The Underlying Event in Hard Scattering Processes

TL;DR

This paper analyzes the underlying event in proton-antiproton collisions at 1.8 TeV, comparing experimental data with QCD Monte Carlo models, and finds PYTHIA provides the best description due to its multiple parton scattering approach.

Contribution

It evaluates and compares different Monte Carlo models' effectiveness in describing the underlying event in high-energy collisions, highlighting PYTHIA's superior performance.

Findings

PYTHIA best matches the experimental data.

ISAJET underestimates beam-beam remnant particles.

HERWIG underestimates beam-beam remnant particles and overestimates initial-state radiation.

Abstract

We study the behavior of the "underlying event" in hard scattering proton-antiproton collisions at 1.8 TeV and compare with the QCD Monte-Carlo models. The "underlying event" is everything except the two outgoing hard scattered "jets" and receives contributions from the "beam-beam remnants" plus initial and final-state radiation. The data indicate that neither ISAJET or HERWIG produce enough charged particles (with PT > 0.5 GeV/c) from the "beam-beam remnant" component and that ISAJET produces too many charged particles from initial-state radiation. PYTHIA which uses multiple parton scattering to enhance the "underlying event" does the best job describing the data.