Level-anticrossing in B(E2) anomaly (I)

Recently, a new mechanism for explaining the B(E2) anomaly was given by F. Pan \emph{et al.} (PRC, 110, 054324, 2024), which is realized in the parameter region from the SU(3) symmetry limit to the O(6) symmetry limit, and seems to be not related to the SU(3) symmetry. However, through SU(3) analysis, a new technique proposed recently, we found that it is not so. The new mechanism is related to level-anticrossing phenomenon, which is related to level-crossing phenomenon in the SU(3) symmetry limit. By incorporating previous ideas, we have a more general explanatory framework for the B(E2) anomaly, which is important for understanding some higher-order interactions in the interacting boson model. Through analysis, it is shown that level-anticrossing in this mechanism mainly results from the third-order interaction $[\hat{L}\times \hat{Q}_{\chi} \times \hat{L}]^{(0)}$. Finally, the B(E2) anomaly in $^{170}$Os is also discussed within this general framework.