The Pentaquark ${\Theta }^{+}$ in $n{K}^{+}$ and $p{K}_S^0$, and its ${\Sigma }_5^{+}$ partner

Abstract

A systematic lowering in mass of strangeness ambiguous $p{K}_S^0$ peaks relative to the $n{K}^{+}$ is noted. We discuss how measurement of $\gamma p\to {\Theta }^{+}{K}_S^0\to p{K}_S^0{K}_S^0\to p{\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ in association with $\gamma p\to {\Theta }^{+}{K}_S^0\to n{K}^{+}{K}_S^0$ can help to clarify the nature of the narrow baryon state claimed in $p{K}_S^0$ invariant mass distributions. This can both establish the ${\Theta }^{+}$ in a single experiment and also reveal, or place severe limits on, the existence of an associated ${\Sigma }_5$ pentaquark.