Extending MCAS to hypernuclei and radiative-capture reactions

TL;DR

This paper extends the MCAS method to analyze hypernuclear spectra and radiative-capture reactions, revealing insights into level splittings, couplings, and potential resonant states in hypernuclei.

Contribution

The work applies MCAS to hypernuclei Lambda9Be and Lambda13C, providing new analysis of level splittings and couplings, and explores radiative-capture reactions using this approach.

Findings

Identified spin-orbit splitting effects in hypernuclear levels.

Explored couplings to collective core states affecting level structure.

Suggested existence of additional low-lying resonant states.

Abstract

Using a Multi-Channel Algebraic Scattering (MCAS) approach we have analyzed the spectra of two hyper-nuclear systems, Lambda9Be and Lambda13C. We have studied the splitting of the two odd-parity excited levels (1/2- and 3/2-) at 11 MeV excitation in Lambda13C, originated by the weak Lambda-nucleus spin-orbit force. We have also considered the splittings of the 3/2+ and 5/2+ levels in both Lambda9Be and Lambda13C, finding how they originate from couplings to the collective 2+ states of the core nuclei. In both hyper-nuclei, we suggest that there could be additional low-lying resonant states in the Lambda-nucleus continua. From the MCAS approach one can extract also the full coupled-channel scattering wave-function to be used in the calculation of various transition matrix elements. As a first application, we have considered the EM-transition matrix elements for the capture reaction Alpha + 3He -> 7Be + Gamma .