3,319 research outputs found

    Quarkonia measurements in heavy-ion collisions in CMS

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    The production of quarkonia is one of the most promising signals at the LHC for the study of the production properties of Quark Gluon Plasma. In addition to the J/psi, the extent to which upsilon is suppressed should give much insight into the new state of matter. The large muon acceptance and the high precision tracker make the CMS detector ideal for studies of this physics. In this note, the performance of the CMS detector for quarkonia measurements in heavy-ion collisions in the dimuon channel is presented. Dimuon reconstruction efficiencies and mass resolution are calculated using detailed detector simulation. Mass spectra and signal to background ratios are estimated with a fast Monte Carlo program. Results obtained with the fast Monte Carlo are compared with more detailed simulations

    Jet Physics in Heavy Ion Collisions with Compact Muon Solenoid detector at the LHC

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    The status of CMS jet simulations and physics analysis in heavy ion collisions is presented. Jet reconstruction and high transverse momentum particle tracking in the high multiplicity environment of heavy ion collisions at the LHC using the CMS calorimetry and tracking system are described. The Monte Carlo tools used to simulate jet quenching are discussed.Comment: Talk given at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, Salt Lake City, Kolkata, India, February 8-12, 2005; 4 pages including 4 figures as EPS-files; prepared using LaTeX package for Journal of Physics

    Hard probes in heavy ion collisions at the LHC: heavy flavour physics

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    We present the results from the heavy quarks and quarkonia working group. This report gives benchmark heavy quark and quarkonium cross sections for pppp and pApA collisions at the LHC against which the AAAA rates can be compared in the study of the quark-gluon plasma. We also provide an assessment of the theoretical uncertainties in these benchmarks. We then discuss some of the cold matter effects on quarkonia production, including nuclear absorption, scattering by produced hadrons, and energy loss in the medium. Hot matter effects that could reduce the observed quarkonium rates such as color screening and thermal activation are then discussed. Possible quarkonium enhancement through coalescence of uncorrelated heavy quarks and antiquarks is also described. Finally, we discuss the capabilities of the LHC detectors to measure heavy quarks and quarkonia as well as the Monte Carlo generators used in the data analysis.Comment: 126 pages Latex; 96 figures included. Subgroup report, to appear in the CERN Yellow Book of the workshop: Hard Probes in Heavy Ion Collisions at the LHC. See also http://a.home.cern.ch/f/frixione/www/hvq.html for a version with better quality for a few plot

    Two-dimensional discrete wavelet analysis of multiparticle event topology in heavy ion collisions

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    The event-by-event analysis of multiparticle production in high energy hadron and nuclei collisions can be performed using the discrete wavelet transformation. The ring-like and jet-like structures in two-dimensional angular histograms are well extracted by wavelet analysis. For the first time the method is applied to the jet-like events with background simulated by event generators, which are developed to describe nucleus-nucleus collisions at LHC energies. The jet positions are located quite well by the discrete wavelet transformation of angular particle distribution even in presence of strong background.Comment: 6 pages, 6 figure

    Photon Physics in Heavy Ion Collisions at the LHC

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    Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One figure added in chapter 5 (comparison with PHENIX data). Some figures and correponding text corrected in chapter 6 (off-chemical equilibrium thermal photon rates). Some figures modified in chapter 7 (off-chemical equilibrium photon rates) and comparison with PHENIX data adde

    Observation of exotic meson production in the reaction πpηπp \pi^{-} p \to \eta^{\prime} \pi^- p at 18 GeV/c

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    An amplitude analysis of an exclusive sample of 5765 events from the reaction πpηπp\pi^{-} p \to \eta^{\prime} \pi^- p at 18 GeV/c is described. The ηπ\eta^{\prime} \pi^- production is dominated by natural parity exchange and by three partial waves: those with JPC=1+,2++,J^{PC} = 1^{-+}, 2^{++}, and 4++4^{++}. A mass-dependent analysis of the partial-wave amplitudes indicates the production of the a2(1320)a_2(1320) meson as well as the a4(2040)a_4(2040) meson, observed for the first time decaying to ηπ\eta^{\prime}\pi^-. The dominant, exotic (non-qqˉ)q\bar{q}) 1+1^{-+} partial wave is shown to be resonant with a mass of 1.597±0.0100.010+0.0451.597 \pm 0.010^{+0.045}_{-0.010} GeV/c^2 and a width of 0.340±0.040±0.0500.340 \pm 0.040 \pm 0.050 GeV/c^2 . This exotic state, the π1(1600)\pi_1(1600), is produced with a tt dependence which is different from that of the a2(1320)a_2(1320) meson, indicating differences between the production mechanisms for the two states.Comment: 5 pages with 4 figure

    Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c

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    A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated by J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and the eta(1440). The mass and width of the eta(1295) were determined to be 1282 +- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of importance include the 1++ and the 1+- waves. Results of the partial wave analysis are combined with results of other experiments to estimate f1(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure

    A partial wave analysis of the π0π0\pi ^0\pi ^0 system produced in πp\pi ^-p charge exchange collisions

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    A partial wave analysis of the of the π0π0\pi ^0\pi ^0 system produced in the charge exchange reaction: πpπ0π0n\pi ^-p\to \pi ^0\pi ^0n at an incident momentum of 18.3GeV/c18.3 GeV/c is presented as a function of π0π0{\pi ^0\pi ^0} invariant mass, mπ0π0m_{\pi^0\pi^0}, and momentum transfer squared, t| {t} |, from the incident π\pi^- to the outgoing π0π0{\pi ^0\pi ^0} system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys Rev

    Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c

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    Details of the analysis of the eta pi- system studied in the reaction pi^{-} p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the data indicates the presence of interference between the a(2)(1320)- and a J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between these waves shows phase motion not attributable solely to the a(2)(1320)-. The data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+} resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105 MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure