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Manuscript Title: Efficient evolution of unpolarized and polarized parton distributions with QCD-PEGASUS
Authors: A. Vogt
Program title: QCD-Pegasus Version: 1.0
Catalogue identifier: ADVN_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 170(2005)65
Programming language: FORTRAN 77 (using the common compiler extension of procedure names with more than six characters).
Computer: All.
Operating system: All.
RAM: negligible (< 1 MB)
Keywords: unpolarized and longitudinally polarized parton distributions, Altarelli-Parisi evolution equations, Mellin-space solutions.
PACS: 12.38.-t, 12.38.Bx.
Classification: 11.5.

Nature of problem:
Solution of the evolution equations for the unpolarized and polarized parton distributions of hadrons at leading order (LO), next-to-leading order and next-to-next-to-leading order of perturbative QCD. Evolution performed either with a fixed number nf of effectively massless quark flavours or in the variable-nf scheme. The calculation of observables from the parton distributions is not part of the present package.

Solution method:
Analytic solution in Mellin space (beyond LO in general by power-expansion around the lowest-order expansion) followed by a fast Mellin inversion to x-space using a fixed one-fits-all contour.

The initial distributions for the evolution are required in a form facilitating an efficient calculation of their complex Mellin moments. The ratio of the renormalization and factorization scales μτ/μ has to be a fixed number.

Running time:
One to ten seconds, on a PC with a 2.0 GHz Pentium-IV processor, for performing the evolution of 200 initial distributions to 500 (x, μ) points each. For more details see section 6 of the manuscript.