The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0:15 nb-1 of integrated luminosity obtained in the 2011 LHC Pb + Pb run at √SNN = 2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.
Aad, G., Abajyan, T., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdelalim, A. A., … Zwalinski, L. (2013). Measurement of Z boson production in Pb-Pb collisions at √SNN = 2.76 TeV with the ATLAS detector. Physical Review Letters, 110(2), 022301-1-022301–18. https://doi.org/10.1103/PhysRevLett.110.022301