The production of $W$ bosons in polarized $p+p$ collisions at RHIC provides an excellent tool to probe the proton's sea quark distributions. At leading order $W^{ -(+)}$ bosons are produced in $\bar{ u}+d\,(\bar{ d}+u)$ collisions, and parity-violating single-spin asymmetries measured in longitudinally polarized $p+p$ collisions give access to the flavor-separated light quark and antiquark helicity distributions. In this proceedings we report preliminary results for the single-spin asymmetry, $A_L$ from data collected in 2012 by the STAR experiment at RHIC with an integrated luminosity of 72 pb$^{ -1}$ at $\sqrt{ s}=510$ GeV and an average beam polarization of 56%.
Categories: nucl-ex