Abstract
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.
Highlights
The ultrarelativistic heavy ion collisions at both the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have been a terrestrial tool to access the properties of the Hot QCD matter and have shown that such a matter expands hydrodynamically with a very small shear viscosity to entropy density ratio, close to a conjectured lower limit for strongly interacting matter [1]
We show the transverse momentum distribution of charm quarks initially produced at 5.02 TeV Pb+Pb collisions by the green line in Fig. 2, which is obtained by the Fixed Order+Next-to-Leading Log (FONLL) QCD [40, 41]
We propose for the first time in ultrarelativistic heavy ion collisions (uRHICs) the measurement of the v1 of leptons from Z0 decay to confirm the electromagnetic origin of the ∆v1D and have a novel constraint on e.m. strength and time evolution
Summary
The ultrarelativistic heavy ion collisions (uRHICs) at both the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have been a terrestrial tool to access the properties of the Hot QCD matter and have shown that such a matter expands hydrodynamically with a very small shear viscosity to entropy density ratio, close to a conjectured lower limit for strongly interacting matter [1]. At the current stage the description of the expanding dynamics in AA collisions appears to be quite solid which is opening new frontiers in the study of uRHICs. The main novel aspects that are becoming accessible are those related to the impact of the strongest electromagnetic field [2, 3] and of the largest relativistic vorticity [4, 5] ever created in a physical system. In the last decade it has been possible to study the dynamics of heavy quarks (HQs), mainly charm quarks, achieving a first phenomenological determination of their interaction with the quark-gluon plasma (QGP) [21,22,23] This opens the possibility to investigate by mean of HQs new aspects coming from the very early stage dynamics. The absolute measurement of v1(pT , η) of these charged leptons l± and its correlation to the D0, D0 will be smoking gun of the electromagnetic origin of the splitting
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