${}^{16}\mathrm{O}{}^{16}\mathrm{O}$ collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider comparing $\alpha$ clustering versus substructure

Collisions of . light and heavy nuclei in relativistic heavy-ion collisions have been shown to be sensitive to nuclear structure. With a proposed ${}^{16}\mathrm{O}{}^{16}\mathrm{O}$ run at the CERN Large Hadron Collider (LHC) and at the BNL Relativistic Heavy Ion Collider (RHIC) we study the potential for finding $\alpha$ clustering in ${}^{16}\mathrm{O}$. Here we use the state-of-the-art iEBE-VISHNU package with ${}^{16}\mathrm{O}$ nucleonic configurations from ab initio nuclear lattice simulations. This setup was tuned using a Bayesian analysis on $p\mathrm{Pb}$ and PbPb systems. We find that the ${}^{16}\mathrm{O}{}^{16}\mathrm{O}$ system always begins far from equilibrium and that at LHC and RHIC it approaches the regime of hydrodynamic applicability only at very late times. Finally, by taking ratios of flow harmonics we are able to find measurable differences between $\alpha$-clustering, nucleonic, and subnucleonic degrees of freedom in the initial state.

Figure 1

Average Knudsen and inverse Reynolds values of regions above the freeze-out temperature (0.151 GeV) vs time for both $\sqrt{s_{NN}}=200$ GeV (top) and $\sqrt{s_{NN}}=6.5$ TeV (bottom) comparing the Woods-Saxon, Woods-Saxon $+$ quarks, and $\alpha$-clustering models with common initial conditions.

Figure 2

Various flow coefficients ($v_n\left\{m\right\}$) vs centrality for both $\sqrt{s_{NN}}=200$ GeV (top) and $\sqrt{s_{NN}}=6.5$ TeV (bottom) comparing the Woods-Saxon, Woods-Saxon $+$ quarks, and $\alpha$-clustering models.

Figure 3

$v_3\left\{2\right\}/v_2\left\{2\right\}$ vs centrality for both $\sqrt{s_{NN}}=200$ GeV (top) and $\sqrt{s_{NN}}=6.5$ TeV (bottom) comparing the Woods-Saxon, Woods-Saxon $+$ quarks, and $\alpha$-clustering models.

Figure 4

$v_4\left\{2\right\}/v_2\left\{2\right\}$ vs centrality for both $\sqrt{s_{NN}}=200$ GeV (top) and $\sqrt{s_{NN}}=6.5$ TeV (bottom) comparing the Woods-Saxon, Woods-Saxon $+$ quarks, and $\alpha$-clustering models.

Figure 5

$v_4{\left\{4\right\}}^4$ vs centrality for both $\sqrt{s_{NN}}=200$ GeV (top) and $\sqrt{s_{NN}}=6.5$ TeV (bottom) comparing the Woods-Saxon, Woods-Saxon $+$ Quarks, and $\alpha$ clustering models.