Evolution of truncated moments of singlet parton distributions

We define truncated Mellin moments of parton distributions by restricting the integration range over the Bjorken variable to the experimentally accessible subset x(0) less than or equal to x less than or equal to 1 of the allowed 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 general (singlet) case in terms of an infinite triangular matrix of anomalous dimensions which couple each truncated moment to all higher moments with orders differing by integers, We show that the evolution of any moment can be determined to arbitrarily good accuracy by truncating the system of coupled moments 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 detail the accuracy of the method in view of applications to precision phenomenology. (C) 2001 Elsevier Science B.V. All rights reserved.