### Speaker

G. Bruce Mainland
(The Ohio State University at Newark)

### Description

Because the existence of families of elements and hadrons was ultimately understood by the realization that atoms and hadrons are composite, in the 1970's many physicists thought that the existence of the four families of leptons and quarks could be understood if leptons and quarks were composite. By the early 1980's, however, the physics community had given up on the idea because it had not been possible to determine the force that binds constituents into leptons and quarks. The development of supercomputers now makes it feasible to study such highly relativistic bound states. Here the possibility is discussed that leptons and quarks are highly relativistic bound states of a scalar and spin-1/2 fermion bound by minimal electrodynamics. These bound states are described by the Bethe-Salpeter equation and have the following three properties, all of which are essential if quarks and leptons are composite: (1) The boundary conditions allow strongly bound solutions when the coupling constant has a magnitude on the order of the fine structure constant. Typically the coupling constant for strongly bound solutions is on the order of or greater than unity. (2) All strongly bound, normalizable solutions must have spin-1/2 if the coupling constant has a magnitude on the order of the fine structure constant. It is remarkable that higher spin, strongly bound solutions are forbidden. (3) Some strongly bound solutions possess a property that suppresses the unobserved decay of a muon into an electron and a photon.

### Primary author

G. Bruce Mainland
(The Ohio State University at Newark)