Low energy kaon-nuclei interaction studies at DAΦNE

The aim of the AMADEUS experiment is to investigate the lowenergy antikaon interaction with nucleons and nuclei, exploiting the unique lowmomentum beam of kaons produced by the DAΦNE collider at LNF-INFN, to constrain hadronic nuclear physics models in the strangeness -1 sector. As a first step the data collected in 2004/2005 by the KLOE collaboration, consisting in a complex of K−absorptions in H,4He,9Be and12C, was analyzed, leading to the first invariant mass spectroscopic study with very low momentum (about 100 MeV) in-flight K−captures. A dedicated pure Carbon target was also implemented in the central region of the KLOE detector, providing a high statistic reference sample of pure at-rest K−nuclear interaction. The first measurement of the non-resonant transition amplitude $\left| {{T_{{K^ - }n \to \Lambda {\pi ^ - }}}} \right|$ at $\sqrt s = 33$ MeV below the ${\text{\bar KN}}$ threshold is presented, in relation with the Λ(1405) properties studies.