Variational calculation of the ppK- system based on chiral SU(3) dynamics

The ppK- system, as a prototype for possible quasibound K̄ nuclei, is investigated using a variational approach. Several versions of energy-dependent effective K̄N interactions derived from chiral SU(3) dynamics are employed as input, together with a realistic NN potential (Av18). Taking into account theoretical uncertainties in the extrapolations below the K̄N threshold, we find that the antikaonic dibaryon ppK- is not deeply bound. With the driving s-wave K̄N interaction the resulting total binding energy is B(ppK-)=20±3 MeV and the mesonic decay width involving K̄N→πY is expected to be in the range 40-70 MeV. Properties of this quasibound ppK- system (such as density distributions of nucleons and antikaon) are discussed. The Λ(1405), as an I=0 quasibound state of K̄ and a nucleon, appears to survive in the ppK- cluster. Estimates are given for the influence of p-wave K̄N interactions and for the width from two-nucleon absorption (K̄NN→YN) processes. With inclusion of these effects and dispersive corrections from absorption, the ppK- binding energy is expected to be in the range 20-40 MeV, whereas the total decay width can reach 100 MeV but with large theoretical uncertainties.