Theoretical analysis of dilepton spectra in heavy ion collisions at GSI-FAIR energies
This paper addresses the theoretical analysis of dilepton spectra in C+C collisions at GSI-SIS energies. Theoretical predictions for the recent data of the HADES Collaboration at SIS energies are made with the help of a hadron-string transport model, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. A mass shift of the ρ meson due to kinematical effects is discussed.

title: The use of Kolmogorov-Smirnov test in event-by-event analysis
abstract: We propose to use the Kolmogorov-Smirnov test to uncover non-statistical differences between events created in heavy ion collisions within the same centrality class. The advantage of the method over other approaches which are currently in use, is that it is sensitive to any difference between the events and is not restricted to simple moments of the distribution of hadrons. The particular application examined here is the identification of the fireball decay due to spinodal fragmentation and/or sudden rise of the bulk viscosity.

title: THE INTERACTION OF ρ AND K+ MESONS WITH MATTER
abstract: We review in this contribution the information we can obtain from heavy-ion experiments about the interaction of mesons with matter. We demonstrate that the vector mesons seen in experiments come predominantly from low densities. Kaons offer a better opportunity but most of the presently available experimental observables do not allow to analyze separately the three essential unknown quantities: the kaon production cross-section in the medium, the K+N potential interaction at finite densities and temperatures and the kaon (elastic or charge exchange) rescattering cross-section in the medium. We propose a measurement which almost exclusively tests the K+N potential.

title: Elliptic flow fluctuations in heavy ion collisions and the perfect fluid hypothesis
abstract: We analyze the recently measured v2 fluctuation in the context of establishing the degree of fluidity of the matter produced in heavy ion collisions. We argue that flow observables within systems with a non-negligible mean free path should acquire a “dynamical” fluctuation, due to the random nature of each collision between the system’s degrees of freedom. Because of this, v2 fluctuations can be used to estimate the Knudsen number of the system produced at the relativistic heavy ion collider (RHIC). To illustrate this quantitatively, we apply the UrQMD model, with scaled cross sections, to show that collisions at RHIC have a Knudsen number at least one order of magnitude below the expected value for an interacting hadron gas. Furthermore, we argue that the Knudsen number is also bound from below by the v2 fluctuation data, because too small a Knudsen number would break the observed scaling of v2 fluctuations due to the onset of turbulent flow. We propose, therefore that v2 fluctuation measurements, together with an understanding of the turbulent regime for relativistic hydrodynamics, will provide an upper as well as a lower limit for the Knudsen number. We also argue that an energy scan of v2 fluctuations could shed light on the onset of the fluid regime.

title: Resonance Absorption and Regeneration in Relativistic Heavy Ion Collisions
abstract: 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.

title: Production and evolution path of dileptons at energies accessible to the HADES detector
abstract: Dilepton production in intermediate energy nucleus-nucleus collisions as well as in elementary proton-proton reactions is analyzed within the ultrarelativistic quantum molecular dynamics transport model. For C+C collisions at 1A GeV and 2A GeV the resulting invariant mass spectra are compared to recent HADES data. We find that the experimental spectrum for C+C at 2A GeV is slightly overestimated by the theoretical calculations in the region around the vector meson peak but fairly described in the low mass region, where the data are satisfactorily saturated by the Dalitz decay of the {eta} meson and the {delta} resonance. At 1A GeV an underestimation of the experimental data is found, pointing that at lower energies the low-mass region is not fully saturated by standardly parametrized {delta} Dalitz decays alone. Furthermore, predictions for dilepton spectra for pp reactions at 1.25, 2.2, and 3.5 GeV and Ar+KCl reactions at 1.75A GeV are presented. The study is complemented by a detailed investigation of the role of absorption of the parent particles on the corresponding dilepton yields in the regime that has so far been probed by HADES.

title: Coordinated multi-wavelength observations of Sgr A*
abstract: We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the !4" 10 6 M! super-massive black hole (SMBH) at the Galactic Center. The goal of these coordinated multi-wavelength observations is to investigate the variable emission from Sgr A* in order to obtain a better understanding of the underlying physical processes in the accretion flow/outflow. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope (July 2005, May 2007) and the ACIS-I instrument aboard the Chandra X- ray Observatory (July 2005). We report on a polarized NIR flare synchronous to a 8" 10 33 erg/s X-ray flare in July 2005, and a further flare in May 2007 that shows the highest sub-flare to flare contrast observed until now. The observations can be interpreted in the framework of a model involving a temporary disk with a short jet. In the disk component flux density variations can be explained due to hot spots on relativistic orbits around the central SMBH. The variations of the sub-structures of the May 2007 flare are interpreted as a variation of the hot spot structure due to di! erential rotation within the disk.

title: Coordinated mm/sub-mm observations of Sagittarius A* in May 2007
abstract: At the center of the Milky Way, with a distance of ~8 kpc, the compact source Sagittarius A* (SgrA*) can be associated with a super massive black hole of ~4x10^6 solar masses. SgrA* shows strong variability from the radio to the X-ray wavelength domains. Here we report on simultaneous NIR/sub-millimeter/X-ray observations from May 2007 that involved the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope, the Australian Telescope Compact Array (ATCA), the US mm-array CARMA, the IRAM 30m mm-telescope, and other telescopes. We concentrate on the time series of mm/sub-mm data from CARMA, ATCA, and the MAMBO bolometer at the IRAM 30m telescope.

title: Radio Observations of AGN in Low Surface Brightness Galaxies
abstract: We present preliminary results of a study of the low frequency radio continuum emission from the nuclei of Giant Low Surface Brightness (LSB) galaxies. We have mapped the emission and searched for extended features such as radio lobes/jets associated with AGN activity. LSB galaxies are poor in star formation and generally less evolved compared to nearby bright spirals. This paper presents low frequency observations of 3 galaxies; PGC 045080 at 1.4 GHz, 610 MHz, 325MHz, UGC 1922 at 610 MHz and UGC 6614 at 610 MHz. The observations were done with the GMRT. Radio cores as well as extended structures were detected and mapped in all three galaxies; the extended emission may be assocated with jets/lobes associated with AGN activity. Our results indicate that although these galaxies are optically dim, their nuclei can host AGN that are bright in the radio domain.