Extending MCAS to hypernuclei and radiative-capture reactions

¹ Istituto Nazionale di Fisica Nucleare, sezione di Padova, via Marzolo 8, Padova I-35131, Italia
² School of Physics, University of Melbourne, Victoria 3010, Australia
³ Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa
⁴ Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB, Canada R3T 2N2

^a e-mail: luciano.canton@pd.infn.it

Abstract

Using a Multi-Channel Algebraic Scattering (MCAS) approach we have analyzed the spectra of two hypernuclear systems, ⁹_ΛBe and ¹³_ΛC. We have studied the splitting of the two odd-parity excited levels (1/2⁻ and 3/2⁻) at 11 MeV excitation in ¹³_ΛC, originated by the weak Λ-nucleus spin-orbit force. We have also considered the splittings of the 3/2⁺ and 5/2⁺ levels in both ⁹_ΛBe and ¹³_ΛC, finding how they originate from couplings to the collective 2 ⁺ states of the core nuclei. In both hypernuclei, we suggest that there could be additional low-lying resonant states in the Λ-nucleus continua. From the MCAS approach one can extract also the full coupled-channel scattering wavefunction 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 α + ³He→⁷Be+γ.