The structure of the shower front of large extensive air showers

Abstract

Using a method described previously (Baxter et al. 1966), an experimental study has been made of the time distribution of energy from the shower front of large extensive air showers detected by the Haverah Park 500-m array. Data are given on the mean time of arrival of energy in showers at axial distances over the range 250–950 m for all zenith angles, while average time distributions of the energy in the shower front are presented for some typical distance and zenith angle intervals. Experimental observations are compared with a theoretical prediction; a real discrepancy appears to exist between theory and experiment since about 25% more energy is observed in the 25 ns after the first detectable signal than is predicted. The result suggests a higher or more concentrated origin for muons than normally assumed.Assessment of measurement errors, particularly those arising from the sampling of a diffuse shower front by detectors of finite size, suggests that no intrinsic differences in the properties of the majority of air showers have yet been detected by this method.