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A search for chargino-neutralino production at the Fermilab Tevatron Collider

Description: We have searched for evidence of supersymmetry with the Collider Detector at Fermilab using trilepton events in p{anti p} collisions at {radical}s = 1.8 TeV. In the Minimal Supersymmetric Standard Model (MSSM), we expect trilepton events from chargino-neutralino ({tilde {xi}}{sup {+-}}{sub 1}{tilde {xi}}{sup 0}{sub 2}) pair production, with subsequent decay into leptons. In all possible combinations of electron and muon channels, we observe no candidate events in 107 pb{sup -1} of data. We present limits on chargino and neutralino production within the framework of a supergravity inspired MSSM: {sigma}{sub {tilde {xi}}{sup {+-}}{sub 1}{tilde {xi}}{sup 0}{sub 2}} {center_dot} BR({tilde {xi}}{sup {+-}}{sub 1}{tilde {xi}}{sup 0}{sub 2} {yields} 3l + X) < 0.34 pb and M{sub {tilde {xi}}{sup {+-}}{sub 1}} > 81.5 GeV/c{sup 2} for tan {beta} = 2, {mu} = -600 GeV/c{sup 2} and M{sub {tilde q}} = M{sub {tilde g}}. We also present limits on a SU(5) x U(1) supergravity model and a 4 and 1/2 parameter Minimal SUGRA model.
Date: December 1, 1997
Creator: Tannenbaum, B.
Partner: UNT Libraries Government Documents Department

Jet Production at the Tevatron

Description: Inclusive jet cross section and dijet angular distribution results from the CDF and D0 collaborations are presented. The possibility that compositeness might be evident at high transverse energies is explored by both experiments. Using the angular distributions, the CDF analysis excludes at the 95% CL regions with {Lambda}{sup +} < 1.8 TeV and {Lambda}{sup -} < 1.6 TeV for a model where all quarks are allowed to be composite objects. The D0 preliminary result excludes at the 95% CL regions with {Lambda}{sup +} < 2.0 TeV for the same model.
Date: June 1, 1997
Creator: Nang, F. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department

Single top production and M{subscriptT Tbar}

Description: Single top production provides opportunities for studying the charged-current weak interaction of the top quark. The t{anti t} invariant mass spectrum M{sub t{anti t}} enables the search for non-standard model t{anti t} resonance states. These two topics have motivated new developments in top quark related analyses at Fermilab Tevatron. This presenta- tion reports the current single top and M{sub t{anti t}} analysis methods and the corresponding results from the collider Run I data collected by the CDF and D#31; experiment. We conclude with the prospects for these studies in the upcoming collider Run II.
Date: May 11, 1999
Creator: Liu, Yi-Cheng
Partner: UNT Libraries Government Documents Department

Inclusive jet production at 630 and 1800 GeV

Description: Inclusive jet cross sections measured at the Fermilab Tevatron p{anti p} Collider are presented and compared to theoretical predictions. The cross sections are reported as a function of jet E{sub T} at beam energies of {radical}s = 0.63 TeV and {radical}s = 1.8 TeV. A recent preliminary result at {radical}s = 1.8 TeV by the CDF collaboration confirms an earlier published result which is in good agreement with Quantum Chromodynamics (QCD) below E{sub T} = 250 GeV, but which shows excess jet production above 250 GeV. A final result by the D0 collaboration is in good agreement with QCD at all E{sub T} . An uncertainty analysis, including a final D0 systematic error matrix, indicates the two measurements are consistent. Preliminary {radical}s = 0.63 TeV cross sections from the two experiments are consistent with one another but somewhat lower than QCD predictions. Likewise, preliminary measurements of the ratio of cross sections at {radical}s = 0.63 TeV and {radical}s = 1.8 TeV are experimentally consistent, but approximately 20% below predictions.
Date: December 1, 1998
Creator: Blazey, Gerald C.
Partner: UNT Libraries Government Documents Department

Neural Networks for Analysis of Top Quark Production

Description: Neural networks (NNs) provide a powerful and flexible tool for selecting a signal from a larger background. The D0 collaboration has used them extensively in studying t{anti t} decays. NNs were essential to the measurement of the t{anti t} production cross section in the all-jets channel (t{anti t} {yields} b {anti b}qqqq), and were also used in the measurement of the mass of the top quark in the lepton+jets channel (t{anti t} {yields} b{anti b}l{nu}q{anti q}). This paper will describe two new applications of neural networks to top quark analysis: the search for single top quark production, and an effort to increase the sensitivity in the dilepton channel t{anti t} {yields} b{anti b}e{anti {mu}}{nu}{anti {nu}} beyond that achieved in the published analysis.
Date: August 4, 1999
Creator: al., B. Abbott et
Partner: UNT Libraries Government Documents Department

