Structure of low-lying states of C 12 and C Λ13 in a beyond-mean-field approach

Based on the beyond-mean-field Skyrme-Hartree-Fock model, we investigate the energy spectra and possible cluster structure in C12 and its Λ hypernucleus CΛ13. The up-to-date Skyrme-type NΛ interaction SLL4 and the reduced NN interaction SGII are employed. Low-lying energy spectra of C12, including the lowest five 0+ states, are predicted and discussed in detail, and found in good agreement with experimental results. The electric quadrupole transition rates and the monopole matrix elements between the 0+ states are also examined. Although typical cluster structures for the 02+ and 03+ states are absent, a linear-chain-like 3α structure is found for the 04+ state. An energy spectrum including both the positive- and negative-parity levels is also given and structures of the corresponding hypernuclear states are discussed in detail. Impurity effects of a Λs or Λp hyperon on the nuclear core states of CΛ13 are demonstrated by the change of collective wave functions.