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We present new limits on resonant tb production in ppbar collisions at sqrt(s) = 1.96 TeV, using 1.9 fb−1 of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a putative tb mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous tb production as modeled by W′ → tb. We set a new limit on a right-handed W′ with standard model-like coupling, excluding any mass below 800 GeV at 95% C.L. For any narrow W′-like state with mass above 800 GeV, the cross-section is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the W′ coupling strength versus W′ mass.
We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680 pb−1 collected with the Collider Detector at Fermilab in Run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific top color-assisted technicolor production model, the leptophobic Z′ with width?{sub Z{prime}} = 0.012M{sub Z{prime}}, we exclude the mass range M{sub Z{prime}}
We search for resonant production of t{bar t} pairs in 4.8 fb−1 integrated luminosity of p{bar p} collision data at √s = 1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the t{bar t} candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant t{bar t} production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of t{bar t} pairs. A benchmark model of leptophobic Z' → t{bar t} is excluded with m{sub Z'}
We measure the t{bar t} production cross section in p{bar p} collisions at √s = 1.96 TeV in the lepton+jets channel. Two complementary methods discriminate between signal and background, b-tagging and a kinematic likelihood discriminant. Based on 0.9 fb−1 of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure [sigma]{sub t{bar t}} = 7.62 ± 0.85 pb, assuming the current world average m{sub t} = 172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top quark mass of 170 ± 7 GeV.
A preliminary analysis of an experiment designed as a sensitive dibaryon resonance search in the reaction pp.-->.p.pi.n is presented. At 2 GeV/c incident momentum, 440,000 unambiguously reconstructed events were obtained. In this preliminary analysis, the results are reported of a search of the pn mass spectrum for evidence of chain decays of possible dibaryon resonances, i.e. pp.-->.d/sup **/, d/sup **/.-->.d/sup **/.pi./sup +/, d/sup */.-->.pn. No evidence of narrow peaks (less than or equal to 7 MeV) is seen in the data for cross-section-times-branching-ratio greater than 50 .mu.b.
Abstract Not Provided.
A search is performed for the production of heavy resonances decaying into top-antitop quark pairs in proton-proton collisions at √s = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 fb–1. The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the tt¯ → WbWb decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. Furthermore, no significant excess of events relative to the expected yield from standard model processes is observed.