Probing the tetrahedral $\alpha$ 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 $\alpha$-cluster signals. In this work, we introduce a controlled sampling scheme that varies the compactness of $\alpha$-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 $\mathrm{Norm}(v_2\{2\}/v_2\{4\})$ and $\mathrm{Norm}(v_2\{2\}/v_3\{2\})$, 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.

7 page, 7 figures