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48,519 Matching Results
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Color coherence in W + jet events
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.
System:
The UNT Digital Library
Determination of the b-quark production cross section in p{anti p} collisions at 630 GeV
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.
System:
The UNT Digital Library
The dijet mass spectrum at D-Zero
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.
System:
The UNT Digital Library
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
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.
System:
The UNT Digital Library
A measurement of the ratio of production cross sections forW + 1 jet to W + 0 jets and comparisons to QCD
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.
System:
The UNT Digital Library
Measurements of trilinear gauge boson couplings
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.
System:
The UNT Digital Library
Photon and diphoton production, and k{sub T} Effects
Isolated photon production at the D0 experiment is reviewed and recent results on di-photon production are presented.
Date:
November 1, 1997
Creator:
Abbott, B.
System:
The UNT Digital Library
Search for heavy neutral gauge bosons at D-Zero
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.
System:
The UNT Digital Library
Search for high mass photon pairs in p{anti p}{yields}{gamma}{gamma}jj events at {radical}s = 1.8 TeV
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 …
Date:
October 1, 1997
Creator:
Abbott, B.
System:
The UNT Digital Library
Search for squarks and gluinos with the D-Zero Detector
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.
System:
The UNT Digital Library
Search for ZX {yields} {nu}{anti {nu}} b {anti b} Events in the D-Zero Detector
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.
System:
The UNT Digital Library
Transverse momentum distributions of W and Z bosons produced in p {anti p} collisions at 1.8 TeV
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.
System:
The UNT Digital Library
D-Zero results on W boson properties
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.
System:
The UNT Digital Library
Rapidity gaps and hard diffraction at the Tevatron
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
System:
The UNT Digital Library
Search for Squarks and Gluinos in Events Containing Jets and a Large Imbalance in Transverse Energy
Using data corresponding to an integrated luminosity of 79 pb{sup -1}, D0 has searched for events containing multiple jets and large missing transverse energy in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, they set limits on the masses of squarks and gluinos and on the model parameters m{sub 0} and m{sub 1/2}, in the framework of the minimal low-energy supergravity models of supersymmetry. For tan {beta} = 2 and A{sub 0} = 0, with {mu} < 0, they exclude all models with m{sub q} {approx} < 250 GeV/c{sup 2}. For models with equal squark and gluino masses, they exclude m < 260 GeV/c{sup 2}.
Date:
February 1, 1999
Creator:
Abbott, B.; Abolins, M.; Abramov, V.; Acharya, B. S.; Adam, I.; Adams, D. L. et al.
System:
The UNT Digital Library
Probing color-singlet exchange at D0
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
System:
The UNT Digital Library
Rapidity gaps in jet events at D0
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
System:
The UNT Digital Library
Application of Clean Water (CWA) Section 404 compensatory wetland mitigation under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
Pursuant to Section 404 of the Clean Water Act (CWA), activities resulting in the discharge of dredge or fill material into waters of the US, including wetlands, require permit authorization from the US Army Corps of Engineers (ACOE). As part of the Section 404 permitting process, compensatory wetland mitigation in the form of wetland enhancement, restoration, or construction may be required to off-set impacts sustained under a Section 404 permit. Under normal circumstances, compensatory mitigation is a relatively straight forward process; however, issues associated with mitigation become more complex at sites undergoing remediation under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), because on-site response/remedial actions involving dredged and fill material are not subject to the formal Section 404 permitting process. These actions are conducted in accordance with the substantive permitting requirements of the ACOE`s Nationwide and individual permitting programs. Wetland mitigatory requirements are determined through application of the US Environmental Protection Agency`s (USEPA`s) 040(b) (1) Guidelines promulgated in 40 CFR Part 230 and are implemented through compliance with substantive permitting requirements during the conduct of response/remedial actions. A programmatic approach for implementing wetland mitigatory requirements is being developed at a former US Department of Energy (DOE) uranium refinery …
Date:
June 1, 1994
Creator:
Abbott, D. J. & Straub, C. A.
System:
The UNT Digital Library
Deuteron photodisintegration : new results from TJNAF.
The first measurements of the differential cross section from d({gamma},p)n up to 4.0 GeV were performed at the Thomas Jefferson National Accelerator Facility (TJNAF, formerly CEBAF). Bremsstrahlung photons from electron beam impinging on a copper radiator and a liquid deuterium target were employed for this experiment. The experiment was performed in Hall C where the photoprotons at forward angles in the center-of-mass were detected in the High Momentum Spectrometer (HMS) and photoprotons at backward angles were detected in the Short Orbit Spectrometer (SOS). The bremsstrahlung photon energy was reconstructed from the measured proton momentum and angle using the two-body kinematics. We report the cross section results at the proton center-of-mass angles of 37{degree} and 90{degree}. These results are in good agreement with previous lower energy measurements. The 90{degree} data continue to show the constituent-counting-rule behavior up to 4 GeV. The results will be compared with models based on QCD as well as those based on meson-exchange theory.
