Showing papers by "Brad Abbott published in 1997"
TL;DR: In this paper, the authors review the direct measurements of the top quark mass Mt using the sample of events collected by the DO and CDF experiments at Fermilab and conclude that the current world average Mt = 174.3 ± 3.2 (stat.) ± 4.0 (syst.) GeV/c2.
Abstract: ▪ Abstract We review the direct measurements of the top quark mass Mt using the sample of events collected by the DO and CDF experiments at Fermilab. Measurements using events in the lepton plus jets, dilepton, and all-hadronic decay modes are reviewed, as is the combination of the results to yield the current world average Mt = 174.3 ± 3.2 (stat.) ± 4.0 (syst.) GeV/c2. We close by estimating the precision attainable with future data sets at Fermilab and the Large Hadron Collider.
84 citations
TL;DR: In this article, a measurement of the ttbar production cross section in ppbar collisions at root(s) = 1.8TeV was presented based on data from an integrated luminosity of approximately 125 pb^-1 accumulated during the 1992-1996 collider run.
Abstract: We present a measurement of the ttbar production cross section in ppbar collisions at root(s) = 1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125 pb^-1 accumulated during the 1992-1996 collider run. We observe 39 ttbar candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7+-2.2 events. For a top quark mass of 173.3GeV/c^2, we measure the ttbar production cross section to be 5.5+-1.8 pb.
41 citations
TL;DR: In this paper, a lower bound on the mass of a first generation scalar leptoquark of $225\mathrm{GeV}{/c}^{2} was established.
Abstract: We have searched for the pair production of first generation scalar leptoquarks in the $\mathrm{eejj}$ channel using the full data set $(123{\mathrm{pb}}^{\ensuremath{-}1})$ collected with the D0 detector at the Fermilab Tevatron during 1992--1996. We observe no candidates with an expected background of approximately 0.4 events. Comparing the experimental 95% confidence level upper limit to theoretical calculations of the cross section with the assumption of a 100% branching fraction of $\mathrm{eq}$, we set a lower limit on the mass of a first generation scalar leptoquark of $225\mathrm{GeV}{/c}^{2}$. The results of this analysis rule out the interpretation of the excess of high ${Q}^{2}$ events at DESY HERA as leptoquarks which decay exclusively to $\mathrm{eq}$.
38 citations
TL;DR: In this article, the authors measured the cross section times branching ratio for gauge boson coupling parameters using the D\O{} detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of $92.8$ TeV.
Abstract: We have measured the $\mathrm{WW}\ensuremath{\gamma}$ gauge boson coupling parameters using $p\overline{p}\ensuremath{\rightarrow}\ensuremath{\ell}\ensuremath{
u}\ensuremath{\gamma}+X$ ( $\ensuremath{\ell}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}e,\ensuremath{\mu}$) events at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8$ TeV. The data, corresponding to an integrated luminosity of $92.8{\mathrm{pb}}^{\ensuremath{-}1}$, were collected using the D\O{} detector at the Fermilab Tevatron Collider. The measured cross section times branching ratio for $p\overline{p}\ensuremath{\rightarrow}W\ensuremath{\gamma}+X$ with ${p}_{T}^{\ensuremath{\gamma}}g10$ GeV/c and ${R}_{\ensuremath{\ell}\ensuremath{\gamma}}g0.7$ is ${11.3}_{\ensuremath{-}1.5}^{+1.7}\ifmmode\pm\else\textpm\fi{}1.5$ pb, in agreement with the standard model prediction. The 1 degree of freedom 95% confidence level limits on individual CP-conserving parameters are $\ensuremath{-}0.93l\ensuremath{\Delta}\ensuremath{\kappa}l0.94$ and $\ensuremath{-}0.31l\ensuremath{\lambda}l0.29$. Similar limits are set on the CP-violating coupling parameters.
30 citations
TL;DR: An upper limit is placed on the production cross section times branching fraction that is well below theoretical expectations for a b{sup {prime} decaying exclusively via FCNC for b{Sup {prime}} masses up to m{sub Z}+m{sub b}.
Abstract: We report on a search for pair production of a fourth generation charge -1/3 quark (b{sup {prime}}) in p{ovr p} collisions at {radical}(s)=1.8TeV by the DO/ experiment at the Fermilab Tevatron using an integrated luminosity of 93pb{sup -1}. Both b{sup {prime}} quarks are assumed to decay via flavor changing neutral currents (FCNC). The search uses the signatures {gamma}+3 jets +{mu}-tag and 2{gamma}+2 jets. We see no significant excess of events over the expected background. We place an upper limit on the production cross section times branching fraction that is well below theoretical expectations for a b{sup {prime}} decaying exclusively via FCNC for b{sup {prime}} masses up to m{sub Z}+m{sub b}. {copyright} {ital 1997} {ital The American Physical Society}
26 citations
TL;DR: In this article, the authors measured the ZZγ and Zγγ couplings by studying 13.1pb -1 of pp→E t γ+X data at √s=1.8TeV with the DO detector at the Fermilab Tevatron Collider.
