Power Corrections to Event Shape Distributions
We estimate the effects of non-perturbative physics on the differential distributions of infrared- and collinear-safe e + e \Gamma event shape variables, by extending the notion of an infrared-regular effective strong coupling, which accounts for the non-perturbative corrections to the mean values of several shape variables, to their distributions. This leads to 1=Q power corrections over a range of values of the shape variables considered, where Q is the centre-of-mass energy. In the case of the thrust variable, the leading correction is simply a shift of the distribution, by an amount proportional to 1=Q. We show that this gives an excellent description of the data throughout a wide range of T and Q. Cavendish--HEP--97/2 April 1997 Research supported in part by the U.K. Particle Physics and Astronomy Research Council and by the EC Programme "Training and Mobility of Researchers", Network "Hadronic Physics with High Energy Electromagnetic Probes", contract ERB FMRX-CT96-0008. y..