Scattering and Absorption ofπ+Mesons in Lead

The interactions of 50±15-Mev ${\pi }^{+}$ mesons in lead were investigated by means of a magnet cloud chamber containing a single $\frac{1}{8}$-inch lead plate. The following cross sections were found: for elastic scattering greater than 40°, 252±36 mb; for star production, 852±82 mb; for charge-exchange scattering, 27±19 mb. Only one of the 52 observed scatters was inelastic. The elastic scattering has a minimum near 90°. The mean free path of ${\pi }^{+}$ mesons in nuclear matter, derived from the inelastic events and large-angle scatters in this experiment, is (9.0±1.5)×${10}^{-13\mathrm{}}$ cm. The results are compared with information from related experiments.