1. L3P institutions: I. Physikalisches Institut, RWTH, D-5100 Aachen, Germany.
2. Laboratoire de Physique et Particules, LAPP, F-74519 Annecy-leVieux, France.
3. John Hopkins University, Baltimore, MD 21218, USA.
4. University of Basel, CH-4056 Basel, Switzerland.
5. Institute of High Energy Physics, IHEP, Beijing, P.R. China.