[1] Lawrence Livermore Natl Lab, POB 808,L-414, Livermore, CA 94551 USA
[2] Univ Paris 11, IN2P3, CNRS, Inst Phys Nucl, F-91406 Orsay, France
[3] TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada
[4] Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany