*Department of Physics, Peking University, Beijing
**Brookhaven National Laboratory, Upton, L. I. , N. Y. 11937, USA
Institute of High Energy Physics, Academia Sinica, Beijing
Cite this article:
CHAO Kuang-ta, CHAU Ling-lie, HUANG Tao et al 1985 Chin. Phys. Lett. 2 117-120