The microscopic (α+3N+N)+Λ cluster model is applied to achieve a unified understanding of the ${}_{\mathrm{\Lambda }}{}^9{}_{}{}^{}\mathrm{Be}$ hypernucleus in the energy region up to $E_{\Lambda }$≃20 MeV. The eigenstates of ${}_{\mathrm{\Lambda }}{}^9{}_{}{}^{}\mathrm{Be}$ consist of low-lying cluster states with ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ (α+α)+Λ structure and high-lying core-excited states with ${}_{}{}^8{}_{}{}^{}\mathrm{*}$ (α+α)+Λ structure (* denotes the intrinsic) excited state). With use of the ${}_{\mathrm{\Lambda }}{}^9{}_{}{}^{}\mathrm{Be}$ wave functions obtained, the production cross sections of ${}_{\mathrm{\Lambda }}{}^9{}_{}{}^{}\mathrm{Be}$ through the ($K^{\mathrm{-}}$ in-flight,${\pi }^{\mathrm{-}}$), (${\pi }^{+}$,$K^{+}$), and ($K^{\mathrm{-}}$ stopped,${\pi }^{\mathrm{-}}$) reactions are evaluated. Each reaction process shows its own selective population of states and hence contributes to the comprehensive test of the theoretical predictions. A quantitative understanding is obtained for the three-peak structure observed in the ($K^{\mathrm{-}}$ in-flight,${\pi }^{\mathrm{-}}$) reaction experiment. The predicted (${\pi }^{+}$,$K^{+}$) excitation function is in good agreement with recent experimental data, and for the first time genuine hypernuclear states came into observation.

• Received 26 October 1987

DOI:https://doi.org/10.1103/PhysRevC.38.854