Directed flow of $\Lambda$, $\bar{\Lambda }$, $K^{\pm }$, $K_S^0$ and $\varphi$ mesons from Beam Energy Scan Au+Au collisions using the STAR experiment

Abstract

We report the results of $v_1$ and $d{v}_1/dy$ near mid-rapidity for $\Lambda$, $\bar{\Lambda }$, $K^{\pm }$, $K_s^0$ and $\varphi$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27 and 39~GeV using the STAR detector at RHIC. The $d{v}_1/dy$ of $\Lambda$ is found to be consistent with that of the proton and shows a change in sign near $\sqrt{s_{\mathrm{NN}}}=11.5$~GeV. The $v_1$ slope for $\bar{\Lambda }$, $\bar{p}$ and $\varphi$ shows a similar trend for $\sqrt{s_{\mathrm{NN}}}$ $>$ 14.5~GeV, while below 14.5~GeV, $\varphi$ $v_1$ is consistent with zero but with a large uncertainty. The $d{v}_1/dy$ for net protons and net kaons is similar for $\sqrt{s_{\mathrm{NN}}}>$ 14.5~GeV, but they deviate at lower beam energies.

Comments: 4 pages, 5 figures, to appear in Strangeness in Quark Matter 2016 proceedings