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− 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.