Affiliation: | a National Laboratory for High Energy Physics, 1-1 Oho, Tsukuba-shi, Ibaraki 305, Japan b Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachiohji-shi, Tokyo 102-03, Japan c Seiko Instruments Inc., 563, Takatsuka-shinden, Matsudo-shi, Chiba 271, Japan |