Impact of initial fluctuations and nuclear deformations in isobar collisions

TL;DR

This paper investigates how initial fluctuations and nuclear deformations influence observable differences in isobar collisions, providing insights into nuclear structure and particle production mechanisms.

Contribution

It introduces a detailed analysis of initial state effects on collision observables, highlighting their varying impacts on multiplicity and eccentricity ratios.

Findings

Initial fluctuations have negligible effects on multiplicity ratios in central collisions.

Nuclear deformations significantly affect eccentricity ratios.

Sensitivity to nucleonic or sub-nucleonic degrees of freedom influences these effects.

Abstract

Relativistic isobar ($^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr) collisions have revealed intricate differences in their nuclear size and shape, inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions. In this study, we investigate the relative differences in the mean multiplicity ($R_{\langle N_{\rm ch}\rangle}$) and the second- ($R_{\epsilon_{2}}$) and third-order eccentricity ($R_{\epsilon_{3}}$) between isobar collisions using initial state models. It is found that initial fluctuations and nuclear deformations have negligible effects on $R_{\langle N_{\rm ch}\rangle}$ in most central collisions, while both are important for the $R_{\epsilon_{2}}$ and $R_{\epsilon_{3}}$, the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom. These features, compared to real data, may probe the particle production mechanism and the physics underlying nuclear structure.