Recent results for STAR $\sqrt{s_{NN}}=4.9$ GeV Al+Au and $\sqrt{s_{NN}}=4.5$ GeV Au+Au Fixed-Target Collisions

TL;DR

This paper reports new measurements of particle spectra and flow in fixed-target collisions at RHIC energies, including the first pion flow measurements at this energy range, demonstrating STAR's capabilities.

Contribution

It presents the first measurements of pion directed and elliptic flow at RHIC energies in fixed-target mode, expanding the understanding of collision dynamics at these energies.

Findings

Mass ordering observed in elliptic flow of pions and protons

First measurements of pion flow at RHIC energies

STAR demonstrates good performance in fixed-target configuration

Abstract

We present recent results from Al(beam)+Au(target) collisions at $\sqrt{s_{NN}}=4.9$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=4.5$\kern 0.16667em GeV from the STAR fixed-target (FXT) program. We report transverse mass spectra of protons, $K^0_S$ and $\Lambda$, rapidity density distributions of $\pi^\pm$, $K^0_S$ and $\Lambda$, directed flow of protons, $\pi^\pm$, $K^0_S$ and $\Lambda$, and elliptic flow of protons and $\pi^{\pm}$. These are the first measurements of pion directed and elliptic flow in this energy range at RHIC. Pion and proton elliptic flow show mass ordering. Measurements are compared with the published results from AGS and RHIC. These results demonstrate that STAR has good performance in the FXT configuration. The implications of these results for future STAR FXT runs are discussed.