What is a Lepton?
Leptons are a family of elemental particles that includes the electron, the muon, the tau, and their associated neutrinos. Like quarks, which make up the protons and neutrons in the atomic nucleus, the lepton is a fermion, meaning it has a quantum spin of ½. Other fundamental particles with different spins are called bosons and mediate force interactions between the fermions. Fermions, made up of the lepton and quark, are the “meat” of matter, while bosons are the “skeleton”. In comparison to quarks, a lepton is light. An electron’s mass is 1⁄1836 of an atomic mass unit (amu), the approximate mass of a hydrogen atom. The non-lepton mass in the hydrogen atom comes from the nucleus. The other two lepton variants – the muon and the tau – are significantly heavier. The tau lepton weighs almost twice as much as a proton. There are three types of lepton, as mentioned before: the electron, the muon, and the tau. Each of these has an associated neutrino – the electron neutrino, the muon neutri
There are three known flavors of lepton: the electron, the muon and the tau. Each flavor is represented by a pair of particles called a weak doublet. One is a massive charged particle that bears the same name as its flavor (like the electron). The other is a nearly massless neutral particle called a neutrino (like the electron neutrino). All six of these particles have corresponding antiparticles (like the positron or the electron antineutrino). All known charged leptons have a single unit of negative or positive electric charge (depending on whether they are particles or antiparticles) and all of the neutrinos and antineutrinos have zero electric charge. The charged leptons have two possible spin states, while only one helicity is observed for the neutrinos (all the neutrinos are left-handed, and all the antineutrinos are right-handed).
