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

TL;DR

This paper extends a relativistic energy density functional to hypernuclei, using in-medium chiral SU(3) dynamics to accurately describe hypernuclear structure and explain the small spin-orbit interaction of the Lambda hyperon.

Contribution

It introduces a novel application of in-medium chiral SU(3) dynamics to hypernuclear structure within a relativistic energy density functional framework.

Findings

Model describes hypernuclear spectra in good agreement with experimental data.

Explains the small Lambda spin-orbit interaction through cancellation of scalar-vector and long-range contributions.

Successfully constrains mean fields using QCD sum rules.

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 $\Lambda$ hyperon in the nucleus using the SU(3) extension of in-medium chiral perturbation theory. The leading long range $\Lambda N$ interaction arises from kaon-exchange and $2\pi$-exchange with $\Sigma$ 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 $\Lambda$ 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.