The measurement of αs( Mτ) in ALEPH

Abstract

The measurement of the τ spectral functions and the extraction of the value α s ( M τ ) in ALEPH detector is described. The present results is α s ( M τ ) = 0.352 ± 0.007 exp ± 0.016 theo , which translates using the renormalization-group equations to α s ( M Z ) = 0.1217 ± 0.0007 exp ± 0.0017 theo ± 0.0010 evol . Combining errors gives α s ( M Z ) = 0.1217 ± 0.0021, which is preliminary in view of the continuing work by theorists and experimentalists.