Spin observables in the $NN\to Y{\Theta }^{+}$ reaction at the threshold and quantum numbers of the ${\Theta }^{+}$ pentaquark

Abstract

General formulae for the spin-spin correlation parameters $C_{i,j}$ and spin-transfer coefficients $K_i^j$ are derived for the reaction $NN\to Y{\Theta }^{+}$ at the threshold for an arbitrary spin of the pentaquark ${\Theta }^{+}$. It is shown that a measurement of the sign of $C_{y,y}$ or an observation of the non-zero polarization transfer from the nucleon to the hyperon $Y$ allow one to determine the P-parity of the ${\Theta }^{+}$ unambiguously and independently on the spin of the ${\Theta }^{+}$. Measurement of these spin observables in the both $pp$- and $pn$- channels of this reaction determines also the isospin of the ${\Theta }^{+}$.

12 pages, Latex