K${}^{-}$-proton scattering and the $\Lambda (1405)$ in dense matter

Abstract

The scattering of antikaons with nucleons is studied in the nuclear environment. Describing the $\text{lam}$ as a $K^{-}$ proton bound state, we find, that due to the Pauli blocking of intermediate states, the mass of the $\Lambda (1405)$ is shifted upwards in energy, above the $K^{-}$ proton threshold and and its width is somewhat broadened. As a consequence the s-wave $K^{-}$--nucleon scattering length turns attractive at finite nucleon density ($\rho \ge 0.25{\rho }_0$) leading to a mean field potential for the $K^{-}$ of about $\sim -100\mathrm{MeV}$ in nuclear matter at ground state density. Consequences for Heavy Ion collisions and possible experimental checks for the structure of the $\text{lam}$ are discussed. (Figures will be sent on request)

Comments: 12 pages 5 figures, SUNY-NTG-94-27