Probing the chiral magnetic wave in pPb and PbPb collisions at √S_NN = 5.02 TeV using charge-dependent azimuthal anisotropies

Charge-dependent anisotropy Fourier coefficients (ν_n) of particle azimuthal distributions are measured in pPb and PbPb collisions at √S_NN = 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients (ν₂) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient ν₃ shows a similar linear dependence with the same slope as seen for ν₂. The observed similarities between the ν₂ slopes for pPb and PbPb, as well as the similar slopes for ν₂ and ν₃ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that, at LHC energies, the observed charge asymmetry dependence of ν₂ in heavy ion collisions arises from a chiral magnetic wave.