Probing the electromagnetic fields in ultrarelativistic collisions with leptons from Z0 decay and charmed mesons

Ultrarelativistic heavy ion collisions are expected to generate a huge electromagnetic field, eB≈1018Gauss, that induces a splitting of the directed flow, v1=〈px/pT〉, of charged particles and anti-particles. Such a splitting for charmed meson manifests even for neutral particle/anti-particles pairs (D0,D‾0), hence being also a unique probe of the formation of the quark-gluon plasma phase. For the first time here we show that electromagnetic field may generate a v1(D0)−v1(D‾0) as huge as the one recently observed at LHC against early expectations. Within this new research topic we point out a novel measurement: v1 of leptons from Z0 decay and its correlation to that of D and B mesons. The correlation for Δv1 of l+−l−, D0−D‾0 and B0−B‾0 would provide a strong probe of the electromagnetic origin of the splitting and hence of the formation of a quark-gluon plasma phase with heavy quarks as degrees of freedom. The case of the v1(l±) presents features due to the peculiar form of the pT spectrum never appreciated before in the study of heavy ion collisions. We specifically predict a sudden change of the Δv1(pT) of leptons at pT=45GeV/c, that can be traced back to a universal relation of Δv1 with the slope of the pT particle distribution and the integrated effect of the Lorentz force.