Study of some two-body non-mesonic decays of ^4_ΛHe and ^5_ΛHe

The Non-Mesonic (NM) decay of ^4_ΛHe and ^5_ΛHe in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations are scarce. The ^4_ΛHe→ d+d, p+t decay channels simultaneously observed by FINUDA on several nuclei are compared: the pt channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are (1.37± 0.37)× 10^-5/K^-_stop and (8.3± 1.0)× 10^-5/K^-_stop, respectively. Due to the capability of FINUDA of identifying ^5_ΛHe hypernuclei, a few ^5_ΛHe→ d+t decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: (3.0± 2.3)× 10^-3.