Abstract: We have measured the ZZγ and Zγγ couplings by studying 13.1pb -1 of pp→E t γ+X data at √s=1.8TeV with the DO detector at the Fermilab Tevatron Collider. This is the first study of hadronic Zγ production in the neutrino decay channel. Combining this measurement with our previous results using Z→ee and μμ yields the most stringent 95% C.L. limits to date on anomalous couplings: |h 30 Z | 40 Z |<0.06 (Λ=750GeV).
22 citations
TL;DR: In this article, the p{sub T} spectrum of W bosons was analyzed and a fit to the spectrum of the photons was obtained, leading to an upper limit on the WW production cross section and limits on anomalous WW and WWZ couplings.
Abstract: The gauge boson pair production processes W{gamma}, WW, WZ, and Z{gamma} were studied using p{bar p} collisions corresponding to an integrated luminosity of approximately 14 pb{sup {minus}1} at a center-of-mass energy of {radical} (s) =18 TeV Analysis of W{gamma} production with subsequent W boson decay to scr(l){nu} (scr(l)=e,{mu}) is reported, including a fit to the p{sub T} spectrum of the photons which leads to limits on anomalous WW{gamma} couplings A search for WW production with subsequent decay to scr(l)scr({bar l}){nu}{bar {nu}} (scr(l)=e,{mu}) is presented, leading to an upper limit on the WW production cross section and limits on anomalous WW{gamma} and WWZ couplings A search for high p{sub T} W bosons in WW and WZ production is described, where one W boson decays to an electron and a neutrino and the second W boson or the Z boson decays to two jets A maximum likelihood fit to the p{sub T} spectrum of W bosons resulted in limits on anomalous WW{gamma} and WWZ couplings A combined fit to the three data sets which provided the tightest limits on anomalous WW{gamma} and WWZ couplings is also described Limits on anomalous ZZ{gamma} and Z{gamma}{gamma} couplings are presented from an analysis of the photonmore » E{sub T} spectrum in Z{gamma} events in the decay channels (ee, {mu}{mu}, and{nu}{nu}) of the Z boson {copyright} {ital 1997} {ital The American Physical Society}« less
20 citations
TL;DR: In this article, color coherence effects in p p collisions at a center of mass energy s = 1.8 TeV were studied with the DO detector during the 1992-1993 run of the Fermilab Tevatron Collider.
18 citations
17 citations
TL;DR: In this paper, a search for new physics has been carried out in the channel pp→γγ+E T, as expected in various supersymmetric models, and limits on production cross sections for selectron, sneutrino, and neutralino pairs, decaying into photons, which range from about 400 fb to 1 pb depending on the sparticle masses.
Abstract: A search for new physics has been carried out in the channel pp→γγ+E T , as expected in various supersymmetric models. We require two photons with transverse energy E T γ >12GeV and pseudorapidity |η γ | T ) is consistent with background and no events have E T >25GeV. We set limits on production cross sections for selectron, sneutrino, and neutralino pairs, decaying into photons, which range from about 400 fb to 1 pb depending on the sparticle masses. A general limit of 185 fb (95% C.L.) is set on σ(pp→γγE T +X), where E T γ >12GeV, |η γ | T >25GeV.
15 citations
TL;DR: In this paper, the authors present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV.
Abstract: We present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p -> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992-1995 run. The data sample corresponds to an integrated luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling parameters, the 95% CL limits on the CP-conserving couplings are -0.33
01 Jan 1997
TL;DR: In this article, preliminary results from an analysis of jet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 93 pb-’ were presented.
Abstract: We present preliminary results from an analysis of jet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 93 pb-’ . Measurements of dijet mass spectra in Fp collisions at fi = 1.8 TeV are compared to next-to-leading order QCD calculations. *Submitted to the International Europhysics Conference on High Energy Physics, August 19 26, 1997, Jerusalem, Israel.
01 Jan 1997
TL;DR: In this paper, preliminary results of a search for a heavy neutral gauge boson, Z', using the decay channel 2' + ee were reported with the DO detector at the Fermilab Tevatron during the 1994-1995 pp collider run at fi = 1.8 TeV and correspond to an integrated luminosity of M 90 pb-
Abstract: We report preliminary results of a search for a heavy neutral gauge boson, Z’, using the decay channel 2’ + ee . The data were collected with the DO detector at the Fermilab Tevatron during the 1994-1995 pp collider run at fi = 1.8 TeV and correspond to an integrated luminosity of M 90 pb-‘. Limits are set on the cross section times branching ratio for the process jjp + 2’ + ee as a function of the 2’ mass. We exclude the existence of a heavy neutral gauge boson of mass less than 660 GeV/c2 (95% CL), assuming a 2’ with the same coupling strengths to quarks and leptons as the standard model 2 boson. Combining this analysis with D0’s 1992-1993 data set increases the limit to mZl > 670 GeV/c2 . *Submitted to the International Europhysics Conference on High Energy Physics, August 19 26, 1997, Jerusalem, Israel.