  Recent progress has been experienced in the field of hypernuclear weak decay,
especially concerning the ratio of the neutron- to proton-induced Lambda
non-mesonic decay rates, G_n/G_p. Theoretical analyses of nucleon coincidence
data have been performed in a finite nucleus framework. They led to the
extraction of G_n/G_p values in agreement with pure theoretical estimates, thus
providing an evidence for the solution of a longstanding puzzle. Here we
present an alternative approach to the problem, based on a nuclear matter
formalism extended to finite nuclei via the local density approximation. The
work is motivated by the exigence to make the determination of G_n/G_p from
data less model dependent. One-meson-exchange potentials are used for
describing both the one- and two-nucleon induced decays, Lambda N -> n N and
Lambda N N -> n N N. For the latter, treated within a microscopic approach, the
channels Lambda n n -> n n n and Lambda p p -> n p p are included in addition
to the mode Lambda n p -> n n p already considered, in a phenomenological way,
in previous studies. The propagation of the final nucleons in the residual
nucleus is simulated by an intranuclear cascade code. We evaluate single and
double coincidence nucleon spectra for the non-mesonic decay of C-12-Lambda.
Through the comparison of our predictions with KEK coincidence data we
determine G_n/G_p=0.43 \pm 0.10 for this hypernucleus, confirming previous
finite nucleus analyses.
