On the Extraction of the Strong Coupling from Hadronic Tau Decay

TL;DR

This paper introduces a new framework for extracting the strong coupling constant from hadronic tau decay data, accounting for non-perturbative effects and duality violations to improve precision.

Contribution

A novel method employing a physically motivated model to better handle non-perturbative effects and duality violations in the extraction of { extalpha}_s from tau decay data.

Findings

Determined { extalpha}_s(m_{ au}^2) of 0.307(19) using fixed-order perturbation theory.

Found { extalpha}_s(m_{ au}^2) of 0.322(26) using contour-improved perturbation theory.

Converted to { extalpha}_s(M_Z^2) values of 0.1169(25) and 0.1187(32) respectively.

Abstract

The finite energy sum rule extraction of the strong coupling {\alpha}_s from hadronic {\tau} decay data provides one of its most precise experimental determinations. As precision improves, small non-perturbative effects become increasingly relevant to both the central value and error. Here we present a new framework for this extraction employing a physically motivated model to accommodate violations of quark-hadron duality and enforcing a consistent treatment of higher-dimension operator product expansion contributions. Using 1998 OPAL data for the non-strange vector and axial-vector spectral functions, we find the n_f=3 values for {\alpha}_s(m_{\tau}^2) of 0.307(19) for fixed-order perturbation theory and 0.322(26) for contour-improved perturbation theory, corresponding to n_f=5 values for {\alpha}_s(M_Z^2) of 0.1169(25) and 0.1187(32), respectively.