Multistep Production of h and Hard p0 Mesons in Subthreshold Au-Au Collisions

J. Weiß, 1 H. W. Wilschut,7 F. Wissmann, 2 and M. Wolf1 1II. Physikalisches Institut, Universität Gießen, D-35392 Gießen, Germany 2Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany 3Grand Accélérateur National d’Ions Lourds, F-14021 Caen Cedex, France 4Instituto de Fı ́sica Corpuscular, Centro Mixto Universidad de Valencia–CSIC, E-46100 Burjassot, Spain 5Institut für Kernphysik, Universität Frankfurt, D-60486 Frankfurt am Main, Germany 6Nuclear Physics Institute, CZ-25068̌ Rež, Czech Republic 7Kernfysisch Versneller Instituut, NL-9747 AA Groningen, The Netherlands (Received 22 January 1998 ) The neutralp0 and h mesons are studied in197Au-197Au collisions at an incident energy of 800A MeV, substantially below the threshold for h production inN-N collisions. While the gross p0 multiplicity increases almost linearly with the number of participant nucleons, the multiplicities of h and hardp0 mesons show a stronger than linear dependence. The nonlinearity is governed by the average transverse-mass excess kmtl 2 s p s 2 2mN d of the mesons and is insensitive to their final-state interaction in the nuclear medium. [S0031-9007(98)06389-3]