Probing the tetrahedral $\alpha$ clusters in relativistic $^{16}$O + $^{16}$O collisions

Abstract

Relativistic $^{16}$O +$^{16}$O collisions probe the Quark-Gluon Plasma formed in small systems, while their collective phenomena illuminate the structure of $^{16}$O. Recently, various configurations of $^{16}$O from \textit{ab initio} calculations were implemented in heavy-ion models, such as the hydrodynamic model and a multiphase transport model (AMPT) to study cluster effects in relativistic $^{16}$O +$^{16}$O collisions. However, divergent predictions across configurations and models complicate interpretations. In this Letter, we isolate the impact of multi-nucleon correlations in relativistic $^{16}$O +$^{16}$O collisions while fixing the one-body density distribution of $^{16}$O. Our results show that the normalized ratios ${\rm Norm}(v_{2}\{2\}/v_{2}\{4\})$ and ${\rm Norm}(v_{2}\{2\}/v_{3}\{2\})$ effectively probe the effects of one-body density (e.g., tetrahedral symmetry) and multi-nucleon correlations (e.g., $\alpha$ clusters). These observables provide critical constraints for refining heavy-ion models, essential for investigating cluster configurations in light nuclei through relativistic heavy-ion collisions.