Investigating the coalescence-inspired sum rule for light nuclei and hypernuclei in heavy-ion collisions

TL;DR

This paper tests the coalescence-inspired sum rule for light nuclei and hypernuclei in heavy-ion collisions, finding approximate validity near mid-rapidity and violations at large rapidity, supported by experimental data and transport model simulations.

Contribution

It introduces a data-driven method to test the sum rule for light nuclei and hypernuclei flow, incorporating mass and charge differences, and predicts hypernuclei flow patterns at 3 GeV.

Findings

Sum rule approximately valid near mid-rapidity

Violations of the sum rule at large rapidity

Transport model reproduces experimental pattern

Abstract

A data-driven idea is presented to test if light nuclei and hypernuclei obey the coalescence-inspired sum rule, i.e., to test if the flow of a light nucleus or hypernucleus is the summed flow of each of its constituents. Here, the mass difference and charge difference among the constituents of light nuclei and hypernuclei are treated appropriately. The idea is applied to the available data for $\sqrt{s_{NN}} = 3$ GeV fixed-target Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), published by the STAR collaboration. It is found that the sum rule for light nuclei is approximately valid near mid-rapidity ($-0.3 < y < 0$), but there is a clear violation of the sum rule at large rapidity ($y < -0.3$). The Jet AA Microscopic Transport Model (JAM), with baryonic mean-field plus nucleon coalescence, generates a similar pattern as obtained from the experimental data. In the present approach, the rapidity dependence of directed flow of the hypernuclei $\mathrm{_{\Lambda}^{3}H}$ and $\mathrm{_{\Lambda}^{4}H}$ is predicted in a model-independent way for $\sqrt{s_{NN}} = 3$ GeV Au+Au collisions, which will be explored by ongoing and future measurements from STAR.