Recent D-Zero results on the top quark

Description: Recent results on top quark physics with the D0 experiment in {anti p}p collisions at {radical}s = 1.8 TeV for an integrated luminosity of 125 pb{sup -1} are reported. The direct measurement of the top quark mass uses single lepton events, giving the result m{sub top} = 173.3 {+-} 5.6(stat) {+-} 6.2(syst) GeV=c{sup 2}. The measurement of the t{anti t} production cross section includes analyses from 8 top decay channels: dilepton (t{anti t} {yields} e{mu}, ee, and {mu}{mu}), electron and neutrino (t{anti t} {yields} e{nu}), and single leptons (t{anti t} {yields} e + jets and t{anti t} {yields} {mu} + jets) with and without b tagging. We measure the t{anti t} production cross section to be 5.5 {+-} 1.8 pb at m{sub top} = 173.3 GeV/c{sup 2}.
Date: July 1, 1997
Creator: Li, Q.
Partner: UNT Libraries Government Documents Department

Production of Gauge Bosons at the Tevatron

Description: The CDF and D0 collaborations have used recent data taken at the Tevatron to perform QCD tests with W and Z bosons decaying leptonically. D0 measures the production cross section times branching ratio for W and Z bosons and determines the branching ratio B(W {yields} l{nu}) = (10.43 {+-} 0.44)% (l = e, {mu}). This also gives an indirect measurement of the total width of the W boson: {Gamma}{sub W} = 2.16 {+-} 0.09 GeV. The W cross section times branching ratio into tau leptons is measured to be {sigma}({anti p}p {yields} W + X)B(W {yields} {tau}{nu}) = 2.38{+-}0.13 nb, from which the ratio of the coupling constants is determined: g{sub {tau}}{sup W}/g{sub e}{sup W} = 1.004 {+-} 0.019 {+-} 0.026. D0`s measurement of the differential d{sigma}/dP{sub T} distribution for the Z boson decaying to electrons, discriminates between different phenomenologic vector boson production models. CDF measures the cross section for the Drell-Yan continuum, and extracts improved limits on compositeness scales for quarks and leptons of {Lambda}{sub ql} {approximately} 3 - 6 TeV, depending on the model. Studies of W + Jet production at CDF and D0 find that the QCD prediction underestimates the production rate of W + 1 Jet events by about a factor of 2 as measured by both collaborations.
Date: June 1, 1997
Creator: Gerber, C.E. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department

Top quark mass and production from CDF

Description: We present the latest results about the top quark obtained by the CDF experiment using a data sample of about 110 pb{sup -1} collected at the Fermilab Tevatron collider. We briefly describe the production cross section determination and the top mass measurement. Finally we review the search for the top quark in rare decay channels and the first direct calculation of the CKM matrix element V{sub tb}.
Date: September 1, 1997
Creator: Leone, S.
Partner: UNT Libraries Government Documents Department

Trilinear gauge couplings at the Fermilab Tevatron

Description: Recent trilinear gauge boson couplings measurements by the CDF and D0 Collaborations at the Fermilab Tevatron are presented. The measurements were done by analyzing diboson production in multiple decay channels and final states. No deviations from the Standard Model description of the WWZ, WW{gamma}, ZZ{gamma} and Z{gamma}{gamma} vertices were found. Limits on anomalous gauge couplings set by these analyses are the tightest available to date.
Date: October 1, 1997
Creator: Landsberg, G.
Partner: UNT Libraries Government Documents Department

Theoretical description of heavy quark production in DIS

Description: We present results from a new event-generator Monte Carlo program for semi- inclusive DIS heavy quark production computed in a composite 3-flavor/4-flavor scheme, which is applicable over a wider range of energy scales than existing calculations. We compare the semi-inclusive distributions in p{sub t}, Q{sup 2} and W at O ({alpha}{sup 1}{sub s}) with recent HERA results. We also compare the inclusive F{sup charm}{sub 2} with the data and the existing O ({alpha}{sup 2}{sub s}) 3-flavor scheme calculation. Both calculations agree will with current HERA data, but the resummed O ({alpha}{sup 1}{sub s}) composite scheme calculation is simpler and more efficient by an order of magnitude.
Date: July 1, 1998
Creator: Amundson, J., FERMI
Partner: UNT Libraries Government Documents Department


Description: The RIKEN-BNL Workshop on Quarkonium Production in Relativistic Nuclear Collisions was held September 28--October 2, 1998, at Brookhaven National Laboratory. The Workshop brought together about 50 invited participants from around the world and a number of Brookhaven physicists from both particle and nuclear physics communities.
Date: April 20, 1999
Creator: Kharzeev, D.
Partner: UNT Libraries Government Documents Department

Prospects for higgs at the Tevatron

Description: The current status of simulation studies for the observation of a standard-model or lightest supersymmetric Higgs boson at TeV33 are reviewed. Latest studies indicate that the mass range 60 < m{sub H} {approx_lt} 130 GeV can be covered at the 5-standard-deviation level with 30 fb{sup -1}, using the WH and ZH channels. This is the full allowed mass range for the lightest Higgs h of minimal supersymmetry.
Date: February 1, 1998
Creator: Womersley, J.
Partner: UNT Libraries Government Documents Department

