Centre d'études et d'expertise sur les risques, l'environnement, la mobilité et l'aménagement

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark–Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton–proton, proton–nucleus and nucleus–nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photoproduction in nucleus–nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7 Framework Programme.

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We investigate pion superfluidity and its effect on meson properties and equation of state at finite temperature and isospin and baryon densities in the frame of standard flavor SU(2) NJL model. In mean field approximation to quarks and random phase approximation to mesons, the critical isospin chemical potential for pion superfluidity is exactly the pion mass in the vacuum, and corresponding to the isospin symmetry spontaneous breaking, there is in the pion superfluidity phase a Goldstone mode which is the linear combination of the normal sigma and charged pion modes. We calculate numerically the gap equations for the chiral and pion condensates, the phase diagrams, the meson spectra, and the equation of state, and compare them with that obtained in other effective models. The competitions between pion superfluidity and color superconductivity at finite baryon density and between pion and kaon superfluidity at finite strangeness density in flavor SU(3) NJL model are briefly discussed.

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We investigate with a transport approach the cold and hot nuclear matter effects on the charmonium transverse momentum distributions in relativistic heavy ion collisions. The newly defined nuclear modification factor r AA = p 2 T AA / p 2 T pp and elliptic flow v 2 for J/ψ are sensitive to the nature of the hot medium and the thermalization of heavy quarks. From SPS through RHIC to LHC colliding energies, we observe dramatic changes in the centrality dependence of r AA . We find that at LHC energy, the finally observed charmonia are dominated by the regeneration from thermalized heavy quarks.

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We study J/ψ production at RHIC and LHC energies with both initial production and regeneration. We solve the coupled set of transport equation for the J/ψ distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/ψ momentum distribution while the elliptic flow is still dominated by initial production. At LHC energy, almost all the initially created J/ψs are dissociated in the medium and regeneration dominates the J/ψ properties. 12.38.Mh, 24.85.+p The goal of high-energy nuclear collisions is to identify and study the equation of state of the Quark-Gluon Plasma (QGP) which is believed to exist at the early stage of our universe [1]. In √ s N N = 200 GeV Au + Au collisions, the observations of jet-quenching [2] and collective flow have demonstrated the formation of hot and dense matter with partonic collectivity [3,4]. Local thermalization of the system created in heavy ion collisions is yet to be tested. Heavy flavors including charm and bottom quarks are powerful tools [5] for studying the early collision dynamics because their masses are much larger than possible excitation, temperature for example, of the system created in collisions at RHIC. Recent results have shown that heavy flavors are all produced in the initial collisions [6,7]. Therefore, studying open charm and charmonium production will yield important information on the properties of QGP. The J/ψ is a particularly sensitive probe of the early stages because its survial probability depends on the environment. Lattice gauge theory calculations have indicated that J/ψs do exist above the critical temperature [8,9].The J/ψ suppression was first proposed as a direct signature to identify the QGP formation twenty years ago [10]. Besides the normal suppression induced by nuclear absorption, the J/ψs initially produced by hard processes are anomalously suppressed [11,12,13,14,15,16,17] by interactions in the hot medium. While charm quark production at the SPS is expected to be small, there are more than 10 cc pairs produced in a central Au + Au collision at RHIC, and is probably more than 200 pairs at the LHC [18]. These uncorrelated charm quark pairs in the QGP can be recombined to form J/ψs. Obviously, regeneration will enhance the J/ψ yield and alter its momentum spectra. Recently, the regeneration approach for J/ψ production at RHIC has been widely discussed with different models, such as thermal production on the hadronizaton hypersurface according to statistic law [19,20,21], the coalescence mechanism [22] and the kinetic model [23,24] which considers continuous J/ψ regeneration in a QGP.The medium created in high-energy nuclear collisions evolves dynamically. In order to extract information about the medium by analyzing the J/ψ distributions, both the hot and dense medium and the J/ψ production processes must be treated dynamically. In this Letter, we treat continuous regeneration of the J/ψ in a QGP self-consistently, including hydrodynamic evolution of t...