Weak decay of Λ hypernuclei: Experimental status

The FINUDA experiment has recently completed an extensive study of the weak decay of p-shell Λ hypernuclei including both Mesonic and Non-Mesonic modes. The present paper is focused on the study of proton spectra from Non-Mesonic Weak Decay, both single and in coincidence with a neutron, which has triggered the investigation of the two nucleon-induced ΛNN→nNN decay channel. Furthermore thanks to the excellent performance of FINUDA in terms of long-term instrumental stability and fully reliable reconstruction and analysis programs it has been possible to isolate and kinematically reconstruct single events related to the occurrence of rare physical processes. Three events corresponding quite safely to the observation of the 2N-induced Non-Mesonic Weak Decay were analyzed and fully reconstructed. They are the experimental evidence for such a process, up to now conjectured only by indirect measurements. Discussion of the results is outlined.