Realistic calculations of K¯NN, K¯NNN, and K¯K¯NN quasibound states

Binding energies and widths of three-body K¯NN, and of four-body K¯NNN and K¯K¯NN nuclear quasibound states are calculated in the hyperspherical basis, using realistic NN potentials and subthreshold energy dependent chiral K¯N interactions. Results of previous K−pp calculations are reproduced and an upper bound is placed on the binding energy of a K−d quasibound state. A self-consistent handling of energy dependence is found to restrain binding, keeping the calculated four-body ground-state binding energies to relatively low values of about 30 MeV. The lightest strangeness −2 particle-stable K¯ nuclear cluster is most probably K¯K¯NN. The calculated K¯N→πY conversion widths range from approximately 30 MeV for the K¯NNN ground state to approximately 80 MeV for the K¯K¯NN ground state.