Energy dependence of $\varphi$-meson production and elliptic flow in Au+Au collisions at STAR

Abstract

We present, the measurements of the $\varphi$-meson production and elliptic flow ($v_2$) at mid-rapidity in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 200 GeV using the STAR detector in the years 2010 and 2011. The energy dependence of nuclear modification factors ($R_{\mathrm{CP}}$) is presented. At the intermediate transverse momentum ($p_T$) the $\Omega /\varphi$ ratio shows a different trend for $\sqrt{s_{NN}}$ = 11.5 GeV compared to higher beam energies. This may suggest change of particle production mechanism at $\sqrt{s_{NN}}$ = 11.5 GeV. The number-of-constituent quark (NCQ) scaling of $v_2$ has been studied at various beam energies. The NCQ scaling holds for all identified particles for $\sqrt{s_{NN}}$ $\ge$ 19.6 GeV, which can be considered as an evidence of partonic collectivity. We observe at $\sqrt{s_{NN}}$ = 7.7 and 11.5 GeV, the $\varphi$-meson $v_2$ falls off the trend from the other hadrons at highest measured $p_T$ values by 1.8$\sigma$ and 2.3$\sigma$, respectively. This may indicate that the hadronic interaction plays an important role at lower beam energies.

Proceedings of 8th International Workshop on Critical Point and Onset of Deconfinement

References in corpus (2)

• Elliptic flow of identified hadrons in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7--62.4 GeV
• An Experimental Exploration of the QCD Phase Diagram: The Search for the Critical Point and the Onset of De-confinement