|Vus| determination from inclusive strange tau decay and lattice HVP

Peter Boyle,Matthew Spraggs,Antonin Portelli,Andreas Jüttner,Randy Lewis,Taku Izubuchi,Hiroshi Ohki,Renwick James Hudspith,Christoph Lehner,Kim Maltman

doi:10.1051/epjconf/201817513011

Abstract

We propose and apply a novel approach to determining |Vus| which uses inclusive strange hadronic tau decay data and hadronic vacuum polarization functions (HVPs) computed on the lattice. The experimental and lattice data are related through dispersion relations which employ a class of weight functions having poles at space-like momentum. Implementing this approach using lattice data generated by the RBC/UKQCD collaboration, we show examples of weight functions which strongly suppress spectral integral contributions from the region where experimental data either have large uncertainties or do not exist while at the same time allowing accurate determinations of relevant lattice HVPs. Our result for |Vus| is in good agreement with determinations from K physics and 3-family CKM unitarity. The advantages of the new approach over the conventional sum rule analysis will be discussed.

Highlights

The Kobayashi-Maskawa matrix element |Vus| is an important parameter for flavor physics, one relevant to searching for new physics beyond the Standard Model (SM) of particle physics
In this report we propose a novel dispersive approach to determining |Vus| using inclusive strange hadronic τ decay data, hadronic vacuum polarization functions (HVPs) computed on the lattice, and weight functions, ωN (s) = 1/ΠkN=1(s + Q2k), Q2k > 0, (1)
We have presented a novel method to extract |Vus| from strange inclusive τ decay distributions

Summary

Introduction

The Kobayashi-Maskawa matrix element |Vus| is an important parameter for flavor physics, one relevant to searching for new physics beyond the Standard Model (SM) of particle physics. There is a long-standing puzzle that the conventional version of the alternate determination employing hadronic τ decay data and flavor-breaking (FB) finite-energy sum rules (FESRs) yields very low |Vus|, recently |Vus| = 0.2186(21) [3], which lies ∼ 3.1σ below 3-family-unitarity expectations. The resulting error is dominated by uncertainties on the relevant weighted inclusive flavor us spectral integrals and is a factor > 2 larger than those from K-decay-based approaches. Implementing this approach using lattice data, we show examples of weight functions which allow the combination of lattice HVPs required for this analysis to be determined with good accuracy while at the same time strongly suppressing spectral integral contributions from the region of the high-multiplicity with larger-error us decay modes. We find results for |Vus| from this approach in good agreement with those obtained from analyses of K physics and three-family CKM unitarity

Conventional and new inclusive determinations

Analysis with lattice HVPs

Findings

Conclusion and Discussion