Particle representation for the kaonic NNK¯ system

Abstract

The kaonic system $NN\overline{K}$ is studied based on the configuration space Faddeev equations. We consider two models associated with isospin ``natural'' basis and isospin ``charge'' basis. One basis is related to another by a unitary transformation. We show that the ``particle representation'' for $NN\overline{K}({s}_{NN}=0)$ system motivated by the charge basis does not describe the system in terms of coupled particle channels $pp{K}^{\ensuremath{-}}/pn{\overline{K}}^{0}$. The coupling is associated with the nondiagonal elements of the matrix representation for the $N\overline{K}$ potential in the charge basis. The matrix can be diagonalized by a simple unitary transformation. With this relation, the Kyoto potential is discussed. The particle configurations of the $NN\overline{K}$ system may be classified by the presence or absence of the Coulomb interaction according to an analogy with the $NNN$ system. The $NN\overline{K}({s}_{NN}=0)$ system is represented by four particle configurations: $pp{K}^{\ensuremath{-}}$, $np{K}^{\ensuremath{-}}$, $np{\overline{K}}^{0}$, and $nn{\overline{K}}^{0}$.