Absolute measurement of the polarization of high energy proton beams at RHIC

The spin physics program at the relativistic heavy ion collider (RHIC) requires knowledge of the beam polarization to better than 5%. Such a goal is made the more difficult by the lack of knowledge of the analyzing power of high energy nuclear physics processes. To overcome this, a polarized hydrogen jet target was constructed and installed at one intersection region in RHIC where it intersects both beams and utilizes the precise knowledge of the jet atomic hydrogen beam polarization to measure the analyzing power in proton- proton elastic scattering in the nuclear Coulomb interference (CNI) region at the prescribed RHIC proton beam energy. The reverse reaction is used to assess the absolute beam polarization. Simultaneous measurements taken with fast high statistics polarimeters that measure the p-carbon elastic scattering process also in the CNI region use the jet results to calibrate the latter. In this presentation, the status of the polarized jet target mechanics, operation, detector systems, and data analysis results are described. The statistical accuracies as well as the systematic uncertainties will be discussed.