Inclusion of W^+- single-spin asymmetry data in a polarised PDF determination via Bayesian reweighting

We discuss how the experimental information from longitudinal single-spin asymmetries for $W^{\pm }$ boson production in polarised proton-proton collisions can be included in a polarised parton determination by Bayesian reweighting of a Monte Carlo set of polarised PDF replicas. We explicitly construct a prior ensemble of polarised parton distributions using available fits to inclusive and semi-inclusive DIS data and we discuss the potential impact of existing and future RHIC measurements on it.