Updated determination of $\alpha_s(m_\tau^2)$ from tau decays

TL;DR

This paper updates the measurement of the strong coupling constant _s at the tau mass scale using recent ALEPH tau decay data, employing multiple methods to ensure reliability and consistency.

Contribution

It provides a new, precise determination of _s(m_ au^2) with a comprehensive analysis of methodologies and a critical review of previous results.

Findings

_s^{(n_f=3)}(m_ au^2) = 0.328 b1 0.012

_s^{(n_f=5)}(M_Z^2) = 0.1197 b1 0.0014

Consistent results across different methods

Abstract

Using the most recent release of the ALEPH $\tau$ decay data, we present a very detailed phenomenological update of the $\alpha_s(m_\tau^2)$ determination. We have exploited the sensitivity to the strong coupling in many different ways, exploring several complementary methodologies. All determinations turn out to be in excellent agreement, allowing us to extract a very reliable value of the strong coupling. We find $\alpha_{s}^{(n_f=3)}(m_\tau^2) = 0.328 \pm 0.012$ which implies $\alpha_{s}^{(n_f=5)}(M_Z^{2}) = 0.1197\pm 0.0014$. We critically revise previous work, and point out the problems flawing some recent analyses which claim slightly smaller values.