A. Jahns

Meson production in pA and AA collisions at AGS energies

Abstract In the framework of the relativistic molecular dynamics approach (RQMD) we study pion and kaon production in the reactions p + Be, p + Au and Si + Au at a beam energy of 14.5 A GeV. In general we find good agreement for various particle yields and their momentum distributions comparing our results with recent experimental data taken at the AGS. In case of the gold target most of the primarily produced particles leave the reaction zone only after multiple interactions with the surrounding medium. For central Si on Au collisions meson and baryon resonance annihilation leads to strong strangeness enrichment. We predict that in effect of the meson cascading roughly half of the final pions are products from delta decays. This can be checked experimentally because of their characteristic momentum distribution.

No transparency in ultrarelativistic nuclear collisions

Abstract Relativistic quantum molecular dynamics (RQMD) simulations of collisions between very massive nuclei predict complete stopping of the baryons at midrapidity. A baryon-free region - as proposed in earlier models - does not form in a beam energy regime up to the highest available energies at the CERN SPS (200 A GeV) and at the future GSI-collider (√ s = 2 × 20 A GeV).

Collective effects and nuclear stopping

One of the most interesting challenges of modern heavy ion physics is the extraction of the equation of state for excited and ultra dense nuclear matter. The temperatures and densities of a possible phase transition to colour deconfinement (quark-gluon plasma) or restored chiral symmetry might, be extracted from observables which are sensitive to collective behaviour. In this paper we give examples for such kind of collective effects and try to point out possible observables for their measurement. We shall focus on:

Antibaryons in massive heavy ion reactions: Importance of potentials

In the framework of relativistic quantum molecular dynamics we investigate antiproton observables in massive heavy ion collisions at alternating-gradient synchrotron 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\ifmmode\bar\else\textasciimacron\fi{} momentum spectra. \textcopyright{} 1996 The American Physical Society.

Antibaryon shadowing in massive Au + Au collisions at 11 AGeV

Abstract Antibaryon production and the strength of annihilation in baryonic matter is studied for massive reactions ( Au + Au ) at the AGS using the microscopic multiple collision approach RQMD.

Physics in the baryon-rich regime☆

Abstract This paper focuses on: • • Explosion of dense matter — expansion, collective motion, cluster formation and their sensitivity on the equation of state • • Formation and observability of anti-matter • • Dileptons, vector mesons and partial symmetry restoration • • Thermal photon spectra • • Formation and observability of baryon-rich, dense strange or (hyper-)matter at collider energies, i. e. at μ init ≈ 0

Is antibaryon annihilation present in pA and AA collisions at 15 A GeV

Abstract Antiproton production and the strength of annihilation in baryonic matter is studied in proton and light ion induced collisions at 15 A GeV on different targets using the microscopic multiple-collision approach RQMD. We predict that annihilation wins over multi-step contributions to the final antiproton yields only in central p collisions on very heavy targets like gold. Central A + A collisions, respectively minimum bias p + A calculations show similar yields as expected from first collisions only, i.e. nearly the same amount of multi-step production and subsequent absorption.

Flavor Flow in Ultrarelativistic Nucleus-Nucleus Collisions: The Rqmd Approach

One of the central goals of today’s nuclear physics is the search for exotic states of strongly interacting matter (e. g. the formation of a quark-gluon plasma). High energetic collisions between two nuclei are the only tool to probe nuclear and quark matter far beyond the nuclear ground state, at densities several times the densities found in the interior of nuclei and at temperatures which were only realized in the universe shortly after the big bang (around 200 MeV). At the high energy laboratories CERN and BNL proton, oxygen and sulphur (CERN-SPS), respectively silicon (BNL-AGS) ions have been accelerated and collided with different targets. The maximum beam energies have been 200 AGeV (at CERN) and 14.5 AGeV (at BNL). Now experiments with truly heavy ion projectiles have just started (with a gold beam at BNL) or are under way (Pb(160 AGeV)+Pb at CERN).