[1] Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA
[2] Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA
[3] Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA
[4] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[5] Univ Calif Santa Cruz, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USA
[6] Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA
[7] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada
[8] Washington Univ, Dept Phys, St Louis, MO 63130 USA
[9] Univ Leeds, Sch Phys & Astron, Leeds LS2 9JT, W Yorkshire, England
[10] Argonne Natl Lab, Argonne, IL 60439 USA
[11] Univ Coll Dublin, Sch Phys, Dublin 4, Ireland
[12] Natl Univ Ireland Univ Coll Galway, Sch Phys, Galway, Ireland
[13] Adler Planetarium & Astron Museum, Dept Astron, Chicago, IL 60605 USA
[14] Univ Utah, Dept Phys & Astron, Salt Lake City, UT 84112 USA
[15] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA
[16] Grinnell Coll, Dept Phys, Grinnell, IA 50112 USA
[17] Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA
[18] Ecole Polytech, CNRS, IN2P3, Lab Leprince Ringuet, F-91128 Palaiseau, France
[19] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA
[20] Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA
[21] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA
[22] Depauw Univ, Dept Phys & Astron, Greencastle, IN 46135 USA
[23] Pittsburg State Univ, Dept Phys, Pittsburg, KS 66762 USA
[24] Anderson Univ, Dept Phys, Anderson, IN 46012 USA
[25] Galway Mayo Inst Technol, Dept Life & Phys Sci, Galway, Ireland
[26] Univ Chicago, Kavli Inst Cosmol Phys, Chicago, IL 60637 USA
[27] Cork Inst Technol, Dept Appl Phys & Instrumentat, Cork, Ireland