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Searches for supersymmetry and Higgs particles with D-Zero

Description: We report on searches for the Supersymmetric and the neutral scalar particles with the D{null} detector at {radical}{ital s} = 1.8 TeV. The three searches that we report here are: (1) SUGRA motivated SUSY search, (2) search for Charginos and neutralinos, and (3) search for heavy neutral scalar particle produced in association with W bosons.
Date: November 1, 1996
Creator: Mondai, N.K.
Partner: UNT Libraries Government Documents Department

Search for squarks and gluinos in p{bar p} collisions at the D0 detector with the jets and missing energy signature

Description: A search for squarks and gluinos has been performed using the D{null} detector at {radical}s = 1.8 TeV Tevatron {ital p{anti p}} collider. Data from the 1992-1993 collider run corresponding to an integrated luminosity of 13.5 pb{sup -1} were examined via the missing {ital E{sub T}} plus jets signature with two separate analyses. No events above the Standard Model backgrounds were observed.
Date: September 1, 1996
Creator: The DO Collaboration
Partner: UNT Libraries Government Documents Department

SUGRA-GUT motivated SUSY search in the dielectron channel at D0

Description: In this paper we present a search for events consistent with the production and decay of supersymmetric particles in the Supergravity- GUT framework in the D{null} detector at Fermilab. We examine the 1994-95 Run 1B data for events containing two or more electrons, two or more jets, and a substantial missing transverse energy. This is complementary to the search in the canonical jets and missing transverse energy channel. We observe 2 events in 92.9 pb{sup -1} or the Run 1B data consistent with the estimated total background contribution of 3.0 {+-} 1.3 events from the Standard Model. The non- observation of excess events has been interpreted as an excluded region on the two-dimensional {ital m}{sub 0} - {ital m}{sub 1/2} plane.
Date: September 1, 1996
Creator: Collaboration, The D0
Partner: UNT Libraries Government Documents Department

Jet azimuthal decorrelation studies with the D-zero detector

Description: Experimental results on the measurement of the azimuthal decorrelation between jets with pseudorapidity separation up to five units are presented. The data were taken at the Fermi National Accelerator Laboratory during the 1992-1993 collider run with the D{null} detector using {ital p{anti p}} collisions at center-of-mass energy {radical}{ital s} = 1.8 TeV. These results are compared to next-to-leading order (NLO) QCD predictions and to two leading-log approximations (LLA) where the leading terms are resummed to all orders in {alpha}{sub s}. The final state jets as predicted by NLO QCD show less azimuthal decorrelation than the data. The parton showering LLA Monte Carlo HERWIG describes the data well; an analytical LLA calculation based on Balitsky-Faclin-Kuraev-Lipatov resummation predicts more decorrelation than is present in the data.
Date: October 1, 1996
Creator: Feher, S.
Partner: UNT Libraries Government Documents Department

The inclusive jet cross section in {bar p}p collisions at {radical}s = 1.8 TeV

Description: We report on the preliminary measurement of the inclusive jet cross section for {vert_bar}{eta}{vert_bar} {le} 0.5 at {radical}s = 1.8 TeV. Two data sets with integrated luminosities of 91 pb{sup {minus}1} and 14 pb{sup {minus}1} were collected at the Fermilab Tevatron {ovr p}p Collider with the D0 detector. The inclusive jet cross sections are measured and reported as a function of transverse jet energy (35 GeV {le} E{sub T} {le} 470 GeV) are in excellent agreement with next-to-leading order QCD. 11 refs., 4 figs.
Date: July 1, 1996
Creator: Bertram, I.A.
Partner: UNT Libraries Government Documents Department

Rapidity gaps in jet events at D{O}

Description: Preliminary results from the D0 experiment on jet production with rapidity gaps in p{bar p} collisions are presented. A class of dijet events with a forward rapidity gap is observed at center-of-mass energies {radical}s = 1800 GeV and 630 GeV. The number of events with rapidity gaps at both center-of-mass energies is significantly greater than the expectation from multiplicity fluctuations and is consistent with a hard single diffractive process. A class of events with two forward gaps and central dijets is also observed at 1800 GeV. This topology is consistent with hard double pomeron exchange. We also present results on the observation of a class of events with low particle multiplicity between jets, attributable to the exchange of a strongly-interacting color-singlet.
Date: July 1, 1996
Creator: Brandt, A.G.
Partner: UNT Libraries Government Documents Department

