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Measurements of trilinear gauge boson couplings

Description: Direct measurements of the trilinear gauge boson couplings by the D0 collaboration at Fermilab are reported. Limits on the anomalous couplings were obtained at a 95% CL from four diboson production processes: W{gamma} production with the W boson decaying to e{nu} or {mu}{nu}, WW production with both of the W bosons decaying to e{nu} or {mu}{nu}, WW/WZ production with one W boson decaying to e{nu} and the other W or Z boson decaying to two jets, and Z{gamma} production with the Z boson decaying to ee, {mu}{mu}, or {nu}{nu}. Limits were also obtained from a combined fit to W{gamma}, WW {yields} dileptons and WW/WZ {yields} e{nu}jj data samples.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Search for heavy neutral gauge bosons at D-Zero

Description: We report preliminary results of a search for a heavy neutral gauge boson, Z`, using the decay channel Z` {yields} ee . The data were collected with the D0 detector at the Fermilab Tevatron during the 1994-1995 p{anti p} collider run at {radical}s = 1.8 TeV and correspond to an integrated luminosity of {approx} 90 pb{sup -1}. Limits are set on the cross section times branching ratio for the process {anti p}p {yields} Z` {yields} ee as a function of the Z` mass. We exclude the existence of a heavy neutral gauge boson of mass less than 660 GeV/c{sup 2} (95% CL), assuming a Z` with the same coupling strengths to quarks and leptons as the standard model Z boson. Combining this analysis with DO`s 1992-1993 data set increases the limit to m{sub Z`} > 670 GeV/c{sup 2}.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Determination of the b-quark production cross section in p{anti p} collisions at 630 GeV

Description: We present a preliminary measurement of the b-quark production cross section in p{anti p} collisions at {radical}s = 630 GeV. The analysis is based on 340 nb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron Collider. We determine the ratio of the b-quark production cross sections at 630 GeV to 1800 GeV and compare our results with the CDF and UA1 measurements, and with the next-to- leading order QCD predictions.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Search for squarks and gluinos with the D-Zero Detector

Description: We report on a search for squarks and gluinos in p{anti p} collisions at {radical} s= 1.8 TeV using the D0 detector at Fermilab. Data corresponding to 79.2 {+-} 4.2 pb{sup -1} were examined for events with large missing transverse energy, three or more jets, and the absence of isolated leptons. No events were observed significantly in excess of Standard Model background predictions, and we place limits on the Minimal Supergravity parameters M{sub 0} and M{sub 1/2}.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Transverse momentum distributions of W and Z bosons produced in p {anti p} collisions at 1.8 TeV

Description: The transverse momentum distributions of W and Z bosons produced in p{anti p} collisions at {radical}s = 1.8 TeV are measured with the D0 detector at Fermilab. The results are compared to QCD calculations which include soft gluon resummation. The transverse momentum distribution of the Z boson is consistent with the calculation of Ladinsky and Yuan, and is used to extract their non-perturbative parameter 92-
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

A measurement of the ratio of production cross sections forW + 1 jet to W + 0 jets and comparisons to QCD

Description: A preliminary measurement of the ratio, R{sup 10}, of the production cross sections for W + 1 Jet and W + 0 Jets processes at {radical}s = 1800 GeV by the D0 Collaboration is presented. A comparison of this ratio is made to next-to-leading order calculations and the implications of these comparisons are discussed.
Date: November 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

D-Zero results on W boson properties

Description: The D0 experiment collected {approx} 15 pb{sup -1} in run 1A (1992- 1993) and {approx} 89 pb{sup -1} in run 1B (1994-1995) of the Fermilab Tevatron Collider using p{anti p} collisions at {radical}s = 1.8 TeV. Results from analyses of events with W and Z bosons are presented for the run 1B data samples. From W {yields} e{nu}, {mu}{nu} and Z {yields} ee, {mu}{mu} decays, the W and Z production cross sections and the W width are determined. Events with W {yields} {tau}{nu} decays are used to determine the ratio of the electroweak gauge coupling constants as a measure of lepton universality. Using W {yields} e{nu} and Z {yields} ee decays, the W boson mass is measured.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Measurement of the angular distribution of electrons from W {right arrow} e{nu} decays observed in p pbar collisions at {squareroot}s = 1.8 TeV

