Quark Mass Corrections to the Perturbative Thrust and its Effect on the determination of ${\alpha }_s$

Abstract

We consider the effects of quark masses to the perturbative thrust in $e^{+}{e}^{-}$ annihilation. In particular we show that perturbative power corrections resulting from non-zero quark masses considerably alters the size of the non-perturbative power corrections and consequently, significantly changes the fitted value of ${\alpha }_s$.

Comments: Latex, 6 pages, 2 figures, minor change in text, added one reference