Hints of energy dependences in AGASA extremely high energy cosmic ray arrival directions

A correlation and probability analysis of the distribution of arrival directions for a sample of AGASA events reported to have energies above 4×10¹⁹eV shows the small scale clustering to remain significant at the 99.5--99.9% C.L. and to be consistent with previous results. For the sample taken as a whole, there are no departures from either homogeneity or isotropy on angular scales greater than 5^∘. The sample of events with E>~6×10¹⁹eV contains no pairs with separations <4^∘. Cross correlating subsamples partitioned by energy reveal three uncorrelated distributions in the intervals (4--5)×10¹⁹eV, (5--8)×10¹⁹eV, and greater than 8×10¹⁹eV. The partition with 5<~E<8×10¹⁹eV is correlated with the supergalactic equatorial plane while the other two groups are statistically consistent with isotropic distributions. The presence of three distinct energy-partitioned groups of events could reflect possible changes in primary composition, different source distributions, differing levels of GZK losses, or deflection effects of magnetic fields.