  We calculate the single-spin asymmetries $A^{W^{\pm}}_{L}$ of $W^{\pm}$
bosons produced in polarized pp collisions with the valence part of the up and
down quark helicity distributions modeled by the light-cone
quark-spectator-diquark model while the sea part helicity distributions of the
up and down quarks treated as parametrization. Comparing our results with those
from experimental data at RHIC, we find that the helicity distributions of sea
quarks play an important role in the determination of the shapes of
$A^{W^{\pm}}_{L}$. It is shown that $A^{W^{-}}_{L}$ is sensitive to $\Delta
\bar u$, while $A^{W^{+}}_{L}$ to $\Delta \bar d$ intuitively. The experimental
data of the polarized structure functions and the sum of helicities are also
important to constrain the sizes of quark helicity distributions both for the
sea part and the valence part of the nucleon.

High Energy Physics - Phenomenology