Measurement of the Z boson Production in Lead-Lead Collisions at sqrt(s_NN)=2.76 TeV with the ATLAS Detector

The ATLAS experiment has observed 1995 Z boson candidates with 0.15 nb−1 of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt(s_NN)=2.76 TeV. 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 our selected sample. Within the statistical and systematic uncertainties, the per-event Z boson yield integrated over rapidity |yZ| < 2.5 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.