Tests of Pythia8 Rescattering Model

TL;DR

This paper investigates the rescattering model in Pythia8 for multiple parton interactions in hadron collisions, analyzing observables sensitive to rescattering effects and tuning parameters to match experimental data.

Contribution

It introduces an analysis of rescattering effects in Pythia8 and identifies observables sensitive to these effects, providing guidance for tuning MPI parameters.

Findings

Charged particle distributions show differences with rescattering.

Jet-balance observables do not show significant differences.

MPI parameters can be tuned to fit data with rescattering.

Abstract

One of the most poorly understood phenomenon in hadron collisions, is the so called multiple parton interaction (MPI). Apart from one quark or gluon each from each colliding proton, additional quarks or gluons can interact as well, and these can not be calculated from first principles. The concept of rescattering has been introduced recently in Pythia8 event generator, where particles originating from these secondary interactions can interact again with quarks or gluons from incoming protons. In this paper, we look at events with a $Z$-boson, to find observables which can potentially be sensitive to this rescattering effect. While jet-balance observables do not show visible difference, charged particle distributions in different azimuthal regions show some difference. The parameters controlling MPI can be tuned to give a good description of data with rescattering.