Mean Free Path of High-Energy Nucleons in the Atmosphere

Abstract

An altitude-variation experiment to determine the absorption mean free path in the atmosphere of high-energy nucleons of the cosmic radiation has been performed using a large ionization chamber and associated counter trays. It is estimated that the nucleons studied in this experiment range in energy from 200 to 2000 Bev, which is a higher energy region than has been investigated previously in similar experiments. The absorption mean free path for protons is found to be 125 plus or minus 9 g/cm/sup 2/ and for neutrons 105 plus or minus 8 g/cm/sup 2/, and the charged-to-neutral ratio is 1.54 plus or minus 0.15. These values are in good agreement with previous altitude variation experiments. There seems to be no change in the mean free path with energy. These results are compared with the calculations of Olbert and Stora, who consider the Fermi model for nuclear interactions with the assumption of no nucleon-antinucleon pair production and partial elasticity for the collision. It is seen that the experimental values fit fairly well into this picture. Evidence is presented for the presence of high-energy nucleons near the cores of air showers, in agreement with previous work. If a power law is fitted to themore » density spectrum of air showers associated with nucleons, a crude value of 0.64 may be found for the exponent. Considering the scarcity of the data on which the evaluation of this particular quantity is based, the result may be in reasonably good agreement with the only previous determination which is equal to 0.5. (auth)« less