lepton

noun

1. A coin used since ancient times in Greece, serving in modern times as one hundredth of a phoenix, a drachma, and a euro (as the Greek form of the Eurocent).
2. A small, bronze Judean coin from the 1st century BCE, considered by some to be the widow's mite.
3. (particle)An elementary particle that has a spin of 1/2 (i.e., is a fermion) and does not interact via the strong nuclear force; examples include the electron, the muon, the neutrino and the tauon.

   “In the present paper we deal with the second order radiative correction to the beta disintegration of nucleon, assuming the Fermi's interaction between necleon and lepton fields, and show that there appears such an ultraviolet divergence as can not be removed by the procedure of renormalization of mass and coupling constant, so far as a single type of coupling is assumed for the decay Hamiltonian.”