[1] Univ Edinburgh, Dept Phys & Astron, Edinburgh EH9 3JZ, Midlothian, Scotland
[2] Columbia Univ, Dept Phys, New York, NY 10027 USA
[3] IBM Corp, Thomas J Watson Res Ctr, Yorktown Hts, NY 10598 USA
[4] KEK, Inst Particle & Nuc Studies, Tsukuba, Ibaraki 3050801, Japan
[5] Brookhaven Natl Lab, RIKEN BNL Res Ctr, Upton, NY 11973 USA
[6] Yale Univ, Dept Phys, New Haven, CT 06520 USA