Nonlinear model ofc-number confined Dirac quarks

We investigate the effect of spin-dependent forces in a recently proposed approach to the problem of extended particles with structure. The forces are introduced by means of two different fourth-order interactions of Fermi type, a vector coupling and a combination of a scalar and pseudoscalar terms. The mass parameter is 286 (393) MeV in the vector (scalar-pseudoscalar) case and the mass of the spin-zero meson turns out to be 582 (552) MeV, close to that of the $\eta$, those of the baryon and the spin-one meson being 1200 and 800 MeV in both cases. As the model has only one flavor, it does not allow other particles.