Observations and implications of the ultrahigh-energy cosmic rays

M. Nagano; A. A. Watson

doi:10.1103/RevModPhys.72.689

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Observations and implications of the ultrahigh-energy cosmic rays

M. Nagano and A. A. Watson

M. Nagano

Department of Applied Physics and Chemistry, Fukui University of Technology, Fukui 910-8505, Japan

A. A. Watson

Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom

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Rev. Mod. Phys. 72, 689 – Published 1 July, 2000

DOI: https://doi.org/10.1103/RevModPhys.72.689

Abstract

The authors define “ultrahigh-energy cosmic rays” (UHECRs) as those cosmic rays with energies above $10^{18} eV .$ It had been anticipated that there would be a cutoff in the energy spectrum of primary cosmic rays around $6 \times 10^{19} eV$ induced by the interaction of the particles with the 2.7-K primordial photons. However, recent experimental data have established that particles exist with energies greatly exceeding this. It follows that the sources of such particles are probably nearby, on a cosmological scale. However, although the trajectories of such energetic particles through the galactic and intergalactic magnetic fields may be nearly rectilinear, no astronomical sources have as yet been identified. This is the enigma of the highest-energy cosmic rays. The paper reviews the history of research in this energy regime and critically assesses the observational results on the energy spectrum, arrival directions, and composition of the primary cosmic rays based on observations made by six experiments. The detection methods currently available are described. Special techniques have been developed as particles of $10^{20} eV$ or higher occur at a rate of only about 1 per ${km}^{2}$ per century. Errors in measurement are given particular attention. The authors also review the theoretical predictions for a number of candidate sources of cosmic rays beyond the predicted cutoff. Finally, the four major projects planned to address the question of the origin of UHECRs are briefly described.

References (288)