The dijet mass spectrum and angular distributions with the D0 detector

Description: We present preliminary results from an analysis of dijet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 91 pb{sup -1}. Measurements of dijet mass spectra and dijet angular distributions in {anti p}p collisions at {radical}s- = 1.8 TeV are compared with next-to-leading order QCD theory.
Date: July 1, 1996
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Search for a fourth generation charge {minus}1/3 quark via flavor changing neutral currents

Description: There is some likelihood that a light (< m{sub t}) fourth generation charge -1/3 quark (b{prime}) would decay predominantly via loop induced flavor changing neutral currents. The charged current decay of b{prime} to charm would be highly Cabibbo suppressed due to the fact that it changes the generation number by two. The D0 experiment has searched for b{prime} pair production where one or both b{prime} quarks decays via b{prime} {r_arrow} b+{gamma}, giving signatures photon + three jets and two photons + two jets. WE don not see a significant excess of such events over background. In both modes, we set an upper limit on the cross section times branching ratio that is sufficient to rule out a standard sequential b{prime} decaying predominantly via FCNC in the mass range m{sub Z}/2 < m{sub b{prime}} < m{sub Z} + m{sub b}. For b{prime} masses larger than this, the dominant FCNC decay mode is expected to be b{prime} {r_arrow} b + Z. 14 refs., 13 figs., 5 tabs.
Date: July 1, 1996
Creator: Collaboration, The D0
Partner: UNT Libraries Government Documents Department

The b{bar b} production cross section and correlations in p{bar p} collisions at {radical}s = 1.8 TeV

Description: The authors present measurements of the b{bar b} production cross section and angular correlations between the b and {bar b}-quarks in p{bar p} collisions using the D0 detector at the Fermilab Tevatron operating at {radical}s = 1.8 TeV. The b-quark production cross section for {vert_bar}y{sup b}{vert_bar} < 1.0 and {rho}{sub {tau}}{sup b} > 8 GeV/c is extracted and found to be consistent with next-to-leading order QCD predictions. In addition, the angular correlations between the b and {bar b}-quarks are found to agree in shape with next-to-leading order QCD predictions.
Date: August 1, 1996
Creator: Gomez, B.; Hoeneisen, B. & Negret, J.P.
Partner: UNT Libraries Government Documents Department

Hard single diffractive jet production at D0

Description: Preliminary results from the D{null} experiment on jet production with forward rapidity gaps in {ital p{anti p}} collisions are presented. A class of dijet events with a forward rapidity gap is observed at center-of-mass energies {radical}s = 1800 GeV and 630 GeV. The number of events with rapidity gaps at both center-of-mass energies is significantly greater than the expectation from multiplicity fluctuations and is consistent with a hard single diffractive process. A small class of events with two forward gaps and central dijets is also observed at 1800 GeV. This topology is consistent with hard double pomeron exchange.
Date: August 1, 1996
Creator: Abachi, S.; Abbott, B.; Abolins, M. & Collaboration, D0
Partner: UNT Libraries Government Documents Department

Inclusive jet cross section at D0

Description: Preliminary measurement of the central ({vert_bar}{eta}{vert_bar} {<=} 0.5) inclusive jet cross sections for jet cone sizes of 1.0, 0.7, and 0.5 at D{null} based on the 1992-1993 (13.7 {ital pb}{sup -1}) and 1994-1995 (90 {ital pb}{sup -1}) data samples are presented. Comparisons to Next-to-Leading Order (NLO) Quantum Chromodynamics (QCD) calculations are made.
Date: September 1, 1996
Creator: Bhattacharjee, M.
Partner: UNT Libraries Government Documents Department

