Affiliation: | (1) Institute for Medium Energy Physics, ETH Zürich, S.I.N., CH-5234 Villigen, Switzerland;(2) Department of Physics, University of British Columbia, V6T2A3 Vancouver, B.C., Canada;(3) H.H. Wells Physical Laboratories, University of Bristol, Bristol, England;(4) Present address: Im Stocker 29, CH-8405 Winterthur, Switzerland |