PIONIC DECAY OF HYPERNUCLEUS HE-5 (LAMBDA) - GREENS-FUNCTION METHOD

The pionic decay of LAMBDAHe-5 is investigated to obtain information o n the LAMBDA-nucleus interaction. Two types of alpha-LAMBDA potentials are used for the purpose. One is a potential with central repulsion ( Isle) and the other is a single Gaussian potential with no repulsion ( SG). The obtained pi- decay rate is 0.35 GAMMA(LAMBDA) for Isle and 0. 27 GAMMA(LAMBDA) for SG, GAMMA(LAMBDA) being the total decay rate of a free LAMBDA particle. The former is in better agreement than the latt er with the experimental value of 0.44 +/- 0.11 GAMMA(LAMBDA). This re sult suggests that the alpha-LAMBDA potential has central repulsion. I n order to discuss final-state nuclear resonance effects Green's funct ion method is introduced in the calculation of the continuum pi- decay spectrum. Both the sharp p3/2 and the broad p1/2 alpha-p resonances p lay roles to build up a peak structure in the spectrum. It is observed that the low-energy nuclear resonances enhance the partial decay rate s.