[1] CERN, Div EP, CH-1211 Geneva 23, Switzerland
[2] Univ Jyvaskyla, Dept Phys, FIN-40351 Jyvaskyla, Finland
[3] Inst Rech Subatom, F-67037 Strasbourg 2, France
[4] Katholieke Univ Leuven, Inst Kern & Stralingsfys, B-3001 Louvain, Belgium
[5] Univ Lyon 1, IN2P3, CNRS, IPN, F-69622 Villeurbanne, France
[6] St Petersburg Nucl Phys Inst, RUS-188350 St Petersburg, Russia
[7] Gesell Schwerionenforsch mbH, D-64291 Darmstadt, Germany