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

TL;DR

This paper reports measurements of neutron skin thickness and nuclear deformation using relativistic heavy-ion collisions, revealing differences in nuclear structure between Ru and Zr isotopes through flow and particle production ratios.

Contribution

It introduces a novel method to extract neutron skin thickness and deformation parameters from heavy-ion collision data, providing new insights into nuclear structure.

Findings

Zr nucleus has a thicker neutron skin than Ru nucleus.

Significant deviations in flow ratios indicate large nuclear deformations.

Data supports nuclear structure calculations of neutron skin and deformation.

Abstract

In these proceedings, we present the measurements of neutron skin thickness and nuclear deformation using isobar $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV by the STAR detector. The significant deviations from unity of the isobar ratios of elliptic flow $v_{2}$, triangular flow $v_{3}$, mean $p_{\rm T}$ fluctuations $\langle\delta p_{\rm T}^{2}\rangle/\langle p_{\rm T}\rangle^{2}$, and asymmetric cumulant ${\rm ac}_{2}\{3\}$ indicate large differences in their quadrupole and octuple deformations. The significant deviations of the isobar ratios of produced hadron multiplicity $N_{\rm ch}$, mean transverse momentum $\langle p_{\rm T}\rangle$, and net charge number $\Delta Q$ 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.