Electromagnetic effects on meson production: a new tool for studying the space-time evolution of heavy ion collisions

We review our studies of spectator-induced electromagnetic (EM) effects on the emission of charged mesons in the final state of ultrarelativistic heavy ion collisions. We argue that these effects offer sensitivity to the distance dE between the charged meson formation zone at freeze-out and the spectator system. As such, they can serve as an independent, new tool to probe the space-time and longitudinal evolution of the system created in the collision. As a phenomenological application for this tool in the context of resonance production and decay, we obtain a first estimate of the time of pion emission from EM effects. This we compare to existing HBT data.