Description: We present a preliminary measurement of the electron angular distribution parameter {alpha}<sub>2</sub> in W {yields} e{nu} events using data collected by the D0 detector during the 1994-1995 Tevatron run. We compare our results with next-to- leading order perturbative QCD, which predicts an angular distribution of (1±{alpha}<sub>1</sub> cos{theta}* +{alpha}<sub>2</sub> cos²{theta}*), where {theta}* is the angle between the charged lepton and the antiproton in the Collins-Soper frame. In the presence of QCD corrections, the parameters {alpha}<sub>1</sub> and {alpha}<sub>2</sub> become functions of p<sup>W</sup><sub>T</sub> , the W boson transverse momentum. We present the first measurement of {alpha}<sub>2</sub> as a function of p<sup>W</sup><sub>T</sub>. This measurement is of importance, because it provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W mass measurement.
Date: July 26, 1999
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Search for ZX {yields} {nu}{anti {nu}} b {anti b} Events in the D-Zero Detector

Description: We report on a search for a new particle, X, decaying via X {yields} b{anti b}, made through associated production with a Z boson. We use data collected with the D0 detector operating at the Fermilab Tevatron p{anti p} collider with {radical}s = 1.8 TeV. We utilize muon-tagged jets to identify b-quarks and the {nu}{anti {nu}} channel to detect Z bosons. Preliminary results on cross section limits for X masses between 90 GeV/c{sup 2} and 180 GeV/c{sup 2} are presented.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Search for high mass photon pairs in p{anti p}{yields}{gamma}{gamma}jj events at {radical}s = 1.8 TeV

Description: A search for new physics in the channel p{anti p} {yields} {gamma}{gamma}jj has been studied. In some extended Higgs models, a light neutral scalar Higgs boson is produced with suppressed couplings to fermions and standard model(SM) strength couplings to vector bosons(bosonic Higgs), thus enhancing the H {yields} {gamma}{gamma} channel. We required one photon in the event with E{sup {gamma}}{sub T} > 20 GeV, {vert_bar}{eta}{sup {gamma}}{vert_bar} < 1.1 or 1.5 < {vert_bar}{eta}{sup {gamma}}{vert_bar} < 2.0 and a second photon with E{sup {gamma}}{sub T} > 15 GeV, {vert_bar}{eta}{sup {gamma}}{vert_bar} < 1.1 or 1.5 < {vert_bar}{eta}{sup {gamma}}{vert_bar} < 2.25. Additionally, we required one hadronic jet in the event with E{sup jet}{sub T} > 20 GeV, {vert_bar}{eta}{sup jet}{vert_bar} < 2.0 and a second hadronic jet with E{sup jet}{sub T} > 15 GeV, {vert_bar}{eta}{sup jet}{vert_bar} < 2.25. The photons are required to have a {summation}{rvec E}{sub T}({gamma}) {>=} 10 GeV, and likewise the jets are required to have a {summation}{rvec E}{sub T}(jet) {>=} 10 GeV. The final M{sub {gamma}{gamma}} distribution is consistent with background and no resonance is observed. A 90(95)% C.L. upper limit cross section vs M{sub {gamma}{gamma}} is calculated, which ranges from 0.6(0.7) pb{sup -1} for M{sub {gamma}{gamma}} = 60 GeV/c{sup 2} to 0.3(0.4) pb{sup -1} for M{sub {gamma}{gamma}} = 130 GeV/c{sup 2}. With standard model coupling strengths between the bosonic Higgs and vector bosons, a 90(95)% C.L. bosonic Higgs lower mass limit is set at 86(81) GeV/c{sup 2}.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

The azimuthal decorrelation of jets widely separated in rapidity

Description: We study the azimuthal decorrelation between jets with pseudorapidity separation up to six units. The data were accumulated using the D0 detector during the 1994-1995 collider run of the Fermilab Tevatron at {radical}s = 1.8 TeV. The data are compared to two parton shower Monte Carlos (HERWIG and PYTHIA) and an analytical prediction using the leading logarithmic BFKL resummation. The final state jets as predicted by the parton showering Monte Carlos describe the data over the entire pseudorapidity range studied. The prediction based on the leading logarithmic BFKL resummation shows more decorrelation than the data as the rapidity interval increases.
Date: November 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

