Fernández-Rañada, Antonio2023-06-212023-06-211984-03-010556-282110.1103/PhysRevD.29.985https://hdl.handle.net/20.500.14352/64900© 1984 The American Physical Society. We are very grateful to Dr. L. García for help in the coinputing process. This work is part of a program partially supported by CAICYT (Coinision Asesora de Investigacion Cientifica y Tecnica) and Institute de Estudios Nucleares of Madrid.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 fourthorder 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 g, 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.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.29.985http://journals.aps.orgopen access537ElectricidadElectrónica (Física)2202.03 Electricidad