A Mixed Tau-Electroproduction Sum Rule for V_us

TL;DR

This paper introduces a new class of sum rules combining electroproduction and tau decay data to improve the determination of |V_us|, reducing theoretical uncertainties and highlighting the potential for more precise measurements.

Contribution

It proposes a novel mixed sum rule approach that suppresses D=2 OPE contributions, enhancing the accuracy of |V_us| extraction from tau decay data.

Findings

Determined |V_{us}| = 0.2202(39) with reduced theoretical error.

Sum rules effectively suppress D=2 OPE contributions.

Experimental errors dominate the current uncertainty.

Abstract

The interpretation of results of recent tau decay determinations of |V_us|, which yield values ~3 sigma low compared to 3-family unitarity expectations, is complicated by the slow convergence of the relevant integrated D=2 OPE series. We introduce a class of sum rules involving both electroproduction and tau decay data designed to deal with this problem by strongly suppressing D=2 OPE contributions at the correlator level. Experimental complications are briefly discussed and an example of the improved control over theoretical errors presented. The uncertainty on the resulting determination, |V_{us}| =0.2202(39), is entirely dominated by experimental errors, and should be subject to significant near-term improvement.