Elliptic flow of transported and non-transported proton in Au+Au collisions within the UrQMD model

With the framework of UrQMD model, by tracing the number of initial quarks in protons, we study the elliptic flow of transported protons, poduced protons and anti-protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 39, 200 GeV. The difference of elliptic flow between transported protons and anti-protons is observed. The results of UrQMD model show a good agreement with the STAR results at low energies, but are deviate at high energies. It partly explains the $v_{2}$ difference between proton and anti-proton observed in the Beam Energy Scan program in Relativistic Heavy Ion Collider~(RHIC).