We present the measurements of the $\phi$-meson production and elliptic flow ($v_{ 2}$) at mid-rapidity in Au + Au collisions at $\sqrt{ s_{ NN}}$ = 7.7 - 200 GeV. The data are collected using the STAR detector in the years 2010 and 2011. The energy dependence of nuclear modification factor ($R_{ \rm{ CP}}$) of $\phi$ meson is presented. The $\phi$-meson $R_{ \rm{ CP}}$ has a value $\geq$ 1.0 for $\sqrt{ s_{ NN}}$ $\leq$ 39 GeV. The $\Omega/\phi$ ratios are also presented and show a different trend at the intermediate transverse momentum ($p_{ T}$) for $\sqrt{ s_{ NN}}$ = 11.5 GeV compared to higher beam energies. The number-of-constituent quark (NCQ) scaling of $v_{ 2}$ has been studied at various beam energies. The NCQ scaling holds for particles and anti-particles separately including the $\phi$ meson for $\sqrt{ s_{ NN}}$ $\geq$ 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 $\phi$-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.
Categories: nucl-ex hep-ex nucl-th
