  We report the results of a new global QCD analysis, which includes
deep-inelastic $e/\mu$ scattering data off proton and deuterium, as well as
Drell-Yan lepton pair production in proton-proton and proton-deuterium
collisions and $W^\pm/Z$ boson production data from $pp$ and $p \bar p$
collisions at the LHC and Tevatron. Nuclear effects in the deuteron are treated
in terms of a nuclear convolution approach with bound off-shell nucleons within
a weak binding approximation. The off-shell correction is controlled by a
universal function of the Bjorken variable $x$ describing the modification of
parton distributions in bound nucleons, which is determined in our analysis
along with the parton distribution functions of the proton. A number of
systematic studies are performed to estimate the uncertainties arising from the
use of various deuterium datasets, from the modeling of higher twist
contributions to the structure functions, from the treatment of target mass
corrections, as well as from the nuclear corrections in the deuteron. We obtain
predictions for the ratios $F_2^n/F_2^p$, and $d/u$, focusing on the region of
large $x$. We also compare our results with the ones obtained by other QCD
analyses, as well as with the recent data from the MARATHON experiment.
