Coulomb Interaction Effects on Pion Production in Au

Coulomb effects on charged pion transverse momentum spectra measured in Au+Au collisions at RHIC-BES energies are investigated. From these spectra the pi(-)/pi(+) ratios as a function of transverse momentum are obtained and used to extract the "Coulomb kick", P-c (a momentum change due to the Coulomb interaction), and initial pion ratio for three different collision energies and various centrality classes. The Coulomb kick shows a decrease with the increase of beam energy and a clear centrality dependence, with larger values for the most central collisions. The results are connected with the kinetic freeze-out dynamics.