A critical look at V_us determinations from hadronic tau decay data

Abstract

A critical review of hadronic tau decay data based determinations of |V_{us}| is given, focussing on the impact of the slow convergence of the integrated D=2 OPE series for the conventional flavor-breaking sum rule determination and the potential role of as-yet-unmeasured multiparticle contributions to the strange spectral distribution. Additional information obtainable from analyses of inclusive strange decay data alone, and from mixed electroproduction-tau sum rules with much reduced OPE uncertainties, is also discussed. Self-consistency tests are shown to favor determinations which reduce somewhat discrepancies with 3-family unitarity expectations.