Search for Correlated High Energy Cosmic Ray Events with CHICOS

We present the results of a search for time correlations in high energy cosmic ray data (primary E > 10^14 eV) collected by the California HIgh school Cosmic ray ObServatory (CHICOS) array. Data from 60 detector sites spread over an area of 400 km^2 were studied for evidence of isolated events separated by more than 1 km with coincidence times ranging from 1 µs up to 1 s. The results are consistent with the absence of excess coincidences except for a 2.9σ excess observed for coincidence times less than 10 µs. We report upper limits for the coincidence probability as a function of coincidence time.