Alpha_s(M_Z) from hadronic tau decays

TL;DR

This paper extracts the strong coupling constant alpha_s at the Z boson mass scale using sum rules from tau decay data, reducing theoretical uncertainties and achieving results consistent with global electroweak fits.

Contribution

It introduces sum rules tailored to suppress uncertainties from higher dimension condensates, improving the precision of alpha_s extraction from tau decay data.

Findings

Alpha_s(M_Z^2)=0.1187(16) from tau decays

Results agree with global electroweak fits

Method reduces theoretical systematic uncertainties

Abstract

We perform an extraction of alpha_s based on sum rules involving isovector hadronic tau decay data. The particular sum rules employed are constructed specifically to suppress contributions associated with poorly known higher dimension condensates, and hence reduce theoretical systematic uncertainties associated with the treatment of such contributions which are shown to be present in earlier related analyses. Running our results from the n_f=3 to n_f=5 regime we find alpha_s(M_Z^2)=0.1187(16), in excellent agreement with the recently updated global fit to electroweak data at the Z scale, 0.1191(27), and other high-scale direct determinations.