EXA2011

The AMADEUS experiment [1] is the proposal presented at the DAFNE collider to investigate the antikaon-nucleon potential in the nuclear enviroment, and it is being preceded by the study of the hadronic interactions of K- in the 4He of the drift chamber of KLOE [2]. Studies on the field has a rather long story at DAFNE, starting with the DEAR and SIDDHARTA [3] experiment measuring the strong interaction in the kaonic hydrogen and other kaonic atoms. The approach proposed by the AMADEUS experiment deals with one of the current hot topics in low-energy QCD, how deep is the antikaon-nucleon potential in the nuclear enviroment, and the possible existance of the kaonic clusters, where and antikaon plays glue-like role to bind nucleons forming deep states with a narrow width. The intense theoretical debate between phenomenological optical potentials included in the original prediction [4] of the deeply bound kaonic nuclear states and the more recent calculations leading to larger widths and shallower potentials, and the different interpretations of the experimental results obtained so far (KEK, FINUDA, DISTO, etc) indicate the strong need of a dedicated experiment to the study of this scientific case. The advantage of the AMADEUS proposal resides in the use of the large drift chamber of KLOE [5] and the almost full acceptance calorimeter, implemented with new devices around the interaction region to measure via missing mass and invariant mass the properties of the dibaryonic and trybarionic states when formed by the interaction of a stopped K- in light nuclei. R&D work has already started to construct a dedicated target and trigger system for further improvements on kaon stopping efficiency and background suppression, taking, moreover, advantage of the high luminosity reached by the recently upgraded [6] DAFNE accelerator. The AMADEUS collaboration is investigating the hadronic interactions of K- in the KLOE setup in the collected data from previous KLOE runs. Being the drift chamber composed mainly by helium, 0.1% of the K- should be stopped in the gas, giving an unique scenario to study the developed hadronic interactions in such an "active target". Results of the analysis of 2005 KLOE data are presented together with a study of the acceptancy of the spectrometer for such kind of evens using Monte Carlo. [1] The AMADEUS collaboration, LNF preprint, LNF–07/24(IR) (2007). [2] O. Vazquez Doce, presentation on 40th LNF Scientific Committee, http://www.lnf.infn.it/committee/ (2010). [3] Y. Akaishi and T. Yamazaki, Phys. Rev. C 65, 044005 (2002). [4] M. Cargnelli et. al., Nucl. Phys. A 835, 27-34 (2010). [5] M. Adinolfi et al., Nucl. Instr. Meth. A 488, 51-73 (2002). [6] M. Zobov et. al., arXiv:0802.2667v1 [physics.acc-ph] (2008).