Hypernuclear weak decay studies with FINUDA

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. Charged mesonic decay rates have been determined based on the analysis of π − kinetic energy spectra, never measured before. The study of proton spectra from non-mesonic weak decay for p-shell hypernuclei, both single and in coincidence with a neutron, has triggered the investigation of the two-nucleon induced ΛNN →nNN decay channel: its weight has been evaluated to be Γ2/ΓNM = 0.21±0.07stat +0.03 sys −0.02 sys. Finally, a direct experimental evidence of the occurrence of the weak reaction Λnp →nnp in nuclei is presented for the first time. Three events have been found which can be attributed to 7 ΛLi and 9 ΛBe two-nucleon induced non-mesonic weak decay; the kinematical analysis is discussed here.