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Manuscript Title: Numerical solution of Q**2 evolution equations for polarized structure functions.
Authors: M. Hirai, S. Kumano, M. Miyama
Program title: BFP1
Catalogue identifier: ADHF_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 108(1998)38
Programming language: Fortran.
Computer: AlphaServer 2100 4/200.
Operating system: OpenVMS V6.1.
Keywords: Particle physics, Elementary, Qcd, Structure function, Polarized parton, Distribution, Q**2 evolution, Numerical solution.
Classification: 11.5.

Nature of problem:
This program solves DGLAP Q**2 evolution equations with or without next- to-leading-order alphas effects for longitudinally polarized parton distributions. The evolved distributions could be convoluted with coefficient functions for calculating the structure function g1. Both flavor-nonsinglet and singlet cases are provided, so that the distributions, xDeltaqNS, xDeltaqs, xDeltaqi+ equivalent to xDeltaqi + xDeltaqibar (i=quark flavor), xDeltag, xg1NS, xg1S, and xg(1,i)+ can be obtained.

Solution method:
The DGLAP integrodifferential equations are simply solved by a brute- force method. We divide the variables x and Q**2 into very small steps, and the integrodifferential equations are solved step by step.

This program is used for calculating Q**2 evolution of a longitudinally polarized flavor-nonsinglet-quark, singlet-quark, Deltaqi+, and gluon distributions in the leading order or in the next-to-leading order of alphas. Q**2 evolution equations are the DGLAP equations. The double precision arithmetic is used. The renormalization scheme is the modified minimal subtraction scheme (MSbar). A user provides the initial distribution as a subroutine or as a data file. Examples are explained in section 4. Then, the user inputs fifteen parameters in section 4.

Running time:
Approximately seven minutes on AlphaServer 2100 4/200 in the nonsinglet case, sixty minutes in the singlet-quark evolution.