Electroproduction and photoabsorption in a model of higher baryon couplings

Abstract

We have studied the two related problems of inelastic e^--N scattering and the total photoabsorption cross section in a relativistic SU(6) × O(3) model of higher baryon couplings developed over the last few years. The hypothesis of duality is incorporated for both these photonic processes by summing over an infinite sequence of s-channel resonances, the facility for which is provided in this model of B̅ _LB(P,V) couplings through a simple structure of the form factor for the supermultiplet transition (L^P→0⁺) and a "Regge universality" condition on the "reduced" coupling constants. A slight variant of this form factor, which has been applied successfully to several two-body processes recently, is found to give rather good fits to the resonance-production region of inelastic e^--N scattering over a wide range of input data. The difference (Δσ_T) of the total photoabsorption cross section on the proton and the neutron targets is also reproduced quite accurately over the whole range of available data. For these two processes, the higher-spin (J=L+1/2, J=L+3/2) states are found to produce dominant contributions over those of the lower-spin (J = L-1/2) states. A comparison of this pattern with a corresponding one operative for the evaluation of electromagnetic masses within this model prompts us to infer almost a "causal" relationship between the positive value of Δσ_T on the one hand and the traditional negative value of (δm_p-δm_n) on the other. However, an important shortcoming of this model is its inability to reproduce the scaling region of deep-inelastic e^--N scattering for very high incident electron energies (ε>10 GeV). This is presumably because of the absence in this model of a mechanism for the inclusion of daughter trajectories, whose contributions are expected to be progressively more important as the energy is increased.