Inclusive jet cross section in p{bar p} collisions with the D0 detector

Description: The authors report on two preliminary measurements of the central inclusive jet cross section at {radical}s = 1.8 TeV. The two data sets with integrated luminosities of 91 pb{sup {minus}1} and 14 pb{sup {minus}1} were collected at the Fermilab Tevatron p{bar p} Collider with the D0 detector. The cross section, reported as a function of transverse jet energy 35 GeV {le} E{sub {tau}} {le} 470 GeV and in the pseudorapidity interval {vert_bar}{eta}{vert_bar} {le} 0.5, is in excellent agreement with next-to-leading order QCD.
Date: July 1, 1996
Creator: Gomez, B.; Hoeneisen, B. & Negret, J.P.
Partner: UNT Libraries Government Documents Department

Direct photon measurements by the D{O} experiment

Description: We report a measurement of the cross section for production of isolated photons with transverse energy E{sub T} > 12 GeV in the central (absolute value of {eta} < 0.9) and forward (1.6 < absolute value of {eta} < 2.5) rapidity regions for {bar p}p collisions at center of mass energy {radical}s = 1.8 TeV, using an integrated luminosity of 13 pb{sup {minus}1}. The cross section is compared with a next-to-leading order (NLO) QCD calculation. We also present preliminary measurements of the center of mass scattering angle distribution and of the correlations between the rapidity of the photon and that of the leading jet in the event.
Date: July 1, 1996
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Searches for supersymmetric particles in p pbar collisions with the D0 detector

Description: We report on searches for supersymmetric particles with the D0 detector at the Fermilab p{ovr p} collider at {radical}s = 1800 GeV. The four searches are: (1) for squarks and gluinos in the jets + missing transverse energy channel, (2) for a light top squark in the jets + missing transverse energy channel, (3) for squarks and gluinos in the dielectron channel, and (4) for charginos and neutralinos in the trilepton channel. The first two searches use data from the 1992- 93 collider run, and the latter two use data from the 1994-95 collider run. 6 refs., 4 figs., 1 tab.
Date: August 1, 1996
Creator: Merritt, W.
Partner: UNT Libraries Government Documents Department

Rapidity gaps between jets at D{O}

Description: We present studies of jet production via color-singlet events with low particle multiplicity between the jets. A preliminary study of the multiplicity in other regions of the color singlet events and the dependence of color-singlet exchange on jet transverse energy is also presented.
Date: July 1, 1996
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Rapidity dependence of the inclusive J/{psi} production in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We have studied the {ital J}/{psi} production in {ital p}{ital {anti p}} collisions at {radical}s = 1.8 TeV with the D{null} detector at the Fermilab Tevatron, using a {mu}{sup +}{mu}{sup -} data sample collected during the 1994-95 running period. We have measured the inclusive {ital J}/{psi} production cross section as a function of the {ital J}/{psi} transverse momentum, {ital P}{sub T}{sup {ital J}/{psi}} in the central and forward rapidity regions. The new measurement of the cross section {ital d{sigma}/dp}{sub T}{sup {ital J}/{psi}} for {vert_bar}{eta}{sup {ital J}/{psi}}{vert_bar} {lt} 0.6 is in a good agreement with the CDF and earlier D{null} results. The cross section measurement {ital d{sigma}/dp}{sub T}{sup {ital J}/{psi}} for 2.5 {lt} {vert_bar}{eta}{sup {ital J}/{psi}}{vert_bar} {lt} 3.7 covers the {ital p}{sub T}{sup {ital J}/{psi}} range from 1 to 16 GeV/c. We combine the measurements in several {vert_bar}{eta}{sup {ital J}/{psi}}{vert_bar} regions to discuss {ital d{sigma}/d{eta}}{sup {ital J}/{psi}} for {ital p}{sub T}{sup {ital J}/{psi}} {gt} 8 GeV/c. The data are compared with the next-to- leading order (NLO) QCD calculations, which take into account different {ital J}/{psi} production mechanisms.
Date: August 1, 1996
Creator: Collaboration, The D0
Partner: UNT Libraries Government Documents Department

Multijet production at D{O}

Description: We describe studies of jet production in {bar p}p collisions at {radical}s = 1.8 TeV. We have investigated topological distributions in inclusive three and four-jet events and find them to be well- described by tree-level QCD matrix elements and also by the HERWIG Monte Carlo. We have measured the ratio of inclusive three-jet to two- jet cross sections as a function of summed jet transverse energy. This is found to be in good qualitative agreement with QCD; the data show some preference for a softer renormalization scale for emission of the third jet.
Date: July 1, 1996
Creator: Womersley, J.
Partner: UNT Libraries Government Documents Department

