Structure of Λ10Be and Λ10B Hypernuclei Studied with the Four-Body Cluster Model

The structure of the isodoublet hypernuclei, B-10(Lambda) and Be-10(Lambda) within the framework of an alpha+alpha+Lambda+N four-body cluster model is studied. Interactions between the constituent subunits are determined to reproduce reasonably well the observed low-energy properties of the alpha alpha, alpha N, alpha Lambda, alpha alpha Lambda, and alpha alpha N subsystems. Furthermore, the two-body Lambda N interaction is adjusted to reproduce the 0(+)-1(+) splitting of H-4(Lambda). The A binding energies of B-10(Lambda) and Be-10(Lambda) are 8.76 MeV and 8.94 MeV, respectively. The energy splitting of the 1(-)-2(-) levels in B-10(Lambda) is 0.08 MeV, which does not contradict the experimental report in BNL-E930. An even-state Lambda N charge symmetry breaking (CSB) interaction determined from the A = 4 systems works repulsively by +0.1 MeV (attractively by -0.1 MeV) in Be-10(Lambda) (B-10(Lambda)). We discuss a possibility that an odd-state CSB interaction improves the fitting to the experimental data of A = 10 double Lambda hypernuclei.