Light fermion bound states in two-particle relativistic quantum mechanics

We study, in the framework of two-particle relativistic quantum mechanics, spin 1/2 fermion-spin-0 boson systems with general classes of interaction having the following properties: they preserve chiral symmetry, confine the two particles into bound states and possess the short distance behavior of vector interactions. The resulting spectrum displays as ground states an infinite number of light fermions with increasing spins, the masses of which vanish with the vanishing of the constituent particle masses. In the absence of short range interactions these fermions have the quantum numbers j = l +1/2; l=0,1,...; n=0. A secondary interaction, here taken illustratively of the L-S coupling type, is needed to give masses to the light high spin fermions. This problem is relevant for the study of the dynamics of preonic systems