${\alpha }_s$ from the (revised) ALEPH data for $\tau$ decay

Abstract

We present a new analysis of ${\alpha }_s$ from hadronic $\tau$ decays based on the recently revised ALEPH data. The analysis is based on a strategy which we previously applied to the OPAL data. We critically compare our strategy to the one traditionally used and comment on the main differences. Our analysis yields the values ${\alpha }_s(m_{\tau }^2)=0.296\pm 0.010$ using fixed-order perturbation theory, and ${\alpha }_s(m_{\tau }^2)=0.310\pm 0.014$ using contour-improved perturbation theory. Averaging these values with our previously obtained values from the OPAL data, we find ${\alpha }_s(m_{\tau }^2)=0.303\pm 0.009$, respectively, ${\alpha }_s(m_{\tau }^2)=0.319\pm 0.012$, as the most reliable results for ${\alpha }_s$ from $\tau$ decays currently available.

Comments: 4 pages, 5 figures. Contribution to the 13th International Workshop on Tau Lepton Physics, Aachen (Germany), Sept. 2014