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Beam Energy and System Size Dependence of Dynamical Net Charge Fluctuations

Description: We present measurements of net charge fluctuations in Au + Au collisions at {radical}s{sub NN} = 19.6, 62.4, 130, and 200 GeV, Cu + Cu collisions at {radical}s{sub NN} = 62.4, 200 GeV, and p + p collisions at {radical}s = 200 GeV using the dynamical net charge fluctuations measure {nu}{sub {+-},dyn}. We observe that the dynamical fluctuations are non-zero at all energies and exhibit a modest dependence on beam energy. A weak system size dependence is also observed. We examine the collision centrality dependence of the net charge fluctuations and find that dynamical net charge fluctuations violate 1/N{sub ch} scaling, but display approximate 1/N{sub part} scaling. We also study the azimuthal and rapidity dependence of the net charge correlation strength and observe strong dependence on the azimuthal angular range and pseudorapidity widths integrated to measure the correlation.
Date: July 21, 2008
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

Hard diffraction at CDF

Description: Recently published and new preliminary results from the analyses of diffractive events selected with a central or a forward rapidity gap are summarized. New measurements of the ratio of dijet production in single diffractive and non-diffractive events obtained from the Roman Pot data are discussed.
Date: June 18, 1999
Creator: Borras, K.
Partner: UNT Libraries Government Documents Department

Hard Diffraction at D-Zero

Description: Preliminary results from the DO experiment on dijet production with forward rapidity gaps in {anti p}p collisions are presented at center-of-mass {radical}s = 1800 GeV and 630GeV. The number oi events with rapidity gaps at both center-of-mass energies is significantly greater than tne expectatmn from multiplicity fluctuations and is consistent with a hard single diffractive process. We also observe an excess of events which contain jets and two rapidity gaps, a topology which is consistent with hard double pomeron exchange.
Date: January 21, 1999
Creator: Rubinov, Paul
Partner: UNT Libraries Government Documents Department

Hard diffraction results using D0

Description: The preliminary results on the search for hard diffraction in pp collisions with the D0 detector at Fermilab are presented. The presence of forward rapidity gaps is observed in events with high transverse momentum jet production at the center of mass energies 1800 and 630 GeV. The fraction of events with rapidity gaps is significantly higher than that expected due to multiplicity fluctuations and is consistent with predictions for hard single diffractive jet production. A class of events containing central dijets and two forward rapidity gaps is observed at {radical}s = 1800 GeV consistent with a hard double pomeron exchange event topology.
Date: June 1, 1997
Creator: Shabalina, E.
Partner: UNT Libraries Government Documents Department

BFKL Tests at the Tevatron

Description: The azimuthal decorrelation of jets as a function of their rapidity separation and the dependence of the fraction of jet events with central rapidity gaps on the center of mass energy are studied in p{anti p} collisions at the Tevatron. The preliminary results on jet decorrelation are in disagreement with calculations based on the Leading Logarithmic Approximation for BFKL resummation. The preliminary results on the {radical}s--dependence of the central rapidity gap events are in disagreement with the two-gluon model for color-singlet exchange.
Date: June 1, 1997
Creator: Goussiou, A. & Collaboration, DO
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

Constraints on PDFs from W and Z rapidity distributions at CDF

Description: The rapidity distributions of W and Z bosons produced in proton anti-proton collisions at CDF are presented. The rapidity distribution of Z bosons, measured for the first time over the entire kinematic range, is better described by NLO QCD (and also by QCD with gluon resummation) than by leading order QCD. The W charge asymmetry data as a function of rapidity strongly constrain the ratio of d and u quark momentum distributions in the proton over the x range of 0.006 to 0.34. The W data are used to rule out recently proposed models for charge and flavor symmetry violation of the sea quark distributions in the nucleon.
Date: July 20, 1999
Creator: Bodek, A.
Partner: UNT Libraries Government Documents Department

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Description: Parity-odd domains, corresponding to non-trivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three particle azimuthal correlator which is a {Rho} even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.
Date: July 5, 2010
Creator: Collaboration, STAR & Abelev, Betty
Partner: UNT Libraries Government Documents Department

Traveling waves and the renormalization group improvedBalitsky-Kovchegov equation

Description: I study the incorporation of renormalization group (RG)improved BFKL kernels in the Balitsky-Kovchegov (BK) equation whichdescribes parton saturation. The RG improvement takes into accountimportant parts of the next-to-leading and higher order logarithmiccorrections to the kernel. The traveling wave front method for analyzingthe BK equation is generalized to deal with RG-resummed kernels,restricting to the interesting case of fixed QCD coupling. The resultsshow that the higher order corrections suppress the rapid increase of thesaturation scale with increasing rapidity. I also perform a "diffusive"differential equation approximation, which illustrates that someimportant qualitative properties of the kernel change when including RGcorrections.
Date: December 1, 2006
Creator: Enberg, Rikard
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

Rapidity gaps in deep inelastic scattering

Description: A simple semiquantitative picture of diffractive electroproduction is described. Although the diffractive component of F{sub 2} is approximately independent of Q{sup 2} and W{sup 2}, this mechanism is ``soft,`` i.e. it depends upon large-distance physics and is not readily describable within perturbative QCD.
Date: December 31, 1995
Creator: Bjorken, J.D.
Partner: UNT Libraries Government Documents Department

