Search For R Parity Violating Supersymmetry In Multilepton Final States With The Do Detector PDF Download

This thesis presents a search for physics beyond the standard model of elementary particles in events containing three or more charged leptons in the final state. The search is based on an R-parity violating supersymmetric model that assumes supersymmetric particles are pair produced at hadron colliders and the R-parity violating coupling is small enough so that these particles "cascade" decay into the lightest supersymmetric particle. The lightest supersymmetric particle may only decay into two charged leptons (electrons or muons) plus a neutrino through a lepton number violating interaction. Proton-antiproton collision events produced with s = 1.96 TeV are collected between March 2002 and August 2004 with an integrated luminosity of 346 pb-1. R-parity violating supersymmetry is sought for in two data samples, one with exactly three leptons and one with four or more leptons. The trilepton sample has a modest background primarily from Drell-Yan events where an additional lepton is a result of photon conversions or jet misidentification while the four or more lepton sample has an extremely low background. In the three lepton samples 6 events are observed while in the four or more lepton sample zero events are observed. These results are consistent with the standard model expectation and are interpreted as mass limits on the lightest neutralino ( c&d5;01 ) and lightest chargino ( c&d5;+/- 1 ) particles. The c&d5;01 mass is constrained to be heavier than 97.7 to 110.4 GeV/ c2, while the c&d5;+/- 1 mass is constrained to be heavier than 185.3 to 202.7 GeV/ c2, depending on the supersymmetry scenario.