Antiproton-proton annihilation into two mesons: SU(3) coupling schemes for quark line rule, s-channel dominance and baryon exchange

Abstract

We use SU(3)- and charge conjugation-invariance to analyse the annihilation of a$\bar pp$ bound state of definiteC-parity into two mesons. We introduce four sets of SU(3) invariant couplings and write down the transformations among them. They allow for a direct interpretation in terms of different physical assumptions. The couplings permit an easy incorporation of the quark line- (or OZI-) rule. The four sets of invariant couplings — even though mathematically equivalent — correspond to different pictures of the annihilation mechanism. One coupling scheme refers to a description of$\bar pp$ annihilation in terms of baryon exchange. A second scheme specifies the octet decomposition of the s-channel intermediate states. The third scheme traces the flow of quarks from the initial$\bar pp$ system to the outgoing mesons. And finally, we use the octet coupling scheme. The latter has no obvious interpretation in form of a simple physical picture but is needed to relate the different coupling schemes by transformation matrices.