FORTRAN PROGRAM FOR A NUMERICAL-SOLUTION OF THE NONSINGLET ALTARELLI-PARISI EQUATION

We investigate a numerical solution of the flavor-nonsinglet Altarelli -Parisi equation with next-to-leading-order alpha(s) corrections by us ing Laguerre polynomials. Expanding a structure function (or a quark d istribution) and a splitting function by the Laguerre polynomials, we reduce an integrodifferential equation to a summation of finite number of Laguerre coefficients, We provide a FORTRAN program for Q(2) evolu tion of nonsinglet structure functions (F-1, F-2, and F-3) and nonsing let quark distributions. This is a very effective program with typical running time of a few seconds on SUN-IPX or on VAX-4000/500. Accurate evolution results are obtained by taking approximately twenty Laguerr e polynomials.