[1] BROOKHAVEN NATL LAB,UPTON,NY 11973
[2] UNIV CAMBRIDGE,CAVENDISH LAB,CAMBRIDGE,ENGLAND
[3] CERN,EUROPEAN ORG NUCL RES,CH-1211 GENEVA 23,SWITZERLAND
[4] UNIV PERUGIA,DEPT PHYS,I-06100 PERUGIA,ITALY
[5] UNIV PERUGIA,IST NAZL FIS NUCL,I-06100 PERUGIA,ITALY