Abu-Zayyad, T., et al., 2000, Phys. Rev. Lett. 84, 4276.
Afanasiev, B. N., et al., 1993, in Proceedings of the Tokyo Workshop on Techniques for the Study of the Extremely High Energy Cosmic Rays, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 35.
Afanasiev, B. N., et al., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 32.
Aglietta, M., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 6, p. 37.
Aharonian, F. A., B. L. Kanevsky, and V. A. Sahakian, 1991, J. Phys. G 17, 1909.
Al-Dargazelli, S. S., A. W. Wolfendale, A. Smialkowsk, and J. Wdowczyk, 1996, J. Phys. G 22, 1825.
Amenomori, M., et al., 1996a, Astrophys. J. 461, 408.
Amenomori, M., et al., 1996b, Astron. Astrophys. 311, 919.
Andrews, D., D. M. Edge, A. C. Evans, R. J. O. Reid, R. M. Tennent, A. A. Watson, J. G. Wilson, and A. M. Wray, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 3, p. 995.
Andrews, D., A. C. Evans, R. R. Hughes, D. J. Marsden, R. J. O. Reid, I. Smolko, R. M. Tennent, A. A. Watson, J. G. Wilson, and A. M. Wray, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 337.
Asakimori, K., et al., 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 25.
Auger, P., P. Ehrenfest, Jr., R. Maze, J. Daudin, C. Robley, and A. Fréon, 1939, Rev. Mod. Phys. 11, 288.
Auger, P., R. Maze, and T. Grivet-Meyer, 1938, Académie des Sciences, Paris, 206, 1721.
Axford, W. I., 1994, Astrophys. J., Suppl. Ser. 90, 937.
Baltrusaitis, R. M., R. Cady, et al., 1985a, Nucl. Instrum. Methods Phys. Res. A 240, 410.
Baltrusaitis, R. M., R. Cady, et al., 1985b, Phys. Rev. Lett. 54, 1875.
Baltrusaitis, R. M., G. L. Cassiday, J. W. Elbert, P. R. Gerhardy, S. Ko, E. C. Loh, Y. Mizumoto, P. Sokolsky, and D. Steck, 1984, Phys. Rev. Lett. 52, 1380.
Baltrusaitis, R. M., G. L. Cassiday, J. W. Elbert, P. R. Gerhardy, E. C. Loh, Y. Mizumoto, P. Sokolsky, and D. Steck, 1985, Phys. Rev. D 31, 2192.
Barshay, S., and G. Kreyerhoff, 1998a, Eur. Phys. J. C 5, 369.
Barshay, S., and G. Kreyerhoff, 1999, Nuovo Cimento A 112, 1463.
Bassi, P., G. Clark, and B. Rossi, 1953, Phys. Rev. 92, 441.
Bell, C. J., et al., 1974, J. Phys. A 7, 990.
Benakli, K., J. Ellis, and D. V. Nanopoulos, 1999, Phys. Rev. D 59, 047301.
Benson, A., A. Smialkowski, and A. W. Wolfendale, 1999, Astropart. Phys. 10, 313.
Berezinsky, V. S., 1988, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 279.
Berezinsky, V. S., 1999, Nucl. Phys. B (Proc. Suppl.) 70, 419.
Berezinsky, V. S., S. V. Bulanov, V. A. Dogiel, V. L. Ginzburg, and V. S. Ptuskin, 1990, Astrophysics of Cosmic Rays (North-Holland, Amsterdam/New York).
Berezinsky, V. S. and S. I. Grigor’eva, 1988, Astron. Astrophys. 199, 1.
Berezinsky, V. S., S. I. Grigor’eva, A. A. Mikhailov, H. Rubinstein, A. A. Ruzmaikin, D. D. Sokoloff, and A. M. Shukurov, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 134.
Berezinsky, V. S., M. Kachelriess, and A. Vilenkin, 1997, Phys. Rev. Lett. 79, 4302.
Berezinsky, V. S., and A. A. Mikhailov, 1999, Phys. Lett. B 449, 237.
Berezinsky, V. S. and G. T. Zatsepin, 1969, Phys. Lett. 28B, 423.
Bergeson, H. E., G. L. Cassiday, T. W. Chiu, D. A. Cooper, J. W. Elbert, E. C. Loh, D. Steck, W. J. West, J. Boone, and J. Linsley, 1977, Phys. Rev. Lett. 39, 847.
Bhattacharjee, P., 1997, Proceedings of ICRR Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 125.
Bhattacharjee, P., and G. Sigl, 2000, Phys. Rep. 327, 110.
Biermann, P. L., 1997, J. Phys. G 23, 1.
Biermann, P. L., and P. A. Streitmatter, 1987, Astrophys. J. 322, 643.
Bird, D., et al., 1993, Phys. Rev. Lett. 71, 3401.
Bird, D., et al., 1994a, Nucl. Instrum. Methods Phys. Res. A 349, 592.
Bird, D., et al., 1994b, Astrophys. J. 424, 491.
Bird, D., et al., 1995, Astrophys. J. 441, 144.
Bird, D., et al., 1999, Astrophys. J. 511, 739.
Birkel, M., and S. Sarkar, 1998, Astropart. Phys. 9, 297.
Blanco-Pillado, J. J., R. A. Vázquez, and E. Zas, 2000, Phys. Rev. D 61, 123003.
Blandford, R. D., 1999, in Proceedings of the Nobel Symposium on Particle Physics and the Universe, Stockholm 2000, Phys. Scr. T85.
Blumenthal, G. R., 1970, Phys. Rev. D 1, 1596.
Boldt, E., and P. Ghosh, 1999, Mon. Not. R. Astron. Soc. 307, 491.
Bonazzola, S., and P. Peters, 1997, Astropart. Phys. 7, 161.
Boothby, K., M. Chantell, K. D. Green, D. B. Kieda, J. Knapp, C. G. Larsen, and S. P. Swordy, 1997, Astrophys. J. Lett. 491, L35.
Bower, A. J., G. Brooke, D. Pearce, J. C. Perrett, and A. A. Watson, 1983, J. Phys. G 9, 1569.
Bower, A. J., G. Cunningham, J. Linsley, R. J. O. Reid, and A. A. Watson, 1983, J. Phys. G 9, L53.
Bunner, A. N., 1964, Ph.D. thesis (Cornell University).
Capdevielle, J. N., 1989, J. Phys. G 15, 909.
Capelle, K. J., J. W. Cronin, G. Parente, and E. Zas, 1998, Astropart. Phys. 8, 321.
Cassiday, G. L., et al., 1989, Phys. Rev. Lett. 62, 383.
Cassiday, G. L. et al., 1990, Astrophys. J. 356, 669.
Cavallo, G., 1978, Astron. Astrophys. 65, 415.
Cesarsky, C. J., 1992, Nucl. Phys. B (Proc. Suppl.) 28, 51.
Cesarsky, C. J., and V. S. Ptuskin, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 341.
Chiba, N., et al., 1992, Nucl. Instrum. Methods Phys. Res. A 311, 338.
Chikashige, Y., and J. Kamoshita, 1998, preprint astro-ph/9812483.
Chudakov, A. E., 1962, in Proceedings of 5th Interamerican Seminar on Cosmic Rays, edited by I. Escobar et al. (Laboratorio de Fisica Cosmic de la Univerisidad Mayor de San Andres, La Paz), Vol. 2, p. XLIX.
Chung, D. J. H., G. R. Farrar, and E. W. Kolb, 1998, Phys. Rev. D 57, 4606.
Clark, G. W., J. Earl, W. L. Kraushaar, J. Linsley, B. B. Rossi, F. Scherb, and D. Scott, 1961, Phys. Rev. 122, 637.
Coleman, S., and S. L. Glashow, 1998, hep-ph/9808446.
Coleman, S. and S. L. Glashow, 1999, Phys. Rev. D 59, 116008.
Cortina, J., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 4, p. 69.
Coy, R. N., G. Cunningham, C. L. Pryke, and A. A. Watson, 1997, Astropart. Phys. 6, 263.
Cronin, J. W., 1999, Rev. Mod. Phys. 71, S165.
Cunningham, G., et al., 1980, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo), Vol. 1, p. 61.
Dai, H. Y., K. Kasahara, Y. Matsubara, M. Nagano, and M. Teshima, 1988, J. Phys. G 14, 793.
Davidson, G. and R. O’Neil, 1964, J. Chem. Phys. 41, 3946.
Dawson, B. R., R. Meyhandan, and K. R. Simpson, 1998, Astropart. Phys. 9, 331.
DeMarzo, C. N., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 87.
Ding, L. K., N. Hotta, K. Kasahara, T. Yuda, and S. Torii, 1984, in Proceedings of the International Symposium on Cosmic Rays and Particle Physics, edited by by T. Yuda and A. Ohsawa (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 142.
Drury, L. O’C., 1994, Contemp. Phys. 35, 232.
Dubovsky, S. L., and P. G. Tinyakov, 1998, JETP Lett. 68, 107.
Dyakonov, N. M., A. A. Ivanov, S. P. Knurenko, V. A. Kolosov, I. Ye. Sleptsov, and G. G. Struchkov, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 4, p. 303.
Edge, D. M., A. C. Evans, H. J. Garmston, R. J. O. Reid, A. A. Watson, J. G. Wilson, and A. M. Wray, 1973, J. Phys. A 6, 1612.
Edge, D. M., J. Lapikens, T. J. L. McCombe, R. J. O. Reid, S. Ridgway, K. E. Turver, A. A. Watson, and A. M. Wray, 1977, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia Bulgaria), Vol. 9, p. 137.
Efimov, N. N., T. A. Egorov, A. V. Glushkov, M. I. Pravdin, and I. Ye. Sleptsov, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 20.
Efimov, N. N., T. A. Egorov, D. D. Krasilnikov, M. I. Pravdin, and I. Ye. Sleptsov, 1988, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo, Japan), Vol. 3, p. 1.
Elbert, J. W., and P. Sommers, 1995, Astrophys. J. 441, 151.
England, C. D., 1984, Ph.D. thesis (University of Leeds).
Epele, L. N., and E. Roulet, 1998, Phys. Rev. Lett. 81, 3295.
Erber, T., 1966, Rev. Mod. Phys. 38, 626.
Farrar, G. R., and P. L. Biermann, 1998, Phys. Rev. Lett. 81, 3579.
Fletcher, R. S., T. K. Gaisser, P. Lipari, and T. Stanev, 1994, Phys. Rev. D 50, 5710.
Frail, D. A., S. R. Kulkarni, L. Nicastro, M. Feroci, and G. B. Taylor, 1997, Nature (London) 389, 261.
Fukuda, Y., et al., 1998a, Phys. Rev. Lett. 81, 1158.
Fukuda, Y., et al., 1998b, Phys. Rev. Lett. 81, 1562.
Gaisser, T. K., 1990, Cosmic Rays and Particle Physics (Cambridge University, Cambridge).
Gaisser, T. K., 1997, Nucl. Phys. B (Proc. Suppl.) 52, 10.
Gaisser, T. K., U. P. Sukhatme, and G. B. Yodh, 1987, Phys. Rev. D 36, 1350.
Gaisser, T. K., et al., 1993, Phys. Rev. D 47, 1919.
Gelmini, G., and A. Kusenko, 2000, Phys. Rev. Lett. 84, 1378.
Gill, A. J., and T. W. B. Kibble, 1994, Phys. Rev. D 50, 3660.
Giller, M., J. L. Osborne, J. Wdowczyk, and A. A. Wolfendale, 1994, J. Phys. G 20, 1649.
Gillman, M. S., and A. A. Watson, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 47.
Glushkov, A. V., V. M. Grigoryev, N. N. Efimov, M. L. Pravdin, O. S. Diminstein, and V. F. Sokurov, 1979, in Proceedings of the 19th International Cosmic Ray Conference, 1979, Kyoto (Institute of Cosmic Ray Research, Tokyo) Vol. 8, p. 158.
Glushkov, A. V., I. T. Makarov, E. S. Nikiforova, M. I. Pravdin, and I. Ye. Sleptsov, 1995, Astropart. Phys. 4, 15.
Glushkov, A. V., et al., 1987, in Proceedings of the 20th International Cosmic Ray Conference, 1987, Moscow (Nauka, Moscow, USSR), Vol. 5, p. 494.
Goldreich, P., and W. H. Julian, 1969, Astrophys. J. 157, 869.
Gonzalez-Mestres, L., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 6, p. 113.
Gonzalez-Mestres, L., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 148.
Greisen, K., 1956, in Progress in Cosmic Ray Physics III, edited by J. G. Wilson (Interscience, New York), p. 3.
Greisen, K., 1965, in Proceedings of the 9th International Cosmic Ray Conference, 1965, London (Institute of Physics, London), Vol. 2, p. 609.
Greisen, K., 1966, Phys. Rev. Lett. 16, 748.
Grigorov, N. L., I. D. Rapoport, I. A. Savenko, V. V. Akimov, and V. E. Nesterov, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 5, p. 1760.
Gunn, J. E., and J. P. Ostriker, 1969, Phys. Rev. Lett. 22, 728.
Halzen, F., R. A. Vázques, T. Stanev, and H. P. Vankov, 1995, Astropart. Phys. 3, 151.
Hara, T., S. Kawaguchi, S. Mikamo, M. Nagano, K. Suga, G. Tanahashi, K. Uchino, and H. Akiyama, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 361.
Hara, T., et al., 1981, in Proceedings of the 17th International Cosmic Ray Conference, 1981, Paris (CENS, Gf-sur-Yvette, France), Vol. 11, p. 231.
Harari, D. S., E. Mollerach, and E. Roulet, 1999, J. High Energy Phys. 08, 022.
Hayashida, N., et al., 1994, Phys. Rev. Lett. 73, 3491.
Hayashida, N., et al., 1995, J. Phys. G 21, 1101.
Hayashida, N., et al., 1996a, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 17.
Hayashida, N., et al., 1996b, Phys. Rev. Lett. 77, 1000.
Hayashida, N., et al., 1997a, in Proceedings of the 23rd International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 4, p. 145.
Hayashida N., et al., 1997b, in Proceedings of the 23rd International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 217.
Hayashida, N., et al., 1999a, Astropart. Phys. 10, 303.
Hayashida, N., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, 1999, Salt Lake City, Vol. 3, p. 256, astro-ph/9906056.
Heck, D., 1998, private communication.
Heck, D., and J. Knapp, 1998, FZKA6097 (Forschungszentrum Karlsruhe, Germany).
Heck, D., J. Knapp, J. N. Capdevielle, G. Schatz, and T. Thouw, 1998, FZKA6019 (Forschungszentrum Karlsruhe, Germany).
Hill, C. T. and D. N. Schramm, 1983, Phys. Lett. 131B, 247.
Hill, C. T., D. N. Schramm, and T. P. Walker, 1987, Phys. Rev. D 36, 1007.
Hillas, A. M., 1968, Can. J. Phys. 46, S623.
Hillas, A. M., 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 355.
Hillas, A. M., 1979, private communication.
Hillas, A. M., 1981, in Proceedings of the 17th International Cosmic Ray Conference, Paris (CENS, Gif-sur-Yvette, France), Vol. 8, p. 193.
Hillas, A. M., 1984, Annu. Rev. Astron. Astrophys. 22, 425.
Hillas, A. M., 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 74.
Hillas, A. M., 1997, Nucl. Phys. B (Proc. Suppl.) 52B, 29.
Hillas, A. M., 1998, Nature (London) 395, 15.
