Antiproton-proton partial-wave analysis below 925 MeV/c
Partial-wave analyses (PWAs) have a long history in the fields of πN and NN scattering. Due to the poor quality of low-energy antiproton beams and the resulting absence of accurate experimental data, analogous model-independent studies of the much more complex \(\bar pp\) system have in the past always been impossible. In recent years, however, experimental progress has been very significant, in particular due to the coming in 1983 of the Low-Energy Antiproton Ring (LEAR) facility at CERN. While in the pre-LEAR era spin-dependent observables and charge-exchange (\(\bar pp \to \bar nn\)) data were almost nonexistent, the situation between 400 and 925 MeV/c is now quite good: the LEAR collaborations PS172, PS173, PS198, and PS199 have measured a variety of observables with impressive accuracy. High-quality analyzing-power data have been obtained for the elastic  and charge-exchange  reactions. Very recently, even charge-exchange depolarization data have become available . Unfortunately, the practical difficulties involved in constructing a high-quality “cooled” antiproton beam of lower momentum are large. Consequently, the \(\bar pp\) database below about 400 MeV/c is still by far not as good as one would like, in striking contrast to the pp case where very accurate data exist as low as T L = 0.35 MeV (P L = 25 MeV/c). It also remains an outstanding experimental challenge to construct a polarized antiproton beam to further probe the spin structure of the interaction.
KeywordsSchrodinger Equation Annihilation Channel Pion Pole Antiproton Beam Coulomb Wave Function
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