Search For New Color Octet Vector Particle Decaying To Ttbar In Ppbar Collisions At Sqrt S
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Search for New Color-Octet Vector Particle Decaying to Ttbar in Ppbar Collisions at $\sqrt{s}
We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb−1 of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study t{bar t} events in the lepton+jets channel with at least one b-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distribution of top quark pairs. We set limits on the massive gluon coupling strength for masses between 400 and 800 GeV/c2 and width-to-mass ratios between 0.05 and 0.50. The coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space.
Search for Neutral Color-Octet Weak-Triplet Scalar Particles in Proton-Proton Collisions at $\sqrt{s}$
A search for pair production of neutral color-octet weak-triplet scalar particles ([Theta]0) is performed in processes where one [Theta]0 decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons. The search is performed with data collected by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 19.7 fb-1 of proton-proton collisions at √s = 8 TeV. The number of observed events is found to be in agreement with the standard model predictions. The 95% confidence level upper limit on the product of the cross section and branching fraction is obtained as a function of the [Theta]0 mass. The 95% confidence level lower bounds on the [Theta]0 mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model.
Search for Heavy, Long-lived Particles that Decay to Photons in Ppbar Collisions at Sqrt(s)
This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in pp̄ collisions at s = 1.96 TEV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570"34 pb−1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3"0.7 events.