73 research outputs found

    Reply to 'Comment on: 'Non-perturbative finite T broadening of the rho meson and dilepton emission in heavy ion-collisions''

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    Nota bene: the numerical calculation underlying Version 1 of this reply and the original work Phys.Rev. C71:064903,2005 contains a basic numerical error (wrong factor in the self-energy formulas of Phys. Rev.C71:064903,2005). This renders the numerical results presented there and in Version 1 of the reply invalid and enforces a careful reinvestigation of Phys. Rev.C71:064903,2005 and the reply. Calculations for an erratum of Phys. Rev. C71:064903,2005 are in progress.Comment: The numerical calculation underlying Version 1 of this reply and the original work Phys.Rev. C71:064903,2005 contains a basic numerical error (wrong factor in the self-energy formulas of Phys. Rev.C71:064903,2005). This renders the numerical results presented there and in Version 1 of the reply invalid and enforces a careful reinvestigation of Phys. Rev.C71:064903,2005 and the reply. Calculations for an erratum of Phys. Rev. C71:064903,2005 are in progres

    Three-particle azimuthal correlations and Mach shocks

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    Measurements of angular correlations of hadrons with a (semi-)hard trigger hadron in heavy-ion collisions at RHIC show large angular structures opposite to the trigger which were a priori unexpected. These away side large angle correlations were first observed in two-particle correlations and have recently also been investigated in three-particle correlation measurements by the PHENIX and STAR collaborations. We show that the correlation signal can be understood in terms of sonic shockwaves ('Mach cones') excited by hard partons supersonically traversing the medium. The propagation of such shocks through the medium evolution is treated in a Monte Carlo (MC) framework. We demonstrate that two- and especially three-particle correlations offer non-trivial insight into the medium-averaged speed of sound and the evolution of flow. Our findings imply that the assumption of "deflected jets" is not necessary to account for the observed correlations.Comment: 4 pages, 3 figure

    Dimuon transverse momentum spectra as a tool to characterize the emission region in heavy-ion collisions

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    Previous dilepton measurements in heavy-ion collisions have mainly focused on invariant mass spectra to clarify in-medium changes of vector meson properties. However, a dimuon is characterized by two scales -- invariant mass MM and transverse momentum pTp_T. Like transverse momentum spectra of hadrons, pTp_T spectra of dileptons arise from an interplay between emission temperature and collective transverse flow, whereas the invariant mass is insensitive to flow. Having two control parameters of which only one is sensitive to flow allows at given MM to characterize the emission region in terms of average temperature and flow. Thus, one is able to study what phases of the fireball evolution radiate into a given mass window. We demonstrate this technique using the dimuon transverse momentum spectra measured by the NA60 collaboration and present strong arguments that a thermalized evolution phase with T>170T > 170 MeV leaves an imprint in the spectra

    Prospects of Medium Tomography using 2-,3- and 4-Particle Correlations for a (semi-)hard Trigger

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    Hard partons propagating through hot and dense matter lose energy, leading to the observed depletion of hard hadron spectra in nucleus nucleus collision as compared to scaled proton proton collisions. This lost energy has to be redistributed in the medium due to the conservation of energy, which is manifest in the p_T dependence of the angular correlation pattern of hadrons associate with a (semi-) hard trigger. While at low p_T a splitting of a broad peak is observed, at high p_T the structure shows vacuum width, albeit with reduced yield. This sugests a transfer of energy from hard partons to a collectively recoiling medium. We present a systematic study of these phenomena using a realistic medium evolution and a Monte-Carlo simulation of the experimental trigger and show what information about the medium can be derived from multiparticle correlations.Comment: Talk given at the XI International Workshop on Correlation and Fluctuation in Multiparticle Production, Hangzhou, China, 21-24 Nov. 200

    Mass and Width of the Rho Meson in a Nuclear Medium from Brown-Rho Scaling and QCD Sum Rules

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    We explore the range of values of the in-medium width of a ρ\rho-meson at rest which is compatibale with the QCD sum rule approach in a nuclear medium assuming vector meson dominance and a Brown-Rho scaling law of the ρ\rho-meson mass with the chiral condensate. The lower and upper bounds for the in-medium width are found to be strongly increasing with the decreasing mass of the ρ\rho-meson (increasing nuclear density). We also study the bounds for the in-medium width in models not satisfying the Brown-Rho scaling law. It is shown that the in-medium width depends on how rapidly the mass decreases in comparison to the change of the quark condensate. The bounds for the in-medium width increase with density only if the relative change of the quark condensate is stronger than the relative decrease in mass. This is important for experimental tests of the Brown-Rho scaling paradigm and other dropping ρ\rho-mass scenarios.Comment: Revised and extended version. In this version we also study the in-medium width for decreasing ρ\rho-masses in models that do not satisfy the Brown-Rho scalin la

    Flow dependence of high pTp_T parton energy loss in heavy-ion collisions

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    The measured transverse momentum spectra and HBT correlations of bulk (i.e. low pTp_T) matter can be well explained by assuming that the soft sector of particles produced in ultrarelativistic heavy-ion collisions is (approximately) thermalized and undergoes collective accelerated expansion in both longitudinal and transverse direction. However, this implies that bulk matter will have a non-vanishing flow component transverse to the trajectory of a high pTp_T partonic jets. In general, this will increase the energy loss experienced by the jet parton and modify the shape of the jet cone. In this paper, we present a systematic study of the magnitude of the additional energy loss induced by flow under realistic assumptions for the medium evolution. We argue that a perturbative QGP description may be sufficient for the measured RAAR_{AA} if flow during the medium evolution is taken into account properly
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