A possibility to determine the P-parity of the $Θ^+$ pentaquark in the ${p}{n}\to Λ^0Θ^+$ reaction

Abstract

Spin structure of the reaction ${\vec p}{\vec n}\to {\vec Λ^0} {\vec Θ}$ is analysed at the threshold in a model independent way under assumption that the $Θ^+$ is an isosinglet. We found that the sign of the spin-spin correlation parameter $C_{x,x}$ being measured in a double-spin experiment, determines the P-parity of the $Θ^+$ unambiguously. Furthermore we show that the polarization coefficients $K_x^x,K_y^y$ and $K_z^z$ which describe the polarization transfer from polarized beam or target to the final $Λ^0$ and $Θ^+$ are nonzero for a positive parity of the $Θ^+$ and equal zero for a negative parity. It allows one to determine the P-parity of the $Θ^+$ in a single-spin measurement, since the polarization of the $Λ^0$ can be measured via its decay $Λ^0\to π^-+ p$.