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Institute
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.
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 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.
Trapping black hole remnants
(2005)
Large extra dimensions lower the Planck scale to values soon accessible. The production of TeV mass black holes at the LHC is one of the most exciting predictions. However, the final phases of the black hole's evaporation are still unknown and there are strong indications that a black hole remnant can be left. Since a certain fraction of such objects would be electrically charged, we argue that they can be trapped. In this paper, we examine the occurrence of such charged black hole remnants. These trapped remnants are of high interest, as they could be used to closely investigate the evaporation characteristics. Due to the absence of background from the collision region and the controlled initial state, the signal would be very clear. This would allow to extract information about the late stages of the evaporation process with high precision.
The recently proposed baryon-strangeness correlation (C_BS) is studied with a string-hadronic transport model (UrQMD) for various energies from E_lab=4 AGeV to \sqrt s=200 AGeV. It is shown that rescattering among secondaries can not mimic the predicted correlation pattern expected for a Quark-Gluon-Plasma. However, we find a strong increase of the C_BS correlation function with decreasing collision energy both for pp and Au+Au/Pb+Pb reactions. For Au+Au reactions at the top RHIC energy (\sqrt s=200 AGeV), the C_BS correlation is constant for all centralities and compatible with the pp result. With increasing width of the rapidity window, C_BS follows roughly the shape of the baryon rapidity distribution. We suggest to study the energy and centrality dependence of C_BS which allow to gain information on the onset of the deconfinement transition in temperature and volume.
We analyze longitudinal pion spectra from E_lab= 2AGeV to sqrt s_NN=200GeV within Landau's hydrodynamical model. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity c_s in the early stage of the reactions. It is found that the sound velocity has a local minimum (indicating a softest point in the equation of state, EoS) at E_beam=30AGeV. This softening of the EoS is compatible with the assumption of the formation of a mixed phase at the onset of deconfinement.
We investigate the sensitivity of several observables to the density dependence of the symmetry potential within the microscopic transport model UrQMD (ultrarelativistic quantum molecular dynamics model). The same systems are used to probe the symmetry potential at both low and high densities. The influence of the symmetry potentials on the yields of pi-, pi+, the pi-/pi+ ratio, the n/p ratio of free nucleons and the t/3He ratio are studied for neutron-rich heavy ion collisions (208Pb+208Pb, 132Sn+124Sn, 96Zr+96Zr) at E_b=0.4A GeV. We find that these multiple probes provides comprehensive information on the density dependence of the symmetry potential.