Time structure of the hadronic component of extensive air showers

Abstract

A detailed study of the time structure of hadrons of energy > 5 GeV in extensive air showers has been carried out at Ootacamund (8.00 gm/cm²) using a total absorption spectrometer at the centre of the T.I.F.R. air shower array. A comparison of the experimental results with theoretical calculations shows that the experimentally observed spectra can be explained only on the basis of a rather large production (∼ 15%) of mucleon-antinucleon pairs among the secondaries of high energy interactions. Also it has been shown that an isobar-cum-pionisation type of model is preferred to a pure pionisation model in ultra high energy interactions. A small fraction of hadrons (∼ 0.5%) of energy > 20 GeV are found to arrive considerably delayed (> 25 ns) with respect to the shower front. While these are indicative of the presence of heavy mass particles (M ∼ 10 GeV/c²) among the hadrons in air showers it is concluded experiments of a more direct nature are essential for establishing the production of heavy mass particles. In this paper all the details regarding the experimental set up, the procedures for classification and analysis of data and the methods adopted for the evaluation of the errors in the measurement of energy and time delay are presented and the main conclusions from the experimental results summarised. Details of calculations of the time structure functions on the basis of different models of high energy interactions and a critical discussion of the comparison of the experimental results with theoretical predictions are presented elsewhere.