Imprints of octupole collectivity in uranium-238 on relativistic heavy-ion flow observables

Some atomic nuclei exhibit enhanced octupole collectivity, reflected in finite reflection-asymmetric multipole correlations rather than necessarily in a rigid static pear-shaped ground state. Low-energy studies indicate finite octupole strength in uranium-238, commonly interpreted as soft or vibrational in nature, in addition to its large prolate quadrupole collectivity [F. K. McGowan and W. T. Milner, Nucl. Phys. A571, 569 (2026) 0375-9474 10.1016/0375-9474(94)90226-7.; T. Kibédi and R. H. Spear, At. Data Nucl. Data Tables80, 35 (2026) 0092640X 10.1006/adnd.2001.0871]. Here, we investigate how such octupole correlations can be encoded in the initial geometry of relativistic heavy-ion collisions and mapped to final-state flow observables. Using state-of-the-art hydrodynamic calculations, we demonstrate quantitative sensitivity to octupole-induced features encoded in the initial-state geometry and suggest a modest effective octupole-correlation strength in uranium-238 that is compatible with the latest high-energy experimental measurements [B. E. Aboona (STAR), Rep. Prog. Phys.88, 108601 (2026) 0034-4885 10.1088/1361-6633/ae0fc3]. These findings provide a complementary probe of odd-order nuclear collectivity and help constrain quark-gluon plasma initial conditions.