2020 Impact factor 3.043
Hadrons and Nuclei
Eur. Phys. J. A 3, 335-349

FOPI Collaboration

Identification of baryon resonances in central heavy-ion collisions at energies between 1 and 2 AGeV

M. Eskef6 - D. Pelte6 - G. Goebels6 - E. Häfele6 - N. Herrmann4,6 - M. Korolija6,12 - Y. Leifels4,6 - H. Merlitz4,6 - S. Mohren6 - M.R. Stockmeier6 - M. Trzaska6 - J.P. Alard3 - A. Andronic1 - R. Averbeck4 - Z. Basrak12 - N. Bastid3 - I. Belyaev7 - D. Best4 - A. Buta1 - R. Caplar12 - N. Cindro12 - J.P. Coffin10 - P. Crochet4,10 - P. Dupieux3 - M. Dzelalija12 - L. Fraysse3 - Z. Fodor2 - A. Genoux-Lubain3 - A. Gobbi4 - K.D. Hildenbrand4 - B. Hong9 - F. Jundt10 - J. Kecskemeti2 - M. Kirejczyk4,11 - R. Kotte5 - R. Kutsche4 - A. Lebedev7 - V. Manko8 - J. Mösner5 - D. Moisa1 - W. Neubert5 - M. Petrovici1 - C. Pinkenburg4 - C. Plettner5 - P. Pras3 - F. Rami10 - V. Ramillien3 - W. Reisdorf4 - J.L. Ritman4 - B. de Schauenburg10 - D. Schüll4 - Z. Seres2 - B. Sikora11 - V. Simion1 - K. Siwek-Wilczynska11 - V. Smolyankin7 - M.A. Vasiliev8 - P. Wagner10 - G.S. Wang4 - K. Wisniewski4,11 - D. Wohlfarth5 - A. Zhilin7

1 National Institute for Physics and Nuclear Engineering, Bucharest, Romania
2 Central Research Institute for Physics, Budapest, Hungary
3 Laboratoire de Physique Corpusculaire, IN2P3/CNRS, and Université Blaise Pascal, Clermont-Ferrand, France
4 Gesellschaft für Schwerionenforschung, Darmstadt, Germany
5 Forschungszentrum Rossendorf, Dresden, Germany
6 Physikalisches Institut der Universität Heidelberg, Heidelberg, Germany
7 Institute for Theoretical and Experimental Physics, Moscow, Russia
8 Kurchatov Institute, Moscow, Russia
9 Korea University, Seoul, Korea
10 Institut de Recherches Subatomiques, IN2P3/CNRS, and Université Louis Pasteur, Strasbourg, France
11 Institute of Experimental Physics, Warsaw University, Poland
12 Rudjer Boskovic Institute, Zagreb, Croatia

Received: 26 June 1998 / Revised version: 2 September 1998 Communicated by V. Metag

Abstract
The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by defolding the $p_{\rm t}$spectra of charged pions by a method which does not depend on a specific resonance shape. In addition the mass distributions of resonances are obtained from the invariant masses of $(p, \pi^{\pm})$ pairs. With both methods the deduced mass distributions are shifted by an average value of -60 MeV/c2 relative to the mass distribution of the free $\Delta(1232)$ resonance, the distributions descent almost exponentially towards mass values of 2000 MeV/c2. The observed differences between $(p, \pi^-)$ and $(p, \pi^+)$pairs indicate a contribution of isospin I = 1/2 resonances. The attempt to consistently describe the deduced mass distributions and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e. to rather low temperatures and large expansion velocities.

PACS
25.75.-q Relativistic heavy-ion collisions - 14.20.Gk Baryon resonances with S=0


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