On power corrections to the event shape distributions in QCD

We study power corrections to the differential thrust, heavy jet mass and C -parameter distributions in the two-jet kinematical region. We argue that a way from the end-point region, e >> Lambda (QCD)/Q, the leading 1/Q-power c orrections are parameterized by a single non-perturbative scale while for e similar to Lambda (QCD)/Q one encounters a novel regime in which power cor rections of the form 1/(Qe)(n) have to be taken into account for arbitrary n. These non-perturbative corrections can be resummed and factor out into a universal non-perturbative distribution, the shape function, and the diffe rential event shape distributions are given by convolution of the shape fun ction with perturbative cross-sections. Choosing a simple ansatz for the sh ape function we demonstrate a good agreement of the obtained QCD prediction s for the distributions and their lowest moments with the existing data ove r a wide energy interval.