OEDIPUS: Onium Evolution, Dipole Interaction and Perturbative Unitarisation Simulation
G. P. Salam
TL;DR
OEDIPUS addresses the problem of modeling small-$x$ evolution in heavy onia and the consequent unitarity issues in high-energy QCD. It employs a Monte Carlo implementation of Mueller's color-dipole framework to generate the full dipole content of evolving onia and to compute onium–onium scattering amplitudes, including multi-pomeron exchanges that restore unitarity. The paper provides a comprehensive description of the algorithmic structure, data types, IO, and practical considerations for carrying out large-scale simulations, including memory management and binning of amplitudes. Together, these contributions enable detailed, unitarised predictions for high-energy onia interactions and offer a flexible toolkit for exploring dipole dynamics, spatial distributions, and scattering cross sections in perturbative QCD.
Abstract
A Monte Carlo simulation program is presented which can be used to determine the small-$x$ evolution of a heavy onium using Mueller's colour dipole formulation, giving the full distribution of dipoles in rapidity and impact parameter. Routines are also provided which calculate onium-onium scattering amplitudes between individual pairs of onium configurations, making it possible to establish the contribution of multiple pomeron exchange terms to onium-onium scattering (the unitarisation corrections).