Microscopic model to nucleon spectra in hypernuclear non-mesonic weak decay

A consistent microscopic model is applied to the calculation of the nucleon emission spectra in the non-mesonic weak decay of Λ-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 interaction, 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. Double-coincidence nucleon spectra are predicted for 12ΛC and compared with recent KEK data. Discrepancies with data remain for proton emission and for both neutron-proton and neutron-neutron emission in the non-back-to-back kinematics region. Motivated by a recent triple-coincidence measurement by FINUDA, we estimate the three-body induced decay, where we have found, Γ3/Γ2≅0.23. Our microscopic model also predicts values for the asymmetry parameter in 12ΛC, consistent with the asymmetry measured at KEK.