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

Abstract

Relativistic $^{16}$O +$^{16}$O collisions provide a valuable opportunity to study both the quark-gluon plasma formed in small systems and the intrinsic structure of $^{16}$O. Recent implementations of \textit{ab initio} nuclear configurations in heavy-ion simulations have produced different predictions for cluster-sensitive observables, making it difficult to identify the origin of possible $α$-cluster signals. In this work, we introduce a controlled sampling scheme that varies the compactness of $α$-cluster-induced multi-nucleon correlations while keeping the one-body density distribution of $^{16}$O fixed. This allows us to separate effects driven by the tetrahedral one-body density from those driven by genuine multi-nucleon correlations. We show that the normalized ratios ${\rm Norm}(v_{2}\{2\}/v_{2}\{4\})$ and ${\rm Norm}(v_{2}\{2\}/v_{3}\{2\})$, together with their initial-state eccentricity counterparts, provide complementary constraints on initial-condition model dependence and cluster compactness. Hybrid hydrodynamic simulations and comparisons with recent LHC measurements further clarify the extent to which the initial-state signals survive final-state evolution. Our results provide a framework for using relativistic light-ion collisions to constrain cluster correlations in $^{16}$O.