Affiliation: | a The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan b Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033, Japan c Department of Physics and Astronomy, California State University, Northridge, CA 91330, and W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125, USA |