Experimental study of the polarization of antiprotons from low-energy antiproton+proton elastic scattering

The polarization of elastically scattered antiprotons in hydrogen, averaged with respect to the energy over the range 49.4-181.0 MeV, is evaluated as a function of the c.m. scattering angle between 16 degrees and 100 degrees . The result is based on an analysis of approximately 50000 pictures taken in the 81-cm Saclay hydrogen bubble chamber, which was exposed to a separated beam from the CERN proton synchrotron. The events used for measuring the polarization were double elastic scatterings of antiprotons. The resulting polarization appears to be rather strong, and does not agree with the predictions given by the current theoretical models.