Spin-flip M1 giant resonance as a challenge for Skyrme forces

TL;DR

This paper examines the challenges faced by Skyrme mean-field models in accurately describing the spin-flip M1 giant resonance in nuclei, highlighting discrepancies and exploring potential improvements involving spin correlations and interactions.

Contribution

It analyzes the limitations of current Skyrme parameterizations in modeling the M1 resonance and discusses possible solutions involving spin-orbit and tensor interactions.

Findings

Current Skyrme models fail to reproduce experimental M1 resonance structures.

The mismatch may be due to inadequate treatment of spin correlations and spin-orbit effects.

Potential improvements involve refining spin-dependent interactions in the models.

Abstract

Despite a great success of the Skyrme mean-field approach in exploration of nuclear dynamics, it seems to fail in description of the spin-flip M1 giant resonance. The results for different Skyrme parameterizations are contradictory and poorly agree with experiment. In particular, there is no parameterization which simultaneously describes the one-peak gross structure of M1 strength in doubly magic nuclei and two-peak structure in heavy deformed nuclei. The reason of this mismatch could lie in an unsatisfactory treatment of spin correlations and spin-orbit interaction. We discuss the present status of the problem and possible ways of its solution. In particular, we inspect i) the interplay of the collective shift and spin-orbit splitting, ii) the isovector M1 response versus isospin-mixed responses, and iii) the role of tensor and isovector spin-orbit interaction.