THE SIGNATURE OF A CORRELATION BETWEEN COSMIC-RAY SOURCES ABOVE 10(19) EV AND LARGE-SCALE STRUCTURE

We analyze the anisotropy signature expected if the high-energy (>10(1 9) eV) cosmic-ray (CR) sources are extragalactic and trace the distrib ution of luminous matter on large scales. We investigate the dependenc e of the anisotropy on both the relative bias between the CR sources a nd the galaxy distribution and on the (unknown) intrinsic CR source de nsity. We find that the expected anisotropy associated with the large- scale structure (LSS) should be detected once the number of CR events observed above 10(19) eV is increased by a factor of similar to 10. Th is would require similar to 30 observation-years with existing experim ents, but less than 1 year with the proposed similar to 5000 km(2) Aug er detectors. We find that the recently reported concentration of the Haverah Park CR events toward the supergalactic plane is not consisten t with the known LSS. If real, the Haverah Park result suggests that t he CR sources are much more concentrated toward the supergalactic plan e than the known LSS. Our results are not sensitive to the number dens ity of CR sources. We show that once the number of detected events is increased by a factor of similar to 10, the number density would be st rongly constrained by considering the probability of having repeating sources.