[1] Columbia Univ, Dept Phys, New York, NY 10027 USA
[2] INFN Sez Perugia, Perugia, Italy
[3] INFN Napoli, Naples, Italy
[4] Harvard Smithsonian, Ctr Astrophys, Cambridge, MA 02138 USA
[5] Univ Perugia, Perugia, Italy
[6] Univ Politecn Bari, Dipartimento Interateneo Fis, Bari, Italy
[7] INFN Bari, Via E Orabona 4, I-70125 Bari, Italy
[8] INFN Sez Pisa, Pisa, Italy
[9] Washington Univ, Dept Phys, St Louis, MO 63130 USA
[10] Case Western Reserve Univ, Dept Phys, Cleveland, OH 44106 USA
[11] Columbia Univ, Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA
[12] Georgia Inst Technol, Sch Phys, 837 State St NW, Atlanta, GA 30332 USA
[13] Georgia Inst Technol, Ctr Relativist Astrophys, 837 State St NW, Atlanta, GA 30332 USA
[14] Univ Calif Santa Cruz, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USA
[15] Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA
[16] Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA
[17] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA
[18] Univ Utah, Dept Phys & Astron, Salt Lake City, UT 84112 USA
[19] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA USA
[20] Univ Wisconsin, Dept Phys, Madison, WI 53706 USA
[21] Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA
[22] Nagoya Univ, Inst Space Earth Environm Res, Nagoya, Aichi 4648601, Japan
[23] Nagoya Univ, Kobayashi Maskawa Inst Origin Particles & Univ, Nagoya, Aichi 4648601, Japan
[24] Univ Siena, Dipartimento Sci Fis Terra Ambiente, Siena, Italy
[25] CNR, ISASI, Rome, Italy
[26] ASI Italian Space Agcy, Sci Res Unit, I-00133 Rome, Italy