On the effect of the $\Delta(1232)$ in hypernuclear non--mesonic weak decay: a microscopic approach

BAUER, E; G. GARBARINO

PHYSICS LETTERS B

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 716 p. 249 - 253

0370-2693

The non--mesonic weak decay of $\Lambda$--hypernuclei is studied within a microscopic diagrammatic approach which includes, for the first time, the effect or the $\Delta$--baryon resonance. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a one--meson exchange weak transition potential, a Bonn nucleon--nucleon strong potential and a $\Delta N\to NN$ strong potential based on the Landau--Migdal theory. Ground state correlations and final state interactions (FSI), at second order in the baryon--baryon strong interaction, are introduced on the same footing for all the isospin channels of one-- and two--nucleon induced decays. Weak decay rates and single and double--coincidence nucleon spectra are predicted for $^{12}_\Lambda$C and compared with recent KEK and FINUDA data. The $\Delta(1232)$ turns out to have a negligible effect on the decay rates, while it introduces new FSI--induced decay mechanisms which lead to an improvement when comparing the obtained nucleon spectra with data. Discrepancies with experiment remain for proton emission, but only for the non--back--to--back kinematics.