Beam-Energy Dependence of Directed Flow of $\Lambda$, $\bar{\Lambda}$, $K^\pm$, $K^0_s$ and $\phi$ in Au+Au Collisions

TL;DR

This study measures the directed flow of various particles in gold-gold collisions across a range of energies, providing data to test models of the quark-gluon plasma and collision dynamics.

Contribution

It presents extensive new measurements of particle flow at multiple energies, enhancing constraints on the equation of state in quantum chromodynamics.

Findings

Flow measurements are sensitive to the collision dynamics.

Departure from coalescence sum-rule offers insights into hadron formation.

Data supports models with flow established before hadronization.

Abstract

Rapidity-odd directed flow measurements at midrapidity are presented for $\Lambda$, $\bar{\Lambda}$, $K^\pm$, $K^0_s$ and $\phi$ at $\sqrt{s_{NN}} =$ 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV in Au+Au collisions recorded by the STAR detector at the Relativistic Heavy Ion Collider. These measurements greatly expand the scope of data available to constrain models with differing prescriptions for the equation of state of quantum chromodynamics. Results show good sensitivity for testing a picture where flow is assumed to be imposed before hadron formation and the observed particles are assumed to form via coalescence of constituent quarks. The pattern of departure from a coalescence-inspired sum-rule can be a valuable new tool for probing the collision dynamics.