Delta M_W < 10 MeV/c² at the LHC: a forlorn hope?

At the LHC, the measurement of the W mass with a precision of \cal{O}(10) MeV/c^2 is both mandatory and difficult. In the analysis strategies proposed so far, shortcuts have been made that are justified for proton-antiproton collisions at the Tevatron, but not for proton-proton collisions at the LHC. The root of the problem lies in the inadequate knowledge of parton density functions of the proton. It is argued that in order to reach a 10 MeV/c^2 precision for the W mass, more precise parton density functions of the proton are needed, and an LHC-specific analysis strategy ought to be pursued. Proposals are made on both issues.