title: Coherent lambda-sigma coupling in s-shell hypernuclei
abstract: It is found that the suppression due to two-body LambdaN-SigmaN coupling solves the overbinding problem in (5)(Lambda)He but it, in turn, causes a severe underbinding in the four-body systems. The shortage of this binding is overcome by introducing explicitly the Lambda-Sigma coupling which is equivalent to the LambdaNN three-body force. This three-body force becomes strong in the 0(+) states of (4)(Lambda)H and (4)(Lambda)He according to the coherently added enhancement. The 0(+)-1(+) splitting in (4)(Lambda)H and (4)(Lambda)He is found partly due to the LambdaN spin-spin interaction and partly due to the Lambda-Sigma coupling in the recent Nijmegen soft-core potential.
authors.affiliation: Institute of Particle and Nuclear Studies, KEK, Tanashi, Tokyo 188-8501, Japan.
authors.initials: Y
authors.lastname: Akaishi
authors.initials: T
authors.lastname: Harada
authors.initials: S
authors.lastname: Shinmura
authors.initials: KS
authors.lastname: Myint