Collective flow in ultrarelativistic $^3$He-Au collisions

TL;DR

This paper investigates how the unique triangular arrangement of nucleons in helium-3 influences the collective flow patterns in ultrarelativistic helium-3-gold collisions, highlighting the role of initial geometry in flow observables.

Contribution

It demonstrates that the initial geometric configuration of helium-3 significantly affects the triangular flow and proposes a new observable ratio to better extract geometric effects from experimental data.

Findings

Triangular flow is enhanced due to helium-3's nucleon configuration.

The ratio v_3{4}/v_3{2} increases with participant nucleons for centralities less than 10%.

Fireball eccentricities reflect the elongated triangular shape of helium-3.

Abstract

The triangular flow in ultrarelativistic $^3$He-Au collisions at RHIC energies is enhanced due to the triangular arrangement of the nucleon configurations in $^3$He. We study the fireball eccentricities in the Glauber Monte Carlo model and find that since the configurations of the projectile $^3$He are elongated triangles, the created fireball has a large ellipticity and a smaller triangularity. The dependence of the triangularity on centrality is weak, so it cannot be extracted from the centrality dependence of the triangular flow $v_3$, as it is dominated by the centrality dependence of the hydrodynamic response. We propose to look at the centrality dependence of the ratio $v_n\{4\}/v_n\{2\}$, where the uncertainties from the hydrodynamic response cancel, and show that the basic signature of the geometry-driven collective flow is the raise of the ratio $v_3\{4\}/v_3\{2\}$ with the number of participant nucleons for centralities less than 10%.