86 Matching Results

Search Results

Advanced search parameters have been applied.

Search for ZZ and Z\gamma^* production in p-barp collisions at sqrt(s) = 1.96 TeV and limits on anomalous ZZZ and ZZ\gamma^* couplings

Description: The authors present a study of {mu}{mu}{mu}{mu}, eeee, and {mu}{mu}ee events using 1 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron p{bar p} Collider at {radical}s = 1.96 TeV. Requiring the lepton pair masses to be greater than 30 GeV, they observe one event, consistent with the expected background of 0.13 {+-} 0.03 events and with the predicted standard model ZZ and Z{gamma}* production of 1.71 {+-} 0.15 events. They set an upper limit on the ZZ and Z{gamma}* cross section of 4.4 pb at the 95% C.L. They also derive limits on anomalous neutral trilinear ZZZ and ZZ{gamma}* gauge couplings. The one-parameter 95% C.L. coupling limits with a form factor scale {Lambda} = 1.2 TeV are -0.28 < f{sub 40}{sup Z} < 0.28, -0.31 < f{sub 50}{sup Z} < 0.29, -0.26 < f{sub 40}{sup y} < 0.26, and -0.30 < f{sub 50}{sup y} < 0.28.
Date: December 1, 2007
Creator: Collaboration, D0
Partner: UNT Libraries Government Documents Department

Recent D0 results on Z{gamma} production

Description: We report on a new search for anomalous {ital ZV}{sub {gamma}} ({ital V = Z}, {gamma}) couplings in the {ital Z}({ital ee}){gamma} mode with 89 pb{sup -1} of data. The following limits on anomalous coupling parameters were set at 95% CL: {vert_bar}{ital h{sup V}}{sub 10, 30}{vert_bar} {lt} 1.9, {vert_bar}{ital h{sup V}}{sub 20, 40}{vert_bar} {lt} 0.4. We also report on the first measurement of {ital Z(vv)}{gamma} production at hadron colliders using 14 pb{sup - 1} of data. Sensitivity to anomalous couplings in this channel is twice as good as that for the combined electron and muon channel analysis reported earlier. We set the following 95% CL limits on the {ital ZV}{gamma} couplings: {vert_bar}{ital h{sup V}}{sub 10, 30}{vert_bar} {lt} 0.9, {vert_bar}{ital h{sup V}}{sub 20, 40}{vert_bar} {lt} 0.2 which are the tightest available at the present time.
Date: November 1996
Creator: Landsberg, G.
Partner: UNT Libraries Government Documents Department

Observation of the top quark

Description: The DO collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb{sup {minus}1}. We have searched for t{bar t} production in the dilepton and single-lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 {plus_minus} 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 {times} 10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199{sub {minus}21}{sup +19} (stat.) {plus_minus}22 (syst.) GeV/c{sup 2} and its production cross section to be 6.4 {plus_minus} 2.2 pb.
Date: May 1, 1995
Creator: Greenlee, H.
Partner: UNT Libraries Government Documents Department

The top quark and more: Some highlights of physics from the D0 experiment

Description: In this paper we describe some highlights of recent physics results from the D0 experiment at the Tevatron {bar p}p collider. One aspect of recent QCD experimentation has been the emphasis on studies of events with rapidity gaps; the characteristics of such events in the D0 data are described. The non-abelian nature of the electroweak interaction is a well defined property of the standard model. The very high energies available at the Tevatron have opened a new window which permits the testing of this aspect of the standard model. The highlight among recent results was the observation of the top quark and this result is discussed. At the highest energy available, D0 is conducting numerous searches for phenomena which might indicate the structure of the world beyond the electroweak scale. We discuss searches for the particles of supersymmetry. The luminosity of the collider will increase dramatically over the next five years. This will open new fields of investigation for an upgraded D0 detector.
Date: February 1, 1996
Creator: Montgomery, H.E.
Partner: UNT Libraries Government Documents Department

