  The first study of W boson production in pPb collisions is presented, for
bosons decaying to a muon or electron, and a neutrino. The measurements are
based on a data sample corresponding to an integrated luminosity of 34.6
inverse nanobarns at a nucleon-nucleon centre-of-mass energy of sqrt(s[NN]) =
5.02 TeV, collected by the CMS experiment. The W boson differential cross
sections, lepton charge asymmetry, and forward-backward asymmetries are
measured for leptons of transverse momentum exceeding 25 GeV, and as a function
of the lepton pseudorapidity in the abs(eta[lab]) < 2.4 range. Deviations from
the expectations based on currently available parton distribution functions are
observed, showing the need for including W boson data in nuclear parton
distribution global fits.
