Elliptic flow parameter and its fluctuation in ${}_{197}\mathrm{Au}+{}_{197}\mathrm{Au}$ collisions at the STAR-BES energies in a multiphase transport model

We study the elliptic flow parameter and its event-by-event fluctuation in ${}_{197}\mathrm{Au}+{}_{197}\mathrm{Au}$ collisions at energies used in the STAR Beam Energy Scan (phase I) program, while using the string melting version of a multiphase transport (ampt) model as a baseline prediction. We employ different methods to determine the elliptic flow parameter, compare their values with each other, and study their dependencies on the collision centrality, transverse momentum, pseudorapidity, and nucleon-nucleon center of mass energy. Within the framework of the ampt model, we examine how the nonflow effects arising out of interparticle correlations influence the values of the elliptic flow parameter. We also study the centrality and energy dependencies of the event-by-event fluctuation of elliptic flow, and compare our simulation results with the STAR experimental data wherever they are available. We observe that the simulation can reasonably well reproduce the shape of the centrality dependence of the elliptic flow and its fluctuation as seen in the experiment. However, the simulation slightly underestimates the integrated values of the elliptic flow parameter, and it does not quite match with the transverse momentum and pseudorapidity dependencies observed in the experiment. We also observe that the contribution of nonflow effects to the centrality dependence of elliptic flow and its fluctuation is marginal. Fluctuations in the elliptic flow depend nonmonotonically on the collision energy involved, in the experiment as well as in the simulation.