Hillas, A. M., 1999, Nucl. Phys. B (Proc. Suppl.) 75B, 109.
Hillas, A. M., J. D. Hollows, H. W. Hunter, and D. J. Marsden, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 533.
Hillas, A. M., D. J. Marsden, J. D. Hollows, and H. W. Hunter, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 3, p. 1001.
Hinton, J. A., 1999, private communication.
Hinton, J. A., A. A. Watson, E. Garcia, R. Lopez, L. Nellen, L. Villaseñor, and A. Zepeda, 1999, in Proceedings of the 26th International Cosmic Ray Conference, 1999, Salt Lake City, Vol. 3, p. 288.
Hoffman, C. M., 1999, Phys. Rev. Lett. 83, 2471.
Honda, K., K. Hashimoto, N. Kawasumi, T. Kutter, M. Nagano, and I. Tsushima, 1997, Phys. Rev. D 56, 3833.
Honda, M., M. Nagano, S. Tonwar, K. Kasahara, T. Hara, N. Hayashida, Y. Matsubara, M. Teshima, and S. Yoshida, 1993, Phys. Rev. Lett. 70, 525.
Huguet, E. and P. Peter, 1999, Astropart. Phys. 12, 277.
Ichimura, M., et al., 1993, Phys. Rev. D 48, 1949.
Inoue, N., et al., 1999a, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 357.
Inoue, N., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 361.
Ip, W. H., and W. I. Axford, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 273.
Jokipii, J. R., and G. E. Morfill, 1985, Astrophys. J., Lett. Ed. 290, L1.
Jokipii, J. R. and G. E. Morfill, 1987, Astrophys. J. 312, 170.
Jones, F. C., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conference Proceedings No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 37.
Kakimoto, F., E. C. Loh, M. Nagano, H. Okuno, M. Teshima, and S. Ueno, 1996, Nucl. Instrum. Methods Phys. Res. A 372, 527.
Kalmykov, N. N., and S. S. Ostapchenko, 1993, Phys. At. Nucl. 56, 346.
Kalmykov, N. N., S. S. Ostapchenko, and A. I. Pavlov, 1997, Nucl. Phys. B (Proc. Suppl.) 52B, 17.
Kang, H., J. P. Rachen, and P. L. Biermann, 1997, Mon. Not. R. Astron. Soc. 286, 257.
Kang, H., D. Ryu, and T. W. Jones, 1996, Astrophys. J. 456, 422.
Karakula, S., J. L. Osborne, E. Roberts, and W. Tkaczyk, 1972, J. Phys. A 5, 904.
Kasahara, K., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 221.
Kasahara, K., S. Torii, and T. Yuda, 1979, in Proceedings of the 16th International Cosmic Ray Conference, 1979, Kyoto (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), Vol. 13, p. 70.
Kellermann, E. W., and L. Towers, 1970, J. Phys. A 3, 284.
Kephart, T. W., and T. J. Weiler, 1996, Astropart. Phys. 4, 271.
Kewley, L. J., R. W. Clay, and B. R. Dawson, 1996, Astropart. Phys. 5, 69.
Klein, S., 1999, Rev. Mod. Phys. 71, 1501.
Knapp, J., 1997, in Invited, Rapporteur, and Highlight Papers of the 25th International Cosmic Ray Conference (World Scientific, Singapore), Vol. 8, p. 83.
Kouveliotou, C., et al., 1998, Nature (London) 393, 235.
Kronberg, P. P., 1994, Rep. Prog. Phys. 57, 325.
Kutter, T., 1999, private communication.
Landau, L. D., and I. J. Pomeranchuk, 1935, Dokl. Akad. Nauk SSSR, Ser. A 92, 535.
Lapikens, 1974, Ph.D. thesis (University of Leeds).
Lawrence, M. A., D. A. Prosser, and A. A. Watson, 1989, Phys. Rev. Lett. 63, 1121.
Lawrence, M. A., R. J. O. Reid, and A. A. Watson, 1991, J. Phys. G 17, 733.
Lee, A. A., and R. W. Clay, 1995, J. Phys. G 21, 1743.
Leibrock, H., A. Haungs, and H. Rebel, 1998, unpublished report (Forschungszentrum Karlsruhe).
Lemoine, M., G. Sigl, and P. Biermann, 1999, e-print, astro-ph/9903124.
Lemoine, M., G. Sigl, A. V. Olinto, and D. N. Schramm, 1997, Astrophys. J. Lett. 486, L115.
Linsley, J., 1963a, Phys. Rev. Lett. 10, 146.
Linsley, J., 1963b, in Proceedings of the 8th International Cosmic Ray Conference, Jaipur (Tata Institute for Fundamental Research), Vol. 4, p. 77.
Linsley, J., 1975, Phys. Rev. Lett. 34, 1530.
Linsley, J., 1997a, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 89.
Linsley, J., 1977b, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 56.
Linsley, J., 1979, in Field Committee Report, “Call for Projects and Ideas in High Energy Astrophysics for the 1980s,” National Science Foundation, unpublished.
Linsley, J., 1980, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo), Vol. 1, p. 1.
Linsley, J., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 1.
Linsley, J., and L. Scarsi, 1962, Phys. Rev. 128, 2384.
Linsley, J., L. Scarsi, and B. Rossi, 1961, Phys. Rev. Lett. 6, 458.
Linsley, J., and A. A. Watson, 1977, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 203.
Lloyd-Evans, J., and A. A. Watson, 1983, Invited Talks, 8th European Cosmic Ray Symposium, edited by N. Iucci et al. (Tecnoprint, Bologna).
Malkan, M. A., and F. W. Stecker, 1998, Astrophys. J. 496, 13.
Mannheim, K., 1995, Astropart. Phys. 3, 295.
Masperi, L., and G. Silva, 1998, Astropart. Phys. 8, 173.
Maze, R., 1938, J. Phys. Radium 9, 162.
McBreen, B., and C. J. Lambert, 1981, Phys. Rev. D 24, 2536.
McCusker, C. B. A. and M. M. Winn, 1963, Nuovo Cimento 28, 175.
Medina Tanco, G. A., 1998a, Astrophys. J. Lett. 495, L71.
Medina Tanco, G. A., 1998b, Astrophys. J. Lett. 505, L79.
Medina Tanco, G. A., 1999, Astrophys. J. Lett. 510, L91.
Medina Tanco, G. A., E. M. de Gouveia Dal Pino, and J. E. Horvath, 1997, Astropart. Phys. 6, 337.
Medina Tanco, G. A., E. M. de Gouveia Dal Pino, and J. E. Horvath, 1998, Astrophys. J. 492, 200.
Medina Tanco, G. A., and A. A. Watson, 1999, Astropart. Phys. 12, 25.
Meisenheimer, K., H.-J. Roser, P. R. Hiltner, M. G. Yates, M. S. Longair, R. Chini, and R. A. Perley, 1989, Astron. Astrophys. 219, 63.
Mèszàros, P., and M. J. Rees, 1997, Astrophys. J. 476, 232.
Miekle, H. H., et al., 1994, J. Phys. G: Nucl. Part. Phys. 20, 637.
Migdal, A. B., 1956, Phys. Rev. 103, 1811.
Mikhailov, A. A., and M. I. Pravdin, 1997, Pis’ma Zh. Eksp. Teor. Fiz. 66, 289 [JETP Lett. 66, 307].
Milgrom, M., and V. Usov, 1995, Astrophys. J. Lett. 449, L37.
Nagano, M., T. Hara, Y. Hatano, N. Hayashida, S. Kawaguchi, K. Kamata, T. Kifune, and Y. Mizumoto, 1984, J. Phys. G 10, 1295.
Nagano, M., D. Heck, K. Shinozaki, N. Inoue, and J. Knapp, 1998, FZKA6191 (Forschungszentrum Karlsruhe, Germany).
Nagano, M., D. Heck, K. Shinozaki, N. Inoue, and J. Knapp, 2000, Astropart. Phys. 13, 277.
Nagano, M., M. Teshima, Y. Matsubara, H. Y. Dai, T. Hara, N. Hayashida, M. Honda, H. Ohoka, and S. Yoshida, 1992, J. Phys. G 18, 423.
Nagano, M., et al., 1986, J. Phys. G 12, 69.
Nakamura, T., 1998, e-print, astro-ph/9807087.
Norman, C. A., D. B. Melrose, and A. Achterberg, 1995, Astrophys. J. 454, 60.
Ohoka, H., et al., 1996, Nucl. Instrum. Methods Phys. Res. A 385, 268.
Olinto, A. V., R. I. Epstein, and P. Blasi, 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City (University of Utah, Salt Lake City) Vol. 4, p. 361.
Ostrowski, M., 1998, Astron. Astrophys. 335, 134.
Padilla, L., et al., 1998, Astron. Astrophys. 337, 43.
Paling, S., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 253.
Penzias, A. A., and R. W. Wilson, 1965, Astrophys. J. 142, 419.
Pierre Auger Project Design Report, 1997, Auger Collaboration, Fermi National Accelerator Laboratory.
Porter, N. A., 1960, Nuovo Cimento 16, 958.
Protheroe, R. J., and P. Biermann, 1996, Astropart. Phys. 6, 45.
Protheroe, R. J., and P. Johnson, 1996, Astropart. Phys. 4, 253.
Puget, J. L., F. W. Stecker, and J. H. Bredekamp, 1976, Astrophys. J. 205, 638.
Rachen, J. P., and P. L. Biermann, 1993, Astron. Astrophys. 272, 161.
Rachen, J. P., T. Stanev, and P. L. Biermann, 1993, Astron. Astrophys. 273, 377.
Ranft, J., 1995, Phys. Rev. D 51, 64.
Rees, M. J., and P. Mèszàros, 1992, Mon. Not. R. Astron. Soc. 258, P41.
Rossi, B., 1934, Ric Sci. Suppl. 1, 579.
Sakaki, N., 1999, private communication.
Sakaki, N., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 217.
Sakaki, N., et al., 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 353.
Sciutto, S. J., 1999, GAP 1999-020 (Auger Project, Fermi National Accelerator Laboratory), see http://www.auger.org/admin
Sigl, G., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 237.
Sigl, G., M. Lemoine, and P. Biermann, 1999, Astropart. Phys. 10, 141.
Sigl, G., M. Lemoine, and A. V. Olinto, 1997, Phys. Rev. D 56, 4470.
Sokolsky, P., 1993, in Proceedings of the Tokyo Workshop on Techniques for the Study of Extremely High Energy Cosmic Rays, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 280.
Sokolsky, P., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 253.
Sokolsky, P., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 65.
Sokolsky, P., P. Sommers, and B. R. Dawson, 1992, Phys. Rep. 217, 225.
Stanev, T., 1997, Astrophys. J. 479, 290.
Stanev, T., P. L. Biermann, J. Lloyd-Evans, J. P. Rachen, and A. A. Watson, 1995, Phys. Rev. Lett. 75, 3056.
Stanev, T., and A. M. Hillas, 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 4, p. 365.
Stanev, T., and H. P. Vankov, 1997, Phys. Rev. D 55, 1365.
Stecker, F. W., 1973, Astrophys. Space Sci. 20, 47.
Stecker, F. W., 1989, Nature (London) 324, 401.
Stecker, F. W. and M. H. Salamon, 1999, Astrophys. J. 512, 521.
Streitmatter, R. E., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 95.
Suga, K., 1962, in Proceedings of 5th Interamerican Seminar on Cosmic Rays, edited by I. Escobar et al. (Laboratorio de Fisica Cosmic de la Universidad Mayor de San Andres, La Paz, Bolivia), Vol. 2, p. XLIX.
Takahara, F., 1990, Prog. Theor. Phys. 83, 1071L.
Takahara, F., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 61.
Takeda, M., et al., 1998, Phys. Rev. Lett. 81, 1163.
Takeda, M., et al., 1999a, Astrophys. J. 522, 225.
Takeda, M., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 3, p. 252.
Takeda, M., et al., 1999c, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 3, p. 276.
Telescope Array Project Design Report, 1998, Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan (in Japanese).
Teshima, M., M. Nagano, T. Hara, N. Hayashida, M. Honda, K. Kamata, T. Kifune, and H. Ohoka, 1990, Phys. Rev. Lett. 64, 1628.
Teshima, M., et al., 1986a, Nucl. Instrum. Methods Phys. Res. A 247, 399.
Teshima, M., et al., 1986b, J. Phys. G 12, 1097.
Totani, T., 1998a, Astrophys. J. Lett. 502, L13.
Totani, T., 1998b, Astrophys. J. Lett. 509, L81.
Toyoda, Y., et al., 1965, in Proceedings of the 9th International Cosmic Ray Conference, London (Institute of Physics, London), Vol. 2, p. 708.
Uchihori, Y., 1999, private communication.
Uchihori, Y., M. Nagano, M. Takeda, M. Teshima, J. Lloyd-Evans, and A. A. Watson, 2000, Astropart. Phys. 13, 151.
Uchihori, Y., et al., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 50.
Vietri, M., 1995, Astrophys. J. 453, 883.
Walker, R., and A. A. Watson, 1981, J. Phys. G 7, 1297.
Walker, R., and A. A. Watson, 1982, J. Phys. G 8, 1131.
Watson, A. A., 1991, Nucl. Phys. B (Proc. Suppl.) 22, 116.
Watson, A. A., 1992, Nucl. Phys. B (Proc. Suppl.) 28, 3.
Watson, A. A., 1997, in Proceedings of ICRR Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 362.
Watson, A. A., and J. G. Wilson, 1974, J. Phys. G 7, 1199.
Waxman, E., 1995, Phys. Rev. Lett. 75, 386.
Waxman, E., and J. Miralda-Escude, 1996, Astrophys. J. Lett. 472, L89.
Wdowczyk, J., W. Thaczyk, and A. W. Wolfendale, 1972, J. Phys. A 5, 1419.
Wdowczyk, J., and A. W. Wolfendale, 1984, J. Phys. A 10, 1453.
Weiler, T. J., 1982, Phys. Rev. Lett. 49, 234.
Weiler, T. J., 1984, Astrophys. J. 285, 495.
Werner, K., 1993, Phys. Rep. 232, 87.
Wibig, T., and A. Wolfendale, 1999a, J. Phys. G 25, 557.
Wibig, T., and A. Wolfendale, 1999b, J. Phys. G 25, 1099.
Winn, M. M., J. Ulrichs, L. S. Peak, C. B. A. McCusker, and L. Horton, 1982, in Catalog of Highest Energy Cosmic Rays, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo, Japan), Vol. 2, p. 1.
Winn, M. M., J. Ulrichs, L. S. Peak, C. B. A. McCusker, and L. Horton, 1986, J. Phys. G 12, 675.
Yodh, G. B., et al., 1983, Phys. Rev. D 27, 1183.
Yoshida, S., G. Sigl, and S. Lee, 1998, Phys. Rev. Lett. 81, 5505.
Yoshida, S., and M. Teshima, 1993, Prog. Theor. Phys. 89, 833.
Yoshida, S., et al., 1994, J. Phys. G 20, 651.
Yoshida, S., et al., 1995, Astropart. Phys. 3, 105.
Zatsepin, Z. T., and V. A. Kuz’min, 1966, Zh. Eksp. Teor. Fiz. Pis'ma Red. 4, 144.

