Low energy antikaon-nucleon/nuclei interaction studies by AMADEUS

The AMADEUS experiment at the DAφNE collider of LNF-INFN deals with the investigation of the at-rest, or low-momentum, K- interactions in light nuclear targets, with the aim to constrain the low energy QCD models in the strangeness sector. The 0 step of the experiment consisted in the reanalysis of the 2004/2005 KLOE data, exploiting K- absorptions in H, 4He, 9Be and 12C, leading to the first invariant mass spectroscopic study with very low momentum (about 100 MeV) in-flight K- captures. With AMADEUS step 1 a dedicated pure Carbon target was implemented in the central region of the KLOE detector, providing a high statistic sample of pure at-rest K- nuclear interaction. The first measurement of the non-resonant transition amplitude |AK- n→Λπ- | at s=33 MeV below the K̄N threshold is presented, in relation with the Λ(1405) properties studies. The analysis procedure adopted in the search for K- multi-nucleon absorption cross sections and Branching Ratios will be also described.