Low-Energy Neutral Pion Photoproduction inH2and He

Abstract

The results of an experiment on the photoproduction of neutral pions from ${\mathrm{H}}_2$ and He in the very low-energy region are compared with the dispersion relation calculations of Chew, Goldberger, Low, and Nambu (C.G.L.N.). For ${\mathrm{H}}_2$, agreement was found for incident $\gamma$-ray energies above 155 Mev for $N^{+}\simeq +0.065\mathrm{}$ and disagreement below for all constant values of $N^{+}$. The He results give support to the C.G.L.N. effectiverange formulas for the small $p$-wave phase shifts.