The masses of the elementary particles as well as their charges and spins
(herein expressed in terms of the elementary charge and Planck's constant,
respectively) belong to the fundamental physical constants. Presently, no
fundamental theory describing them is available, so their values remain
mysterious. In this work we offer an approach based on the Brown-York
quasi-local energy which includes the self-energy of an object. In order to
compute this energy we model the spacetime of the renormalized electron (and
other leptons) by the Kerr-Newman metric. Placing conditions on the associated
energies at different radii we arrive at various constraints on the mass,
charge and spin.Comment: 4 pages, 1 figur