The effect of the in-medium ${\Theta }^{+}$ pentaquark on the kaon optical potential

Abstract

The kaon nuclear optical potential is studied including the effect of the ${\Theta }^{+}$ pentaquark. The one-nucleon contribution is obtained using an extension of the Jülich meson-exchange potential as bare kaon-nucleon interaction. Significant differences between a fully self-consistent calculation and the usually employed low-density $T\rho$ approach are observed. The influence of the one-nucleon absorption process, $KN\to {\Theta }^{+}$, on the kaon optical potential is negligible due to the small width of the pentaquark. In contrast, the two-nucleon mechanism, $KNN\to {\Theta }^{+}N$, estimated from the coupling of the pentaquark to a two-meson cloud, provides the required amount of additional kaon absorption to reconcile with data the systematically low $K^{+}$-nucleus reaction cross sections found by the theoretical models.

Comments: 9 pages, 6 figures. Extended discussion on absorption and reaction cross sections. Accepted in Phys. Lett. B