Physics with the D0 calorimeter

Description: The D{null} detector, located at the Fermi National Accelerator Laboratory in Batavia, Illinois, USA, is a large hermetic detector designed to study the products of {ital p}{ital {anti p}} collisions at a center of mass energy of {radical}s = 1.8 TeV. The centerpiece of the detector is uranium/liquid argon sampling calorimetry, which provides high resolution detection of the physics signatures of interest - electrons, photons, jets and missing transverse energy - over a full solid angle. We discuss below how the calorimeter information is used to detect the final states relevant to the physics we are pursuing, and describe a number of physics processes and results that demonstrate the utility of some of our design choices.
Date: August 1, 1996
Creator: Kotcher, J.
Partner: UNT Libraries Government Documents Department

New particle searches at the Tevatron (I)

Description: Searches for new particles in p{ovr p} collisions at {radical}s = 1.8 TeV are ongoing at the Fermilab Tevatron collider using the CDF and D0 detectors. Current results from searches for heavy charged vector bosons and fourth generation quarks as well as for Supersymmetric partners of Standard Model quarks and gluons are presented. 11 refs., 4 figs.
Date: May 1, 1996
Creator: Gallas, E.
Partner: UNT Libraries Government Documents Department

Measurement of the t {anti t} cross section at D0

Description: We have measured the t{anti t} cross-section in p{anti p} collisions at {radical}s = 1.8 TeV using dilepton and single lepton final states. This analysis uses approximately 106 pb{sup -1} of data collected with the D0 detector at Fermilab during the 1992-1996 run. We observe 37 events with an expected background of 13.4 {+-} 3.4 events, giving {sigma}{sub t{anti t}} of 5.3 {+-} 1.8 pb for m{sub t} = 169 GeV. 4 refs., 1 fig., 1 tab.
Date: August 1, 1996
Creator: Kehoe, R.L.
Partner: UNT Libraries Government Documents Department

Measurement of the top quark mass at D0

Description: D{null} has measured the top quark mass using a sample of 32 single- lepton events selected from approximately 115 pb{sup -1} of {radical}s = 1.8 TeV {ital p}{ital {anti p}} collisions collected from 1992-1996. The result is {ital m}{sub t} = 169 {+-} 8({ital stat}){+-} 8 ({ital syst}) GeV/c{sup 2}. Using a sample of 3 {ital e{mu}} events, D{null} measures {ital m}{sub t} = 158 {+-} 24({ital stat}) {+-} 10({ital syst}) GeV/c{sup 2}.
Date: November 1, 1996
Creator: Varnes, E.W.
Partner: UNT Libraries Government Documents Department

Object based data access at the D0 experiment

Description: The D{O} Experiment at Fermilab is currently participating in the FNAL Computing Division`s ``Computing for Analysis Project`` (CAP) to investigate object based data storage and access. Following a short description of the CAP system architecture, the D{O} data model is explored. A brief discussion of the method of operation of the CAP system leads into a concluding section.
Date: November 1, 1995
Creator: Fuess, S.
Partner: UNT Libraries Government Documents Department

Performance and calibration of the D0 uranium liquid-argon calorimeter

Description: The performance of the D{phi} uranium liquid-argon calorimeter is discussed, as well as the electromagnetic energy calibration. Results from test beam studies and collider data are incorporated to estimate the energy scale. The {phi} symmetry of the events is used to improve the understanding of the electromagnetic part of the calorimeter, and the EM energy scale is determined from Z {yields} e{sup +}e{sup {minus}} events. The calorimeter`s response to other resonances is also investigated.
Date: January 1, 1995
Creator: Guida, J.
Partner: UNT Libraries Government Documents Department

Top quark study in all-jets channel at D0

Description: We report on the search for top quark decays into all-jets at the Tevatron collider. We measure preliminary cross sections of 4.4 {+-} 4.9 pb and 3.9 {+-} 9.8 pb for {ital t}{ital {anti t}} production, using singly and doubly {ital b}-tagged all-jets channels, respectively.
Date: November 1, 1996
Creator: Won, E.
Partner: UNT Libraries Government Documents Department