D0 measurements of beauty production in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We report a number of results on beauty production from the D{null} experiment at the Fermilab Tevatron Collider operating at {radical}s = 1.8 TeV. Measurements of the {ital b}{ital {anti b}} production cross section using single muon, muon plus jet and dimuon plus jet triggers, in the data collected in 1992-93, are presented. A preliminary measurement of the {ital b}{ital {anti b}} angular correlations using the dimuon data sample is also presented. We find that the {ital b}-quark production cross section for {vert_bar}{ital Y}{sup b}{vert_bar} {lt} 1.0 and {ital p}{sub T}{sup b} {gt} 8 GeV/c is systematically higher than, although consistent within errors with, the next-to-leading order (NLO) QCD predictions. A similar comparison with QCD is observed in the {ital b}{ital {anti b}} ({mu}{mu}) angular correlations, where the shape of the distribution indicates a sizable contribution fro the NLO process.
Date: September 1, 1996
Creator: Baarmand, M.M.
Partner: UNT Libraries Government Documents Department

D0 top quark cross section for the 1992--1995 tevatron run

Description: We present a measurement of the t{bar t} cross section in p{bar p} collisions at {radical}s = 1.8 TeV using dilepton and single lepton final states. This analysis uses about 100 pb{sup -1} of data collected with the D0 detector at Fermilab during the 1992-1995 run. Analyses in two other final states are also presented. 13 refs., 3 figs., 2 tabs.
Date: October 1, 1996
Creator: Bantly, J.
Partner: UNT Libraries Government Documents Department

The dijet mass spectrum with the D0 detector

Description: The authors present preliminary results from an analysis of dijet data collected during the 1994--1995 Tevatron Collider run with an integrated luminosity of 91 pb{sup {minus}1}. Measurements of dijet mass spectrum distributions in {anti p}p collisions at {radical}s = 1.8 TeV are compared with next-to-leading order QCD theory.
Date: September 1, 1996
Creator: Choi, S.
Partner: UNT Libraries Government Documents Department

Hadronic calibration of D0 calorimetry

Description: The D{null} detector is used to study {ital p{anti p}} collisions at the 1.8 TeV center-of-momentum energies available at the Fermilab Tevatron. The heart of the detector is a hermetic calorimeter employing uranium absorber and liquid argon as the ionization sampling medium. Several analyses require a well-understood jet energy scale. This paper describes how this calibration is obtained.
Date: September 1, 1996
Creator: Kehoe, R.
Partner: UNT Libraries Government Documents Department

The inclusive jet cross section at {radical}s = 630 GeV at D0

Description: The authors present a preliminary measurement of the cross section for central inclusive jet production at {radical}s = 630 GeV using {approximately} 400 nb{sup {minus}1} of data collected during the December 1995 Fermilab collider run at D0. These results are compared to NLO QCD predictions.
Date: September 1, 1996
Creator: Krane, J.
Partner: UNT Libraries Government Documents Department

Jet angular decorrelation and color coherence in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We present three QCD studies based on data collected by the d{O} detector during the 1992-1993 and 1994-1995 runs at the Fermilab Tevatron collider at center of mass energy {radical}s = 1.8 TeV. The first study is an analysis of jet-jet azimuthal decorrelation as a function of jet rapidity separation. The second and third studies are probes of color coherence effects in hadronic collisions - one using multi-jet events and the other using W+jet events.
Date: August 1, 1996
Creator: Jaques, J.
Partner: UNT Libraries Government Documents Department

A study of multi-jet production ratios in p{anti p} collisions at D0

Description: The authors study inclusive jet multiplicity ratios in multi-jet events from p{anti p} collisions at {radical}s = 1.8 TeV recorded using the D0 detector at the Fermilab Tevatron collider. Preliminary average multi-jet production ratios are presented as a function of the scalar jet transverse energy and compared to NLO calculations.
Date: September 1, 1996
Creator: Gallas, E.
Partner: UNT Libraries Government Documents Department