The core of the program
consists of routines for adding a gluon to a colour dipole, so as
to produce two colour dipoles. The transverse position and rapidity
of the gluon are chosen randomly, in accord with the distributions
derived by Mueller in

Nucl. Phys. B415 (1994) 373. The branching of one dipole into
two is repeated recursively until the rapidity of any new gluons
would be larger than the rapidity to which the onium is being
evolved, giving the complete dipole structure of the onium. This
can be done for any number of initial onia, of arbitrary size.

The resulting dipole
structures can then be processed in whichever way the user wishes.
For example one can make a histogram of the number of dipoles as a
function of their size and position, to help understand which
impact parameters are relevant for onium-onium interaction.

One of the main advantages
of using the Monte Carlo approach over analytical techniques, is
that it is very easy to determine quantities which depend on the
correlations between different dipoles in the same onium. The
OEDIPUS distribution includes example routines for doing this.

In particular, there are
highly optimised routines for determining the multiple scattering
interactions between pairs of onia. These store the probability
distribution of the single interaction (1-pomeron) for each impact
parameter allowing to reuse the data from a run to determine many
different quantities (e.g. two-pomeron interaction, fully
unitarised amplitude, cross section for any number of cut pomerons,
etc...).

Back to

OEDIPUS home page.

*Gavin Salam*

June 3, 1996