The Production of Charged Photomesons from Helium. Hydrogen-Helium Ratios. II

Abstract

A study similar to that made by the same authors on hydrogen and deuterium has been made of charged photomesons produced from helium. Measurements were made at the three angles of 45°, 90°, and 135°. ${\pi }^{+}$ mesons were detected by scintillation counters and delayed coincidence detection. ${\pi }^{+}$ and ${\pi }^{-}$ mesons were detected with Ilford C2-200μ nuclear emulsions. The $\frac{{\pi }^{-}}{{\pi }^{+}}$ ratios are 0.99±0.15, 1.07±0.17, and 0.91±0.13 for angles of 45°, 90°, and 135°, respectively. The total cross section for ${\pi }^{+}$ meson production is 4.8±1.0×${10}^{-29\mathrm{}}$ ${\mathrm{cm}}^2$ ${\mathrm{proton}}^{-1\mathrm{}}$ $Q^{-1\mathrm{}}$ for helium as compared to 10.3±2.1×${10}^{-29\mathrm{}}$ for hydrogen. This indicates that a proton in helium is about one half as effective as a free proton for the photoproduction of ${\pi }^{+}$ mesons. A comparison is made of the ${\pi }^{+}$ meson production from hydrogen, deuterium, helium, and carbon.