Evolution of truncated moments of singlet parton distributions

We define truncated Mellin moments of parton distributions by restricting t he integration range over the Bjorken variable to the experimentally access ible subset x(0) less than or equal to x less than or equal to 1 of the all owed kinematic range 0 less than or equal to x less than or equal to 1. We derive the evolution equations satisfied by truncated moments in the genera l (singlet) case in terms of an infinite triangular matrix of anomalous dim ensions which couple each truncated moment to all higher moments with order s differing by integers, We show that the evolution of any moment can be de termined to arbitrarily good accuracy by truncating the system of coupled m oments to a sufficiently Large but finite size, and show how the equations can be solved in a way suitable for numerical applications, We discuss in d etail the accuracy of the method in view of applications to precision pheno menology. (C) 2001 Elsevier Science B.V. All rights reserved.