A consistent microscopic diagrammatic approach is applied for the first time
to the calculation of the nucleon emission spectra in the non-mesonic weak
decay of Lambda-hypernuclei. We adopt a nuclear matter formalism extended to
finite nuclei via the local density approximation, a one--meson exchange weak
transition potential and a Bonn nucleon-nucleon strong potential. Ground state
correlations and final state interactions, at second order in the
nucleon--nucleon interaction, are introduced on the same footing for all the
isospin channels of one- and two-nucleon induced decays. Single and
double--coincidence nucleon spectra are predicted for 12_Lambda^C and compared
with recent KEK and FINUDA data. The key role played by quantum interference
terms allows us to improve the predictions obtained with intranuclear cascade
codes. Discrepancies with data remain for proton emission.Comment: 11 pages, 6 figures, 2 tables. To be published in Physics Letters
