Can we use hadronic tau decay for V_us determination

TL;DR

This paper investigates the use of hadronic tau decays to determine the CKM matrix element V_us, addressing discrepancies in spectral functions and incorporating new tensor interactions to improve precision.

Contribution

It introduces corrections from centi-weak tensor interactions to tau decay analyses, enabling a more accurate extraction of V_us consistent with other methods.

Findings

New value of |V_us|=0.2246 +/- 0.0012

Derived f(0)=0.9645 +/- 0.0055

Calculated F_K/F_pi=1.196 +/- 0.007

Abstract

It is known that the discrepancy in pion spectral functions extracted from positron-electron annihilation and tau decay leads to different predictions for the muon anomalous magnetic moment. We will show that this discrepancy effects also the extraction of the Cabibbo angle from the hadronic tau decays. The corrections to the tau branching fractions, corresponding to the presence of new centi-weak tensor interactions, allow us to extract the Cabibbo angle from tau decays in agreement with its other precision determinations. Thus a more precise value of |V_us|=0.2246 +/- 0.0012 is obtained and as a consequence f(0)=0.9645 +/- 0.0055 and F_K/F_pi=1.196 +/- 0.007.