Energy flow in QCD and event shape functions

Hadronization corrections to the thrust and related event shape distributio ns in the two-jet kinematical region of e(+)e(-) annihilation are summarize d by nonperturbative shape functions. The moments of shape functions are gi ven by universal matrix elements in QCD, which describe the energy flow in QCD final states. We show how the nonperturbative structure of these matrix elements may be inferred from resummed perturbation theory and Lorentz inv ariance. This analysis suggests the same functional forms for the shape fun ctions as were found in phenomenological studies, and sheds light on the ph ysical significance of the parameters that characterize these functions, (C ) 2001 Published by Elsevier Science B.V.