Photoproduction of positive pions from helium and hydrogen

Absolute yields of π⁺ mesons photoproduced from helium and hydrogen have been measured at 65°, 90°, 110°, 135° to the 320 MeV bremsstrahlung beam of the Glasgow electron synchrotron. Pions in the energy ranges 11–37 MeV and 63–69 MeV were detected in a scintillation counter telescope using a delayed coincidence technique. The photoproduction of π⁺ mesons from a bound proton in the helium nucleus is compared to that from a free proton.