The ultra-relativistic ultra-relativistic heavy ion collision is the source of many interesting phenomena. In the ultra-peripheral collision the electromagnetic interaction between colliding ions is a source of virtual photons, which can interact between each other. This photon-photon interaction creates the e+,e- pairs in the broad configuration space around the center-of-mass point. The produced charged leptons can interact electromagnetically with positively charged ions.
In the present study the impact parameter space distribution of electrons and positrons are calculated within the b-space EPA model of such collisions. The evolution due to the electromagnetic interaction of e+,e- with nuclei is discussed, and the distortion of rapidity and transverse momentum distributions are shown.
The first exploratory results for the reaction Pb+Pb at sqrt(s_NN)=17.3 GeV (SPS) and 200 GeV (RHIC) energies are shown. We provide results for selected creation points and when integrating over their position as dictated by the b-space EPA model.
We observe strong effects at low transverse momenta, so far not measured regions of the phase space. In particular, we predict a possible sizable accumulation of electrons with rapidities close to the beam rapidity.
The electromagnetic effects lead to asymmetry in the production of electrons and positrons when the previous calculation described only interaction of the spectator with charged pions.