Nonmesonic Hyperon Weak Decay Spectra in $^{12}_{\Lambda}$C}

TL;DR

This paper models the nonmesonic weak decay of the hypernucleus $^{12}_\Lambda$C using a combination of shell-model decay dynamics and intranuclear cascade simulations, comparing results with experimental data.

Contribution

It introduces a combined theoretical approach using IPSM and intranuclear cascade to analyze hypernuclear decay spectra and correlations.

Findings

Calculated decay spectra agree with KEK and FINUDA data.

The ratio of emitted neutron-neutron to neutron-proton pairs matches experimental results.

The model effectively describes both inclusive and exclusive decay observables.

Abstract

We study the nonmesonic weak decay (NMWD) $\Lambda N \to nN$ of the ${}^{12}_{\Lambda} C$ hypernucleus induced by the nucleon $N=n,p$ with transition rate $\Gamma_N$. The nuclear process is described by the interplay of two models; one describing the NMWD of hyperon $\Lambda$ in the nuclear environment, and the other taking into account the Final State Interaction (FSI) of the two outgoing nucleons with the residual nucleus. The first one is done in the framework of the Independent-Particle Shell-Model (IPSM), with the decay dynamics represented by the exchange of $\pi+ \eta+ K+\rho+\omega+K^*$ mesons with usual parametrization. For the second one is used a time dependent multicollisional intranuclear cascade schema (implemented in the CRISP code - Collaboration Rio-S\~ao Paulo). The results obtained for inclusive and exclusive kinetic energy spectra, and the angular correlation are compared with recent data from KEK and FINUDA experiments. The calculated ratio $(\Gamma_n / \Gamma_p)^{\partial{\tiny FSI}}$, between the numbers of emitted back-to-back $nn$ and $np$ pairs, is in good agreement with the experimental data.