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 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
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
resonance, the
distributions descent almost exponentially towards mass values of 2000
MeV/c2. The observed differences between
and
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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