Cluster model theory of the Lambda 9Be hypernucleus.

The microscopic (..cap alpha..+3N+N)+..lambda.. cluster model is applied to achieve a unified understanding of the /sub ..lambda..//sup 9/Be hypernucleus in the energy region up to E/sub ..lambda../approx. =20 MeV. The eigenstates of /sub ..lambda..//sup 9/Be consist of low-lying cluster states with /sup 8/Be (..cap alpha..+..cap alpha..)+..lambda.. structure and high-lying core-excited states with /sup 8/Be* (..cap alpha..+..cap alpha..)+..lambda.. structure (* denotes the intrinsic) excited state). With use of the /sub ..lambda..//sup 9/Be wave functions obtained, the production cross sections of /sub ..lambda..//sup 9/Be through the (K/sup -/ in-flight,..pi../sup -/), (..pi../sup +/,K/sup +/), and (K/sup -/ stopped,..pi../sup -/) 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/sup -/ in-flight,..pi../sup -/) reaction experiment. The predicted (..pi../sup +/,K/sup +/) excitation function is in good agreement with recent experimental data, and for the first time genuine hypernuclear states came into observation.