|The Underlying Event in Hard Scattering Processes
(for the CDF Collaboration)
Contribution to Snowmass 2001
October 1, 2001
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.
Zipped Postscript (PS) file (18 pages).