Recent Tevatron results on b quark production

Description: A number of recent B physics results from the CDF and D0 experiments at the Fermilab Tevatron Collider is reported. Measurements of open b quark production cross section in the central and forward rapidity regions in p{anti p} interactions at {radical}s = 1800 GeV are presented. The measurements are used to evaluate the rapidity dependence of b quark production. We also report recent results on correlated b {anti b} production: a measurement of b {anti b} angular correlations using dimuon triggers (D0) and the first direct measurement of b {anti b} rapidity correlations (CDF). The results from the various measurements are compared with the next-to-leading order QCD predictions. Finally, a measurement by CDF of the polarization of {psi}(2S) mesons is compared with the predictions of the Color Octet Model.
Date: June 1, 1999
Creator: Baarmand, Marc M.
Partner: UNT Libraries Government Documents Department

Hyperon production asymmetries in 500 GeV/c pion nucleus Interactions

Description: We present a preliminary study from Fermilab experiment E791 of {Lambda}{sup 0}/{anti {Lambda}}{sup 0}, {Xi}{sup -}/{Xi}{sup +} and {Omega}{sup -}/{Omega}{sup +} production asymmetries from {pi}{sup -} nucleus interactions at 500 Gev/c. The production asymmetries for these particles are studied as a function of x{sub F} and p{sup 2}{sub T}. We observed an asymmetry in the target fragmentation region for {Lambda}{sup 0}`s larger than that for {Xi}`s, suggesting diquark effects. The asymmetry for {Omega}`s is significatively smaller than for the other two hyperons consistent with the fact that {Omega}`s do not share valence quarks with either the pion or the target particle. In the beam fragmentation region, the asymmetry tends to 0.1 for both {Lambda}{sup 0}`s and {Xi}`s. The asymmetries vs p{sup 2}{sub T} are approximately constant for the three strange baryons under study.
Date: October 1, 1997
Creator: Solano, J.; Magnin, J.; Simao, F.R.A. & Collaboration, E791
Partner: UNT Libraries Government Documents Department

Top Quark Production and Decay Measurements from CDF

Description: The CDF collaboration is completing a number of studies on the top quark, based on samples collected during Run I of the Tevatron Collider. The production and decay properties of the top quark are being examined in most of the t {anti t} decay channels, and many of these results have recently been published. The study of the top quark has moved beyond measurements of its mass and production cross section, to detailed studies of W polarization in top decays, single top production, branching fractions, the W - t - b coupling, and search for rare decays.
Date: January 1, 1999
Creator: Tollefson, K.
Partner: UNT Libraries Government Documents Department

Properties of b-quark production at the Tevatron

Description: We report on results obtained by the D0 and CDF collaborations on the properties of b-quark production in p{anti p} collisions at ps = 1:8 TeV. The D0 experiment has measured the inclusive production cross section for muons originating from b-quark decays in the forward region, corresponding to the rapidity range 2:4 < j y {sup {mu}} j < 3:2. Combined with previous measurements in the central region, these results permit a comparison of the rapidity dependence of the b-quark production cross section with the predictions of next-to-leading order QCD. The CDF experiment has achieved the #12;rst direct measurement of b {anti b} rapidity correlations at a hadron collider, with the ratio of the cross sections obtained in two rapidity bins. This measurement is a direct probe of the high-x gluon content of the proton.
Date: October 1, 1998
Creator: Stichelbaut, Frederic
Partner: UNT Libraries Government Documents Department

Photon and di-photon results from CDF and D0

Description: Measurements by the Fermilab D0 and CDF collaborations of prompt photon events in p{anti p} collisions at {radical}s = 1.8 TeV are reported. The measured isolated photon cross sections are compared to current parton distribution functions and NLO QCD predictions. The cross section ratio of forward to central {eta} bins and {eta} distributions are presented and compared with theoretical predictions. {gamma}+2jet events yield insight into final state radiation. A new measurement of {gamma}+{mu} events is presented which probes the charm content of the proton. Finally, di-photon results are presented as a probe of initial state radiation; these results are compared to NLO QCD, Pythia parton showers, and resummation models.
Date: May 11, 1999
Creator: Hanlet, Pierrick
Partner: UNT Libraries Government Documents Department

Prospects for Higgs discovery at the Tevatron

Description: This report presents the results of a Fermilab study of the sensitivity for Higgs boson production at the upgraded Tevatron in Run II. The study extends previous Tevatron results by combining all possible search channels, considering the production of higher mass Higgs bosons and interpreting the results in the context of supersymmetric Higgs production as well as Standard Model production.
Date: October 14, 1999
Creator: Roco, Maria Teresa P.
Partner: UNT Libraries Government Documents Department