In-medium chiral SU(3) dynamics and hypernuclear structure

Abstract

A previously introduced relativistic energy density functional, successfully applied to ordinary nuclei, is extended to hypernuclei. The density-dependent mean field and the spin-orbit potential are consistently calculated for a $Λ$ hyperon in the nucleus using the SU(3) extension of in-medium chiral perturbation theory. The leading long range $ΛN$ interaction arises from kaon-exchange and $2π$-exchange with $Σ$ hyperon in the intermediate state. Scalar and vector mean fields reflecting in-medium changes of the quark condensates are constrained by QCD sum rules. The model, applied to oxygen as a test case, describes spectroscopic data in good agreement with experiment. In particular, the smallness of the $Λ$ spin-orbit interaction finds a natural explanation in terms of an almost complete cancellation between scalar-vector background contributions and long-range terms generated by two-pion exchange.

10 pages, 2 figures, elsart class. Minor revisions