Neutral-strange-particle production in 200-Gev/cpπ+K+interactions on Au, Ag, and Mg

We have used the Fermilab 30-in. bubble-chamber-hybrid spectrometer to study neutral-strange-particle production in the interactions of 200-GeV/c protons and ${\pi }^{+}$ and $K^{+}$ mesons with nuclei of gold, silver, and magnesium. Average multiplicities and inclusive cross sections for $K^0$ and $\Lambda$ are measured, and a power law is found to give a good description of their $A$ dependence. The exponent characterizing the $A$ dependence is consistent with being the same for $K^0$ and $\Lambda$ production, and also the same for proton and ${\pi }^{+}$ beams. Average $K^0$ and $\Lambda$ multiplicities, as well as their ratio, have been measured as functions of the numbers of projectile collisions ${\nu }_p$ and secondary collisions ${\nu }_s$ in the nucleus, and indicate that rescattering contributes significantly to enhancement of $\Lambda$ production but not to $K^0$ production. The properties of events with multiple $K^0\text{'}\mathrm{s}$ or $\Lambda \text{'}\mathrm{s}$ also corroborate this conclusion. $K^0$ rapidities are in the central region and decrease gently with increasing ${\nu }_p$, while $\Lambda$ rapidities are in the target-fragmentation region and are independent of ${\nu }_p$. $K^0$ and $\Lambda$ multiplicities increase with the rapidity loss of the projectile, but their rapidities do not.