Coupled-channels Faddeev AGS calculation of $K^{-}ppn$ and $K^{-}ppp$ quasi-bound states
Using separable $\bar{K}N-\pi\Sigma$ potentials in the Faddeev equations, we calculated the binding energies and widths of the $K^{-}pp$, $K^{-}ppn$ and $K^{-}ppp$ quasi-bound states on the basis of three- and four-body Alt-Grassberger-Sandhas equations in the momentum representation. One- and two-pole version of $\bar{K}N-\pi\Sigma$ interaction are considered and the dependence of the resulting few-body energy on the two-body $\bar{K}N-\pi\Sigma$ potential was investigated. The $s$-wave [3+1] and [2+2] sub-amplitudes are obtained by using the Hilbert-Schmidt expansion procedure for the integral kernels. As a result, we found a four-body resonance of the $K^{-}ppn$ and $K^{-}ppp$ quasi-bound states with a binding energy in the range $B_{K^{-}ppn}\sim{55-70}$ and $B_{K^{-}ppp}\sim{90-100}$ MeV, respectively. The calculations yielded full width of $\Gamma_{K^{-}ppn}\sim{16-20}$ and $\Gamma_{K^{-}ppp}\sim{7-20}$ MeV.