Rapidity Gap Results from Tevatron

Description: Results of rapidity gap physics in the CDF and DO Collaborations are presented. In particular, hard diffraction (diffractive dijet and heavy flavor quark production, dijet production in Double Pomeron Exchange) and color-singlet exchange are described.
Date: April 8, 1999
Creator: Terashi, K.
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

Hadron distributions - recent results from the CERN experiment NA44

Description: Proton distributions at midrapidity have been measured for 158A{circ}GeV/c Pb + Pb collisions in the focusing spectrometer experiment NA44 at CERN. A high degree of nuclear stopping is found in the truly heavy ion collisions. Systematic results of single particle transverse momentum distributions of pions, kaons, and protons, of 200A-GeV/c S+S and 158A{circ}GeV/c Pb+Pb central collisions will be addressed within the context of thermalization. By comparing these data with thermal and transport models, freeze-out parameters such as the temperature parameter T{sub fo} and mean collective flow velocity ({Beta}) are extracted. Preliminary results of the particle ratios of K{sup -}/K{sup +} and p/p are discussed in the context of cascade models of RQMD and VENUS.
Date: September 1, 1996
Creator: Xu, N.
Partner: UNT Libraries Government Documents Department

Diffractive results from the Tevatron

Description: Hard diffraction in events with dijets and rapidity gaps has been studied by D0 and CDF for three processes: hard color singlet exchange, hard single diffraction, and hard double pomeron exchange, using Tevatron {anti p}p data at {radical}s = 630 GeV and 1.8 TeV. Measurements of rates, {eta}, E{sub T} and {radical}s dependencies are presented and comparisons made with predictions of several models.
Date: May 27, 1999
Creator: Alves, Gilvan A.
Partner: UNT Libraries Government Documents Department

Energy and rapidity dependence of beauty production at Tevatron

Description: The CDF and D0 experiments have measured bb production in pp interactions at {radical}s = 1800 GeV and 630 GeV (the energy at which the previous measurement was performed by the UAl experiment). The Tevatron measurements are used to evaluate, for the first time, the center-of-mass energy and rapidity dependence of b-quark production cross section measured with the same detectors. Preliminary results from these measurements are presented and compared with the next-to-leading order QCD predictions.
Date: September 1, 1997
Creator: Ba, M.M.
Partner: UNT Libraries Government Documents Department

Properties of events with a rapidity gap between jets in CDF

Description: We present the {eta} and E{sub T} dependence of dijet events produced by color-singlet exchange in {anti p}p collisions at {radical}s = 1.8 TeV using data collected by the CDF collaboration at the Fermilab Tevatron. In a sample of events with two forward jets, where the jets are on opposite sides in rapidity with {vert_bar}{eta}{vert_bar} > 1. 8 and E{sub T} > 20 GeV, we find 1.13 {+-} 0.12(stat) {+-} 0. 11(syst)% have a rapidity gap between the jets consistent with color- singlet exchange. This signal has no significant dependence on the jet E{sub T} or the rapidity interval between the jets.
Date: June 1, 1997
Creator: Melese, P.
Partner: UNT Libraries Government Documents Department

B-physics results from D-Zero

Description: A number of B-physics results from the D0 experiment at the Fermilab Tevatron Collider is reported. Measurements of b{anti b} production in p{anti p} interactions at {radical}s = 1800 GeV and 630 GeV are used to evaluate, for the first time with the same detector, the center-of-mass energy and rapidity dependence of b-quark production cross section. A measurement of the b{anti b} angular correlations using dimuon triggers is also presented. Preliminary results from these measurements are compared with the next-to-leading order QCD predictions. Finally, dimuon data samples are used to study P{sub T} and rapidity dependence of b-produced and direct charmonium production.
Date: January 1, 1998
Creator: Baarmand, M.M.
Partner: UNT Libraries Government Documents Department

Diffractive phenomena at Tevatron

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 single diffractive process. A class of events with two forward gaps and central dijets are also observed at 1800 GeV. This topology is consistent with hard double pomeron exchange. We also present proposed plans for extending these analysis into Run II through the use of a forward proton detector.
Date: July 1, 1997
Creator: Santoro, A. & Collaboration, DO
Partner: UNT Libraries Government Documents Department

Brahms Experiment at RHIC Day-1 Physics

Description: The BRAHMS experiment is designed to measure semi-inclusive spectra of charged hadron over a wide range of rapidity. It will yield information on particle production, both at central rapidity and in the baryon rich fragmentation region. The physics plans for measurements in the first year of running at RHIC are discussed.
Date: March 23, 1999
Creator: Videbaek, Flemming
Partner: UNT Libraries Government Documents Department

Hard diffraction at the Tevatron

Description: Experimental results on hard diffraction from CDF and D0 at the Tevatron are reviewed and compared with results from H1 and ZEUS at HERA and with theoretical expectations.
Date: June 29, 1999
Creator: Goulianos, K.
Partner: UNT Libraries Government Documents Department

B Physics at D0

Description: The Fermilab Tevatron (p{bar p}), operating at {radical}s = 1.96 TeV, is a rich source of B hadrons. The large acceptance in terms of rapidity and transverse momentum of the charged particle tracking system and the muon system make the upgraded Run II D0 detector an excellent tool for B physics. In this article, we report on selected physics results based on the first 250 pb{sup -1} of Run II data. This includes results on the X(3872) state, semileptonic B decays, B hadron lifetimes, flavour oscillations, and the rare decay B{sub s} {yields} {mu}{sup +}{mu}{sup -}.
Date: July 12, 2004
Creator: Stark, Jan
Partner: UNT Libraries Government Documents Department