Abstract
A liquid scintillation counter, of area 1000 cm2 and depth 15 cm has been developed for experiments on the delayed particles in extensive air showers. The scintillator was used in conjunction with two trays of Geiger counters to select showers of average density 10/m2; the prompt and delayed particles traversing the scintillator were recorded photographically in an arrangement in which possible sources of spurious delays were eliminated.
The existence of delayed particles has been confirmed and the delay distribution obtained over the range (3-70) × 10-8 second. This distribution could be represented by an exponential function with half of the delayed particles arriving within (10 ± 2) × 10-8 second. The total fraction of shower particles that suffer delays in the above range was found to be (0.85 ± 0.05)%.
There is evidence that showers with delayed events do not differ in average density from those without such events.
A control experiment was carried out to investigate any spurious effects; this revealed μ-e decay events in the scintillator at approximately the expected rate.