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

Abstract

A consistent microscopic model is applied to the calculation of the nucleon emission spectra in the nonmesonic 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 12 ΛC 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 12 ΛC, consistent with the asymmetry measured at KEK.