Measurement of elliptic flow of light nuclei at $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV at RHIC

Abstract

We present measurements of 2${}^{nd}$ order azimuthal anisotropy ($v_2$) at mid-rapidity $(|y|<1.0)$ for light nuclei d, t, ${}^3$He (for $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and anti-nuclei $\bar{\mathrm{d}}$ ($\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, and 19.6 GeV) and ${}^3\overline{\mathrm{He}}$ ($\sqrt{s_{NN}}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The $v_2$ for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{\mathrm{p}}$. We observe mass ordering in nuclei $v_2(p_T)$ at low transverse momenta ($p_T<2.0$ GeV/$c$). We also find a centrality dependence of $v_2$ for d and $\bar{\mathrm{d}}$. The magnitude of $v_2$ for t and ${}^3$He agree within statistical errors. Light-nuclei $v_2$ are compared with predictions from a blast wave model. Atomic mass number ($A$) scaling of light-nuclei $v_2(p_T)$ seems to hold for $p_T/A<1.5$ GeV/$c$. Results on light-nuclei $v_2$ from a transport-plus-coalescence model are consistent with the experimental measurements.

13 pages and 10 figures