Production ofWbosons in proton-nucleus collisions

It is shown that nuclear effects can cause an enhancement in the cross section for production of $W$ bosons in a proton-nucleus collision. The cross section near threshold is a few orders of magnitude higher than expected from a linear dependence on the atomic number. Encouraging implications for experiments with fixed targets at laboratory energies of ${10}^{3}$ GeV and higher are discussed. We also discuss lepton-pair production off nuclei.