Theoretical analysis of a possible observation of the chiral magnetic effect in Au + Au collisions within the RHIC beam energy scan program

In terms of the hadron-string-dynamics (HSD) approach, we investigate the correlation function in the azimuthal angle ψ of charged hadrons that is expected to be sensitive to a signal of local strong parity violation. Our analysis of Au+Au collisions is based on the recent STAR data within the RHIC beam-energy-scan (BES) program. The HSD model reasonably reproduces STAR data for s_NN=7.7 GeV, while there are some deviations from the experiment at the collision energy of 11.5 GeV and an increase of deviations between theory and experiment at s_NN=39 GeV. For reference, the results for s_NN=200 GeV are given as well. The role of the retarded electromagnetic field is discussed and a compensation effect for the action of its electric and magnetic components is pointed out. We conclude that the recent RHIC BES data at s_NN=7.7 and 11.5 GeV can be understood on the hadronic level without involving the idea of a strong parity violation; however, the HSD model fails to reproduce data for s_NN∼40 GeV and above which suggests that at these energies one has to take into account explicit partonic (quark-qluon) degrees of freedom for a proper treatment of the dynamics as well as a coupling of the partons to fluctuating color fields.