  The main open problem in the physics of Lambda-hypernuclei is the lack of a
sound theoretical interpretation of the large experimental values for the ratio
G_n/G_p. To approach the problem, we have incorporated a Lambda N-> nN
one-meson-exchange model in an intranuclear cascade code for a finite nucleus
calculation of the nucleon-nucleon (angular and energy) coincidence
distributions in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C
hypernuclei. The two-nucleon induced decay mechanism, Lambda np-> nnp, has been
taken into account by means of the polarization propagator formalism in local
density approximation. With respect to single nucleon spectra studies, the
treatment of two-nucleon correlations allow a cleaner and more direct
determination, from data, of G_n/G_p. Our results agree with the preliminary
coincidence data of KEK-E462 for 5_Lambda-He. This allows us to conclude that
G_n/G_p for 5_Lambda-He should be close to 0.46, the value predicted by our
one-meson-exchange model for this hypernucleus. Unfortunately, to disentangle
one- and two-body induced decay channels from experimental non-mesonic decay
events, three-nucleon coincidences should be measured.
