[1] Univ Utah, Dept Phys & Astron, Salt Lake City, UT USA
[2] Univ Nacl Autonoma Mexico, Inst Fis, Mexico City, DF, Mexico
[3] Univ Autonoma Chiapas, Tuxtla Gutierrez, Chiapas, Mexico
[4] Univ Michoacana, Morelia, Michoacan, Mexico
[5] Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA
[6] Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA
[7] Inst Nacl Astrofis Opt & Electr, Puebla, Mexico
[8] Polish Acad Sci, Inst Nucl Phys, IFJ PAN, PL-31342 Krakow, Poland
[9] Benemerita Univ Autonoma Puebla, Fac Ciencias Fis Matemat, Puebla, Mexico
[10] Univ Guadalajara, Dept Fis, Ctr Univ Valles, Guadalajara, Mexico
[11] Univ Wisconsin, Dept Phys, 1150 Univ Ave, Madison, WI 53706 USA
[12] Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA
[13] Univ Guadalajara, Dept Fis, Ctr Univ Ciencias Exactase Ingn, Guadalajara, Mexico
[14] Univ Nacl Autonoma Mexico, Inst Astron, Mexico City, DF, Mexico
[15] Univ Maryland, Dept Phys, College Pk, MD 20742 USA
[16] Univ Libre Bruxelles, Interuniv Inst High Energies, Brussels, Belgium
[17] Los Alamos Natl Lab, Div Phys, Los Alamos, NM USA
[18] Max Planck Inst Nucl Phys, D-69117 Heidelberg, Germany
[19] Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City, DF, Mexico
[20] Univ Politecn Pachuca, Pachuca, Hgo, Mexico
[21] Penn State Univ, Dept Phys, 104 Davey Lab, University Pk, PA 16802 USA
[22] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[23] Inst Politecn Nacl, Ctr Invest Computac, Mexico City, DF, Mexico
[24] Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA
[25] Univ Autonoma Estado Hidalgo, Pachuca, Mexico
[26] Univ Nacl Autonoma Mexico, Inst Ciencias Nucl, Mexico City, DF, Mexico
[27] Georgia Inst Technol, Sch Phys, Atlanta, GA 30332 USA
[28] Georgia Inst Technol, Ctr Relativist Astrophys, Atlanta, GA 30332 USA
[29] IPN, Ctr Invest & Estudios Avanzados, Dept Phys, Mexico City, DF, Mexico
[30] Univ Canterbury, Dept Phys & Astron, Private Bag 4800, Christchurch, New Zealand
[31] DESY, D-15738 Zeuthen, Germany
[32] Univ Libre Bruxelles, Fac Sci, CP230, B-1050 Brussels, Belgium
[33] Univ Copenhagen, Niels Bohr Inst, DK-2100 Copenhagen, Denmark
[34] Stockholm Univ, Oskar Klein Ctr, SE-10691 Stockholm, Sweden
[35] Stockholm Univ, Dept Phys, SE-10691 Stockholm, Sweden
[36] Friedrich Alexander Univ Erlangen Nurnberg, Erlangen Ctr Astroparticle Phys, D-91058 Erlangen, Germany
[37] Marquette Univ, Dept Phys, Milwaukee, WI 53201 USA
[38] MIT, Dept Phys, Cambridge, MA 02139 USA
[39] Rhein Westfal TH Aachen, Inst Phys 3, D-52056 Aachen, Germany
[40] South Dakota Sch Mines & Technol, Dept Phys, Rapid City, SD 57701 USA
[41] Univ Geneva, Dept Phys Nucl & Corpusculaire, CH-1211 Geneva, Switzerland
[42] Univ Alberta, Dept Phys, Edmonton, AB T6G 2E1, Canada
[43] Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA
[44] Johannes Gutenberg Univ Mainz, Inst Phys, Staudinger Weg 7, D-55099 Mainz, Germany
[45] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[46] Ohio State Univ, Dept Phys, 174 W 18th Ave, Columbus, OH 43210 USA
[47] Ohio State Univ, Ctr Cosmol & Astroparticle Phys, 174 W 18th Ave, Columbus, OH 43210 USA
[48] Ohio State Univ, Dept Astron, 174 W 18Th Ave, Columbus, OH 43210 USA
[49] Ruhr Univ Bochum, Fak Phys & Astron, D-44780 Bochum, Germany
[50] Univ Wuppertal, Dept Phys, D-42119 Wuppertal, Germany