The effect of the spectator charge on the charged pion spectra in peripheral ultrarelativistic heavy-ion collisions

Abstract

We estimate the electromagnetic effect of the spectator charge on the momentum spectra of charged pions produced in peripheral Pb+Pb collisions at SPS energies. We find a large effect which results in strongly varying structures in the xF dependence of the π+/π− ratio, especially at low transverse momenta where a deep valley in the above ratio is predicted at xF∼ 0.15–0.20. The effect depends on initial conditions. Thus, it provides new information on the space and time evolution of the non-perturbative pion creation process.