Production of W bosons in p-Pb collisions measured with ALICE at the LHC.

W bosons, which are produced in hard scattering processes of partons in collisions of hadrons, do not interact strongly with the medium produced in high-energy heavy-ion collisions. Therefore, in p-Pb collisions the measurement of W-boson yields represents a standard candle to check the validity of binary scaling and can provide important constraints on the parton distribution functions, which can be modified in nuclei with respect to protons or neutrons.