[c1] Abu-Zayyad, T., et al., 2000, Phys. Rev. Lett. 84, 4276.

[c2] Afanasiev, B. N., et al., 1993, in Proceedings of the Tokyo Workshop on Techniques for the Study of the Extremely High Energy Cosmic Rays, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 35.

[c3] Afanasiev, B. N., et al., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 32.

[c4] Aglietta, M., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 6, p. 37.

[c5] Aharonian, F. A., B. L. Kanevsky, and V. A. Sahakian, 1991, J. Phys. G 17, 1909.

[c6] Al-Dargazelli, S. S., A. W. Wolfendale, A. Smialkowsk, and J. Wdowczyk, 1996, J. Phys. G 22, 1825.

[c7] Amenomori, M., et al., 1996a, Astrophys. J. 461, 408.

[c8] Amenomori, M., et al., 1996b, Astron. Astrophys. 311, 919.

[c9] Andrews, D., D. M. Edge, A. C. Evans, R. J. O. Reid, R. M. Tennent, A. A. Watson, J. G. Wilson, and A. M. Wray, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 3, p. 995.

[c10] Andrews, D., A. C. Evans, R. R. Hughes, D. J. Marsden, R. J. O. Reid, I. Smolko, R. M. Tennent, A. A. Watson, J. G. Wilson, and A. M. Wray, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 337.

[c11] Asakimori, K., et al., 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 25.

