879 research outputs found

    Is There a Significant Excess in Bottom Hadroproduction at the Tevatron?

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    We discuss the excess in the hadroproduction of B mesons at the Tevatron. We show that an accurate use of up-to-date information on the B fragmentation function reduces the observed excess to an acceptable level. Possible implications for experimental results reporting bottom quark cross sections, also showing an excess with respect to next-to-leading order theoretical predictions, are discussed.Comment: 5 pages, Latex, 4 figures. Submitted to Phys. Rev. Let

    Role Conflict: Society\u27s Dilemma with Excellence in Marketing

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    In recent years, the American market system has come under increasing criticism from those it serves. Many young people, radicals, members of minority groups and even middle-of-the-roaders are concerned about such things as poor product quality, poor variety, unsafe products. and misleading advertising. From almost any vantage point, flaws in the American economic system are visible

    Detecting an Invisibly Decaying Higgs Boson at a Hadron Supercollider

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    We demonstrate that an invisibly decaying Higgs boson with Standard Model coupling strength to top--anti-top can be detected at the LHC for masses up to about 250 GeV.Comment: 7 pages, requires phyzzx.tex and tables.tex, revised to convert results from SSC to LHC and include additional top quark mass cases, full postscript file including embedded figure available via anonymous ftp at ucdhep.ucdavis.edu as [anonymous.gunion]hinvisible_revised.ps, preprint UCD-93-2

    J/psi Production via Fragmentation at the Tevatron

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    The production of \jpsi at large transverse momenta (\pt > M_\jpsi) in ppˉp\bar p collisions is considered by including the mechanism of fragmentation. Both contributions of fragmentation to \jpsi and of fragmentation to χ\chi states followed by radiative decay to \jpsi are taken into account. The latter is found to be dominant and larger than direct production. The overall theoretical estimate is shown to be nearly consistent with the experimental observation.Comment: LaTeX, 7 pages. Preprint FNT/T-94/13, LNF-94/024(P). Data taken from a reference were incorrect and have been changed. Complete postscript file available via anonymous ftp at cobra1.pv.infn.it, as pub/jpsi.ps(.Z)(.gz

    QCD Corrections to Toponium Production at Hadron Colliders

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    Toponium production at future hadron colliders is investigated. Perturbative QCD corrections to the production cross section for gluon fusion are calculated as well as the contributions from gluon-quark and quark-antiquark collisions to the total cross section. The dependence on the renormalization and factorization scales and on the choice of the parton distribution functions is explored. QCD corrections to the branching ratio of ηt\eta_{t} into γγ\gamma\gamma are included and the two-loop QCD potential is used to predict the wave function at the origin. The branching ratio of ηt\eta_{t} into γZ\gamma Z, ZZZZ, HZHZ and WWWW is compared with the γγ\gamma\gamma channel.Comment: 16 pages (latex) 9 figures (postscript) available upon request, TTP92-3

    Direct Photons at RHIC

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    The PHENIX experiment has measured direct photons in sNN=200\sqrt{s_{NN}} = 200 GeV Au+Au collisions and p+p collisions. The fraction of photons due to direct production in Au+Au collisions is shown as a function of pTp_T and centrality. This measurement is compared with expectation from pQCD calculations. Other possible sources of direct photons are discussed.Comment: 7 pages, 5 figures, presented at Hot Quarks 2004, Taos, N

    Low-Energy Supersymmetry and the Tevatron Bottom-Quark Cross Section

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    A long-standing discrepancy between the bottom-quark production cross section and predictions of perturbative quantum chromodynamics is addressed. We show that pair production of light gluinos, of mass 12 to 16 GeV, with two-body decays into bottom quarks and light bottom squarks, yields a bottom-quark production rate in agreement with hadron collider data. We examine constraints on this scenario from low-energy data and make predictions that may be tested at the next run of the Fermilab Tevatron Collider.Comment: Version in Phys. Rev. Lett., 4 pp., 1 ps fig., uses RevTeX, added why moderate gluino masses are not ruled out, updated reference

    Higgs Radiation off Top Quarks at the Tevatron and the LHC

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    Higgs bosons can be searched for in the channels ppˉ/ppttˉH+Xp\bar p/pp\to t\bar tH+X at the Tevatron and the LHC. We have calculated the QCD corrections to these processes in the Standard Model at next-to-leading order. The higher-order corrections reduce the renormalization and factorization scale dependence considerably and stabilize the theoretical predictions for the cross sections. At the central scale μ=(2mt+MH)/2\mu=(2m_t+M_H)/2 the properly defined KK factors are slightly below unity for the Tevatron (K0.8K \sim 0.8) and slightly above unity for the LHC (K1.2K \sim 1.2).Comment: 5 pages, latex, 2 figure

    QCD Corrections to Electroweak Annihilation Decays of Superheavy Quarkonia

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    QCD corrections to all the allowed decays of superheavy groundstate quarkonia into electroweak gauge and Higgs bosons are presented. For quick estimates, approximations that reproduce the exact results within less than at worst two percent are also given.Comment: 20 pages RevTeX, 9 figures. The complete paper, including figures, is also available via anonymous ftp at (129.13.102.139) as ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-05/ttp95-05.ps, or via www at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints

    D^* production from e^+e^- to ep collisions in NLO QCD

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    Fragmentation functions for D mesons, based on the convolution of a perturbative part, related to the heavy quark perturbative showering, and a non-perturbative model for its hadronization into the meson, are used to describe D^* production in e^+e^- and ep collisions. The non-perturbative part is determined by fitting the e^+e^- data taken by ARGUS and OPAL at 10.6 and 91.2 GeV respectively. When fitting with a non perturbative Peterson fragmentation function and using next-to-leading evolution for the perturbative part, we find an epsilon parameter sensibly different from the one commonly used, which is instead found with a leading order fit. The use of this new value is shown to increase considerably the cross section for D^* production at HERA, suggesting a possible reconciliation between the next-to-leading order theoretical predictions and the experimental data.Comment: 20 pages, LaTeX2e, 8 Postscript figure
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