Rescattering effects in the quark model for meson-baryon couplings

Abstract

The eikonal approximation in high-energy scattering is used as a basis for the evaluation of scattering corrections to meson-baryon couplings in the independent quark model. These corrections, which reduce the SU(6) symmetry (characteristic of the impulse approximation) to a mere SU(3) symmetry, are found to be typically of the order of 20-30% on the coupling constants. An important part of the correction, which arises from the purely "SU(3)-isotropic" component of the meson-quark amplitude, has exactly the same structure as the SU(6)-invariant couplings and hence can be interpreted as a renormalization effect. The remaining corrections, which may be called the "true scattering effects," lead to an explicit formula for the F/D ratio in octet couplings in terms of the meson-quark scattering parameters which differs from its SU(6) value of 2/3 by about 4%. These corrections also give an enhancement factor for decuplet decays which increases the predicted rate for N^*→Nπ by about 30%. It is argued that the nature of these numerical results is rather insensitive to the precise validity or lack of validity of the eikonal approximation.