Search for the Trilepton Signal of the Minimal Supergravity Model in D0 Run II

A search for associated chargino neutralino pair production is
performed in the trilepton decay channel qq -> chi^+-_1 +
chi^0_2 -> l+- + nu + chi^0_1 + mu^+- + mu^+- chi^0_1, using
data collected with the D0 detector at a center-of-mass energy of
1.96 TeV at the Fermilab Tevatron Collider. The data sample
corresponds to an integrated luminosity of ~300 pb^-1. A dedicated
event selection is applied to all samples including the data sample
and the Monte Carlo simulated samples for the Standard Model
background and the Supersymmetry signal. Events with two muons plus
an additional isolated track, replacing the requirement of a third
charged lepton in the event, are analyzed. Additionally, selected
events must have a large amount of missing transverse energy due to
the neutrino and the two LSP. After all selection cuts are applied,
2 data events are found, with an expected number of background
events of 1.75 +- 0.34(stat.) +- 0.46 (syst.). No evidence for
Supersymmetry is found and limits on the production cross-section
times leptonic branching fraction are set. When the presented
analysis is considered in combination with three other decay
channels, no evidence for Supersymmetry is found. Limits on the
production cross-section times leptonic branching fraction are set.
A lower chargino mass limit of 117 GeV at 95% CL is then derived
for the mSUGRA model in a region of parameter space with enhanced
leptonic branching fractions.