Evidence for the Multiple Production of Mesons in a Single Nucleon-Nucleon Collision

Abstract

Evidence has been obtained for the multiple production of mesons in a single nucleon-nucleon collision in a photographic emulsion exposed to the cosmic radiation at an altitude of 95,000 ft. The nuclear encounter in which the mesons were created was produced by a primary proton of 3\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ev energy. Directly in line with the incident proton 7 particles of minimum ionization were emitted in a central core with an angular divergence of 0.003 radian. In addition 8 other minimum ionization particles were emitted in a wider diffuse cone of 0.13 radian angular divergence. Only one track had the appearance of a fragment which, however, could have been a proton of 10-Mev energy. Most of the particles in the central core had energies in excess of 250 Bev, while those in the diffuse cone were of much lower energies as determined by small angle scattering measurements. A pair of very small angular divergence was produced in the central core 4800 microns from the point of origin of the nuclear interaction. Assuming that the pair were produced by a gamma-ray from the decay of a neutral meson, a lower limit of 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}15}$ second was deduced for its mean life. Both the angular and the energy distribution of the emitted particles is in good agreement with the assumption that in the center-of-mass system the mesons are emitted in two distinct cones of angular width of about 30\ifmmode^\circ\else\textdegree\fi{} forward and backward with reference to the direction of the primary proton. The average multiplicity of 15 agrees with the recent calculation by Fermi, and according to his prediction about one-half of the particles could be made up of nucleon-antinucleon pairs.