DENSITY-DEPENDENCE IN KAONIC ATOMS

We study phenomenologically the density dependence of the K- optical potential V(opt)(r) at zero kinetic energy by fitting it to a comprehensive set of atomic data across the periodic table. Two families of solutions offer improved fits over that for the standard tffrho(r) parameterization of V(opt). One family contains solutions for V(opt) with RMS radii larger than those of the matter density rho, as expected from finite-range folding corrections. The other family offers substantially improved fits to the data and gives rise to Re V(opt) of a size smaller than that of rho. The new family contains solutions for which V(opt) is attractive inside the nucleus and on its surface, becoming repulsive at large distances. The repulsion can be made to approximately agree with the low-density limit V(opt) --> trho where t is the free-space KNBAR t matrix. It is argued that this sign flip might be expected from the underlying nuclear propagation of the LAMBDA (1405).