K̄-nuclear deeply bound states?

Following the prediction by Akaishi and Yamazaki of relatively narrow K̄-nuclear states, deeply bound by over 100 MeV where the main decay channel K̄N → π∑ is closed, several experimental signals in stopped K^- reactions on light nuclei have been interpreted recently as due to such states. In this talk I review (i) the evidence from K ^--atom data for a deep K̄-nucleus potential, as attractive as V_K̄-(ρo) ∼ - (150 - 200) MeV at nuclear matter density, that could support such states; and (ii) the theoretical arguments for a shallow potential, V_K̄(ρo) ∼ - (40 - 60) MeV. I then review a recent work by Mareš, Friedman and Gal in which K̄-nuclear bound states are generated dynamically across the periodic table, using a RMF Lagrangian that couples the K̄ to the scalar and vector meson fields mediating the nuclear interactions. The reduced phase space available for K absorption from these bound states is taken into account by adding a density- and energy-dependent imaginary term, underlying the corresponding K̄-nuclear level widths, with a strength constrained by K^--atom fits. Substantial polarization of the core nucleus is found for light nuclei, with central nuclear densities enhanced by almost a factor of two. The binding energies and widths calculated in this dynamical model differ appreciably from those calculated for a static nucleus. These calculations provide a lower limit of Γ_K̄ ∼ 50 ± 10 MeV on the width of nuclear bound states for K̄ binding energy in the range B_K̄ = 100 - 200 MeV.