Measurement of prompt D0and D0meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at √sNN=5.02TeV

Abstract

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ( v2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) between D0(uc) and D0(uc) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of v2. The rapidity-averaged value is found to be v2 =0.001 ±0.001(stat)±0.003(syst)in PbPb collisions at √sNN=5.02TeV. In addition, the influence of the collision geometry is explored by measuring the D0and D0mesons v2and triangular flow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0meson v2values is observed, while the v3is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.