Electromagnetic interaction of low transverse momentum charged leptons with heavy nuclei in ultra-peripheral ultra-relativistic heavy-ion collisions

Abstract

AbstractThe photon–photon interaction in ultra-relativistic heavy-ion collision is a source of the charged lepton pairs. The photon-photon fusion leads to the lepton creation in broad configuration space around the “collision” point. Those created close to heavy nuclei may undergo strong electromagnetic interaction with them. The impact parameter space distributions of electrons/positrons and charged muons are calculated within the b-space EPA model of such collisions. The evolution of $$e^+/e^-$$ e + / e - and $$\mu ^+/\mu ^-$$ μ + / μ - distributions due to the electromagnetic interaction of leptons with nuclei is studied, and the distortion of rapidity and transverse momentum distributions are shown. A part of the analysis is independent of the production model. We show the first exploratory results for the reaction Pb + Pb at $$\sqrt{s_{NN}} = $$ s NN = 17.3 GeV (SPS) and 200 GeV (RHIC) energies. We provide results for selected creation points and when integrating over their positions as dictated by the b-space EPA model. We observe sizeable effects for $$e^+ / e^-$$ e + / e - and much smaller effects for $$\mu ^+ / \mu ^-$$ μ + / μ - . We predict a possible sizeable accumulation of leptons with rapidities close to the beam rapidity. The EM effects lead to asymmetry in the production of $$e^+$$ e + and $$e^-$$ e - or $$\mu ^+$$ μ + and $$\mu ^-$$ μ - .