Effective field theory for collective rotations and vibrations of triaxially deformed nuclei

TL;DR

This paper extends the effective field theory for triaxially deformed nuclei to include vibrational modes, improving the description of energy spectra and high-spin states in certain Ru isotopes.

Contribution

It introduces a generalized EFT Hamiltonian incorporating vibrations, enhancing the modeling of collective nuclear motions beyond pure rotations.

Findings

Vibrational degrees of freedom improve high-spin state descriptions.

The EFT accurately reproduces energy spectra of multiple bands.

Including vibrations resolves discrepancies in gamma-band predictions.

Abstract

The effective field theory (EFT) for triaxially deformed even-even nuclei is generalized to include the vibrational degrees of freedom. The pertinent Hamiltonian is constructed up to next-to-leading order. The leading order part describes the vibrational motion, and the NLO part couples rotations to vibrations. The applicability of the EFT Hamiltonian is examined through the description of the energy spectra of the ground state bands, $\gamma$-bands, and $K=4$ bands in the $^{108, 110, 112}$Ru isotopes. It is found that by taking into account the vibrational degrees of freedom, the deviations for high-spin states in the $\gamma$-band observed in the EFT with only rotational degrees of freedom disappear. This supports the importance of including vibrational degrees of freedom in the EFT formulation for the collective motion of triaxially deformed nuclei.