Electromagnetic Perturbations onπNNandπNN*Couplings in the Chew-Low Model: General Features

Abstract

Electromagnetic perturbations on $\ensuremath{\pi}\mathrm{NN}$ and $\ensuremath{\pi}N{N}^{*}$ couplings are studied in the $N\ensuremath{-}{N}^{*}$ reciprocal bootstrap model. In the present paper we confine ourselves to rather general features, making the linear-$D$ approximation for simplicity. There are several self-consistent coupling shifts, much as in the analogous $\mathrm{SU}(3)$ reciprocal bootstrap. It is shown that, except for even-$J$ exchanges in the $t$ channel, the "driving terms" are orthogonal to these self-consistent coupling shifts. Thus, as in the $\mathrm{SU}(3)$ case, no simple predictions can be made for coupling shifts in the linear-$D$ approximation.