Pionic and electromagnetic production of η in a model of higher baryon couplings

Abstract

An s-channel analysis of η-production processes induced by pions and photons on protons is made in the momentum region 2.9-13.3 GeV/c. The analysis is carried out in a model of higher baryon couplings, which is characterized by a relativistic extension of a broken SU₆⊗O₃ with partial symmetry scheme for B̅ B_LP and B̅ B_LV couplings in a unified fashion. In this high-energy extension of the model we incorporate seven baryon trajectories, viz., N_α(938), N_β(1530), N_β'(1715), N_β''(1675), N_γ(1520), N_γ'(1675), and N_δ(1860), for which we carry out piecewise summations over the contributions of the particles involved in the corresponding towers, formally up to infinity. The predictions of the theory are compared with experiment with respect to the (i) total and differential cross sections and the recoil neutron polarization for the process π^-p→ηn, and (ii) differential cross sections for the process γp→ηp at several incident energies. In general the agreement with experiment is rather good up to ∼10 GeV/c. The reasons for the success up to this momentum, as well as the limitations to extension beyond this value, are discussed in the context of contemporary ideas.