Study of Inclusiveγandπ0Production in 12.4-GeV/cppInteractions

From an exposure of the Argonne National Laboratory 12-foot bubble chamber to a beam of 12.4-GeV/c protons we have obtained a 3649-event sample of the reaction $\mathrm{pp}\to \gamma +\mathrm{anything}$, where we observe photon conversions into $e^{+}{e}^{-}$ pairs in the liquid hydrogen. We find that the invariant cross section for this reaction does not separate in its $x$ and $P_{\perp }$ dependence at our energy. By setting upper bounds on the cross sections for inclusive $\eta$ and ${\Sigma }^0$ production, we show that ${\pi }^0$ decay is the dominant source of photons and therefore measure the cross section for inclusive ${\pi }^0$ production to be $\sigma \left({\pi }^0\right)=(31.5\mathrm{}\pm 2.6)$ mb. Comparison with the inclusive ${\pi }^{+}$ and ${\pi }^{-}$ cross sections at 12.0 GeV/c shows that the relation $2\sigma \left({\pi }^0\right)=\sigma \left({\pi }^{+}\right)+\sigma \left({\pi }^{-}\right)$ is well satisfied. We confirm earlier indications that the average number of ${\pi }^0\text{'}\mathrm{s}$ per inelastic $\mathrm{pp}$ interaction is approximately independent of the number of associated charged particles produced.