Inclusive and Exclusive observables from dipoles in high energy collisions

TL;DR

The paper introduces DIPSY, a Monte Carlo event generator built on Mueller's dipole cascade with non-leading corrections and saturation, designed to describe exclusive final states in high-energy hadronic collisions. It provides a detailed framework to translate inclusive dipole evolution into exclusive final states by identifying backbone gluons, applying proper weighting, converting to momentum space, and adding final-state radiation and hadronization. The work emphasizes self-consistency, frame independence, and data-driven tuning, presenting substantial comparisons to pp and γ*p data and to the PYTHIA 8 baseline for minimum-bias observables. Overall, it demonstrates that a dipole-based approach can yield competitive exclusive-state predictions and offers a unique lens on soft and semi-hard QCD dynamics in both hadronic and heavy-ion collisions.

Abstract

We present a new model for simulating exclusive final states in minimum-bias collisions between hadrons. In a series of papers we have developed a Monte Carlo model based on Mueller's dipole picture of BFKL-evolution, supplemented with non-leading corrections, which has shown to be very successful in describing inclusive and semi-inclusive observables in hadron collisions. In this paper we present a further extension of this model to also describe exclusive final states. This is a highly non-trivial extension, and we have encountered many details that influence the description, and for which no guidance from perturbative QCD could be found. Hence we have had to make many choices based on semi-classical and phenomenological arguments. The end result is a new event generator called DIPSY which can be used to simulate complete minimum-bias non-diffractive hadronic collision events. Although the description of data from the Tevatron and LHC is not quite as good as for PYTHIA, the most advanced of the general purpose event generator programs for these processes, our results are clearly competitive, and can be expected to improve with careful tuning. In addition, as our model is very different from conventional multiple scattering scenaria, the DIPSY program can be used to gain deeper insight in the soft and semi-hard processes involved both in hadronic and heavy ion collisions.