The lateral distribution of extensive air showers produced by cosmic rays above 10(19) eV as measured by water-Cerenkov detectors

Measurements of the lateral distribution function (Idf) of Extensive Air Showers (EAS) as recorded by the array of water-Cerenkov detectors at Haverah Park are described, and accurate experimental parameterizations expressing the mean Idf for 2 x 10(17) <E <4 x 10(18) eV, 50 <r <700 m, and theta <45 degrees are given. An extrapolation of these relations to the regime E greater than or equal to 10(19) eV and r >700 m is described: extrapolation in this energy domain appears valid, and an approximate correction term is given for the larger core distances. The results of recent Monte Carlo simulations of shower development and detector behavior are compared to the parameterized Idf. The agreement is good increasing confidence that these simulations may be trusted as design tools for the Auger project, a proposed 'next generation' detector system. (C) 1997 Elsevier Science B.V.