$Z$ Boson Production in p+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ATLAS Detector

The ATLAS experiment has measured the production of $Z$ bosons in p+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV from the 2013 LHC run. The $Z$ bosons are reconstructed via the di-electron and di-muon decay channels. Results from the two channels are consistent and combined to obtain a total cross-section of 144.1 $\pm$ 4.9 (stat.) $\pm$ 8.3 (syst.) $\pm$ 4.9 (lumi.) nb within the fiducial acceptance region. The rapidity and momentum differential cross-sections are also presented. A significant excess in the direction of the Pb beam is observed in the rapidity distribution relative to a pQCD calculation which does not include nuclear modifications to the parton distribution functions. In addition the centrality dependence of the $Z$ boson production is measured and considered within the frameworks of a standard Glauber model as well as extensions of the model which allow for fluctuations in the inclusive nucleon-nucleon cross-section. The centrality dependence of the $Z$ boson yield per event is compared to the yield of inclusive charged particle production, and found to be similar.