The current experimental status of baryon exchange

Abstract

The experimental situation on the importance of the baryon exchange (B.E.) process for reactions meson + baryon → meson’ + baryon’ is investigated. Some general comments are made about the expected absolute cross-sections, angular distributions and incident momentum dependence of the B. E. mechanism. It is found that it should be easiest to study the process when the incident momentum is in the few GeV/c region. The simplest reactions in which to search for B.E. are those for which meson exchange (M.E.) is forbidden. Of these, K−p → Ξ−K+, K−p → Σ−π+ and π−p → Σ−K+ all show forward baryon peaks of the order of 10 µb/sr. Results are presented in a table. A study of reactions for which B.E. is forbidden (\(\overline K\)N →N\(\overline K\); or Δ\(\overline K\)) reveals that several of these processes exhibit enhancements in the backward meson hemisphere. These are probably due to mechanisms of the type\(\overline K\)N → Y* →N\(\overline K\), and this emphasizes the need for high-energy experiments for investigating B.E. The majority of reactions are allowed both for B.E. and M.E. Of those cases which have been studied in sufficient detail, a large number show backward meson peaks with cross-sections similar to those observed in M.E.-forbidden reactions. Results on some of these reactions are presented in a table. Although it seems that B.E. can be regarded as an established process, some details deserve further study, and suggestions are made for experiments which would enable a better understanding to be obtained of the B.E. mechanism.