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Hard diffraction

Description: An introduction to the rapidly developing subject of diffractive processes containing jets is given, with emphasis on an s-channel picture of the dynamics.
Date: March 1, 1994
Creator: Bjorken, J.D.
Partner: UNT Libraries Government Documents Department

Prospects for spin physics at RHIC

Description: The proposal to perform polarized proton-proton collisions at collider energies at RHIC is reviewed. After a brief reminder of the desirability of high energy spin physics measurements, we discuss the machine parameters and detector features which are taken to define a program of spin physics at RHIC. Some of the many physics processes which can provide information on polarized parton distributions and the spin-dependence of QCD and the electroweak model at RHIC energies are discussed.
Date: June 1, 1995
Creator: Robinett, R.W.
Partner: UNT Libraries Government Documents Department

Production of jets at the Tevatron

Description: Measurements of the inclusive jet cross section and the dijet angular distribution using data from the Tevatron are presented Comparisons to NLO QCD show good agreement below 250 GeV, but CDF data show an excess at higher E{sub T}; qualitative agreement is seen between the CDF and D0 cross sections. Analysis of the dijet angular distributions exclude quark compositeness below 2.1 TeV.
Date: July 1, 1997
Creator: Heuring, T.
Partner: UNT Libraries Government Documents Department

Next-to-leading order corrections to e{sup +}e{sup -} {yields} four jets

Description: I present a general purpose Monte Carlo program for calculating the next-to-leading order corrections to arbitrary four-jet quantities in electron-positron annihilation. In the current version of the program, some subleading in color terms are neglected. As an example, I calculate the four-jet rate in the Durham scheme as well as the Bengtsson-Zerwas angular distribution at O ({alpha}{sub s}{sup 3}) and compare the results to existing data.
Date: July 1, 1997
Creator: Signer, A.
Partner: UNT Libraries Government Documents Department

Measurement and simulation of jet mass caused by a high-aspect ratio pertubation

Description: Inertial confinement fusion (ICF) capsule performance can be negatively impacted by the presence of hydrodynamic instabilities. To perform a gas fill on an ICF capsule current plans involve drilling a small hole and inserting a fill tube to inject the gas mixture into the capsule. This introduces a perturbation on the capsule, which can seed hydrodynamic instabilities. The small hole can cause jetting of the shell material into the gas, which might adversely affect the capsule performance. We have performed simulations and experiments to study the hydrodynamic evolution of jets from high-aspect ratio holes, such as the fill tube hole. Although simulations using cold materials over predict the amount of mass in the jet, when a reasonable amount of preheat (< 1 eV) is introduced, the simulations are in better agreement with the experiment.
Date: January 1, 2009
Creator: Keiter, Paul A; Cooley, James; Kyrala, George; Wilson, Doug; Blue, Brent; Elliott, Jim et al.
Partner: UNT Libraries Government Documents Department

Studies of topological distributions of the three- and four-jet events in {bar p}p collisions at {radical}s = 1800 GeV with the D0 detector

Description: The global topologies of three- and four-jet events produced in {bar p}p interactions are described. the three- and four-jet events are selected from data recorded by the D0 detector at the Tevatron Collider operating at a center-of-mass energy of {radical}s = 1800 GeV. the measured normalized distributions of various topological variables are compared with parton-level predictions of the tree- level QCD calculations. The parton-level QCD calculations are found to be in good agreement with the data. The studies also show that the topological distributions of the different subprocesses involving different numbers of quarks are very similar and reproduce the measured distributions well.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Isolated prompt photon plus jet photoproduction at HERA

Description: The cross section for photoproduction of a prompt photon in association with a jet is studied in Next-to-Leading Order at the DESY ep collider HERA. The effect of various cuts imposed on the cross section by the ZEUS collaboration including isolation cuts on the photon is examined. Comparisons with the ZEUS preliminary data using various parametrizations of the photon structure function is made, and good agreement is found. The preliminary data is not yet precise enough to make a distinction between various models for the photon structure function.
Date: June 10, 1997
Creator: Gordon, L.E.
Partner: UNT Libraries Government Documents Department

Azimuthal decorrelation of jets widely separated in rapidity at D0

Description: We present preliminary results from an analysis of the azimuthal decorrelation of dijet events as a function of their separation in pseudorapidity using the data collected during the 1994-1995 collider run. These results are compared to a parton shower Monte Carlo (HERWIG) and a theoretical prediction using BFKL resummation.
Date: September 1, 1996
Creator: Jun, Soon Yung
Partner: UNT Libraries Government Documents Department

Color coherent radiation in multijet events from p{bar p} collisions at {radical}s = 1.8 TeV