[c12] Auger, P., P. Ehrenfest, Jr., R. Maze, J. Daudin, C. Robley, and A. Fréon, 1939, Rev. Mod. Phys. 11, 288.

[c13] Auger, P., R. Maze, and T. Grivet-Meyer, 1938, Académie des Sciences, Paris, 206, 1721.

[c14] Axford, W. I., 1994, Astrophys. J., Suppl. Ser. 90, 937.

[c15] Baltrusaitis, R. M., R. Cady, et al., 1985a, Nucl. Instrum. Methods Phys. Res. A 240, 410.

[c16] Baltrusaitis, R. M., R. Cady, et al., 1985b, Phys. Rev. Lett. 54, 1875.

[c17] Baltrusaitis, R. M., G. L. Cassiday, J. W. Elbert, P. R. Gerhardy, S. Ko, E. C. Loh, Y. Mizumoto, P. Sokolsky, and D. Steck, 1984, Phys. Rev. Lett. 52, 1380.

[c18] Baltrusaitis, R. M., G. L. Cassiday, J. W. Elbert, P. R. Gerhardy, E. C. Loh, Y. Mizumoto, P. Sokolsky, and D. Steck, 1985, Phys. Rev. D 31, 2192.

[c19] Barshay, S., and G. Kreyerhoff, 1998a, Eur. Phys. J. C 5, 369.

[c20] Barshay, S., and G. Kreyerhoff, 1999, Nuovo Cimento A 112, 1463.

[c21] Bassi, P., G. Clark, and B. Rossi, 1953, Phys. Rev. 92, 441.

[c22] Bell, C. J., et al., 1974, J. Phys. A 7, 990.

[c23] Benakli, K., J. Ellis, and D. V. Nanopoulos, 1999, Phys. Rev. D 59, 047301.

[c24] Benson, A., A. Smialkowski, and A. W. Wolfendale, 1999, Astropart. Phys. 10, 313.

[c25] Berezinsky, V. S., 1988, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 279.

[c26] Berezinsky, V. S., 1999, Nucl. Phys. B (Proc. Suppl.) 70, 419.

[c27] Berezinsky, V. S., S. V. Bulanov, V. A. Dogiel, V. L. Ginzburg, and V. S. Ptuskin, 1990, Astrophysics of Cosmic Rays (North-Holland, Amsterdam/New York).

[c28] Berezinsky, V. S. and S. I. Grigor’eva, 1988, Astron. Astrophys. 199, 1.

[c29] Berezinsky, V. S., S. I. Grigor’eva, A. A. Mikhailov, H. Rubinstein, A. A. Ruzmaikin, D. D. Sokoloff, and A. M. Shukurov, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 134.

[c30] Berezinsky, V. S., M. Kachelriess, and A. Vilenkin, 1997, Phys. Rev. Lett. 79, 4302.

[c31] Berezinsky, V. S., and A. A. Mikhailov, 1999, Phys. Lett. B 449, 237.

[c32] Berezinsky, V. S. and G. T. Zatsepin, 1969, Phys. Lett. 28B, 423.

[c33] Bergeson, H. E., G. L. Cassiday, T. W. Chiu, D. A. Cooper, J. W. Elbert, E. C. Loh, D. Steck, W. J. West, J. Boone, and J. Linsley, 1977, Phys. Rev. Lett. 39, 847.

[c34] Bhattacharjee, P., 1997, Proceedings of ICRR Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 125.

[c35] Bhattacharjee, P., and G. Sigl, 2000, Phys. Rep. 327, 110.

[c36] Biermann, P. L., 1997, J. Phys. G 23, 1.

[c37] Biermann, P. L., and P. A. Streitmatter, 1987, Astrophys. J. 322, 643.

[c38] Bird, D., et al., 1993, Phys. Rev. Lett. 71, 3401.

[c39] Bird, D., et al., 1994a, Nucl. Instrum. Methods Phys. Res. A 349, 592.

[c40] Bird, D., et al., 1994b, Astrophys. J. 424, 491.

[c41] Bird, D., et al., 1995, Astrophys. J. 441, 144.

[c42] Bird, D., et al., 1999, Astrophys. J. 511, 739.

[c43] Birkel, M., and S. Sarkar, 1998, Astropart. Phys. 9, 297.

[c44] Blanco-Pillado, J. J., R. A. Vázquez, and E. Zas, 2000, Phys. Rev. D 61, 123003.

[c45] Blandford, R. D., 1999, in Proceedings of the Nobel Symposium on Particle Physics and the Universe, Stockholm 2000, Phys. Scr. T85.

[c46] Blumenthal, G. R., 1970, Phys. Rev. D 1, 1596.

[c47] Boldt, E., and P. Ghosh, 1999, Mon. Not. R. Astron. Soc. 307, 491.

[c48] Bonazzola, S., and P. Peters, 1997, Astropart. Phys. 7, 161.

[c49] Boothby, K., M. Chantell, K. D. Green, D. B. Kieda, J. Knapp, C. G. Larsen, and S. P. Swordy, 1997, Astrophys. J. Lett. 491, L35.

[c50] Bower, A. J., G. Brooke, D. Pearce, J. C. Perrett, and A. A. Watson, 1983, J. Phys. G 9, 1569.

[c51] Bower, A. J., G. Cunningham, J. Linsley, R. J. O. Reid, and A. A. Watson, 1983, J. Phys. G 9, L53.

[c52] Bunner, A. N., 1964, Ph.D. thesis (Cornell University).

[c53] Capdevielle, J. N., 1989, J. Phys. G 15, 909.

[c54] Capelle, K. J., J. W. Cronin, G. Parente, and E. Zas, 1998, Astropart. Phys. 8, 321.

[c55] Cassiday, G. L., et al., 1989, Phys. Rev. Lett. 62, 383.

[c56] Cassiday, G. L. et al., 1990, Astrophys. J. 356, 669.

[c57] Cavallo, G., 1978, Astron. Astrophys. 65, 415.

[c58] Cesarsky, C. J., 1992, Nucl. Phys. B (Proc. Suppl.) 28, 51.

[c59] Cesarsky, C. J., and V. S. Ptuskin, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 341.

[c60] Chiba, N., et al., 1992, Nucl. Instrum. Methods Phys. Res. A 311, 338.

[c61] Chikashige, Y., and J. Kamoshita, 1998, preprint astro-ph/9812483.

[c62] Chudakov, A. E., 1962, in Proceedings of 5th Interamerican Seminar on Cosmic Rays, edited by I. Escobar et al. (Laboratorio de Fisica Cosmic de la Univerisidad Mayor de San Andres, La Paz), Vol. 2, p. XLIX.

[c63] Chung, D. J. H., G. R. Farrar, and E. W. Kolb, 1998, Phys. Rev. D 57, 4606.

[c64] Clark, G. W., J. Earl, W. L. Kraushaar, J. Linsley, B. B. Rossi, F. Scherb, and D. Scott, 1961, Phys. Rev. 122, 637.

[c65] Coleman, S., and S. L. Glashow, 1998, hep-ph/9808446.

[c66] Coleman, S. and S. L. Glashow, 1999, Phys. Rev. D 59, 116008.

[c67] Cortina, J., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 4, p. 69.

[c68] Coy, R. N., G. Cunningham, C. L. Pryke, and A. A. Watson, 1997, Astropart. Phys. 6, 263.

[c69] Cronin, J. W., 1999, Rev. Mod. Phys. 71, S165.

[c70] Cunningham, G., et al., 1980, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo), Vol. 1, p. 61.

[c71] Dai, H. Y., K. Kasahara, Y. Matsubara, M. Nagano, and M. Teshima, 1988, J. Phys. G 14, 793.

[c72] Davidson, G. and R. O’Neil, 1964, J. Chem. Phys. 41, 3946.

[c73] Dawson, B. R., R. Meyhandan, and K. R. Simpson, 1998, Astropart. Phys. 9, 331.

[c74] DeMarzo, C. N., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 87.

[c75] Ding, L. K., N. Hotta, K. Kasahara, T. Yuda, and S. Torii, 1984, in Proceedings of the International Symposium on Cosmic Rays and Particle Physics, edited by by T. Yuda and A. Ohsawa (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 142.

[c76] Drury, L. O’C., 1994, Contemp. Phys. 35, 232.

[c77] Dubovsky, S. L., and P. G. Tinyakov, 1998, JETP Lett. 68, 107.

[c78] Dyakonov, N. M., A. A. Ivanov, S. P. Knurenko, V. A. Kolosov, I. Ye. Sleptsov, and G. G. Struchkov, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 4, p. 303.