W and Z production cross sections at D0

Description: We present a measurement of the production cross section times branching ratio for {ital W} and {ital Z} bosons decaying to the electrons or muons in {ital p}{ital {anti p}} collisions at {radical}s = 1.8 TeV using data recorded at the Tevatron during the 1994-1995 collider run. Using the ratio of these two measurements, we derive the {ital W} leptonic branching fraction and the width of the {ital W} boson.
Date: November 1, 1996
Creator: Tarazi, J.N.
Partner: UNT Libraries Government Documents Department

Measurement of the W boson mass

Description: We present a preliminary measurement of the {ital W} boson mass using data collected by the D{null} experiment at the Fermilab Tevatron during the 1994-1995 collider run 1b. We use {ital W} {r_arrow} {ital e}{nu} decays to extract the {ital W} mass from the observed spectrum of transverse mass of the electron ({vert_bar}{eta}{vert_bar} {lt} 1. 2) and the inferred neutrino We use {ital Z}{sup 0} {r_arrow} {ital ee} decays to constrain our model of the detector response. We measure {ital m}{sub W}/{ital m}{sub Z} = 0.8815 {+-} 0.0011({ital stat}) {+-} 0.0014({ital syst}) and {ital m}{sub W} = 80.38 {+-} 0.07 ({ital W stat}) {+-} 0.13({ital syst}) GeV. Combining this result with our previous measurement from the 1992-1993 data, we obtain {ital m}{sub W} = 80.37 {+-} 0.15 GeV (errors combined in quadrature).
Date: November 1, 1996
Creator: Kotwal, A.V.
Partner: UNT Libraries Government Documents Department

A preliminary measurement of the W boson mass using W {yields} e{nu} decays at D0

Description: The preliminary measurement of the W boson mass from {ital e}{nu} decays produced in {ital p}{ital {anti p}} collisions at {radical}s = 1.8 TeV using the D{null} detector for the 1994-1995 Fermilab run is presented. The analysis uses events with electrons in the central region ({vert_bar}{eta}{vert_bar} {lt} 1.2).From a sample of 32,856 {ital W} decay and 1562 dielectron events we measure the {ital W} mass to be 80.38{+-} 0.07(stat.){+-}0.13(syst.){+-}0.13 (scale) GeV/c{sup 2}. The technique for determining the mass and its systematic errors is discussed.
Date: July 1, 1996
Creator: Flattum, E.M.
Partner: UNT Libraries Government Documents Department

Measurement of M{sub w} using the transverse mass ratio of W and Z

Description: We report on the measurement of {ital W} boson mass from a direct determination of the ratio of the transverse masses of {ital W} and {ital Z} using the D{null} detector at the Fermilab Tevatron {ital p}{ital {anti p}} collider operating at {radical}s = 1.8 TeV. The analysis is a preliminary result based on a partial data sample of 13 {ital pb}{sup -1} using {ital W} {r_arrow} {ital e}{nu} and {ital Z} {r_arrow} {ital ee} decays.
Date: November 1996
Creator: Rajagopalan, S.
Partner: UNT Libraries Government Documents Department

Jet shapes at D0 and CDF

Description: The distribution of the transverse energy in jets has been measured in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron collider using the CDF and DO detectors. This measurement of the jet shape is made as a function of jet transverse energy in both experiments and as a function of the jet pseudorapidity in the D0 experiment. Comparisons to Monte Carlo simulations and next-to-leading order partonic QCD calculations, {Omicron}({alpha}{sub s}{sup 3}), are presented.
Date: May 1, 1995
Creator: Streets, K.T.
Partner: UNT Libraries Government Documents Department

Observation of the top quark

Description: The D0 collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb{sup {minus}1}. We have searched for t{bar t} production in the dilepton and single lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 {plus_minus} 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 {times} 10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199{sub {minus}21}{sup +19} (stat.) {plus_minus}22 (syst.) GeV/c{sup 2} and its production cross section to be 6.4 {plus_minus} 2.2 pb.
Date: May 1, 1995
Creator: Klima, B.
Partner: UNT Libraries Government Documents Department

Top quark physics at the D0 experiment

Description: In this paper I present the latest results on top quark physics from the D0 collaboration since the discovery of the top quark in March 1995. I summarize the discovery results, discuss progress since the discovery, and show how we can measure the top quark mass using three separate techniques. The measurements were made at the Fermilab Tevatron, a p{bar p} collider with {radical}s = TeV, using {approximately}50 pb{sup {minus}1} data collected from 1992 to early 1995.
Date: January 1, 1996
Creator: Heinson, A.P.
Partner: UNT Libraries Government Documents Department