Description: We report on a study of color coherence effects in p{bar p} collisions based on data collected by the D0 detector during the 1992-1993 run of the Fermilab Tevatron collider at the center of mass energy {radical}s = 1.8 TeV. We demonstrate initial-to-final state color interference effects by measuring spatial correlations between soft and hard jets in multijet events. The data are compared to Monte Carlo simulations with different color coherence implementations and to the predictions of a NLO parton level calculation.
Date: August 1, 1995
Creator: Abachi, S.; Ahn, S. & Baldin, B.
Partner: UNT Libraries Government Documents Department

Search for double parton scattering in the 4 jet channel at D0

Description: We have searched for double parton scattering in the 4-jet channel with an integrated luminosity of 4.4 pb{sup -1}, collected using the D{O} detector during 1994-1995 Fermilab Collider run at a center of mass energy ({radical}s) of 1.8 TeV. We present the preliminary observation of a statistically significant excess of signal.
Date: September 1, 1996
Creator: Yu, Yeonsik
Partner: UNT Libraries Government Documents Department

Rapidity gaps between jets at D0 and CDF

Description: Results are presented from analyses of particle multiplicity distributions between high transverse energy jets produced at the Fermilab Tevatron p{bar p} collider at {radical}s = 1.8 Tev. D0 and CDF examine the particle multiplicity distribution between the two highest transverse energy jets. Both experiments observe a significant excess of events at low tagged particle multiplicity which is consistent with a strongly interacting color-singlet exchange process.
Date: August 1, 1995
Creator: Bertram, I.
Partner: UNT Libraries Government Documents Department

Rapidity gaps in hard processes at D0

Description: Latest results on jet production with rapidity gaps at the Fermilab Tevatron Collider are presented. Jet production via color-singlet exchange at high momenta transfer is observed as a class of events with low particle multiplicity (or rapidity gaps) between the two highest transverse energy jets. The particle multiplicity in various regions, and the dependencies on jet pseudorapidity separation and jet transverse energy are studied for these events. Results from two classes of dijet events with one or two forward rapidity gaps are also presented. The topology of these events is consistent with expectations for hard single diffraction and hard double pomeron exchange processes, respectively.
Date: September 1, 1996
Creator: Perkins, J.
Partner: UNT Libraries Government Documents Department

Jet physics and QCD tests at the Tevatron collider

Description: Results are presented detailing the status of tests of perturbative QCD in hard parton-parton collisions generated by high energy collisions of protons and antiprotons at the Fermilab Collider. Recent data fro the CDF and DO experiments are compared to Next-to-Leading Order QCD calculations in hadronic jet production, prompt photon production, jet production in events with W bosons, and b-quark production.
Date: February 1, 1994
Creator: Plunkett, R.
Partner: UNT Libraries Government Documents Department

Tests of perturbative QCD at CDF

Description: The inclusive jet cross-section measured by CDF is in excellent agreement with NLO QCD below E{sub T} of 200 GeV. Above 200 GeV the measured cross-section begins to deviate from the QCD predictions with an excess of 20-50% in the 260-360 GeV range. A similar excess is observed in the two-jet mass distribution and the {Sigma} E{sub T} cross-section. The prompt photon cross-section from the CDF is in qualatative agreement with next-to-leading order QCD but has a steeper slope at low p{sub T}. Recent studies suggest that addition of soft radiation to NLO QCD may steepen the cross-section at low p{sub T}.
Date: October 1, 1995
Creator: Buckley-Geer, E.
Partner: UNT Libraries Government Documents Department

W/Z + jets production at the tevatron {bar p}p collider

Description: Both the D0 and CDF experiments at Fermilab Tevatron collider at {radical}s = 1.8TeV have accumulated over 13pb{sup {minus}1} of data during the 1992--1993 collider run. Each experiment collected more than 10,000 W {yields} l + {nu} and 1,000 Z {yields} l + {bar l} candidates for each lepton species (e and {mu}). Using this large data sample of W and Z candidates, the two experiments are actively testing perturbative QCD predictions. Among the studies that are in progress, preliminary results of Z+jets characteristics, multiplicity distributions of associated jets, and a determination of the strong coupling constant using the ratio of the +ljet to W + Ojet cross sections are presented.
Date: June 1, 1995
Creator: Yu, Jaehoon
Partner: UNT Libraries Government Documents Department

Exploiting the single-lepton event structure in the search for the top quark

Description: We discuss whether the event structure can be useful in searching for the top quark in the single-lepton channel at the Tevatron, where the main obstacle is a considerable background from QCD W+ multijet production. We restrict our discussion to the case of a Standard Model top quark of heavy mass, M{sub top}>100 GeV.
Date: June 1, 1993
Creator: Cobal, M.; Leone, S. & Grassman, H.
Partner: UNT Libraries Government Documents Department

