Distortion effects in light hypernuclei

Abstract

We have studied the particle-bound levels in the hypernuclei 3A'4H, ]He, ]Li and 8'9Be in the framework of the full microscopic Resonating Group Method (RGM). In a first step we have solved the respective nuclear many-body problem within the RGM. For each hypernucleus we have then performed a static calculation, in which the nuclear degrees of freedom were kept fixed, and a dynamical calculation in which nuclear degrees of freedom were allowed to vary. The differences between these two studies allowed us to investigate nuclear distortion effects caused by the presence of the A-particle. We find the nuclear distortion effects to be inverse proportional to the binding of the nuclear constituents. Thus, the strongest effects are observed for 3aH and for 9aBe. Our dynamical approach does not show the strong overbinding of 5aHe and 9Be as reported in other cluster model studies. Our results for the p-shell hypernuclei agree reasonably well with those obtained in a semi-microscopic Orthogonal Condition Model (OCM) study which used the same effective AN-interaction as employed in our calculation.

Theoretical evidence for di-molecular rotational behaviour in the hypernuclei ? 8 Li and ? 8 Be

“…[5,9]. In our study of 4He and 4H we have therefore used kF= 0.8 fm-1 which reproduces the B A-value of 4 H within a similar approach as the present one [10]. We then calculate a bound 0 + level in 4He at B Z = 3.8 MeV in rather good agreement with the experimental candidate.…”

“…It is very illuminating to compare the results of our calculation of ~Li and SzBe with a similar study of the hypernuclei SALi and ~Be [10]. Such a comparison is meaningful as both studies have been performed within the same microscopic multichannel formalism based on (3 N) + e + hyperon (A-or Z-particles, respectively) cluster functions.…”

“…Within this 7Li + A 2-cluster model space one obtains the same sequence of states as in the full microscopic 3H § § 3-cluster space. In the latter the BA-Values of the states are only slightly increased (by about 100-200 keV) clearly indicating that distortion effects play a minor role [10] and that the states are well approximated by microscopic 7Li § A and 7Li* § configurations, where the latter refers to the first excited state in 7Li.…”

Electromagnetic production of the hypertriton

“…Many models of the hypertriton have been developed using Faddeev equations [1,4,17], the resonating group method [18], variational methods [19], and hyperspherical harmonics [20]. We choose the simple model developed in Ref.…”