SU(3) rigid triaxiality in ¹⁵⁴Sm

The ¹⁵⁴Sm nucleus, which has long been regarded as a typical quantum system exhibiting axial symmetry, has been recently suggested to exhibit a small degree of triaxiality by Otsuka et al.. This small triaxiality was recently observed using the $γ$ decay of the ¹⁵⁴Sm isovector giant dipole resonance. Thus further studying this small triaxiality is very necessary for understanding the nature of the collectivity in nuclei. In this paper, the rigid triaxiality in ¹⁵⁴Sm is investigated using the newly proposed SU3-IBM theory. If the irreducible representation (irrep) of the ground state is (18,2) in the SU(3) symmetry limit, the new model can effectively reproduce the experimental data of ¹⁵⁴Sm, showing good agreements with realistic energy spectra, B(E2) values, and quadrupole moments. This result further confirms the vality of the SU3-IBM for the description of the rigid triaxiality in realistic nuclei, and reveals the SU(3) dominance of the collectivity motions in nuclei.