Antibaryons in massive heavy ion reactions: Importance of potentials

Abstract

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 thep momentum spectra.PACS numbers: 14.20 Dh, 25.70.-z Antibaryon production is a promising observable for collective effects in nucleus-nucleus collisions. On the other hand, N 's suffer strong final-state interactions. These interactions have two components which can be related to the N self-energy in matter: collisions and annihilation on baryons[1] (imaginary part, semiclassically given by 2ImV = σvρ) and a piece in the real part (ReV = t NN ρ in the impuls approximation). In the semiclassical limit the real part of the self-energy can be approximated by potential-type interaction[2] or a mean field. Here we will focus on the effect of the real part. The motivation is that the long-range force of baryons acting on ap is expected to be stronger than for protons since the Lorentz-scalar and the Lorentz-vector parts of a meson exchange potential now have the same sign. The influence of baryonic mean-fields on baryons and mesons is well established. Therefore there should also be some influence onp's. The substantial impact of mean-fields on particle spectra was studied earlier [3,4]. Following these ideas, we now investigate observables in nucleus-nucleus collisions, where BB-potentials come into play. For this purpose, we employed a simple modelinteraction, knowing that this choice is far from being unique. In principle, one has to calculate the medium-dependent mean-field and the crosssection selfconsistently to understand N behaviour in matter. We calculate the forces acting on a N in a baryonic medium only after freeze-out. However, by taking the free interaction -annihilation, elastic scattering, non-annihilating inelastic channels -for NN in the collision term during the dynamical evolution the real potential is included effectively. Our approach is similar in its spirit to the usual treatment of the Coulomb distortion of particle spectra which is also restricted to final-state interactions [5]. Addition of free interactions and mean-field contribution would cause 1

Beaviset al.Reply

“…They also add useful plots presenting the "pure production" and the "no shielding" results of the ARC model. Similar calculations using the RQMD model were published several years ago [3,4].We are delighted to see that our data have prompted the authors of the ARC and RQMD models to refine their calculations to better describe our results [2,5]. We note that it is still possible to use very different theoretical approaches to produce results which now agree with our measurements made at low transverse momenta.…”

Strange Hadrons Bridge Between Quarks and Stars

“…Other analyses favor shallow real and deep imaginary potentials 48 . More recent analyses of the production of antiprotons in reactions with heavy ions resulted in real attractive potentials in the range of 100 to 150 MeV 51,52,53 .…”

Exploring the nuclear potential of antihyperons with antiprotons at ${\overline{\rm\bf P}}{\rm\bf ANDA}$

“…Later, X-ray transitions in antiprotonic atoms [6][7][8][9][10] gave also hints for an attractive potential albeit with large uncertainties [11,12]. More comprehensive studies [13] of antiprotonic X-rays as well as recent analyses of the production of antiprotons in reactions with heavy ions resulted in attractive real potentials in the range of about −100 to −150 MeV [14][15][16]. It is obvious that G-parity can only provide a link between the NN and Supported from the Bundesministerium für Bildung und Forschung (bmb+f) under contract number 06MZ225I and at Mainz bei the Sonderforschungsbereich 443 of the Deutsche Forschungsgemeinschaft.…”