Electromagnetic effects as a new source of information on the space-time evolution of heavy ion collisions

¹ H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland
² University of Rzeszów, Rejtana 16, 35-959 Rzeszów, Poland

^a e-mail: nikolaos.davis@ifj.edu.pl

Published online: 5 December 2017

Abstract

We review our studies of spectator-induced electromagnetic (EM) effects on charged pion emission in ultrarelativistic heavy ion collisions. These effects are found to consist in the electromagnetic charge splitting of pion directed flow as well as very large distortions in spectra and ratios of produced charged particles. As it emerges from our analysis, they offer sensitivity to the actual distance, d_E, between the pion formation zone at freeze-out and the spectator matter. As a result, this offers a new possibility of studying the space-time evolution of dense and hot matter created in the course of the collision. Having established that d_E traces the longitudinal evolution of the system and therefore rapidly decreases as a function of pion rapidity, we investigate the latter finding in view of pion feed-over from intermediate resonance production. As a result, we obtain a first estimate of the pion decoupling time from EM effects which we compare to existing HBT data. We conclude that spectator-induced EM interactions can serve as a new tool for studying the space-time characteristics and longitudinal evolution of the system. We discuss the future perspectives for this activity on the basis of existing and future data from the NA61/SHINE experiment.