The dijet mass spectrum at D-Zero

Description: 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{sup -1}. Measurements of dijet mass spectra in {anti p}p collisions at {radical}s = 1.8 TeV are compared to next-to-leading order QCD calculations.
Date: November 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Rapidity gaps and hard diffraction at the Tevatron

Description: Preliminary results on jet production with rapidity gaps in p{anti p} collisions are presented for both D0 and CDF. An excess of events with a forward rapidity gap is observed at both {radical}s=1800 GeV and 630 GeV, consistent with a hard single diffractive process. The first evidence for diffractive W production is presented. A class of events with two forward gaps and central dijets is observed at {radical}s=1800 GeV, a topology that is consistent with hard double pomeron exchange. Kinematic properties of events containing rapidity gaps are measured.
Date: June 1, 1997
Creator: Abbott, B. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department

Color coherence in W + jet events

Description: We report on preliminary studies of color coherence effects in p{anti p} collisions, based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron collider, at a center of mass energy {radical}s = 1.8 TeV. Color interference effects are studied by examining particle distribution patterns in W + Jet events. The data are compared to Monte Carlo simulations with different color coherence implementations and to a recent analytic Modified-Leading-Log perturbative calculation based on the Local Parton-Hadron Duality hypothesis. Soft particle radiation is enhanced in the event plane relative to the transverse plane, in agreement with calculations in which the effects of color coherence are fully included.
Date: November 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Rapidity gaps in jet events at D0

Description: Preliminary results from the D0 experiment on jet production with rapidity gaps in 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 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.
Date: July 1, 1997
Creator: Abbott, B.; Abolins, M.; Acharya, B.S. & Collaboration, D0
Partner: UNT Libraries Government Documents Department

Probing color-singlet exchange at D0

Description: We present latest preliminary results on hard color-singlet exchange in proton-antiproton collisions. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, dijet pseudorapidity separation, and proton-antiproton center-of-mass energy. These results are qualitatively consistent with a color-singlet fraction that increases with increasing quark-initiated processes.
Date: July 1, 1997
Creator: Abbott, B.; Abolins, M.; Acharya, B.S. & Collaboration, D0
Partner: UNT Libraries Government Documents Department

Multi-agent cooperative systems applied to precision applications

Description: Regulatory agencies are imposing limits and constraints to protect the operator and/or the environment. While generally necessary, these controls also tend to increase cost and decrease efficiency and productivity. Intelligent computer systems can be made to perform these hazardous tasks with greater efficiency and precision without danger to the operators. The Idaho national Engineering and Environmental Laboratory and the Center for Self-Organizing and Intelligent Systems at Utah State University have developed a series of autonomous all-terrain multi-agent systems capable of performing automated tasks within hazardous environments. This paper discusses the development and application of cooperative small-scale and large-scale robots for use in various activities associated with radiologically contaminated areas, prescription farming, and unexploded ordinances.
Date: March 1, 1998
Creator: McKay, M.D.; Anderson, M.O.; Gunderson, R.W.; Flann, N. & Abbott, B.
Partner: UNT Libraries Government Documents Department

High risk of permafrost thaw

Description: In the Arctic, temperatures are rising fast, and permafrost is thawing. Carbon released to the atmosphere from permafrost soils could accelerate climate change, but the likely magnitude of this effect is still highly uncertain. A collective estimate made by a group of permafrost experts, including myself, is that carbon could be released more quickly than models currently suggest, and at levels that are cause for serious concern. While our models of carbon emission from permafrost thaw are lacking, experts intimately familiar with these landscapes and processes have accumulated knowledge about what they expect to happen, based on both quantitative data and qualitative understanding of these systems. We (the authors of this piece) attempted to quantify this expertise through a survey developed over several years, starting in 2009. Our survey asked experts what percentage of surface permafrost they thought was likely to thaw, how much carbon would be released, and how much of that would be methane, for three time periods and under four warming scenarios that are part of the new IPCC Fifth Assessment Report.
Date: November 1, 2011
Creator: Schuur, E.A.G.; Abbott, B.; Koven, C.D,; Riley, W.J.; Subin, Z.M. & al, et
Partner: UNT Libraries Government Documents Department

