Internal-target polarized Drell-Yan Experiment at RHIC

We present physics motivations and experimental considerations for an internal-target polarized Drell-Yam dimuon experiment at RHIC. Dimuons from the Drell-Yan process are detected using a spectrometer based on the existing Fermilab-E906/SeaQuest spectrometer. The primary goal of the proposed experiment is to extract the Sivers parton distribution function in the valence-quark region from the measurement of the single transverse-spin asymmetry. The sensitivity of the proposed internal-target experiment will provide a stringent test of the QCD prediction that the Sivers function in the Drell-Yan process has an opposite sign with respect to that in deep-inelastic scattering. Results of some initial studies of the expected sensitivity are shown.