Resonant states of the neutron-rich Λ hypernucleus 7ΛHe

The structure of the neutron-rich Lambda hypernucleus, He-7(Lambda) is studied within the framework of an alpha + Lambda + n + n four-body cluster model. We predict second 3/2(+) and 5/2(+) states, corresponding to a 0s Lambda coupled to the second 2(+) state of He-6, as narrow resonant states with widths of Gamma similar to 1 MeV to be at 0.03 and 0.07 MeV with respect to the alpha + Lambda + n + n threshold. From a separate estimate of the differential cross section for the Li-7(gamma, K+)He-7(Lambda) reaction, we suggest a possibility to observe these states at the Thomas Jefferson National Accelerator Facility (JLab) in the future. We also calculate the second 2(+) state of He-6 as a resonant state within the framework of an alpha + n + n three-body cluster model. Our result is 2.81 MeV with Gamma = 4.63 MeV with respect to the alpha + n + n threshold. This energy position is similar to 1 MeV higher, and with a much broader decay width, than the recent SPIRAL data. We suggest that an experiment at JLab to search for the second 3/2(+) and 5/2(+) states of He-7(Lambda) would provide an opportunity to confirm the second 2(+) state of the core nucleus He-6.