Longitudinal flow and onset of deconfinement

The effects of the onset of deconfinement on longitudinal and transverse flow are studied. First, we analyze longitudinal pion spectra from $E_{\rm lab}= 2A$ GeV to $\sqrt{s_{\rm NN}}=200$ GeV within Landau's hydrodynamical model and the UrQMD transport approach. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity $c_s^2$ 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 $E_{\rm beam}=30A$ GeV. This softening of the EoS is compatible with the assumption of the formation of a mixed phase at the onset of deconfinement. Furthermore, the energy excitation function of elliptic flow ($v_2$) from $E_{\rm beam}=90A$ MeV to $\sqrt{s_{\rm NN}}=200$ GeV is explored within the UrQMD framework and discussed in the context of the available data. The transverse flow should also be sensitive to changes in the equation of state. Therefore, the underestimation of elliptic flow by the UrQMD model calculation above $E_{\rm lab}= 30A$ GeV might also be explained by assuming a phase transition from a hadron gas to the quark gluon plasma around this energy. This would be consistent with the model calculations, indicating a transition from hadronic matter to ``string matter'' in this energy range.Comment: Proceedings of the 3rd International Workshop The Critical Point and Onset of Deconfinement, Firenze, Ital

How to Create Black Holes on Earth?

We present a short overview on the ideas of large extra-dimensions and their implications for the possible production of micro black holes in the next generation particle accelerator at CERN (Geneva, Switzerland) from this year on. In fact, the possibility of black hole production on earth is currently one of the most exciting predictions for the LHC accelerator and would change our current understanding of physics radically. While it is impossible to discuss the models and implications in full detail here, this article is thought to serve as a starting point for the interested physics students with some basic knowledge about general relativity and particle physics.Comment: Published versio

Evidence for the Onset of Deconfinement from Longitudinal Momentum Distributions? Observation of the Softest Point of the Equation of State

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.Comment: 3 pages, 2 figure

Probing hadronization and freeze-out with multiple strange hadrons and strange resonances

The production of multiple strange baryons in pp interactions is studied. Here one can directly probe the microscopic decay of color flux tubes, allowing to differentiate between different string models and a statistical description of the hadronization. To analyse the different stages of a heavy ion collision the time evolution of the elastic and inelastic collision rates in central Pb+Pb interactions are studied. The microscopic simulation supports the idea of separated phases (non-equilibrium -> chemical freeze-out -> kinetic freeze-out) in the evolution of the system. The spectra and abundances of Lambda(1520), K 0(892) and other resonances are used to study the break-up dynamics of the source between chemical and thermal freeze-out

Excitation Function of the Longitudinal Expansion in Central Nuclear Collisions

Longitudinal hadron spectra from Proton-Proton (pp) and nucleus-nucleus (AA) collisions from $E_{lab}= 2$ AGeV to $\sqrt s=200$ AGeV are investigated. The widths of the rapidity spectra for various particle species increases monotonously with energy. The present calculation indicates no sign of a step like behaviour as excepted from the Kaon transverse mass systematics. For Pions, the transport simulation is consistent with a Landau type scaling of the rapidity widths, both in central AA reactions and in pp collisions. However, other hadron species do not follow the Landau scaling. The present model predicts a decreasing rapidity width with particle mass for newly produced particles, not supporting a Landau type flow interpretation.Comment: Proceedings of the ICPAQGP 0

No Black Holes at IceCube

We discuss modifications of the neutrino-nucleon cross section due to a minimal length scale. It is shown that the enhancement of the nu-N cross section due to new physics is suppressed. Especially the potential observation rate of micro black holes at neutrino telescopes is strongly reduced.Comment: 10 pages, 5 figures, submitted to Journal of Cosmology and Astroparticle Physic

No black holes at IceCube

We discuss modifications of the neutrino-nucleon cross section due to a minimal length scale. It is shown that the enhancement of the nu-N cross section due to new physics is suppressed. Especially the potential observation rate of micro black holes at neutrino telescopes is strongly reduced