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Recent results from the PEP4-TPC on quark fragmentation

Description: The physics goals for the PEP-4/PEP-9 experiment concentrate on two areas: the fragmentation properties of quarks and gluons produced in e+e- annihilation, and the investigation of hadron production in 2-photon collisions. Only the first of these topics is addressed. Despite the many successes of QCD in the description of deep inelastic reactions, the basic fragmentation process of quarks and gluons is not very well understood. This lack of knowledge has been shown to jeopardize precise test of… more
Date: November 12, 1983
Creator: Hofmann, W.
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Partner: UNT Libraries Government Documents Department
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Compositeness and QCD at the SSC

Description: Compositeness may be signaled by an increase in the production of high transverse momentum hadronic jet pairs or lepton pairs. The hadronic jet signal competes with the QCD production of jets, a subject of interest in its own right. Tests of perturbative QCD at the SSC will be of special interest because the calculations are expected to be quite reliable. Studies show that compositeness up to a scale of 20 to 35 TeV would be detected in hadronic jets at the SSC. Leptonic evidence would be disco… more
Date: October 12, 1987
Creator: Barnes, V.; Blumenfeld, B.; Cahn, R.; Chivukula, S.; Ellis, S.; Freeman, J. et al.
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Partner: UNT Libraries Government Documents Department
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Global quark polarization in non-central A+A collisions

Description: Partons produced in the early stage of non-central heavy-ioncollisionscan develop a longitudinal fluid shear because of unequal localnumber densities of participant target and projectile nucleons. Undersuch fluid shear, local parton pairs with non-vanishing impact parameterhave finite local relative orbital angular momentum along the directionopposite to the reaction plane. Such finite relative orbitalangularmomentum among locally interacting quark pairs can lead to global quarkpolarization alo… more
Date: October 12, 2007
Creator: Gao, Jian-Hua; Chen, Shou-Wan; Deng, Wei-tian; Tang, Zuo-Tang; Wang, Qun & Wang, Xin-Nian
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Partner: UNT Libraries Government Documents Department
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Novel QCD Effects from Initial and Final State Interactions

Description: Initial-state and final-state interactions which are conventionally neglected in the parton model, have a profound effect in QCD hard-scattering reactions. The effects, which arise from gluon exchange between the active and spectator quarks, cause leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and the breakdown of the Lam-Tung relation in Drell-Yan reactions. Diffractive deep inelastic scattering also leads to nuclear shadowing… more
Date: September 12, 2007
Creator: Brodsky, Stanley J.
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Partner: UNT Libraries Government Documents Department
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Pseudorapidity Asymmetry and Centrality Dependence of Charged Hadron Spectra in d+Au collisions at sqrt(sNN) = 200 GeV

Description: The pseudorapidity asymmetry and centrality dependence of charged hadron spectra in d+Au collisions at {radical}s{sub NN} = 200 GeV are presented. The charged particle density at mid-rapidity, its pseudorapidity asymmetry and centrality dependence are reasonably reproduced by a Multi-Phase Transport model, by HIJING, and by the latest calculations in a saturation model. Ratios of transverse momentum spectra between backward and forward pseudorapidity are above unity for p{sub T} below 5 GeV/c. … more
Date: January 12, 2005
Creator: Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
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Partner: UNT Libraries Government Documents Department
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The QCD/SM working group: Summary report

Description: Quantum Chromo-Dynamics (QCD), and more generally the physics of the Standard Model (SM), enter in many ways in high energy processes at TeV Colliders, and especially in hadron colliders (the Tevatron at Fermilab and the forthcoming LHC at CERN), First of all, at hadron colliders, QCD controls the parton luminosity, which rules the production rates of any particle or system with large invariant mass and/or large transverse momentum. Accurate predictions for any signal of possible ''New Physics'… more
Date: January 12, 2004
Creator: al., W. Giele et
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Partner: UNT Libraries Government Documents Department
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Heavy octets and Tevatron signals with three or four b jets

Description: Hypothetical color-octet particles of spin 0, pair-produced at hadron colliders through their QCD coupling, may lead to final states involving three or four b jets. We analyze kinematic distributions of the 3b final state that differentiate the scalar octets from supersymmetric Higgs bosons. Studying the scalar sector that breaks an SU(3) x SU(3) gauge symmetry down to the QCD gauge group, we find that the scalar octet is resonantly produced in pairs via a spin-1 octet (coloron). A scalar octet… more
Date: August 12, 2011
Creator: Bai, Yang & Dobrescu, Bogdan A.
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Partner: UNT Libraries Government Documents Department
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Novel QCD Phenomenology

Description: I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion rati… more
Date: August 12, 2011
Creator: Brodsky, Stanley J. & /SLAC /Southern Denmark U., CP3-Origins
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Partner: UNT Libraries Government Documents Department
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Influence of Bottom Quark Jet Quenching on Single ElectronTomography of Au+Au

Description: High transverse momentum single (non-photonic) electrons are shown to be sensitive to the stopping power of both bottom, b, and charm, c, quarks in AA collisions. We apply the DGLV theory of radiative energy loss to predict c and b quark jet quenching and compare the FONLL and PYTHIA heavy flavor fragmentation and decay schemes. We show that single electrons in the p{sub T} = 5-10 GeV range are dominated by the decay of b quarks rather than the more strongly quenched c quarks in Au+Au collision… more
Date: July 12, 2005
Creator: Djordjevic, Magdalena; Gyulassy, Miklos; Vogt, Ramona & Wicks, Simon
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Partner: UNT Libraries Government Documents Department
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Threshold resummation and the total cross section for top quark production

Description: We discuss the motivation for resummation of the effects of initial-state soft gluon radiation, to all orders in the strong coupling strength, for processes in which the near-threshold region in the partonic subenergy is important. We summarize our calculation of the total cross section for top quark production at hadron colliders. Comments are included on the differences between our treatment of subleading logarithmic terms and other methods.
Date: June 12, 1997
Creator: Berger, E. L. & Contopanagos, H.
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Partner: UNT Libraries Government Documents Department
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Supersymmetric Higgs Pair Production at Hadron Colliders

Description: We study the pair production of neutral Higgs bosons through gluon fusion at hadron colliders in the framework of the Minimal Supersymmetric Standard Model. We present analytical expressions for the relevant amplitudes, including both quark and squark loop contributions, and allowing for mixing between the superpartners of left- and right-handed quarks. Squark loop contributions can increase the cross section for the production of two CP--even Higgs bosons by more than two orders of magnitude, … more
Date: May 12, 1999
Creator: Mizukoshi, Jose
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Impact parameter dependence of J/psi and Drell-Yan Production in Heavy Ion Collisions at sqrt(s{sub NN}) = 17.3 GeV

Description: In heavy-ion collisions,J/psi and Drell-Yan production are expected to be affected by nuclear modifications to the free nucleon structure functions. If these modifications, referred to here as shadowing, are proportional to the local nuclear density, the per nucleon cross sections will depend on centrality. Differences in quark and gluon shadowing will lead to a new source of impact parameter dependence of the J/psi to Drell-Yan production ratio. We calculate this ratio in the CERN NA50 accepta… more
Date: August 12, 1998
Creator: Emel'yanov, V.; Khodinov, A.; Klein, S.R. & Vogt, R.
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Partner: UNT Libraries Government Documents Department
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