✍ Scribed by N. Kaiser; W. Weise
No coin nor oath required. For personal study only.
A detailed comparison is made between the spin-orbit interactions in Λ hypernuclei and ordinary nuclei. We argue that there are three major contributions to the spin-orbit interaction: (1) a short-range component involving scalar and vector mean fields; (2) a "wrong-sign" spin-orbit term generated by the pion exchange tensor force in second order; and (3) a three-body term induced by two-pion exchange with excitation of virtual (1232)-isobars (à la Fujita-Miyazawa). For nucleons in nuclei the long-range pieces related to the pion-exchange dynamics tend to cancel, leaving room dominantly for spin-orbit mechanisms of shortrange origin (parametrized, e.g., in terms of relativistic scalar and vector mean fields terms). In contrast, the absence of an analogous 2π -exchange three-body contribution for Λ hyperons in hypernuclei leads to an almost complete cancellation between the short-range (relativistic mean-field) component and the "wrongsign" spin-orbit interaction generated by second order π -exchange with an intermediate Σ hyperon. These different balancing mechanisms between short-and long-range components are able to explain simultaneously the very strong spin-orbit interaction in ordinary nuclei and the remarkably weak spin-orbit splitting in Λ hypernuclei.
📜 SIMILAR VOLUMES
We devise a nucleon-nucleon interaction V, + XV,, + y V, to study the effects of the spinorbit and tensor interactions by varying x and y. For negative parity lp-lh states in 160, we find that in a TDA calculation, the weighted sum of the eigenenergies CJ(2J+ 1) L,E,(J, T) is zero for a pure two-bod