Spin physics at LEAR

The original physics motivation for the existence of broad baryonium resonances in the anti-NN system is reviewed, and information is given on experiment PS172, whose main objective is to measure the two-body channels anti-pp → ππ, KK, and anti-pp, and subsequently to identify such resonances by partial-wave analysis of the final states. The importance of pursuing the study of the anti-NN → anti-NN channel to distinguish baryonium resonances from ordinary qanti-q mesons is stressed, and a program is presented to measure, on a polarized target, the reactions anti-pp → anti-nn and anti-np → anti-np after ACOL construction. 15 refs