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Manuscript Title: The package PAKPDF 1.1 of parametrizations of parton distribution functions in the proton.
Authors: K. Charchula
Program title: PAKPDF 1.1
Catalogue identifier: ACGU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 69(1992)360
Programming language: Fortran.
Computer: IBM 3090.
Operating system: MVS, VMS.
RAM: 45K words
Word size: 32
Keywords: Particle physics, Elementary, Empirical model, Perturbative quantum, Chromodynamics (qcd), Improved qcd, Parton model, Standard model, Altarelli-parisi Equation, Deep inelastic Scattering, Parton distribution Functions (pdfs), Structure functions, Cross sections.
Classification: 11.6.

Nature of problem:
In the framework of the QCD Improved Parton Model parton distribution functions play a basic role enabling to relate theoretically calculated hardpartonic cross section with experimentally measured one. Their specific features determine the behaviour of hadronic cross sections at high energies. The accurate knowlegde of PDFS is important especially in precision studies of the Standard Model, in estimating possible sources of background in search for New Physics and in predictions for forthcoming colliders. A collection of all recent parametrizations of parton distribution functions allows an easy and fast access to various PDFS in a wide kinematic range.

Solution method:
Solutions of the Altarelli-Parisi equation with input distributions appropiately determined from experimental data have been parametrized in an analytic form with Q**2 dependent parameters or through the look-up containing grids in (x,Q**2) variables with an interpolating procedure. The collection of parametrizations has a modular form consisting of several procedures with a unified calling format.

Restrictions:
All parametrizations are applicable in a restricted region of (x,Q**2) variables, dependent on a particular parametrization. Extensive warnings/errors messages are provided to control the validity region of input parameters of the procedures.

Running time:
Calculation of parton distributions for all flavours at 100 various (x,Q**2) points takes approximately 0.04 seconds CPU time on an IBM 3090.