Production of Strange Particles by 2.77-BeV/cπ+Mesons on Hydrogen

Abstract

The Brookhaven 20-in. liquid-hydrogen bubble chamber was exposed to a beam of 2.77-BeV/c separated ${\pi }^{+}$ mesons. In a detailed study involving strange-particle production the well-known $K^{*}$ (mass 900 MeV) and ${Y_1}^{*}$ (mass 1385 MeV) were observed. The former was produced in the final state ${\Sigma }^{+}{\pi }^{+}{K}^0$, and the latter in the states ${\pi }^{+}{\pi }^{+}{\Lambda }^0{K}^0$ and ${\pi }^{+}{K}^{+}{\Lambda }^0$. It was necessary to include both $K$ and $K^{*}$ exchanges in order to explain the $K^{*}$ decay angular distributions. The decay angular distribution of the ${Y_1}^{*}$ gave evidence for a strong ${Y_1}^{*}$ polarization as well as spin $\ge \frac{3}{2}$. Furthermore, an examination of the reaction ${\pi }^{+}p{K}^0{K}^0$ showed that the (${\pi }^{+}p$) emerged as ${N^{*}}_{\frac{3}{2},\frac{3}{2}}$ coupled with a ($K^0{K}^0$) enhancement in the mass region from 1000 to 1040 MeV.