Ω and φ in Au + Au ~collisions at srt~= 200 and 11.5 GeV from a multiphase transport model

Within the framework of a multiphase transport model, we study the production and properties of $\Omega$ and $\phi$ in Au + Au collisions with a new set of parameters for $\sqrt{s_{NN}}$ = 200 GeV and with the original set of parameters for $\sqrt{s_{NN}}$ = 11.5 GeV, respectively. The AMPT model with the string melting version provides a reasonable description at $\sqrt{s_{NN}}$ = 200 GeV and while the AMPT model with default version describes the data well at $\sqrt{s_{NN}}$ = 11.5 GeV. It indicates that the system created at top RHIC energy is dominated by partonic interaction and while the hadronic interaction becomes important at lower beam energy, such as $\sqrt{s_{NN}}$ = 11.5 GeV. The comparison of $N(\Omega ^++\Omega^-)/[2N(\phi)]$ ratio between data and calculations further supports the argument. Our calculations can generally describe the data of nuclear modification factor as well as elliptic flow.