On the determination of the parity of the ${\Theta }^{+}$

Abstract

We critically examine the possibility of determining the parity of the ${\Theta }^{+}(1540)$ from the reactions $NN\to {\Theta }^{+}Y$ ($Y$ = $\Lambda$, $\Sigma$) recently discussed in the literature. Specifically, we study the energy dependence of those observables that were suggested to be the most promising ones to unravel the parity of the ${\Theta }^{+}$, namely the spin correlation coefficient $A_{xx}$, and the spin transfer coefficient $D_{xx}$. We show that the energy dependence of ${\sigma }_0(1+A_{xx})$, corresponding to the spin-triplet production cross section, guarantees unambiguous information on the parity of the ${\Theta }^{+}$. Here, ${\sigma }_0$ denotes the unpolarized cross section. Also, the possibility to determine the parity of the ${\Theta }^{+}$ through the energy dependence of ${\sigma }_0{D}_{xx}$ is discussed.

Comments: 13 pages, 6 figures