Production of the pentaquark ${\Theta }^{+}$ in $np$ scattering

Abstract

We study $np\to \Lambda {\Theta }^{+}$ and $np\to {\Sigma }^0{\Theta }^{+}$ processes for both of the positive and negative parities of the ${\Theta }^{+}$. Employing the effective chiral Lagrangians for the $KNY$ and $K^{\ast }NY$ interactions, we calculate differential cross sections as well as total cross sections for the $np\to {\Sigma }^0{\Theta }^{+}$ and $np\to \Lambda {\Theta }^{+}$ reactions. The total cross sections for the positive-parity ${\Theta }^{+}$ turn out to be approximately ten times larger than those for the negative parity ${\Theta }^{+}$ in the range of the CM energy ${\sqrt{s}}_{\mathrm{th}}\le \sqrt{s}\le 3.5\mathrm{GeV}$. The results are rather sensitive to the mechanism of $K$ exchanges in the $t$ -- channel.

Comments: 9 pages and 11 figures