[1] NYU, Dept Phys, Ctr Cosmol & Particle Phys, New York, NY 10003 USA
[2] Princeton Univ Observ, Princeton, NJ 08544 USA
[3] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[4] Apache Point Observ, Sunspot, NM 88349 USA
[5] Eotvos Lorand Univ, Dept Phys, H-1518 Budapest, Hungary
[6] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[7] Univ Tokyo, Inst Cosm Ray Res, Midori Ku, Tokyo 1888502, Japan
[8] Univ Chicago, Ctr Astron & Astrophys, Chicago, IL 60637 USA
[9] Univ Sussex, Sussex Astron Ctr, Brighton BN1 9QJ, E Sussex, England
[10] USN Observ, Washington, DC 20392 USA
[11] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[12] Univ Tokyo, Sch Sci, Dept Astron, Tokyo 1130033, Japan
[13] Univ Tokyo, Sch Sci, Res Ctr Early Universe, Tokyo 1130033, Japan
[14] Drexel Univ, Dept Phys, Philadelphia, PA 19104 USA
[15] Ohio State Univ, Dept Astron, Columbus, OH 43210 USA