DZero data-intensive computing on the Open Science Grid

Description: High energy physics experiments periodically reprocess data, in order to take advantage of improved understanding of the detector and the data processing code. Between February and May 2007, the DZero experiment has reprocessed a substantial fraction of its dataset. This consists of half a billion events, corresponding to about 100 TB of data, organized in 300,000 files. The activity utilized resources from sites around the world, including a dozen sites participating to the Open Science Grid consortium (OSG). About 1,500 jobs were run every day across the OSG, consuming and producing hundreds of Gigabytes of data. Access to OSG computing and storage resources was coordinated by the SAM-Grid system. This system organized job access to a complex topology of data queues and job scheduling to clusters, using a SAM-Grid to OSG job forwarding infrastructure. For the first time in the lifetime of the experiment, a data intensive production activity was managed on a general purpose grid, such as OSG. This paper describes the implications of using OSG, where all resources are granted following an opportunistic model, the challenges of operating a data intensive activity over such large computing infrastructure, and the lessons learned throughout the project.
Date: September 1, 2007
Creator: Abbott, B.; U., /Oklahoma; Baranovski, A.; Diesburg, M.; Garzoglio, G.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Search for pair production of the scalar top quark in the electron+muon final state

Description: We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ({tilde t}{sub 1}) in p{bar p} collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb{sup -1}. The scalar top quarks are assumed to decay into a b quark, a charged lepton, and a scalar neutrino ({tilde {nu}}), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and improved exclusion limits at the 95% C.L. are set in the (M{sub {tilde t}{sub 1}}, M{sub {tilde {nu}}}) mass plane.
Date: September 1, 2010
Creator: Abazov, V.M.; Abbott, B.; Abolins, M.; Acharya, B.S.; Adams, M.; Adams, T. et al.
Partner: UNT Libraries Government Documents Department

Combination of CDF and D0 measurements of the $W$ boson helicity in top quark decays

Description: We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb{sup -1} of p{bar p} collisions collected during Run II of the Fermilab Tevatron Collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f{sub 0}) and right-handed (f{sub +}) helicities, we find f{sub 0} = 0.722 {+-} 0.081 [{+-} 0.062 (stat.) {+-} 0.052 (syst.)] and f{sub +} = -0.033 {+-} 0.046 [{+-} 0.034 (stat.) {+-} 0.031 (syst.)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f{sub 0} = 0.682 {+-} 0.057 [{+-} 0.035 (stat.) {+-} 0.046 (syst.)] and f{sub +} = ?0.015 {+-} 0.035 [{+-} 0.018 (stat.) {+-} 0.030 (syst.)]. The results are consistent with standard model expectations.
Date: February 1, 2012
Creator: Aaltonen, T.; Abazov, V. M.; Abbott, B.; Acharya, B. S.; Adams, M.; Adams, T. et al.
Partner: UNT Libraries Government Documents Department

Combined CDF and D0 Upper Limits on Standard Model Higgs Boson Production with up to 8.2 fb$^{-1}$ of Data

Description: We combine results from CDF and D0's direct searches for the standard model (SM) Higgs boson (H) produced in p{bar p} collisions at the Fermilab Tevatron at {radical}s = 1.96 TeV. The results presented here include those channels which are most sensitive to Higgs bosons with mass between 130 and 200 GeV/c{sup 2}, namely searches targeted at Higgs boson decays to W{sup +}W{sup -}, although acceptance for decays into {tau}{sup |+} {tau}{sup -} and {gamma}{gamma} is included. Compared to the previous Tevatron Higgs search combination, more data have been added and the analyses have been improved to gain sensitivity. We use the MSTW08 parton distribution functions and the latest gg {yields} H theoretical cross section predictions when testing for the presence of a SM Higgs boson. With up to 7.1 fb{sup -1} of data analyzed at CDF, and up to 8.2 fb{sup -1} at D0, the 95% C.L. upper limits on Higgs boson production is a factor of 0.54 times the SM cross section for a Higgs boson mass of 165 GeV/c{sup 2}. We exclude at the 95% C.L. the region 158 &lt; m{sub H} &lt; 173 GeV/c{sup 2}.
Date: March 1, 2011
Creator: Aaltonen, T.; Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M. et al.
Partner: UNT Libraries Government Documents Department