Solving the Altarelli-Parisi equations with truncated moments

The technique of truncated moments of parton distributions allows us to stu dy scaling violations without making any assumption on the shape of parton distributions. The numerical implementation of the method is, however, diff icult, since the evolution equations for truncated moments are not diagonal . We present a simple way to improve the efficiency of the numerical soluti on of the evolution equations for truncated moments. As a result, the numbe r of truncated moments needed to achieve the required precision in the evol ution is significantly smaller than in the original formulation of the tech nique. The method presented here can also be used to obtain the value of pa rton distributions in terms of truncated moments, and, therefore, it can be viewed as a technique for the solution of the Altarelli-Parisi equations. (C) 2001 Elsevier Science B.V. All rights reserved.