Multiple Meson Production by Photons in Hydrogen

Abstract

The analysis of 235 events of double meson production by photons with energy up to 1.1 Bev (reaction $\ensuremath{\gamma}+p\ensuremath{\rightarrow}p+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$) observed in a ${\mathrm{H}}_{2}$ diffusion cloud chamber has produced the following results. The cross section rises rapidly at about 500 Mev to a value of approximately 70 \ensuremath{\mu}b. The angular, momentum, and $Q$ distributions of the reaction products cannot be satisfactorily accounted for either by a pure statistical model, or by a pure isobaric state model, or by a model assuming interaction of the incoming photon with the meson cloud of the proton, leading to $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ interaction. The observation of 14 cases of the reactions $\ensuremath{\gamma}+p\ensuremath{\rightarrow}p+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}+{\ensuremath{\pi}}^{0}$ and $\ensuremath{\gamma}+p\ensuremath{\rightarrow}n+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$ suggests that the combined cross section for these reactions is about 10 \ensuremath{\mu}b between 700 and 1000 Mev.