Studies of the top quark with the D0 detector

Description: The observation of the top quark by the D0 experiment, at Fermilab`s Tevatron proton-antiproton collider, is briefly reviewed. The analysis of the top quark mass in the lepton plus jets decay channels, resulting in m{sub t} {approx} 200 GeV/c{sup 2} is reviewed; and a preliminary mass analysis from the dilepton decay channels resulting in m{sub t} = 145 {plus_minus} 25 (statistical) {plus_minus} 20 (systematic) GeV/c{sup 2} is presented. These mass measurements are compared with Standard Model limits from CERN`s LEP experiments and the published CDF measurement. Preliminary observation of top quark-W boson correlation is shown.
Date: January 1, 1996
Creator: Stephens, R.W.
Partner: UNT Libraries Government Documents Department

Search for the top quark at D0 using multivariate methods

Description: We report on the search for the top quark in p{bar p} collisions at the Fermilab Tevatron ({radical}s = 1.8 TeV) in the di-lepton and lepton+jets channels using multivariate methods. An H-matrix analysis of the e{mu} data corresponding to an integrated luminosity of 13.5{plus_minus}1.6 pb{sup {minus}1} yields one event whose likelihood to be a top quark event, assuming m{sub top} = 180 GeV/c{sup 2}, is ten times more than that of WW and eighteen times more than that of Z {yields} {tau}{tau}. A neural network analysis of the e+jets channel using a data sample corresponding to an integrated luminosity of 47.9{plus_minus}5.7 pb{sup {minus}1} shows an excess of events in the signal region and yields a cross-section for t{bar t} production of 6.7{plus_minus}2.3 (stat.) pb, assuming a top mass of 200 GeV/c{sup 2}. An analysis of the e+jets data using the probability density estimation method yields a cross-section that is consistent with the above result.
Date: July 1, 1995
Creator: Bhat, P.C.
Partner: UNT Libraries Government Documents Department

The search for squarks, gluinos and stop squarks in D0

Description: Searches through data collected by D0 at Fermilab during the 1992-- 1993 p {bar p} collider run for the supersymmetric partners to the quark and the gluon, the squark and gluino, including a low mass scalar top squark, are reviewed. A set of classic searches were conducted for missing E{sub T} plus jets signatures. No evidence of positive signals is reported, but limits are set on the squark and gluino masses.
Date: August 1, 1995
Creator: Claes, D.
Partner: UNT Libraries Government Documents Department

Observation of the top quark

Description: The DO collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb{sup {minus}1}. We have searched for t{bar t} production in the dilepton and single-lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 {plus_minus} 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 {times} 10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199{sub {minus}21}{sup +19} (stat.) {plus_minus}22 (syst.) GeV/C{sup 2} and its production cross section to be 6.4 {plus_minus} 2.2 pb.
Date: September 1, 1995
Creator: Protopopescu, P.
Partner: UNT Libraries Government Documents Department

Jet correlation studies as a function of rapidity interval at D0

Description: During the 1992--93 collider run of the Fermilab Tevatron the D0 experiment accumulated a large sample of events with jets in the final state. Since the D0 detector can trigger on jets over the entire pseudorapidity range {vert_bar}{eta}{vert_bar} < 3.2, we collected a sample of events containing jets separated by large rapidity intervals. Such events may not be well described by LO or NLO QCD perturbative calculations due to the increased importance of additional gluon radiation which tends to decorrelate the leading jets in the event. These contributions can be included using a leading-log approximation (LLA) where the leading logarithmic terms are resummed calculation of Del Duca and Schmidt. We present the first experimental measurement of jet-jet {phi} correlations as a function of the rapidity interval of the {eta} ordered jets. We compare these results to JETRAD, HERWIG and BFKL resummation predictions.
Date: June 1, 1995
Creator: Heuring, T.C.
Partner: UNT Libraries Government Documents Department