Analysis of large-scale anisotropy of ultra-high energy cosmic rays in HiRes data

Stereo data collected by the HiRes experiment over a six year period are examined for largescale anisotropy related to the inhomogeneous distribution of matter in the nearby Universe. We consider the generic case of small cosmic-ray deflections and a large number of sources tracing the matter distribution. In this matter tracer model the expected cosmic ray flux depends essentially on a single free parameter, the typical deflection angle θs. We find that the HiRes data with threshold energies of 40 EeV and 57 EeV are incompatible with the matter tracer model at a 95% confidence level unless θs > 10 ◦ and are compatible with an isotropic flux. The data set above 10 EeV is compatible with both the matter tracer model and an isotropic flux. University of Utah, Department of Physics and High Energy Astrophysics Institute, Salt Lake City, UT 84112, USA. Los Alamos National Laboratory, Los Alamos, NM 87545, USA. Rutgers — The State University of New Jersey, Department of Physics and Astronomy, Piscataway, NJ 08854, USA. Institute of High Energy Physics, Beijing, China Columbia University, Department of Physics and Nevis Laboratories, New York, NY 10027, USA. Montana State University, Department of Physics, Bozeman, MT, USA Université Libre de Bruxelles (ULB), CP225, Bld. du Triomphe, B-1050 Brussels, Belgium University of Tokyo, Institute for Cosmic Ray Research, Kashiwa City, Chiba 277-8582, Japan. University of New Mexico, Department of Physics and Astronomy, Albuquerque, NM 87131, USA.