Measurement of Z boson Production in Lead–Lead Collisions at image with the ATLAS Detector

The ATLAS experiment has observed 1995 Z boson candidates from an integrated luminosity image collected in the 2011 LHC Pb + Pb run at image. The Z bosons are reconstructed via di-electron and di-muon decay channels. The results from both channels are consistent with each other and are combined. The background is less than 3% of the selected sample. Within the statistical and systematic uncertainties, the per-event Z boson yield integrated over rapidity image is proportional to the number of binary collisions estimated by the Glauber model. The elliptic flow coefficient of the azimuthal distribution of the Z boson with respect to the event plane is consistent with zero.