Probing the QCD phase diagram with measurements of φ-meson production and elliptic flow in heavy-ion collisions at STAR

We present measurements of φ-meson production and elliptic flow (v₂) at mid-rapidity in Au + Au collisions at √S_NN = 7.7 – 200 GeV. Energy dependence of nuclear modification factor (R_CP) of φ meson is presented. The φ-meson R_CP has a value ≥ 1.0 for √S_NN ≤ 39 GeV. The Ω/φ ratios are also presented and show a different trend at the intermediate transverse momentum (p_T) for √S_NN = 11.5 GeV compared to higher beam energies. The number-of-constituent quark (NCQ) scaling of v₂ has been studied at various beam energies. The NCQ scaling holds for particles and anti-particles separately including the φ meson for √S_NN ≥ 19.6 GeV, which can be considered as an evidence of partonic collectivity. We observe that φ-meson v₂ falls off the trend from the other hadrons at highest measured p_T values by 1.8σ and 2.3σ at √S_NN = 7.7 and 11.5 GeV, respectively.