[c79] Edge, D. M., A. C. Evans, H. J. Garmston, R. J. O. Reid, A. A. Watson, J. G. Wilson, and A. M. Wray, 1973, J. Phys. A 6, 1612.

[c80] Edge, D. M., J. Lapikens, T. J. L. McCombe, R. J. O. Reid, S. Ridgway, K. E. Turver, A. A. Watson, and A. M. Wray, 1977, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia Bulgaria), Vol. 9, p. 137.

[c81] Efimov, N. N., T. A. Egorov, A. V. Glushkov, M. I. Pravdin, and I. Ye. Sleptsov, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 20.

[c82] Efimov, N. N., T. A. Egorov, D. D. Krasilnikov, M. I. Pravdin, and I. Ye. Sleptsov, 1988, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo, Japan), Vol. 3, p. 1.

[c83] Elbert, J. W., and P. Sommers, 1995, Astrophys. J. 441, 151.

[c84] England, C. D., 1984, Ph.D. thesis (University of Leeds).

[c85] Epele, L. N., and E. Roulet, 1998, Phys. Rev. Lett. 81, 3295.

[c86] Erber, T., 1966, Rev. Mod. Phys. 38, 626.

[c87] Farrar, G. R., and P. L. Biermann, 1998, Phys. Rev. Lett. 81, 3579.

[c88] Fletcher, R. S., T. K. Gaisser, P. Lipari, and T. Stanev, 1994, Phys. Rev. D 50, 5710.

[c89] Frail, D. A., S. R. Kulkarni, L. Nicastro, M. Feroci, and G. B. Taylor, 1997, Nature (London) 389, 261.

[c90] Fukuda, Y., et al., 1998a, Phys. Rev. Lett. 81, 1158.

[c91] Fukuda, Y., et al., 1998b, Phys. Rev. Lett. 81, 1562.

[c92] Gaisser, T. K., 1990, Cosmic Rays and Particle Physics (Cambridge University, Cambridge).

[c93] Gaisser, T. K., 1997, Nucl. Phys. B (Proc. Suppl.) 52, 10.

[c94] Gaisser, T. K., U. P. Sukhatme, and G. B. Yodh, 1987, Phys. Rev. D 36, 1350.

[c95] Gaisser, T. K., et al., 1993, Phys. Rev. D 47, 1919.

[c96] Gelmini, G., and A. Kusenko, 2000, Phys. Rev. Lett. 84, 1378.

[c97] Gill, A. J., and T. W. B. Kibble, 1994, Phys. Rev. D 50, 3660.

[c98] Giller, M., J. L. Osborne, J. Wdowczyk, and A. A. Wolfendale, 1994, J. Phys. G 20, 1649.

[c99] Gillman, M. S., and A. A. Watson, 1993, in Proceedings of the 23rd International Cosmic Ray Conference, 1993, Calgary (University of Calgary, Calgary, Canada), Vol. 2, p. 47.

[c100] Glushkov, A. V., V. M. Grigoryev, N. N. Efimov, M. L. Pravdin, O. S. Diminstein, and V. F. Sokurov, 1979, in Proceedings of the 19th International Cosmic Ray Conference, 1979, Kyoto (Institute of Cosmic Ray Research, Tokyo) Vol. 8, p. 158.

[c101] Glushkov, A. V., I. T. Makarov, E. S. Nikiforova, M. I. Pravdin, and I. Ye. Sleptsov, 1995, Astropart. Phys. 4, 15.

[c102] Glushkov, A. V., et al., 1987, in Proceedings of the 20th International Cosmic Ray Conference, 1987, Moscow (Nauka, Moscow, USSR), Vol. 5, p. 494.

[c103] Goldreich, P., and W. H. Julian, 1969, Astrophys. J. 157, 869.

[c104] Gonzalez-Mestres, L., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 6, p. 113.

[c105] Gonzalez-Mestres, L., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 148.

[c106] Greisen, K., 1956, in Progress in Cosmic Ray Physics III, edited by J. G. Wilson (Interscience, New York), p. 3.

[c107] Greisen, K., 1965, in Proceedings of the 9th International Cosmic Ray Conference, 1965, London (Institute of Physics, London), Vol. 2, p. 609.

[c108] Greisen, K., 1966, Phys. Rev. Lett. 16, 748.

[c109] Grigorov, N. L., I. D. Rapoport, I. A. Savenko, V. V. Akimov, and V. E. Nesterov, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 5, p. 1760.

[c110] Gunn, J. E., and J. P. Ostriker, 1969, Phys. Rev. Lett. 22, 728.

[c111] Halzen, F., R. A. Vázques, T. Stanev, and H. P. Vankov, 1995, Astropart. Phys. 3, 151.

[c112] Hara, T., S. Kawaguchi, S. Mikamo, M. Nagano, K. Suga, G. Tanahashi, K. Uchino, and H. Akiyama, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 361.

[c113] Hara, T., et al., 1981, in Proceedings of the 17th International Cosmic Ray Conference, 1981, Paris (CENS, Gf-sur-Yvette, France), Vol. 11, p. 231.

[c114] Harari, D. S., E. Mollerach, and E. Roulet, 1999, J. High Energy Phys. 08, 022.

[c115] Hayashida, N., et al., 1994, Phys. Rev. Lett. 73, 3491.

[c116] Hayashida, N., et al., 1995, J. Phys. G 21, 1101.

[c117] Hayashida, N., et al., 1996a, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 17.

[c118] Hayashida, N., et al., 1996b, Phys. Rev. Lett. 77, 1000.

[c119] Hayashida, N., et al., 1997a, in Proceedings of the 23rd International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 4, p. 145.

[c120] Hayashida N., et al., 1997b, in Proceedings of the 23rd International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 217.

[c121] Hayashida, N., et al., 1999a, Astropart. Phys. 10, 303.

[c122] Hayashida, N., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, 1999, Salt Lake City, Vol. 3, p. 256, astro-ph/9906056.

[c123] Heck, D., 1998, private communication.

[c124] Heck, D., and J. Knapp, 1998, FZKA6097 (Forschungszentrum Karlsruhe, Germany).

[c125] Heck, D., J. Knapp, J. N. Capdevielle, G. Schatz, and T. Thouw, 1998, FZKA6019 (Forschungszentrum Karlsruhe, Germany).

[c126] Hill, C. T. and D. N. Schramm, 1983, Phys. Lett. 131B, 247.

[c127] Hill, C. T., D. N. Schramm, and T. P. Walker, 1987, Phys. Rev. D 36, 1007.

[c128] Hillas, A. M., 1968, Can. J. Phys. 46, S623.

[c129] Hillas, A. M., 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 355.

[c130] Hillas, A. M., 1979, private communication.

[c131] Hillas, A. M., 1981, in Proceedings of the 17th International Cosmic Ray Conference, Paris (CENS, Gif-sur-Yvette, France), Vol. 8, p. 193.

[c132] Hillas, A. M., 1984, Annu. Rev. Astron. Astrophys. 22, 425.

[c133] Hillas, A. M., 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 74.

[c134] Hillas, A. M., 1997, Nucl. Phys. B (Proc. Suppl.) 52B, 29.

[c135] Hillas, A. M., 1998, Nature (London) 395, 15.

[c136] Hillas, A. M., 1999, Nucl. Phys. B (Proc. Suppl.) 75B, 109.

[c137] Hillas, A. M., J. D. Hollows, H. W. Hunter, and D. J. Marsden, 1970, Acta Phys. Acad. Sci. Hung. 29, Suppl 3, 533.

[c138] Hillas, A. M., D. J. Marsden, J. D. Hollows, and H. W. Hunter, 1971, in Proceedings of the 12th International Cosmic Ray Conference, 1971, Hobart (University of Tasmania, Hobart, Australia), Vol. 3, p. 1001.

[c139] Hinton, J. A., 1999, private communication.

[c140] Hinton, J. A., A. A. Watson, E. Garcia, R. Lopez, L. Nellen, L. Villaseñor, and A. Zepeda, 1999, in Proceedings of the 26th International Cosmic Ray Conference, 1999, Salt Lake City, Vol. 3, p. 288.

[c141] Hoffman, C. M., 1999, Phys. Rev. Lett. 83, 2471.

[c142] Honda, K., K. Hashimoto, N. Kawasumi, T. Kutter, M. Nagano, and I. Tsushima, 1997, Phys. Rev. D 56, 3833.

[c143] Honda, M., M. Nagano, S. Tonwar, K. Kasahara, T. Hara, N. Hayashida, Y. Matsubara, M. Teshima, and S. Yoshida, 1993, Phys. Rev. Lett. 70, 525.