Date:
November 18, 1997
Creator:
Abbott, D. J.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Cummings, W. J.; Geesaman, D. F. et al.
System:
The UNT Digital Library
Experience with certifying borated stainless steel as a shipping cask basket material
The original cask designs for a cask demonstration project featured fuel baskets constructed of borated stainless steel (bss) as a structural material. The project is intended to demonstrate casks that can be used for both shipping and storing spent nuclear fuel assemblies. The baskets were intended to maintain the fuel assemblies in a subcritical array for both normal and accident conditions. The Nuclear Regulatory Commission, however, judged bss to be unacceptable as a structural material. The cask designs were subsequently modified. The knowledge gained during this cask demonstration project may be applicable to development of bss as a basket material in future cask design. 6 refs., 2 figs., 2 tabs.
Date:
January 1, 1990
Creator:
Abbott, D.G. (EG and G Idaho, Inc., Idaho Falls, ID (USA)) & Nickell, R.E. (Applied Science and Technology, Inc., Poway, CA (USA))
System:
The UNT Digital Library
CODA performance in the real world
The most ambitious implementation of the Jefferson Lab data acquisition system (CODA) to date is for the CLAS spectrometer in Experimental Hall B. CLAS has over 40,000 instrumented channels and uses up to 30 front-end (FASTBUS/VME) crates in the DAQ subsystem. During the initial experiments the authors found that performance of the fully instrumented DAQ system did not scale as expected based on single point to point benchmarks. Over the past year the authors have been able to study various performance bottlenecks in the CLAS DAQ system including front-end real time performance, switched 100BaseT Ethernet data transport, and online data distribution and recording. Performance tuning was necessary for components on both real time (VxWorks) and UNIX (Solaris) operating systems. In addition, a new efficient Event Transfer System (ET) was developed to provide faster online monitoring while having minimal impact on data throughput to storage. They discuss these issues and efforts to overcome the real world problems associated with running a high performance DAQ system on a variety of commercial hardware and software.
Date:
June 1, 1999
Creator:
Abbott, D.J.; Heyes, W.G.; Jastrzembski, E.; MacLeod, R.W.; Timmer, C. & Wolin, E.
System:
The UNT Digital Library
Quasifree (e,e'p) Reactions and Proton Propagation in Nuclei
The (e,e'p) reaction was studies on targets of C, Fe, and Au at momentum transfers squared Q{sup 2} of 0.6, 1.3, 1.8 and 3.3 GeV{sup 2} in a region of kinematics dominated by quasifree electron-proton scattering. Missing energy and missing momentum distributions are reasonably well described by plane wave impulse approximation calculations with Q{sup 2} and A dependent corrections that measure the attenuation of the final state protons.
Date:
June 1, 1998
Creator:
Abbott, David; Ahmidouch, A.; Amatuni, Ts. A.; Armstrong, C.; Arrington, J.; Assamagan, J. A. et al.
System:
The UNT Digital Library
Rheological characterization of nuclear waste using falling-ball rheometry
Knowledge of the rheological properties of saturated solutions containing solid particles is very important in nuclear waste management technology. For example, the nuclear waste in the Hanford Site high-level radioactive waste tanks contains strong electrolyte solutions with a high concentration of solids. Previous attempt using rotational viscometers to determine the rheology has shown unusual thixotropic and shear thinning behaviors with a lack of reproducibility. Using falling-ball rheometry, the rheology of the undisturbed simulant may be determined with much better reproducibility. In this study, a well-mixed simulant which has similar chemical composition to the actual waste will be tested. Falling-ball size and density will be varied to get data in a wide range of shear rates. To determine the rheogram, several methods will be tried to match the observed data. Based on these tests, a rheogram can be determined from the model and its best-fit parameters. The simulant shows shear-thinning behavior and a yield stress. This would suggest a H-B model. But when fitting to one of the simulants which showed a very low yield stress, the predictions assuming no yield and assuming yield resulted in no improvement in the fit when assuming yield.
Date:
July 1, 1994
Creator:
Abbott, J. R.; Unal, C.; Stephens, T.; Pasamehmetoglu, K. O.; Graham, A. L. & Edwards, J. N.
System:
The UNT Digital Library
Roles and Delegation of Authority (R/DA) System
The processes of defining managerial roles and providing for delegation of authority are essential to any enterprise. At most large organizations, these processes are defined in policy manuals and through sets of standard operating procedures for many, if not all, business and administrative functions. Many of these staff-initiated, administrative functions require the routing of documents for approval to one or more levels of management. These employee-oriented, back office types of workflows tend to require more flexibility in determining to whom these documents should go to, while, at the same time, providing the responsible parties with the flexibility to delegate their approval authority or allow others to review their work. Although this practice is commonplace in manual, paper-based processes that exist in many organizations, it is difficult to provide the same flexibility in the more structured, electronic-based, workflow systems.
Date:
October 21, 1999
Creator:
Abbott, John P.; Hutchins, James C. & Schoch, David G.
System:
The UNT Digital Library