A Method to Polarize Stored Antiprotons to a High Degree
  Polarized antiprotons can be produced in a storage ring by spin--dependent interaction in a purely electron--polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies $T\approx 40-170$ MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach $P=0.2-0.4$. Polarized antiprotons would open new and unique research opportunities for spin--physics experiments in $\bar{p}p$ interactions. 
F. Rathmann, P. Lenisa, E. Steffens, M. Contalbrigo, P.F. Dalpiaz, A.   Kacharava, A. Lehrach, B. Lorentz, R. Maier, D. Pras...