[c144] Huguet, E. and P. Peter, 1999, Astropart. Phys. 12, 277.

[c145] Ichimura, M., et al., 1993, Phys. Rev. D 48, 1949.

[c146] Inoue, N., et al., 1999a, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 357.

[c147] Inoue, N., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 361.

[c148] Ip, W. H., and W. I. Axford, 1991, in Proceedings of the International Symposium on Astrophysical Aspects of the Most Energetic Cosmic Rays, edited by M. Nagano and F. Takahara (World Scientific, Singapore), p. 273.

[c149] Jokipii, J. R., and G. E. Morfill, 1985, Astrophys. J., Lett. Ed. 290, L1.

[c150] Jokipii, J. R. and G. E. Morfill, 1987, Astrophys. J. 312, 170.

[c151] Jones, F. C., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conference Proceedings No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 37.

[c152] Kakimoto, F., E. C. Loh, M. Nagano, H. Okuno, M. Teshima, and S. Ueno, 1996, Nucl. Instrum. Methods Phys. Res. A 372, 527.

[c153] Kalmykov, N. N., and S. S. Ostapchenko, 1993, Phys. At. Nucl. 56, 346.

[c154] Kalmykov, N. N., S. S. Ostapchenko, and A. I. Pavlov, 1997, Nucl. Phys. B (Proc. Suppl.) 52B, 17.

[c155] Kang, H., J. P. Rachen, and P. L. Biermann, 1997, Mon. Not. R. Astron. Soc. 286, 257.

[c156] Kang, H., D. Ryu, and T. W. Jones, 1996, Astrophys. J. 456, 422.

[c157] Karakula, S., J. L. Osborne, E. Roberts, and W. Tkaczyk, 1972, J. Phys. A 5, 904.

[c158] Kasahara, K., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 221.

[c159] Kasahara, K., S. Torii, and T. Yuda, 1979, in Proceedings of the 16th International Cosmic Ray Conference, 1979, Kyoto (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), Vol. 13, p. 70.

[c160] Kellermann, E. W., and L. Towers, 1970, J. Phys. A 3, 284.

[c161] Kephart, T. W., and T. J. Weiler, 1996, Astropart. Phys. 4, 271.

[c162] Kewley, L. J., R. W. Clay, and B. R. Dawson, 1996, Astropart. Phys. 5, 69.

[c163] Klein, S., 1999, Rev. Mod. Phys. 71, 1501.

[c164] Knapp, J., 1997, in Invited, Rapporteur, and Highlight Papers of the 25th International Cosmic Ray Conference (World Scientific, Singapore), Vol. 8, p. 83.

[c165] Kouveliotou, C., et al., 1998, Nature (London) 393, 235.

[c166] Kronberg, P. P., 1994, Rep. Prog. Phys. 57, 325.

[c167] Kutter, T., 1999, private communication.

[c168] Landau, L. D., and I. J. Pomeranchuk, 1935, Dokl. Akad. Nauk SSSR, Ser. A 92, 535.

[c169] Lapikens, 1974, Ph.D. thesis (University of Leeds).

[c170] Lawrence, M. A., D. A. Prosser, and A. A. Watson, 1989, Phys. Rev. Lett. 63, 1121.

[c171] Lawrence, M. A., R. J. O. Reid, and A. A. Watson, 1991, J. Phys. G 17, 733.

[c172] Lee, A. A., and R. W. Clay, 1995, J. Phys. G 21, 1743.

[c173] Leibrock, H., A. Haungs, and H. Rebel, 1998, unpublished report (Forschungszentrum Karlsruhe).

[c174] Lemoine, M., G. Sigl, and P. Biermann, 1999, e-print, astro-ph/9903124.

[c175] Lemoine, M., G. Sigl, A. V. Olinto, and D. N. Schramm, 1997, Astrophys. J. Lett. 486, L115.

[c176] Linsley, J., 1963a, Phys. Rev. Lett. 10, 146.

[c177] Linsley, J., 1963b, in Proceedings of the 8th International Cosmic Ray Conference, Jaipur (Tata Institute for Fundamental Research), Vol. 4, p. 77.

[c178] Linsley, J., 1975, Phys. Rev. Lett. 34, 1530.

[c179] Linsley, J., 1997a, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 89.

[c180] Linsley, J., 1977b, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 56.

[c181] Linsley, J., 1979, in Field Committee Report, “Call for Projects and Ideas in High Energy Astrophysics for the 1980s,” National Science Foundation, unpublished.

[c182] Linsley, J., 1980, in Catalog of Highest Energy Cosmic Ray, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo), Vol. 1, p. 1.

[c183] Linsley, J., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 1.

[c184] Linsley, J., and L. Scarsi, 1962, Phys. Rev. 128, 2384.

[c185] Linsley, J., L. Scarsi, and B. Rossi, 1961, Phys. Rev. Lett. 6, 458.

[c186] Linsley, J., and A. A. Watson, 1977, in Proceedings of the 15th International Cosmic Ray Conference, 1977, Plovdiv (Bulgarian Academy of Sciences, Sofia, Bulgaria), Vol. 12, p. 203.

[c187] Lloyd-Evans, J., and A. A. Watson, 1983, Invited Talks, 8th European Cosmic Ray Symposium, edited by N. Iucci et al. (Tecnoprint, Bologna).

[c188] Malkan, M. A., and F. W. Stecker, 1998, Astrophys. J. 496, 13.

[c189] Mannheim, K., 1995, Astropart. Phys. 3, 295.

[c190] Masperi, L., and G. Silva, 1998, Astropart. Phys. 8, 173.

[c191] Maze, R., 1938, J. Phys. Radium 9, 162.

[c192] McBreen, B., and C. J. Lambert, 1981, Phys. Rev. D 24, 2536.

[c193] McCusker, C. B. A. and M. M. Winn, 1963, Nuovo Cimento 28, 175.

[c194] Medina Tanco, G. A., 1998a, Astrophys. J. Lett. 495, L71.

[c195] Medina Tanco, G. A., 1998b, Astrophys. J. Lett. 505, L79.

[c196] Medina Tanco, G. A., 1999, Astrophys. J. Lett. 510, L91.

[c197] Medina Tanco, G. A., E. M. de Gouveia Dal Pino, and J. E. Horvath, 1997, Astropart. Phys. 6, 337.

[c198] Medina Tanco, G. A., E. M. de Gouveia Dal Pino, and J. E. Horvath, 1998, Astrophys. J. 492, 200.

[c199] Medina Tanco, G. A., and A. A. Watson, 1999, Astropart. Phys. 12, 25.

[c200] Meisenheimer, K., H.-J. Roser, P. R. Hiltner, M. G. Yates, M. S. Longair, R. Chini, and R. A. Perley, 1989, Astron. Astrophys. 219, 63.

[c201] Mèszàros, P., and M. J. Rees, 1997, Astrophys. J. 476, 232.

[c202] Miekle, H. H., et al., 1994, J. Phys. G: Nucl. Part. Phys. 20, 637.

[c203] Migdal, A. B., 1956, Phys. Rev. 103, 1811.

[c204] Mikhailov, A. A., and M. I. Pravdin, 1997, Pis’ma Zh. Eksp. Teor. Fiz. 66, 289 [JETP Lett. 66, 307].

[c205] Milgrom, M., and V. Usov, 1995, Astrophys. J. Lett. 449, L37.

[c206] Nagano, M., T. Hara, Y. Hatano, N. Hayashida, S. Kawaguchi, K. Kamata, T. Kifune, and Y. Mizumoto, 1984, J. Phys. G 10, 1295.

[c207] Nagano, M., D. Heck, K. Shinozaki, N. Inoue, and J. Knapp, 1998, FZKA6191 (Forschungszentrum Karlsruhe, Germany).

[c208] Nagano, M., D. Heck, K. Shinozaki, N. Inoue, and J. Knapp, 2000, Astropart. Phys. 13, 277.

[c209] Nagano, M., M. Teshima, Y. Matsubara, H. Y. Dai, T. Hara, N. Hayashida, M. Honda, H. Ohoka, and S. Yoshida, 1992, J. Phys. G 18, 423.

[c210] Nagano, M., et al., 1986, J. Phys. G 12, 69.

[c211] Nakamura, T., 1998, e-print, astro-ph/9807087.

[c212] Norman, C. A., D. B. Melrose, and A. Achterberg, 1995, Astrophys. J. 454, 60.

[c213] Ohoka, H., et al., 1996, Nucl. Instrum. Methods Phys. Res. A 385, 268.

