Deformation probes for light nuclei in their collisions at relativistic energies

TL;DR

This study explores how anisotropic flow and momentum fluctuations in relativistic light nucleus collisions can reveal nuclear deformation and alpha-cluster structures, highlighting the importance of realistic density models for accurate interpretation.

Contribution

It introduces a detailed analysis of deformation probes in light nuclei collisions, emphasizing the impact of alpha-cluster configurations on deformation measurements.

Findings

Linear relations hold for realistic deformation parameters.

Deviations occur with complex alpha-cluster configurations.

Realistic density distributions are crucial for accurate deformation extraction.

Abstract

We have investigated the performance of anisotropic flows $\langle v_n^2 \rangle$, transverse momentum fluctuations $\langle \delta p_T^2 \rangle $, and their correlations $\langle v_n^2 \delta p_T \rangle$ in central collisions at relativistic energies as probes of deformation parameters $\beta_n$ of colliding nuclei, if these nuclei are light nuclei with large $\beta_n$ and different configurations of $\alpha$ clusters. The effects from higher-order $\beta_n$ terms are illustrated by derived relations based on the overlap of two nuclei with uniform density distributions and by dynamic simulations of collisions of heavy nuclei whose density distributions are of a deformed Woods-Saxon (WS) form. While the linear relations between $\beta^2_n$, $\langle v_n^2 \rangle$, and $\langle \delta p_T^2 \rangle$ and that between $\beta^3_n$ and $\langle v_n^2 \delta p_T \rangle$ can be violated for extremely large $\beta_{n}$, they are mostly valid for realistic values of $\beta_n$, as long as the density distribution of colliding nuclei can be described by a deformed WS form. However, these linear relations are generally not valid with more realistic density distributions of light nuclei with $\alpha$ clusters, and the amount of deviation depends on the detailed $\alpha$-cluster configurations. Care must be taken when one tries to extract the deformation of light nuclei, and specific probes for $\alpha$-cluster structures in these nuclei are very much needed.