Measurements of Vector Boson Production in lead-lead and proton-lead Collisions with the ATLAS Detector

Photons and weak bosons do not interact strongly, and thus their production yields provide direct tests of scaling with a number of binary nucleon--nucleon collisions in the heavy--ion environment. In addition they should be sensitive to the nuclear modification of parton distribution functions~(nPDF). Proton-lead collisions also provide an excellent opportunity to test nPDF in a less dense environment than lead--lead via looking at forward--backward production of weak bosons. The ATLAS detector has proven to be an excellent apparatus in measurements involving photons, electrons and muons, the latter being products of weak boson decays, in the high occupancy environment produced in heavy--ion collisions. The experiment has recorded $30\;\mathrm{ nb^{-1}}$ of proton--lead data and $140\; \mathrm{\mu b^{-1}}$ of lead--lead data, both of which have similar integrated partonic luminosities. We present the prompt photon, $Z$~and $W$~boson yields as a function of centrality, and also differentially in transverse momentum and rapidity, in lead--lead and proton--lead collisions from the ATLAS experiment. For $W$~bosons also a lepton charge asymmetry has been studied, which may also shed light on nPDF.