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The cumulant method is applied to study elliptic flow (v_2) in Au+Au collisions at sqrt s=200 AGeV, with the UrQMD model. In this approach, the true event plane is known and both the non-flow effects and event-by-event spatial (epsilon) and v_2 fluctuations exist. Qualitatively, the hierarchy of v_2 's from two, four and six-particle cumulants is consistent with the STAR data, however, the magnitude of v_2 in the UrQMD model is only 60% of the data. We find that the four and six-particle cumulants are good measures of the real elliptic flow over a wide range of centralities except for the most central and very peripheral events. There the cumulant method is affected by the v_2 fluctuations. In mid-central collisions, the four and six-particle cumulants are shown to give a good estimation of the true differential v_2, especially at large transverse momentum, where the two-particle cumulant method is heavily affected by the non-flow effects.
We study the effects of isovector-scalar meson delta on the equation of state (EOS) of neutron star matter in strong magnetic fields. The EOS of neutron-star matter and nucleon effective masses are calculated in the framework of Lagrangian field theory, which is solved within the mean-field approximation. From the numerical results one can find that the delta-field leads to a remarkable splitting of proton and neutron effective masses. The strength of delta-field decreases with the increasing of the magnetic field and is little at ultrastrong field. The proton effective mass is highly influenced by magnetic fields, while the effect of magnetic fields on the neutron effective mass is negligible. The EOS turns out to be stiffer at B < 10^15G but becomes softer at stronger magnetic field after including the delta-field. The AMM terms can affect the system merely at ultrastrong magnetic field(B > 10^19G). In the range of 10^15 G - 10^18 G the properties of neutron-star matter are found to be similar with those without magnetic fields.
The regeneration of hadronic resonances is discussed for heavy ion collisions at SPS and SIS-300 energies. The time evolutions of Delta, rho and phi resonances are investigated. Special emphasize is put on resonance regeneration after chemical freeze-out. The emission time spectra of experimentally detectable resonances are explored.
We predict transverse and longitudinal momentum spectra and yields of rho 0 and omega mesons reconstructed from hadron correlations in C+C reactions at 2~AGeV. The rapidity and pT distributions for reconstructable rho 0 mesons differs strongly from the primary distribution, while the omega's distributions are only weakly modified. We discuss the temporal and spatial distributions of the particles emitted in the hadron channel. Finally, we report on the mass shift of the rho 0 due to its coupling to the N*(1520), which is observable in both the di-lepton and pi pi channel. Our calculations can be tested with the Hades experiment at GSI, Darmstadt.
The D-meson spectral density at finite temperature is obtained within a self-consistent coupled-channel approach. For the bare meson-baryon interaction, a separable potential is taken, whose parameters are fixed by the position and width of the Lambda_c (2593) resonance. The quasiparticle peak stays close to the free D-meson mass, indicating a small change in the effective mass for finite density and temperature. However, the considerable width of the spectral density implies physics beyond the quasiparticle approach. Our results indicate that the medium modifications for the D-mesons in nucleus-nucleus collisions at FAIR (GSI) will be dominantly on the width and not, as previously expected, on the mass.
Results from various theoretical approaches and ideas presented at this exciting meeting (summary talk at the 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP - 2005)) are reviewed. I also point towards future directions, in particular hydrodynamic behaviour induced by jets traveling through the quark-gluon plasma, which might be worth looking at in more detail.
Nuclear collisions at intermediate, relativistic, and ultra-relativistic energies offer unique opportunities to study in detail manifold fragmentation and clustering phenomena in dense nuclear matter. At intermediate energies, the well known processes of nuclear multifragmentation -- the disintegration of bulk nuclear matter in clusters of a wide range of sizes and masses -- allow the study of the critical point of the equation of state of nuclear matter. At very high energies, ultra-relativistic heavy-ion collisions offer a glimpse at the substructure of hadronic matter by crossing the phase boundary to the quark-gluon plasma. The hadronization of the quark-gluon plasma created in the fireball of a ultra-relativistic heavy-ion collision can be considered, again, as a clustering process. We will present two models which allow the simulation of nuclear multifragmentation and the hadronization via the formation of clusters in an interacting gas of quarks, and will discuss the importance of clustering to our understanding of hadronization in ultra-relativistic heavy-ion collisions.
We study Mach shocks generated by fast partonic jets propagating through a deconfined strongly-interacting matter. Our main goal is to take into account different types of collective motion during the formation and evolution of this matter. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies as compared to the case of jet propagation in a static medium. The observed broadening of the near-side two-particle correlations in pseudorapidity space is explained by the Bjorken-like longitudinal expansion. Three-particle correlation measurements are proposed for a more detailed study of the Mach shock waves.
We study the phase diagram of dense, locally neutral three-flavor quark matter within the framework of the Nambu--Jona-Lasinio model. In the analysis, dynamically generated quark masses are taken into account self-consistently. The phase diagram in the plane of temperature and quark chemical potential is presented. The results for two qualitatively different regimes, intermediate and strong diquark coupling strength, are presented. It is shown that the role of gapless phases diminishes with increasing diquark coupling strength.
Within the ADD-model, we elaborate an idea by Vacavant and Hinchliffe and show quantitatively how to determine the fundamental scale of TeV-gravity and the number of compactified extra dimensions from data at LHC. We demonstrate that the ADD-model leads to strong correlations between the missing E_T in gravitons at different center of mass energies. This correlation puts strong constraints on this model for extra dimensions, if probed at sqr s=5.5 TeV and sqrt s=14 TeV at LHC.