about dimension D = 6 and 8 operator product expansion (OPE) contributions on the theory side of the relevant FESR [1, 2], yields results ∼ 3σ low compared to the expectations of three-family unitarity
Problems with the theory-side OPE assumptions in this conventional implementation have been identified in Ref. [4], and an alternate implementation of the FB FESR framework proposed, in which, rather than making assumptions about their values, the relevant effective D > 4 OPE condensates are obtained from fits to data
Even after taking into account the most recent updates of the results for exclusive strange BFs, the assumptions for the effective D = 6 and 8 OPE condensates underlying the conventional implementation of the FB FESR framework still produce results for |Vus| displaying unphysical s0- and weight-dependence
Summary
The conventional implementation of the flavor-breaking (FB) finite-energy sum rule (FESR) determination of |Vus|, employing (i) inclusive non-strange and strange branching fractions (BFs) and (ii) certain assumptions about dimension D = 6 and 8 OPE contributions on the theory side of the relevant FESR [1, 2], yields results ∼ 3σ low compared to the expectations of three-family unitarity. The most recent such determination, by the HFLAV collaboration, reported at this meeting, for example, yields 0.2195(18) [3].
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