Study of Neutral Pion Production in Proton-Proton Collisions

A large lead glass Čerenkov counter has been used to measure the energy spectrum of gamma rays resulting from neutral pions produced in proton-proton collisions. A liquid hydrogen target was bombarded with protons of 447 Mev, 415 Mev, and 397 Mev. Gamma rays emitted at 90° to the incident proton beam were detected by a counter telescope comprised of an anticoincidence counter, a $\frac{1}{8}$-in. lead converter, two coincidence counters, and the lead glass counter. Pulses from the lead glass counter were fed through a gating circuit into a one-hundred channel pulse-height analyzer. The three pulse-height spectra obtained have been compared with those predicted from the phenomenological theory, to estimate the contributions of the various possible final angular momentum states. It is found that the spectra are consistent with isotropic emission of the ${\pi }^0\text{'}\mathrm{s}$ in the center-of-mass system. The differential cross sections for ${\pi }^0$ production are 12.6±2.0, 9.0±1.9, and 7.4±1.7 microbarns/sterad at 445, 415, and 397 Mev, respectively.