Final Report Summary - POLPBAR (Production of Polarized Antiprotons)
Since the antiproton is an anti-particle, no conventional method (involving bulk matter) to align the spin vectors of an antiproton-ensemble is applicable - they would immediately annihilate with protons of the material and disappear. The method of choice is to use a stored beam of (originally) unpolarized particles, and - by interaction with a very thin polarized hydrogen atoms injected into a storage cell - slowly accumulate one preferred polarization state over the other (this is termed "spin-filtering"). From experiments we have performed within this project, we know that this method works for protons and there is every reason to expect that it will work for antiprotons as well, but the final experimental proof has not yet been provided: due to the non-availability of the currently only antiproton storage ring (AD at CERN), this will have to wait for a future opportunity.