Constraints on neutron skin thickness and nuclear deformations using relativistic heavy-ion collisions from STAR

Abstract

In these proceedings, we present the measurements of neutron skin thickness and nuclear deformation using isobar ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV by the STAR detector. The significant deviations from unity of the isobar ratios of elliptic flow $v_2$, triangular flow $v_3$, mean $p_{\mathrm{T}}$ fluctuations $⟨\hat{I}´p_{\mathrm{T}}^2⟩/⟨p_{\mathrm{T}}{⟩}^2$, and asymmetric cumulant ${\mathrm{ac}}_2\{3\}$ indicate large differences in their quadrupole and octuple deformations. The significant deviations of the isobar ratios of produced hadron multiplicity $N_{\mathrm{ch}}$, mean transverse momentum $⟨p_{\mathrm{T}}⟩$, and net charge number $\hat{I}”Q$ indicate a halo-type neutron skin for the Zr nucleus, much thicker than for the Ru nucleus, consistent with nuclear structure calculations. We discuss how we extract the neutron skin thickness, the symmetry energy slope parameter, and deformation parameters from data.

Presented at Quark Matter 2022, Karkow, Poland, April 4-10, 2022