The angular distribution and attenuation of the star-producing component of cosmic rays

Some properties of cosmic rays at 3570 m have been studied by observing nuclear dis-integrations in G5 emulsion under lead absorbers. Good geometrical definition was ensured by making these absorbers in the form of inverted lead cones of various half-angles. The nuclear cascade process is such that the overall attenuation in lead of the star-producing component increases with energy, the attenuation length varying from 370 ± 30 to 210 ± 70 g cm -2 over the range of energy responsible for the stars examined. Interpretation of the results to give the angular distribution of the star-producing radiation depends upon the nature of the cascade process. However, it is certainly more collimated than a cos 2 Θ steradian -1 distribution, where Θ is the zenith angle, and may be of the form cos 4 Θ steradian -1 for the high-energy component. For the charged component alone a direct measurement gave cos 5 ± 1 Θ steradian -1 . The rate of production in emulsion under no absorber of all stars with three or more heavy prongs is 17·0 ± 0·4 cm -3 day -1 .