Parton distribution functions give the number of partons (quarks and
gluons) in a high momentum proton or other hadron. Precisely, the
gives the distribution of partons as a function of the variables a, A, x
and mu. Parton distribution functions (in the "MS-bar"
convention) are precisely defined
in terms of matrix elements of operators. An introduction to parton
distribution functions (200 Kbytes, gzipped Postscript) may prove
useful. A set of notes from the 1996 SLAC Summer Institute on the basics of QCD perturbation theory
(1000 Kbytes, gzipped Postscript) may also prove useful as background.
Parton distribution functions are determined from data from particle
physics experiments. Several sets of parton distribution functions
are available. In these pages, we provide information about parton
distributions fitted to data by three groups, MRS, CTEQ, and GRV.
Each group provides parton distributions in the form of a
computer code. To see the differences among parton distributions, it
is useful to make graphs.
In these pages, we provide computer
code that can produce any of the parton distributions. The
code interpolates the desired parton distribution function from a table
written in a standard form. A brief explanation of the program that
interpolates the parton data may be useful. There are some caveats.
Parton distribution tables in the standard form
We also provide a somewhat more elaborate
computer code that reads the data for several parton
distribution sets, holds them all in memory, and interpolates from any of the tables as requested.
To produce the values of parton distribution functions from a parton
distribution set not included here, one need only generate the parton
table in the standard form.
One application of parton distributions is the calculation of
the structure functions measured in deeply inelastic scattering.
Code for such
calculations is available from
HEPDATA site at Durham.
Another application is the calculation of
cross sections to produce jets in hadron collisions.
Code for this is available.
Diffractive parton distributions
We also present a set of diffractive parton distributions from F. Hautmann and D. E. Soper, Phys. Rev. D 63, 011501 (2000). A diffractive parton distribution represents the probability to find
a certain kind of parton in an incoming hadron under the condition that the hadron remains intact except for a small momentum transfer (as described in
the reference above and references cited there). Diffractive parton distributions can be used to calculate diffractive deeply inelastic scattering.
Davison E. Soper and Parvez Anandam
Institute of Theoretical Science
University of Oregon
Eugene OR 97403. USA.