Parton Distributions from W+- and Z Production in Polarized pp and pn Collisions at RHIC

We study the production of $W^{\pm}$ and $Z$ gauge bosons in proton-proton and proton-neutron collisions up to a center-of-mass energy $\sqrt s=0.5\ TeV$, in connection with the realistic possibility of having proton-deuteron collisions at RHIC with a high luminosity. We stress the importance of measuring unpolarized cross sections for a better determination of the flavor asymmetry of the sea quarks. Since polarized proton beams will be available at RHIC, we evaluate several spin-dependent observables like, double helicity asymmetries $A_{LL}$ as a test of the sea quark polarization, double transverse spin asymmetries $A_{TT}$ as a practical way to determine a new structure function, the nucleon transversity distribution $h_1(x)$, and parity-violating asymmetries $A_L$ as a further test of our present knowledge of polarized parton distributions.