nLab lepton

Idea

In the standard model of particle physics, a lepton is a fermion that couples to the electromagnetic field or the weak nuclear force nut not to the strong nuclear force. (Otherwise one speaks of hadrons.)

flavors of fundamental fermions in the standard model of particle physics:
generation of fermions	1st generation	2nd generation	3d generation
quarks ($q$)
up-type	up quark ($u$)	charm quark ($c$)	top quark ($t$)
down-type	down quark ($d$)	strange quark ($s$)	bottom quark ($b$)
leptons
charged	electron	muon	tauon
neutral	electron neutrino	muon neutrino	tau neutrino
bound states:
mesons	light mesons: pion ($u d$) ρ-meson ($u d$) ω-meson ($u d$) f1-meson a1-meson	strange-mesons: ϕ-meson ($s \bar s$), kaon, K*-meson ($u s$, $d s$) eta-meson ($u u + d d + s s$) charmed heavy mesons: D-meson ($u c$, $d c$, $s c$) J/ψ-meson ($c \bar c$)	bottom heavy mesons: B-meson ($q b$) ϒ-meson ($b \bar b$)
baryons	nucleons: proton $(u u d)$ neutron $(u d d)$

Properties

• anomalous magnetic moment

• baryon-lepton symmetry

Related concepts

• dilepton

• hadron

• lepton current

• leptonic decay

References

• Francis Halzen, Alan Martin, Quarks and Leptons: An Introductory Course in Modern Particle Physics, Wiley 1984 (pdf)

• Ferruccio Feruglio, Saul Ramos-Sanchez: Quark and lepton masses, Encyclopedia of Particle Physics [arXiv:2506.20755]

See also:

• Wikipedia, Lepton