How to measure the parity of the ${\Theta }^{+}$ in $\vec{p}\vec{p}$ collisions

Abstract

Triggered by a recent paper by Thomas, Hicks and Hosaka, we investigate which observables can be used to determine the parity of the ${\Theta }^{+}$ from the reaction $\vec{p}\vec{p}\to {\Sigma }^{+}{\Theta }^{+}$ near its production threshold. In particular, we show that the sign of the spin correlation coefficient $A_{xx}$ for small excess energies yields the negative of the parity of the ${\Theta }^{+}$. The argument relies solely on the Pauli principle and parity conservation and is therefore model--independent.

Comments: References completed, discussion on possible influence of background added; conclusions unchanged