Initial state fluctuations and final state correlations: Status and open questions
The recent appreciation of the importance of event-by-event fluctuations in relativistic heavy-ion collisions has lead to a large amount of diverse theoretical and experimental activity. In particular, there is significant interest in understanding the fluctuations in the initial stage of a collision, how exactly these fluctuations are propagated through the system evolution, and how they are manifested in correlations between measured particles. In order to address these questions a workshop was organized on ‘initial state fluctuations and final state correlations’, held at ECT* in Trento, Italy during the week of 2–6 July 2012. The goal was to collect recent work in order to provide a coherent picture of the current status of our understanding, to identify important questions that remain open, and to set a course for future research. Here we report the outcome of the presentations and discussions, focusing on the most important conclusions.

title: Triangular flow in relativstic heavy ion collisions in an event-by-event hybrid approach
abstract: Triangular flow has been shown to be an interesting new observable to gain insights about the properties of hot and dense strongly interacting matter as it is produced in heavy ion collisions at RHIC and LHC. The potential of triangular flow for constraining the initial state granularity is explored by performing an explicit calculation of the triangularity and the final state anisotropic flow for initial states that exhibit different amounts of fluctuations. We present triangular flow results for Au+Au collisions at the highest RHIC energy calculated in a hybrid approach that includes a non-equilibrium initial evolution and an ideal hydrodynamic expansion with a hadronic afterburner in 3+1 dimensions. Triangular flow results for Pb+Pb collisions at LHC energies employing the same parameters that work at RHIC are compared to ALICE data. In addition, by comparing the hybrid approach calculation with a pure transport approach, the influence of viscosity is studied.

title: Centrality and system size dependence of (multi-strange) hyperons at 40A and 158A GeV: A comparison between a binary collision model and a Boltzmann + hydrodynamic hybrid model
abstract: We present results on the centrality and system size dependence of (multi-strange) hyperons in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $40A$ and $158A$ GeV from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD-v2.3) model and a coupled Boltzmann $+$ hydrodynamics calculation. The second approach is realized in a hybrid fashion based on UrQMD, with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. This implementation allows a comparison of microscopic transport calculations with hydrodynamic simulations to explore the transition from a system that is not fully equilibrated, such as $\mathrm{C}+\mathrm{C}$ or $\mathrm{Si}+\mathrm{Si}$ collisions, to a supposedly fully equilibrated system, such as that created in $\mathrm{Pb}+\mathrm{Pb}$ reactions. The results of our calculations are compared to measurements of the (anti-)hyperon yields at midrapidity ($|y|\ensuremath{\leqslant}0.5$) and total multiplicities performed by the NA49 and NA57 Collaborations at $40A$ and $158A$ GeV. Furthermore, we compare our predictions to the centrality dependence of $\ensuremath{\Lambda},\overline{\ensuremath{\Lambda}}$, and ${\ensuremath{\Xi}}^{\ensuremath{-}}$ rapidity spectra and total multiplicities at $40A$ and $158A$ GeV, where possible.

title: What the collective flow excitation function can tell about the quark–gluon plasma
abstract: Recent STAR data from the RHIC beam energy scan (BES) show that the slope of the net-proton directed flow v 1 at midrapidity changes sign twice within the collision energy range 7.7–39 GeV. To investigate this phenomenon, we study the collision energy dependence of v 1 utilizing a hybrid model which combines Boltzmann transport and hydrodynamic approach. Calculations with dynamically evolved initial and final state show no qualitative difference between an equation of state with a cross-over and one with a first-order phase transition, in contrast to earlier pure fluid predictions. Our analysis of the elliptic flow v 2 shows that pre-equilibrium transport dynamics are partially compensating for the diminishing contribution to the elliptic flow from the hydrodynamical phase at lower energies, which leads to a qualitative agreement with STAR BES results in midcentral collisions. No compensation from transport is found for integrated v 3 , which decreases from ≈0.02 at s N N = 27 GeV to ≈0.005 at s N N = 7.7 GeV in midcentral collisions.

title: Anisotropic flow in transport + hydrodynamics hybrid approaches
abstract: This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and the transition criteria between transport and hydrodynamics are discussed. The results for anisotropic flow in (event-by-event) hybrid approaches are presented. Some hybrid approaches rely on hadronic transport for the late stages for the reaction (so called afterburner) and others employ transport approaches for the early non-equilibrium evolution. In addition, there are ‘full’ hybrid calculations where a fluid evolution is dynamically embedded in a transport simulation. After demonstrating the success of hybrid approaches at high Relativistic Heavy Ion Collider and Large Hadron Collider energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.

title: Initial State Fluctuations and Final State Correlations in Relativistic Heavy-Ion Collisions
abstract: We review the phenomenology and theory of bulk observables in ultra- relativistic heavy-ion collisions, focussing on recent developments involving event-by- event uctuations in the initial stages of a heavy ion collision, and how they manifest in observed correlations. We rst dene the relevant observables and show how each measurement is related to underlying theoretical quantities. Then we review the prevailing picture of the various stages of a collision, including the state-of-the-art modeling of the initial stages of a collision and subsequent hydrodynamic evolution, as well as hadronic scattering and freeze-out in the later stages. We then discuss the recent results that have shaped our current understanding and identify the challenges that remain. Finally, we point out open issues and the potential for progress in the eld.

title: LOST POWER INFLUENCE ON THE SYNCHROTRON ACCELERATING GAP. (IN GERMAN)

title: Damping antennas for spurious RF-modes in electron-positron storage rings
abstract: The maximum beam currents in DORIS were limited mainly by instabilities induced by the rf-cavities. To overcome this difficulty, the higher cavity modes must be damped. Special damping antennas were developed for this purpose.

title: Temperature Dependence of the K Absorption Edge of Lithium
abstract: The shape of the K absorption edge of Li has been measured at 293, 373, 443, and ∼480 K (liquid) by photoyield methods. Unpublished transmission data on the shape of the edge at and below room temperature have been reanalyzed. There is a marked increase of the width of the edge with increasing temperature above 293 K, indicating that the lattice plays a major role in the broadening of the edge.