Alpha_s Determination from Tau Decays: Theoretical Status

Abstract

The total tau hadronic width can be accurately calculated using analyticity and the operator product expansion. The result turns out to be very sensitive to the value of alpha_s(m_tau^2), providing a precise determination of the strong coupling constant. The theoretical description of this observable is updated, including the recently computed O(alpha_s^4) contributions. The experimental determination of alpha_s(m_tau^2) and its actual uncertainties are discussed.

Comments: Invited talk at the Flavianet topical workshop on "Low energy constraints on extensions of the Standard Model", Kazimierz, Poland, 23-27 July 2009