Inclusive $\gamma$, ${\pi }^0$, $K^0$, and $\Lambda$ production in 12.4-GeV/c $pp$ interactions

In an exposure of the Argonne National Laboratory 12-foot hydrogen bubble chamber to a beam of 12.4-GeV/c protons, we have measured the total and differential cross sections for the inclusive reactions $p+p\to \gamma +X$, ${\pi }^0+X$, $K^0+X$, and $\Lambda +X$, as well as estimates for the inclusive $\eta$ and ${\Sigma }^0$ cross sections. We present the average number of ${\pi }^0$, $K^0$, and $\Lambda$ as a function of the associated charge multiplicity. We observe that the average charge multiplicity in $pp$ collisions is the same whether or not a ${\pi }^0$, $K^0$, or $\Lambda$ is also produced in the interaction. Invariant cross sections are presented as a function of $P_T^2$ and $x$, the Feynman scaling variable. The ${\pi }^0$ differential cross sections are consistent with the relation $\frac{d\sigma }{\mathrm{dP}}\left({\pi }^0\right)=\frac{1}{2}\left[\frac{d\sigma }{\mathrm{dP}}\right({\pi }^{+})+\frac{d\sigma }{\mathrm{dP}}({\pi }^{-}\left)\right]$ for all pion momenta $P$. The differential cross section for $\Lambda$ production indicates a break in the distribution of $|t-t_{min}|=1.4\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The polarization of the $\Lambda \text{'}\mathrm{s}$ is found to be consistent with zero for all values of $x$.