Large Cosmic Ray Showers and Mesons

Abstract

IT has been pointed out recently by Bhabha, Carmichael and Chou¹ that a meson may produce a large cosmic ray shower by knocking on an atomic electron in a close collision; this electron then produces a shower by the ordinary cascade process. Previously, Bhabha² had come to the conclusion that large knock-on showers are comparatively unimportant; but he had based his argument on the assumption that the scattering of mesons by electrons could be described by the Dirac relativistic theory. However, Massey and Corben³ have shown that the effect of the spin of the meson is greatly to increase the scattering for high energies of the incident meson and the knocked-on electron. Using Massey and Corben's formula, Bhabha, Carmichael and Chou have shown that the experimental results of Carmichael and Chou⁴ can be reasonably well explained, whereas the previous theory predicted too few large showers.