How to calibrate the polarization of a high energy proton beam? A   theoretical prospect
  In view of the realistic possibility for operating high-energy polarized proton beams in future collider machines, it is highly desirable to propose for such beams, an absolute calibration allowing to measure accurately their degree of polarization. We consider more specifically one practical method based on pp elastic scattering near the forward direction and we discuss its limitations. 
C. Bourrely and J. Soffer