Quark-meson coupling model for baryon wave functions and properties.

Abstract

A scalar-isoscalar quark-meson interaction is used to mix fundamental pseudoscalar mesons directly into the wave functions of baryons. The parameters of the model are constrained using properties of the ground-state baryon spectrum, such as charge radii, strong decay widths, and the pion-nucleon coupling constant. Physical wave functions of the ground-state baryons are presented. With the physical wave functions, we calculate nucleon electric form factors and spin-$\frac{3}{2}$ baryon quadrupole moments. The addition of mesons produces effects on baryon properties comparable to effects due to spatial excitations of quarks. Although missing from most calculations, kaons and $\ensuremath{\eta}$'s are found to be as important as pions in the baryon spectrum. Including mesons in the physical wave functions of baryons leads to the existence of low-energy resonances consisting primarily of three quarks in the ground state surrounded by a meson field. Most of these resonances decouple from the common production channels, but seven are expected to be observable. An additional $N({\frac{1}{2}}^{+})$ resonance state is calculated to have a mass close to that of the Roper resonance but a $\ensuremath{\pi}N$ width much smaller. A $\ensuremath{\Delta}({\frac{3}{2}}^{+})$ candidate state is calculated to have a mass and $\ensuremath{\pi}N$ width close to the experimental values for the $\ensuremath{\Delta}(1600)$.