The IBM Description of the B(E2) Anomaly: Dynamical Triaxiality and Configuration Mixing

A theoretical investigation has been carried out to examine the effects of dynamical triaxility and configuration mixing on the $B(E2)$ anomaly, characterized by $B_{4\mathrm{/}2}=B(E2;4_1^{+}\to 2_1^{+})\mathrm{/}B(E2;2_1^{+}\to 0_1^{+})<1.0$ and $R_{4\mathrm{/}2}=E(4_1^{+})\mathrm{/}E(2_1^{+})\ge 2.0$, within the framework of the interacting boson model (IBM). The results indicate that the effective $\gamma$ deformation may undergo substantial changes with increasing angular momentum in the $B(E2)$ anomaly system governed by an IBM Hamiltonian involving rotor-like terms. Further calculations reveal that mixing between normal and intruder states may facilitate the emergence of $B(E2)$ anomaly, thereby providing additional theoretical insights into this unusual phenomenon.