Distribution of Arrival Times of Air Shower Particles

We have studied the instantaneous distribution of particles in extensive air showers at sea level by measuring the relative delays between particles with three liquid scintillation counters. The delays measured were in the range from 5 to 300 mμsec. The sizes of the showers were in the range from 10⁵ to 10⁶ particles. Using statistical methods of analysis we have found that at a given instant most electrons with energies of ~20 Mev lie in a flat disk of thickness between 1 and 2 meters. The particles which can penetrate at least 20 cm of lead lie in a disk of thickness between 2 and 3 meters. The disk of penetrating particles follows behind the disk of electrons by less then 3 meters. We measured the projected zenith angles of the axes of individual showers by measuring the delays between widely spaced counters. The standard deviation of a measurement of the sine of the projected zenith angle of a shower was 0.13. The root mean square of the sines of the projected zenith angles was found to be 0.24+/-0.015. If we assume a ⁿθ distribution law for the projected zenith angles we find n=15+/-1.2. We determined the spatial orientations of the axes of individual showers by measuring the projections of the zenith angles on two mutually perpendicular planes.