Exploring the compactness of $\alpha$ cluster in ${}^{16}$O nuclei with relativistic ${}^{16}$O+${}^{16}$O collisions

Abstract

Probing the $\alpha$ cluster of ${}^{16}$O with the relativistic ${}^{16}$O+${}^{16}$O collisions has raised great interest in the heavy ion community. However, the effects of the $\alpha$ cluster on the soft hadron observables vary largely among different studies. In this paper, we explain the differences by the compactness of the $\alpha$ cluster in oxygen, using iEBE-VISHNU hydrodynamic simulations with different initial state $\alpha$ cluster configurations. We also find several observables, such as the intensive skewness of the $[p_{\mathrm{T}}]$ correlator ${\Gamma }_{p_{\mathrm{T}}}$, the harmonic flows $v_2\{2\}$, $v_2\{4\}$, $v_3\{2\}$, and the $v_n^2-\delta [p_{\mathrm{T}}]$ correlations $\rho (v_2^2,[p_{\mathrm{T}}])$, $\rho (v_3^2,[p_{\mathrm{T}}])$ in ${}^{16}$O+${}^{16}$O collisions are sensitive to the compactness of the $\alpha$ cluster in the colliding nuclei, which can be used to constrain the configurations of ${}^{16}$O in the future. Our study serves as an important step toward the quantitative exploration of the $\alpha$ cluster configuration in the light nuclei with relativistic heavy ion collisions.

Comments: 9 pages, 9 figures, published version + appendix (initial state calculations)