The elliptic flow in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV at STAR

We present elliptic flow, $v_2$, measurements for charged and identified particles at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV at STAR. We compare the inclusive charged hadron $v_2$ to those from high energies at RHIC ($\sqrt{s_{NN}}$ = 62.4 and 200 GeV), at LHC ($\sqrt{s_{NN}}$ = 2.76 TeV). A significant difference in $v_2$ between baryons and anti-baryons is observed and the difference increases with decreasing beam energy. We observed the $v_2$ of $\varphi$ meson is systematically lower than other particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 11.5 GeV.