  Differential cross sections for the Drell-Yan process, including Z boson
production, using the dimuon decay channel are measured in proton-lead (pPb)
collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data
sample recorded with the CMS detector at the LHC is used, corresponding to an
integrated luminosity of 173 nb$^{-1}$. The differential cross section as a
function of the dimuon mass is measured in the range 15-600 GeV, for the first
time in proton-nucleus collisions. It is also reported as a function of dimuon
rapidity over the mass ranges 15-60 GeV and 60-120 GeV, and ratios for the
p-going over the Pb-going beam directions are built. In both mass ranges, the
differential cross sections as functions of the dimuon transverse momentum
$p_\mathrm{T}$ and of a geometric variable $\phi^*$ are measured, where
$\phi^*$ highly correlates with $p_\mathrm{T}$ but is determined with higher
precision. In the Z mass region, the rapidity dependence of the data indicate a
modification of the distribution of partons within a lead nucleus as compared
to the proton case. The data are more precise than predictions based upon
current models of parton distributions.
