Electroproduction and Photoabsorption in a Model of Higher Baryon Couplings

Abstract

We have studied the two related problems of inelastic ${e}^{\ensuremath{-}}\ensuremath{-}N$ scattering and the total photoabsorption cross section in a relativistic SU(6) \ifmmode\times\else\texttimes\fi{} 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 ${\overline{B}}_{L}B(P,V)$ couplings through a simple structure of the form factor for the supermultiplet transition (${L}^{P}\ensuremath{\rightarrow}{0}^{+}$) 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 ${e}^{\ensuremath{-}}\ensuremath{-}N$ scattering over a wide range of input data. The difference ($\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$) 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 ($J=L+\frac{1}{2}, J=L+\frac{3}{2}$) states are found to produce dominant contributions over those of the lower-spin ($J=L\ensuremath{-}\frac{1}{2}$) 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 $\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$ on the one hand and the traditional negative value of ($\ensuremath{\delta}{m}_{p}\ensuremath{-}\ensuremath{\delta}{m}_{n}$) on the other. However, an important shortcoming of this model is its inability to reproduce the scaling region of deep-inelastic ${e}^{\ensuremath{-}}\ensuremath{-}N$ scattering for very high incident electron energies ($\ensuremath{\epsilon}>10$ 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.