Many-body cascade calculation of final state interactions in _\Lambda ^{12}C nonmesonic weak decay

Abstract

We study the nonmesonic weak decay (NMWD) N → nN of 12 C hypernucleus induced by one nucleon N = n, p. The whole process is described by two coupled models: one for the primary NMWD of hyperon in the nuclear environment, and the other taking into account the final state interactions (FSI) of the two outgoing nucleons within the residual nucleus. The NMWD dynamics is represented by the one-meson-exchange potential with usual parametrization, while the independent-particle shell model is used as the nuclear structure framework. The FSI are accounted for by a time-dependent multicollisional Monte Carlo cascade scheme, implemented within the CRISP code (Collaboration Rio-São Paulo), which describes in a phenomenological way both the nucleon-nucleon scattering inside the nucleus and the escaping of nucleons from the nuclear surface. An evaporation phase is included to cool down the cascade residual nucleus as well. We analyze the singlenucleon kinetic energy spectra, and the two-nucleon coincidence spectra as a function of both: (i) the sum of the kinetic energies and (ii) the opening angle. The theoretical results are compared with recent data from KEK and FINUDA experiments, obtaining fairly good agreement for inclusive and exclusive kinetic energy spectra. Further theoretical improvements are required to explain angular distributions.

Nuclear photoproduction of vector mesons within a Monte Carlo approach

“…The Pauli exclusion principle is taken into account in CRISP dynamics by rejecting collisions that lead to the final state violating the Pauli principle. All these features enabled CRISP code to successfully simulate reactions induced by protons [40,44], photons [39,41,45,46], electrons [47,48], and other processes such as kaon [49] production and hypernuclei decay [50][51][52]. The effectiveness of such an approach can be verified in the study of evaporation/fission competition [53][54][55], which explained for the first time the saturation below the unit of fissility for heavy nuclei observed in experiments.…”

Nonmesonic Weak Decay Spectra of Light Hypernuclei

“…More, we will seize the opportunity to discuss the spectra of other two light hypernuclei, namely of 4 Λ H, and 5 Λ He, taking care of measurements done on the latter at KEK [32][33][34], and FINUDA [36]. Theoretical expressions for different NM weak decay spectra within the IPSM that are used here have been presented previously [10,[25][26][27][28][29] and will not be repeated here.…”

Photon and proton induced fission on heavy nuclei at intermediate energies

“…This code has been developed for more than ten years [8][9][10][11][12][13][14] and it has been applied in the study of fission induced by photons and protons, and for the study of hyper-nuclear decay [15]. It has also been used in the development of new nuclear reactor technologies [16][17][18].…”