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 p(t) > 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.
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Updated: Thursday, 2002 January 24 13:09:08 CST automatically from input from Carol Picciolo