? and φ in Au + Au collisions at (sNN)1/2= 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 ? andφ in Au + Au collisions with a new set of parameters for (sNN)1/2= 200 GeV and with the original set of parameters for (sNN)1/2= 11.5 GeV. The AMPT model with string melting provides a reasonable description at (sNN)1/2= 200 GeV,while the default AMPT model describes the data well at (sNN)1/2= 11.5 GeV. This indicates that the system created at top RHIC energy is dominated by partonic interactions, while hadronic interactions become important at lower beam energy, such as (sNN)1/2= 11.5 GeV. The comparison of N(?++?-)/[2N(φ)] 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.