Role of the isovector nucleon-nucleus interaction potential in nonmesonic hypernuclear decay

Abstract

We develop a theoretical finite nucleus framework for the evaluation of the coincidence number of pairs ${N}_{\mathit{nN}}$ and the asymmetry parameter ${a}_{\ensuremath{\Lambda}}$ in nonmesonic hypernuclear decay $\ensuremath{\Lambda}N\ensuremath{\rightarrow}\mathit{nN}$, and introduce the effect of final-state interactions. The primary nonmesonic weak hyperon-nucleon decay process is described through the independent-particle shell model. We work within the $2p1h$ subspace of final states, assuming a simple approach for finite nuclei based on the eikonal approximation. An optical potential including the nucleon-nucleus isoscalar and isovector interactions is introduced to take into account the minimum nuclear-medium effects. The calculated values for ${}_{\ensuremath{\Lambda}}^{5}\mathrm{He}$ and ${}_{\ensuremath{\Lambda}}^{12}\mathrm{C}$ show that our treatment of final-state interactions, even those considered as restricted to a subspace of states, brings the independent-particle model results closer to the experimental data.