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Measurement of charge multiplicity asymmetry correlations in high-energy nucleus-nucleus collisions at sNN =200 GeV


A study is reported of the same- and opposite-sign charge-dependent azimuthal correlations with respect to the event plane in Au+Au collisions at sNN=200 GeV. The charge multiplicity asymmetries between the up/down and left/right hemispheres relative to the event plane are utilized. The contributions from statistical fluctuations and detector effects were subtracted from the (co-)variance of the observed charge multiplicity asymmetries. In the mid- to most-central collisions, the same- (opposite-) sign pairs are preferentially emitted in back-to-back (aligned on the same-side) directions. The charge separation across the event plane, measured by the difference, Δ, between the like- and unlike-sign up/down-left/right correlations, is largest near the event plane. The difference is found to be proportional to the event-by-event final-state particle ellipticity (via the observed second-order harmonic v2obs), where Δ=[1.3±1.4(stat)-1.0+4.0(syst)]×10- 5+[3.2±0.2(stat)-0.3+0.4(syst)]×10-3v2obs for 20-40% Au+Au collisions. The implications for the proposed chiral magnetic effect are discussed. © 2014 American Physical Society.

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