[1] TH AACHEN, 3 PHYS INST, AACHEN, WEST GERMANY
[2] VUB, ULB, INTERUNIV INST HIGH ENERGIES, BRUSSELS, BELGIUM
[3] CERN, GENEVA, SWITZERLAND
[4] ECOLE POLYTECH PARIS, LAB PHYS NUCL HAUT ENERGIES, PARIS, FRANCE
[5] UNIV MILAN, IST FIS, MILAN, ITALY
[6] LAB ACCELERATEUR LINEAIRE, ORSAY, FRANCE
[7] UCL, LONDON, ENGLAND
[8] INFN, MILAN, ITALY