Paper detail

Updated determination of $α_s(m_τ^2)$ from tau decays

Using the most recent release of the ALEPH $τ$ decay data, we present a very detailed phenomenological update of the $α_s(m_τ^2)$ 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 $α_{s}^{(n_f=3)}(m_τ^2) = 0.328 \pm 0.012$ which implies $α_{s}^{(n_f=5)}(M_Z^{2}) = 0.1197\pm 0.0014$. We critically revise previous work, and point out the problems flawing some recent analyses which claim slightly smaller values.