Impact of nuclear shape fluctuations in high-energy heavy ion collisions

TL;DR

This paper studies how nuclear shape fluctuations influence the initial geometry and flow observables in high-energy heavy ion collisions, revealing their effects on eccentricity and size distributions.

Contribution

It introduces a method to analyze the impact of nuclear shape fluctuations on collision initial states and their observable consequences.

Findings

Shape fluctuations increase variance and alter skewness and kurtosis of initial geometry parameters.

Triaxiality fluctuations diminish differences between prolate and oblate shapes.

In large fluctuations, observables approach values for rigid triaxial nuclei.

Abstract

The shape of atomic nuclei is often interpreted to possess a quadrupole deformation that fluctuates around some average profile. We investigate the impact of nuclear shape fluctuations on the initial state geometry in heavy ion collisions, particularly its eccentricity $\varepsilon_2$ and inverse size $d_{\perp}$, which can be related to the elliptic and radial flow in the final state. The fluctuation in overall quadrupole deformation enhances the variances and modifies the skewness and kurtosis of the $\varepsilon_2$ and $d_{\perp}$ in a controllable manner. The fluctuation in triaxiality reduces the difference between prolate and oblate shape for any observable, whose values, in the large fluctuation limit, approach those obtained in collisions of rigid triaxial nuclei. The method to disentangle the mean and variance of the quadrupole deformation is discussed.