Study of chirally motivated low-energy K^- optical potentials

The K^- optical potential in the nuclear medium is evaluated self consistently from a free-space K^-N t matrix constructed within a coupled-channel chiral approach to the low-energy K̄N data. The chiral-model parameters are fitted to a select subset of the low-energy data plus the K^- atomic data throughout the periodic table. The resulting attractive K^- optical potentials are relatively 'shallow', with central depth of the real part about 55 MeV, for a fairly reasonable reproduction of the atomic data with χ²/N≈2.2. Relatively 'deep' attractive potentials of depth about 180 MeV, which result in other phenomenological approaches with χ²/N≈1.5, are ruled out within chirally motivated models. Different physical data input is required to distinguish between shallow and deep K^- optical potentials. The (K^-_stop,π) reaction could provide such a test, with exclusive rates differing by over a factor of three for the two classes of potentials. Finally, forward (K^-,p) differential cross sections for the production of relatively narrow deeply bound K^- nuclear states are evaluated for deep K^- optical potentials, yielding values considerably lower than those estimated before.