Rapidity correlations between high p{sub T} intermediate vector bosons and jets in {bar p}p collisions at {radical}s = 1.8 TeV

Description: D{O} has used W {yields} e{nu} and Z {yields} e{sup +}e{sup -} events produced in association with a high p{sub T}, jet to examine the effects of strong radiative corrections. We have compared the primary jet pseudorapidity distribution, as a function of reconstructed W or Z boson rapidity to leading order (LO) and Next-to-Leading order (NLO) QCD Monte Carlo generators, as well as a model based on extended color dipoles. We find that the primary jet is more central than either LO or NLO expectations. None of the Monte Carlo programs does a good job of predicting the shape of the jet distributions as a function of intermediate vector bosons rapidity.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Multijet events at the Tevatron proton-antiproton collider

Description: The characteristics of three-jet, four-jet, and five-jet events observed by the CDF and D0 experiments at the Fermilab Tevatron {bar p}p collider are compared with leading order QCD matrix element predictions, and with the predictions from a parton shower Monte Carlo program.
Date: July 1, 1995
Creator: Geer, S.
Partner: UNT Libraries Government Documents Department

Photon production at CDF and D0

Description: Prompt photon production has been studied in {bar p}p collisions at {radical}s = 1.8 TeV using the CDF and D0 detectors at Fermilab. The measured inclusive isolated photon spectral at CDF and Do are used to test NLO QCD predictions. The CDF result shows that additional soft radiation (K{sub T}) in excess of NLO QCD is required to explain the data. No new resonance is observed in the photon + jet mass spectrum from D0 which is consistent with NLO QCD predictions. The pseudorapidity distribution of the leading jet in photon events at CDF is compared to different parton distribution sets. The angular distribution is found to be better explained by a larger Bremsstrahlung contribution.
Date: July 1, 1995
Creator: Lamoureux, J.I.
Partner: UNT Libraries Government Documents Department

Inclusive jet cross section measurement at CDF

Description: The CDF Collaboration has measured the inclusive jet cross section using 1992-93 collider data at 1.8 TeV. The CDF measurement is in very good agreement with NLO QCD predictions for transverse energies (E{sub T}) below 200 GeV. However, it is systematically higher than NLO QCD predictions for E{sub T} above 200 GeV.
Date: August 1, 1996
Creator: Pagliarone, C.
Partner: UNT Libraries Government Documents Department

A study of quark and gluon jets and of the long distance QCD force field at the Z{sup 0}

Description: Quantum Chromodynamics (QCD) is widely accepted as the correct theory of the strong nuclear force in elementary particle physics. The precision to which QCD has been tested is relatively limited, however, compared to the precision to which other interactions such as the electro-weak one have been tested. In part, this is because the large value of the QCD coupling constant, {alpha}{sub s}, renders theoretical calculations based on perturbation theory relatively imprecise. The confinement of quarks and gluons inside hadrons also leads to uncertainty because the theoretical predictions cannot, in general, be tested directly against the experimental measurements but are subject to hadronization corrections. From an experimental standpoint, it has proven difficult to isolate gluon jets inside multi-jet events in an unbiased manner so as to determine gluon jet properties using model independent methods. Basic quark-gluon interactions such as the four-jet matrix element in e{sup +}e{sup -} annihilations have been relatively untested due to the lack of a data sample with sufficient statistics. Perturbation theory has essentially nothing to say about the properties of the hadronization process itself. It is for these reasons that QCD has remained relatively untested.
Date: October 1, 1993
Creator: Gary, J.W.
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

Rapidity gaps between jets at D0

Description: Results are presented from an analysis of the particle multiplicity distribution between high transverse energy jets produced at the Fermilab Tevatron p{bar p} Collider at {radical}s = 1.8 Tev. Using the D0 detector, we examine the particle multiplicity distribution between the two highest transverse energy jets. For events with large rapidity separation, we observed a significant excess of events at low tagged-particle multiplicity which is consistent with a strongly interacting color-singlet exchange process.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Probing pomeron structure at Fermilab

Description: Using the CDF detector, dijet and W production with rapidity gaps has been searched for as evidence for hard-pomeron induced diffraction. Diffractive W`s are sensitive to a pomeron with a hard-quark structure, while diffractive dijets are sensitive to both hard-gluon and hard-quark structure. No evidence of diffractive W`s has been found down to the few percent level and the fraction of diffractive dijets is measured to be ({minus}0.03 {plus_minus} 0.37)%, or consistent with zero. The existence of colorless exchange between jets has been confirmed. Both the DO and CDF detectors show a statistically significant excess of dijet events with rapidity gaps between the jets at the level of 1-2% of all dijets.
Date: May 1, 1995
Creator: Melese, P. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department