The Residual Range of Delayed Particles in Extensive Air Showers

Abstract

The arrival times of the penetrating particles of extensive air showers relative to that of the electrons have been studied by means of short reaction time Geiger counters. A 50 channel hodoscope has been used to identify the penetrating particles and measure their residual ranges where these lay between 15 and 30 cm of lead. From observations on 782 showers of median density 70 particles m-' in which a Penetrating component was detected, it was deduced that between 3 and 9 particles in 104 shower particles from showers of median density 28 particles m-', have delays <5 X 10-8 sec and are able to penetrate 15 em of lead. It follows that 81-94 per cent. of the delayed particles found by Jelley and Whitehouse (1953) without the use of absorbers, must be stopped by 15 cm of lead. This indicates a height of production below 0·8 km for at least half of these particles.