The antikaon–nucleus interaction and alternative views to deeply bound antikaonic nuclear systems

Abstract

We present an overview of the latest theoretical studies on the antikaon properties in the nuclear medium, in connection with the recent experimental claims of very deeply bound antikaon nuclear states. We argue that proper many-body formulations using modern realistic antikaon–nucleon interactions are not able to generate such systems. Instead, a simple two-nucleon antikaon absorption mechanism where the remaining nucleus acts as spectator explains the enhancement observed in semi-inclusive proton momentum spectra, seen as a bump in the KEK PS-E549 experiment on a 4He target or as a peak in the FINUDA experiment on a 6Li target. This signal is clearly visible in another FINUDA experiment measuring the invariant mass of Λ-proton pairs after two-nucleon kaon absorption. We also show that another peak of this experiment, seen at lower invariant masses and interpreted as a bound K−pp state, is simply generated by the same two-nucleon absorption mechanism followed by final-state interactions of the produced particles with the residual nucleus. Our conclusion is that all the experimental claims for the formation of very deeply bound antikaonic nuclear systems receive an alternative explanation in terms of conventional nuclear processes.