922 research outputs found

    Finite Temperature Phase Diagrams of Gauge Theories

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    We discuss finite temperature phase diagrams of SU(N) gauge theory with massless fermions as a function of the number of fermion flavors. Inside the conformal window we find a phase boundary separating two different conformal phases. Below the conformal window we find different phase structures depending on if the beta function of the theory has a first or higher order zero at the lower boundary of the conformal window. We also outline how the associated behaviors will help in distinguishing different types of theories using lattice simulations.Comment: 5 pages, 5 figure

    Freezeout of resonances and nuclear fragments at RHIC

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    We quantify the conditions at which ``composites'', the resonances and bound states d,He3d,He^3 are produced at RHIC. Using Hubble-like model for late stages, one can analytically solve the rate equations and also calculate the relevant optical depth factors. We calculate also the modification of ρ\rho masse and width, and predict a radiacal shape change of σ\sigma.Comment: 6 pages, proccedings of 19th Winter Workshop on Nuclear Dynamics, Breckenridge, Colorado, February 200

    QCD phases at high density and instantons

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    The talk is an introduction into diquark condensation phenomena which occur in QCD at high energy density. They are driven by instantons and instanton-antiinstanton pairs (or ``molecules''), which generate attraction in some qq channels. A number of phases is possible, with or without restoration of chiral symmetry: the work is not finished and we do not yet know which take place in real QCD. We also emphasize that specific diquark correlations play a significant role in baryon structure, in particular making that of a nucleon very different of a Δ\Delta (or other member of a decuplet). This ``small NcN_c'' scenario based on comparison to QCD with two colors is contrasted with the ``large NcN_c'' one.Comment: invited talk at "QCD at finite baryon density", Bielefeld, 199

    On the Origin of the "Ridge" phenomenon induced by Jets in Heavy Ion Collisions

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    We argue that "ridge" in 2-particle correlation function associated with hard trigger at RHIC heavy ion collisions is naturally explained by an interrelation of jet quenching and hydrodynamical transverse flow. The excess particles forming the ridge are produced by QCD bremsstrahlung along the beam (and thus have wide rapidity distribution) and then boosted by transverse flow. Nontrivial correlation between directions of the jet and the radial flow is provided by jet quenching: our straightforward and basically parameter-independent calculation reproduces the angular shape, width and other properties of the "ridge"

    Anisotropy of photon production: Initial eccentricity or magnetic field

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    Recent measurements of the azimuthal anisotropy of direct photons in heavy-ion collisions at the energies of RHIC show that it is of the same order as the hadronic one. This finding appears to contradict the expected dominance of photon production from a quark-gluon plasma at an early stage of a heavy-ion collision. A possible explanation of the strong azimuthal anisotropy of the photons, given recently, is based on the presence of a large magnetic field in the early phase of a collision. In this letter, we propose a method to experimentally measure the degree to which a magnetic field in heavy-ion collisions is responsible for the observed anisotropy of photon production. The experimental test proposed in this letter may potentially change our understanding of the non-equilibrium stage and possible thermalization in heavy-ion collisions.Comment: 4 pages, 3 figures; version accepted for publication: discussions extended, MC calculations adde

    Nonperturbative contributions to the QCD pressure

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    We summarize the most important arguments why a perturbative description of finite-temperature QCD is unlikely to be possible and review various well-established approaches to deal with this problem. Then, using a recently proposed method, we investigate nonperturbative contributions to the QCD pressure and other observables (like energy, anomaly and bulk viscosity) obtained by imposing a functional cutoff at the Gribov horizon. Finally, we discuss how such contributions fit into the picture of consecutive effective theories, as proposed by Braaten and Nieto, and give an outline of the next steps necessary to improve this type of calculation.Comment: 15 pages, 13 figures, uses xcolor.sty; in v2 quality of some figures has been improved, discussion of other approaches has been extende