[c214] Olinto, A. V., R. I. Epstein, and P. Blasi, 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City (University of Utah, Salt Lake City) Vol. 4, p. 361.

[c215] Ostrowski, M., 1998, Astron. Astrophys. 335, 134.

[c216] Padilla, L., et al., 1998, Astron. Astrophys. 337, 43.

[c217] Paling, S., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 253.

[c218] Penzias, A. A., and R. W. Wilson, 1965, Astrophys. J. 142, 419.

[c219] Pierre Auger Project Design Report, 1997, Auger Collaboration, Fermi National Accelerator Laboratory.

[c220] Porter, N. A., 1960, Nuovo Cimento 16, 958.

[c221] Protheroe, R. J., and P. Biermann, 1996, Astropart. Phys. 6, 45.

[c222] Protheroe, R. J., and P. Johnson, 1996, Astropart. Phys. 4, 253.

[c223] Puget, J. L., F. W. Stecker, and J. H. Bredekamp, 1976, Astrophys. J. 205, 638.

[c224] Rachen, J. P., and P. L. Biermann, 1993, Astron. Astrophys. 272, 161.

[c225] Rachen, J. P., T. Stanev, and P. L. Biermann, 1993, Astron. Astrophys. 273, 377.

[c226] Ranft, J., 1995, Phys. Rev. D 51, 64.

[c227] Rees, M. J., and P. Mèszàros, 1992, Mon. Not. R. Astron. Soc. 258, P41.

[c228] Rossi, B., 1934, Ric Sci. Suppl. 1, 579.

[c229] Sakaki, N., 1999, private communication.

[c230] Sakaki, N., et al., 1997, in Proceedings of the 25th International Cosmic Ray Conference, 1997, Durban, edited by M. S. Potgieter, B. C. Raubenheimer, and D. J. van der Walt (World Scientific, Singapore), Vol. 5, p. 217.

[c231] Sakaki, N., et al., 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 1, p. 353.

[c232] Sciutto, S. J., 1999, GAP 1999-020 (Auger Project, Fermi National Accelerator Laboratory), see http://www.auger.org/admin

[c233] Sigl, G., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 237.

[c234] Sigl, G., M. Lemoine, and P. Biermann, 1999, Astropart. Phys. 10, 141.

[c235] Sigl, G., M. Lemoine, and A. V. Olinto, 1997, Phys. Rev. D 56, 4470.

[c236] Sokolsky, P., 1993, in Proceedings of the Tokyo Workshop on Techniques for the Study of Extremely High Energy Cosmic Rays, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 280.

[c237] Sokolsky, P., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 253.

[c238] Sokolsky, P., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 65.

[c239] Sokolsky, P., P. Sommers, and B. R. Dawson, 1992, Phys. Rep. 217, 225.

[c240] Stanev, T., 1997, Astrophys. J. 479, 290.

[c241] Stanev, T., P. L. Biermann, J. Lloyd-Evans, J. P. Rachen, and A. A. Watson, 1995, Phys. Rev. Lett. 75, 3056.

[c242] Stanev, T., and A. M. Hillas, 1999, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 4, p. 365.

[c243] Stanev, T., and H. P. Vankov, 1997, Phys. Rev. D 55, 1365.

[c244] Stecker, F. W., 1973, Astrophys. Space Sci. 20, 47.

[c245] Stecker, F. W., 1989, Nature (London) 324, 401.

[c246] Stecker, F. W. and M. H. Salamon, 1999, Astrophys. J. 512, 521.

[c247] Streitmatter, R. E., 1998, in Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers from ${> 10}^{20}$ eV Particles from Space, AIP Conf. Proc. No. 433, edited by J. F. Krizmanic, J. F. Ormes, and R. E. Streitmatter (AIP, Woodbury, NY), p. 95.

[c248] Suga, K., 1962, in Proceedings of 5th Interamerican Seminar on Cosmic Rays, edited by I. Escobar et al. (Laboratorio de Fisica Cosmic de la Universidad Mayor de San Andres, La Paz, Bolivia), Vol. 2, p. XLIX.

[c249] Takahara, F., 1990, Prog. Theor. Phys. 83, 1071L.

[c250] Takahara, F., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 61.

[c251] Takeda, M., et al., 1998, Phys. Rev. Lett. 81, 1163.

[c252] Takeda, M., et al., 1999a, Astrophys. J. 522, 225.

[c253] Takeda, M., et al., 1999b, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 3, p. 252.

[c254] Takeda, M., et al., 1999c, in Proceedings of the 26th International Cosmic Ray Conference, Salt Lake City, Vol. 3, p. 276.

[c255] Telescope Array Project Design Report, 1998, Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan (in Japanese).

[c256] Teshima, M., M. Nagano, T. Hara, N. Hayashida, M. Honda, K. Kamata, T. Kifune, and H. Ohoka, 1990, Phys. Rev. Lett. 64, 1628.

[c257] Teshima, M., et al., 1986a, Nucl. Instrum. Methods Phys. Res. A 247, 399.

[c258] Teshima, M., et al., 1986b, J. Phys. G 12, 1097.

[c259] Totani, T., 1998a, Astrophys. J. Lett. 502, L13.

[c260] Totani, T., 1998b, Astrophys. J. Lett. 509, L81.

[c261] Toyoda, Y., et al., 1965, in Proceedings of the 9th International Cosmic Ray Conference, London (Institute of Physics, London), Vol. 2, p. 708.

[c262] Uchihori, Y., 1999, private communication.

[c263] Uchihori, Y., M. Nagano, M. Takeda, M. Teshima, J. Lloyd-Evans, and A. A. Watson, 2000, Astropart. Phys. 13, 151.

[c264] Uchihori, Y., et al., 1996, in Proceedings of the International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 50.

[c265] Vietri, M., 1995, Astrophys. J. 453, 883.

[c266] Walker, R., and A. A. Watson, 1981, J. Phys. G 7, 1297.

[c267] Walker, R., and A. A. Watson, 1982, J. Phys. G 8, 1131.

[c268] Watson, A. A., 1991, Nucl. Phys. B (Proc. Suppl.) 22, 116.

[c269] Watson, A. A., 1992, Nucl. Phys. B (Proc. Suppl.) 28, 3.

[c270] Watson, A. A., 1997, in Proceedings of ICRR Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future Observatories, edited by M. Nagano (Institute of Cosmic Ray Research, University of Tokyo, Tokyo, Japan), p. 362.

[c271] Watson, A. A., and J. G. Wilson, 1974, J. Phys. G 7, 1199.

[c272] Waxman, E., 1995, Phys. Rev. Lett. 75, 386.

[c273] Waxman, E., and J. Miralda-Escude, 1996, Astrophys. J. Lett. 472, L89.

[c274] Wdowczyk, J., W. Thaczyk, and A. W. Wolfendale, 1972, J. Phys. A 5, 1419.

[c275] Wdowczyk, J., and A. W. Wolfendale, 1984, J. Phys. A 10, 1453.

[c276] Weiler, T. J., 1982, Phys. Rev. Lett. 49, 234.

[c277] Weiler, T. J., 1984, Astrophys. J. 285, 495.

[c278] Werner, K., 1993, Phys. Rep. 232, 87.

[c279] Wibig, T., and A. Wolfendale, 1999a, J. Phys. G 25, 557.

[c280] Wibig, T., and A. Wolfendale, 1999b, J. Phys. G 25, 1099.

[c281] Winn, M. M., J. Ulrichs, L. S. Peak, C. B. A. McCusker, and L. Horton, 1982, in Catalog of Highest Energy Cosmic Rays, edited by M. Wada (World Data Center of Cosmic Rays, Institute of Physical and Chemical Research, Itabashi, Tokyo, Japan), Vol. 2, p. 1.

[c282] Winn, M. M., J. Ulrichs, L. S. Peak, C. B. A. McCusker, and L. Horton, 1986, J. Phys. G 12, 675.

[c283] Yodh, G. B., et al., 1983, Phys. Rev. D 27, 1183.

[c284] Yoshida, S., G. Sigl, and S. Lee, 1998, Phys. Rev. Lett. 81, 5505.

[c285] Yoshida, S., and M. Teshima, 1993, Prog. Theor. Phys. 89, 833.

[c286] Yoshida, S., et al., 1994, J. Phys. G 20, 651.

[c287] Yoshida, S., et al., 1995, Astropart. Phys. 3, 105.

[c288] Zatsepin, Z. T., and V. A. Kuz’min, 1966, Zh. Eksp. Teor. Fiz. Pis'ma Red. 4, 144.

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