Underlying Event Studies at RHIC

TL;DR

This paper investigates the underlying event in proton-proton collisions at RHIC, comparing experimental results with theoretical predictions to better understand the components contributing to collision outcomes.

Contribution

It provides preliminary analysis of the underlying event at RHIC energies and compares findings with PYTHIA simulations and Tevatron data, enhancing understanding of non-hard scattering processes.

Findings

Significant contributions from underlying event components identified

Differences observed between jet structure and underlying event particle distributions

Comparison with PYTHIA and Tevatron data highlights energy dependence of underlying event

Abstract

By studying p-p collisions we hope to improve our understanding of the fundamental constituents of matter and how they form into colorless objects. Measurements of the inclusive jet cross-sections and fragmentation properties have confirmed that QCD based calculations give a good description of the hard scattering processes. However, as our analysis of jets has improved it has become clear that there is significant contribution to these measurements from processes other than those directly related to the initial hard scattering - the so-called underlying event. Several processes contribute to the underlying event, namely the beam-beam remnants, initial and final state radiation and multiple parton interactions. The structure of the jet and the underlying event are strikingly different in both their particle compositions and momentum distributions. Only by understanding both components can one fully describe a p-p collision. I will discuss preliminary results from studies of the underlying event in p-p collisions at sqrt(s) = 200 GeV at RHIC, and compare to PYTHIA predictions, as well as earlier results from the Tevatron at 1.8-1.96 TeV.