Phys. Rev. Lett.
82,
5194–5197
(1999)
Observation of the East-West Anisotropy of the Atmospheric Neutrino Flux
T. Futagami et al. (Super-Kamiokande Collaboration)
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T. Futagami21, Y. Fukuda1, T. Hayakawa1, K. Inoue1, K. Ishihara1, H. Ishino1, Y. Itow1, T. Kajita1, J. Kameda1, S. Kasuga1, K. Kobayashi1, Y. Kobayashi1, Y. Koshio1, M. Miura1, M. Nakahata1, S. Nakayama1, Y. Obayashi1, A. Okada1, K. Okumura1, N. Sakurai1, M. Shiozawa1, Y. Suzuki1, H. Takeuchi1, Y. Takeuchi1, Y. Totsuka1, S. Yamada1, M. Earl2, A. Habig2, E. Kearns2, M. D. Messier2, K. Scholberg2, J. L. Stone2, L. R. Sulak2, C. W. Walter2, M. Goldhaber3, T. Barszczak4, D. Casper4, W. Gajewski4, W. R. Kropp4, S. Mine4, L. R. Price4, M. Smy4, H. W. Sobel4, M. R. Vagins4, K. S. Ganezer5, W. E. Keig5, R. W. Ellsworth6, S. Tasaka7, A. Kibayashi8, J. G. Learned8, S. Matsuno8, V. J. Stenger8, D. Takemori8, T. Ishii9, J. Kanzaki9, T. Kobayashi9, K. Nakamura9, K. Nishikawa9, Y. Oyama9, A. Sakai9, M. Sakuda9, O. Sasaki9, S. Echigo10, M. Kohama10, A. T. Suzuki10, T. J. Haines11,4, E. Blaufuss12, B. K. Kim12, R. Sanford12, R. Svoboda12, M. L. Chen13, J. A. Goodman13, G. W. Sullivan13, J. Hill14, C. K. Jung14, K. Martens14, C. Mauger14, C. McGrew14, E. Sharkey14, B. Viren14, C. Yanagisawa14, W. Doki15, M. Kirisawa15, S. Inaba15, K. Miyano15, H. Okazawa15, C. Saji15, M. Takahashi15, M. Takahata15, K. Higuchi16, Y. Nagashima16, M. Takita16, T. Yamaguchi16, M. Yoshida16, S. B. Kim17, M. Etoh18, A. Hasegawa18, T. Hasegawa18, S. Hatakeyama18, T. Iwamoto18, M. Koga18, T. Maruyama18, H. Ogawa18, J. Shirai18, A. Suzuki18, F. Tsushima18, M. Koshiba19, Y. Hatakeyama20, M. Koike20, M. Nemoto20, K. Nishijima20, H. Fujiyasu21, Y. Hayato21, Y. Kanaya21, K. Kaneyuki21, Y. Watanabe21, D. Kielczewska22,4, J. S. George23,*, A. L. Stachyra23, L. L. Wai23,†, R. J. Wilkes23, and K. K. Young23,‡ (Super-Kamiokande Collaboration)
1Institute for Cosmic Ray Research, University of Tokyo, Tanashi, Tokyo 188-8502, Japan
2Department of Physics, Boston University, Boston, Massachusetts 02215
3Physics Department, Brookhaven National Laboratory, Upton, New York 11973
4Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575
5Department of Physics, California State University, Dominguez Hills, Carson, California 90747
6Department of Physics, George Mason University, Fairfax, Virginia 22030
7Department of Physics, Gifu University, Gifu, Gifu 501-1193, Japan
8Department of Physics and Astronomy, University of Hawaii, Honolulu, Hawaii 96822
9Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
10Department of Physics, Kobe University, Kobe, Hyogo 657-8501, Japan
11Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87544
12Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803
13Department of Physics, University of Maryland, College Park, Maryland 20742
14Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3800
15Department of Physics, Niigata University, Niigata, Niigata 950-2181, Japan
16Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
17Department of Physics, Seoul National University, Seoul 151-742, Korea
18Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan
19The University of Tokyo, Tokyo 113-0033, Japan
20Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan
21Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
22Institute of Experimental Physics, Warsaw University, 00-681 Warsaw, Poland
23Department of Physics, University of Washington, Seattle, Washington 98195-1560
Received 13 January 1999; published in the issue dated 28 June 1999
The east-west anisotropy, caused by the deflection of primary cosmic rays in the Earth's magnetic field, is observed for the first time in the flux of atmospheric neutrinos. Using a 45 kt yr exposure of the Super-Kamiokande detector, 552 e-like and 633 μ-like horizontally going events are selected in the momentum range between 400 and 3000 MeV/c. The azimuthal distributions of e-like and μ-like events agree with the expectation from atmospheric neutrino flux calculations, verifying that the flux of atmospheric neutrinos in the GeV energy range is reasonably well modeled by calculations that account for the geomagnetic field.
© 1999 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.82.5194
DOI:
10.1103/PhysRevLett.82.5194
PACS:
96.40.Tv, 14.60.Pq, 95.85.Ry
*Present address: Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125. †Present address: Department of Physics, Stanford University, Stanford, CA 94305. ‡Deceased.
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