Probing the sea contribution to the protons' spin

Longitudinal single-spin asymmetries (AL) of parity-violating W bosons are measured with PHENIX via the decay daughter muons in = 500 GeV p + p collisions at RHIC. These proceedings report on the latest W±→μ±ν asymmetry results obtained during the 2011 RHIC run using the forward muon-arm detector in PHENIX.