Extraction of Neutron-Skin Parameters in Zr+Zr and Ru+Ru Collisions at $\sqrt{s_{\text{NN}}}$ = 200 GeV

Abstract

The initial nuclear geometry of colliding nuclei, manifested in proton and neutron density profiles, plays a key role in determining final-state effects in high-energy heavy-ion collisions. We study ${}^{96}\text{Ru}+{}^{96}\text{Ru}$ and ${}^{96}\text{Zr}+{}^{96}\text{Zr}$ collisions at $\sqrt{s_{\text{NN}}}=200$ GeV incorporating an isospin-dependent Woods-Saxon distribution to account for neutron-skin effects in the UrQMD model. By systematically scanning the proton surface diffuseness parameter $a_{\text{p,Zr}}$ of the ${}^{96}\text{Zr}$ nucleus and performing a ${\chi }^2$ analysis by comparing with STAR experimental data, we extract the relative neutron-skin thickness difference $0.278\pm 0.018$ fm between the two isobaric systems using the net-charge yield difference $\Delta Q$. We further show that the neutron-skin effect evidently modifies the baryon-to-charge transport ratio $R_{B/Q}=⟨B⟩/\Delta Q\times \Delta Z/A$, and substantially influences the observed $R_{B/Q}>1$ behavior in central collisions. This work indicates that nuclear structure effects contribute non-negligibly to baryon transport observables without a baryon junction hypothesis, and underscores the importance of precise initial-state geometry constraints for exploring novel QCD phenomena in relativistic heavy-ion collisions.

The authors withdraw this manuscript because a non-realistic issue have been identified in the analysis. We are working on a more realistic way to improve our analysis and prepare a revised manuscript for future submission