  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.
