High-Energy Meson Production

Abstract

The angular distributions of penetrating secondary particles from showers originating in lead and in carbon have been studied. Because the distributions for the two materials are very similar, it seemed meaningful to analyze them in terms of nucleon-nucleon collisions. From the kinetics of such collisions, it is possible to estimate the energy of the primary producing the interaction. If the angular distribution in the center-of-mass system is uniform, then $\frac{F(\ensuremath{\theta})}{1\ensuremath{-}F(\ensuremath{\theta})}={{\ensuremath{\gamma}}_{c}}^{2}{tan}^{2}\ensuremath{\theta}$ where $F(\ensuremath{\theta})$ is the fraction of the shower particles emitted within an angle $\ensuremath{\theta}$ in the laboratory system and ${\ensuremath{\gamma}}_{c}$ is the $\ensuremath{\gamma}$ of the center-of-mass motion. By making plots of $log[\frac{F}{(1\ensuremath{-}F)}]$ vs $logtan\ensuremath{\theta}$, the ${\ensuremath{\gamma}}_{c}$ of the interaction is found. Also, it is established that the angular distribution of particles produced in 10-40 Bev interactions is uniform in the center-of-mass system.The average number of mesons produced in showers of about 30-Bev primary energy is 3 to 4. From estimates of secondary momenta it appears that, on the average, the mesons are produced with about 500-Mev energy in the center-of-mass system. Thus the collision of a 30-Bev nucleon with a target nucleon would seem to be, on the average, not 100 percent inelastic.A rough determination has been made of the mean free path for penetrating shower production versus energy for the secondary $\ensuremath{\pi}$-mesons. The cross section for further meson production is found to be about 0.1 geometric in lead at 1 Bev rising to geometric for energies greater than 4 Bev. The secondaries produced in meson-nucleon collisions seem to be distributed uniformly in the center-of-mass system.Arguments are presented to show that less than 15 percent of the secondaries of penetrating showers are heavy mesons.