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 69 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 microseconds up to 1 second. We report upper limits for the coincidence probability as a function of coincidence time. 
R. D. McKeown, B. E. Carlson, E. Brobeck, C. J. Jillings, M. B.   Larson, T. W. Lynn, J. E. Hill, B. J. Falkowski, R. Seki, ...