The average properties and fluctuations of the lateral distribution of large air showers

In this paper we describe the results of measurements on the lateral distribution of the water-Cerenkov signal recorded in showers initiated by primaries of energy greater than 2.1017eV. The measurements were made using the deep water-Cerenkov detectors of the Haverah Park infilled array (Edge et al 1977) during the period November 1976 - December 1980. Since our report at the Kyoto Conference (England et all 1979) we have almost doubled the data set which now consists of approximatively 1300 showers with zenith angles less than 450 and with primary energies in the range 2.1017 to 1019eV. The variation of the lateral structure function with energy and with zenith angle are described and the fluctuations in shower structure observed at fixed energy and zenith angle are derived. The elongation rate has been evaluated under certain assumptions