Latitude and Altitude Dependence of the Local Hard Showers of Cosmic Rays

Abstract

The latitude effect of the local hard showers penetrating at least 350 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$ of lead has been measured at two airplane altitudes, and found to be (12±2) percent between Rome, New York, and Canal Zone. The two separate latitude effects, obtained respectively at 30,500 ft. (300 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$) and at 25,000 ft. (383 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$ coincide within the experimental errors. This slow dependence on altitude of the latitude effect seems to allow an estimate of the energy of the hard shower producing particles as they arrive at the apparatus. An average energy of 20 to 30 Bev is obtained from the present data and the current ideas on the absorption of the nucleonic component. This large value is discussed in connection with other experiments and in view of the fact that at sea level or at mountain altitudes pi-mesons of that energy have a large probability of undergoing a nuclear collision before decaying into mu-mesons. The measured altitude dependence of hard showers gives for the absorption mean free path of the producing radiation in air, the value of 112±2 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$, if interpreted in terms of a simple exponential. However, because of the geometry of the apparatus, the value 140 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^2$, as obtained from the data according to the Gross transform, seems to be more acceptable when referred to strictly vertical particles. The latitude effect of the normal penetrating component was 1.33 at 30,500 ft., 1.24 at 25,000 ft., and 1.08 at sea level.