K−-Nucleus Optical Potential inK−-Mesonic Atoms

Direct numerical calculations in $K^{-}$-mesonic atoms have shown that the perturbation theory commonly used is inadequate. The theory fails to describe the very strong repulsive (level-shift) effect due to the absorptive part of the optical potential. Because of this large repulsive effect, the optical potentials best fitted to the recent level-shift and width data are found to be attractive. The potential may be very attractive, but not enough to produce a $K^{-}$-nucleus bound state by the strong interaction against the strong repulsive effect of the large imaginary part: The latter works as if it were a hard core. Taking the $3d$ state of the $K^{-}-{\mathrm{S}}^{32}$ atom as a model, we also examine how well we can determine the nuclear-density parameters from the $K^{-}$-mesonic-atom spectra within the optical-potential model.