Parity-violating asymmetry of W bosons produced in p-p collisions

The parity-violating asymmetry is an ideal tool to study the quark helicity distribution in the proton. We study the parity-violating asymmetry of W+/- bosons produced by longitudinally polarized p-p collision in RHIC, based on predictions of quark distributions of the proton in the SU(6) quark-spectator-diquark model and a perturbative QCD based counting rule analysis. We find that the two models give nearly equal asymmetry for W+ but that for W- quite different. Therefore future experiments on such quantity can help to clarify different predictions of the value Δd(x)/d(x) at x->1 in the proton