Browsing by Subject "GMSB"
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Item Search for New Physics in the Exclusive Gamma+MET Final State in p-pbar Collisions at Sqrt(s) = 1.96 TeV(2012-12-03) Aurisano, Adam 1982-This dissertation presents a search for heavy, long-lived, neutral particles that decay to photons in proton anti-proton collisions with a center of mass energy of 1.96 TeV at the Collider Detector at Fermilab (CDF) experiment. Such particles are typical of models of Gauge Mediated Supersymmetry Breaking (GMSB). We select events with a single photon, missing transverse energy, and little other activity in the detector. We model the photon arrival time for Standard Model and non-collision sources using a data-driven method and consider photons which have a time of arrival at the detector which is significantly delayed relative to predictions. Using 6.3 fb^?1 of data collected from December 2004 to June 2010, we observe 322 events in the signal region compared to a background prediction of 287 ? 24 events. While the data are consistently above predictions, we report a model excess with a significance of 1.2 standard deviations from the null hypothesis.Item Search for Supersymmetry Using Diphoton Events in Proton-Antiproton Collisions at a Center of Mass Energy of 1.96 TeV(2010-07-14) Lee, Eun SinThis dissertation presents the results of a search for supersymmetry in protonantiproton collisions with a center of mass energy of 1.96 TeV studied with the Collider Detector at Fermilab. Our strategy is to select collisions with two photons in the nal state that have the properties of being the decays of very massive supersymmetric particles. This includes looking for large total energy from the decayed particles as well as for the presence of particles that leave the detector without interacting. We nd no events using 2.6 fb-1 of data collected during the 2004-2008 collider run of the Fermilab Tevatron which is consistent with the background estimate of 1.4 +/- 0.4 events. Since there is no evidence of new particles we set cross section limits in a gaugemediated supersymmetry model with e 01 ! eG, where the e 01 and eG are the lightest neutralino and the gravitino (the lightest supersymmetric particle), respectively. We set limits on models as a function of the e 01 mass and lifetime, producing the world's most sensitive search for e 01by excluding masses up to 149 GeV=c2 for e 01 lifetimes much less than 1 ns.