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Phasespace Correlations of Antideuterons in Heavy Ion Collisions (1995)

Marcus Bleicher Christian Spieles André Jahns Raffaele Mattiello Heinz Sorge Horst Stöcker Walter Greiner

In the framework of the relativistic quantum molecular dynamics approach (RQMD) we investigate antideuteron (d) observables in Au+Au collisions at 10.7 AGeV. The impact parameter dependence of the formation ratios d/p2 and d/p2 is calculated. In central collisions, the antideuteron formation ratio is predicted to be two orders of magnitude lower than the deuteron formation ratio. The d yield in central Au+Au collisions is one order of magnitude lower than in Si+Al collisions. In semicentral collisions di erent configuration space distributions of p s and d s lead to a large squeeze out e ect for antideuterons, which is not predicted for the p s.

Antibaryons in massive heavy ion reactions : importance of potentials (1995)

Christian Spieles Marcus Bleicher André Jahns Raffaele Mattiello Heinz Sorge Horst Stöcker Walter Greiner

In the framework of RQMD we investigate antiproton observables in massive heavy ion collisions at AGS energies and compare to preliminary results of the E878 collaboration. We focus here on the considerable influence of the real part of an antinucleon nucleus optical potential on the ¯p momentum spectra. Pacs-numbers: 14.20 Dh, 25.70.-z

Hypermatter : properties and formation in relativistic nuclear collisions (1995)

Lars Gerland Christian Spieles Marcus Bleicher Panajotis Papazoglou Jörg Brachmann Adrian Dumitru Horst Stöcker Walter Greiner Jürgen Schaffner Carsten Greiner

The extension of the Periodic System into hitherto unexplored domains - anti- matter and hypermatter - is discussed. Starting from an analysis of hyperon and single hypernuclear properties we investigate the structure of multi-hyperon objects (MEMOs) using an extended relativistic meson field theory. These are contrasted with multi-strange quark states (strangelets). Their production mechanism is stud- ied for relativistic collisions of heavy ions from present day experiments at AGS and SPS to future opportunities at RHIC and LHC. It is pointed out that abso- lutely stable hypermatter is unlikely to be produced in heavy ion collisions. New attention should be focused on short lived metastable hyperclusters ( / 10 10s) and on intensity interferometry of multi-strange-baryon correlations.

Dynamics of strangeness production and strange matter formation (1996)

Christian Spieles Marcus Bleicher Lars Gerland Horst Stöcker Carsten Greiner

We want to draw the attention to the dynamics of a (finite) hadronizing quark matter drop. Strange and antistrange quarks do not hadronize at the same time for a baryon-rich system1. Both the hadronic and the quark matter phases enter the strange sector fs 6= 0 of the phase diagram almost immediately, which has up to now been neglected in almost all calculations of the time evolution of the system. Therefore it seems questionable, whether final particle yields reflect the actual thermodynamic properties of the system at a certain stage of the evolution. We put special interest on the possible formation of exotic states, namely strangelets (multistrange quark clusters). They may exist as (meta-)stable exotic isomers of nuclear matter 2. It was speculated that strange matter might exist also as metastable exotic multi-strange (baryonic) objects (MEMO s 3). The possible creation in heavy ion collisions of long-lived remnants of the quark-gluon-plasma, cooled and charged up with strangeness by the emission of pions and kaons, was proposed in 1,4,5. Strangelets can serve as signatures for the creation of a quark gluon plasma. Currently, both at the BNL-AGS and at the CERN-SPS experiments are carried out to search for MEMO s and strangelets, e. g. by the E864, E878 and the NA52 collaborations9,

Intermediate mass dileptons from secondary Drell-Yan processes (1998)

Christian Spieles Lars Gerland Nils Hammon Marcus Bleicher Steffen A. Bass Horst Stöcker Walter Greiner C. Lourenco Ramona Vogt

Recent reports on enhancements of intermediate and hight mass muon pairs producedin heavy ion collisions have attracted much attention.

Critical review of quark gluon plasma signatures (1999)

Stefan Scherer Steffen A. Bass Marcus Bleicher Mohamed Belkacem Larissa V. Bravina Jörg Brachmann Adrian Dumitru Christoph Ernst Lars Gerland Markus Hofmann Ludwig Neise Manuel Reiter Sven Soff Christian Spieles Henning Weber Eugene E. Zabrodin Detlef Zschiesche Joachim A. Maruhn Horst Stöcker Walter Greiner

Noneequilibrium models (three-fluid hydrodynamics and UrQMD) use to discuss the uniqueness of often proposed experimental signatures for quark matter formation in relativistic heavy ion collisions. It is demonstrated that these two models - although they do treat the most interesting early phase of the collisions quite differently(thermalizing QGP vs. coherent color fields with virtual particles) - both yields a reasonable agreement with a large variety of the available heavy ion data.

Dissociation rates of J / psi's with comoving mesons : thermal versus nonequilibrium scenario. (1998)

Christian Spieles Ramona Vogt Lars Gerland Steffen A. Bass Marcus Bleicher Horst Stöcker Walter Greiner

We study J/psi dissociation processes in hadronic environments. The validity of a thermal meson gas ansatz is tested by confronting it with an alternative, nonequilibrium scenario. Heavy ion collisions are simulated in the frame- work of the microscopic transport model UrQMD, taking into account the production of charmonium states through hard parton-parton interactions and subsequent rescattering with hadrons. The thermal gas and microscopic transport scenarios are shown to be very dissimilar. Estimates of J/psi survival probabilities based on thermal models of comover interactions in heavy ion collisions are therefore not reliable.

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