Leptons is one of the fundamental particles of matter. Lepton is a Greek word for ‘small mass’. Leptons have an electric charge, mass, and spin. Leptons respond to three fundamental forces, the gravitation, weak interactions and gravitation. The world is said to be made up of Quarks and Leptons. Since these are one of the basic building blocks of matter they are termed as elementary particles. One of the important features of Lepton is that they either carry an electric charge of at least one unit or remain neutral.
There are six different types of Leptons each having different properties and electrical charges. The electron neutrino, electron, muon neutrino, muon, tau neutrino, and tau. Three of the leptons have an electrical charge and three of them do not carry any charge.
|Muon||μ-||μ+||2.20 x 10-6|
|Tau||τ-||τ+||2.96 x 10-3|
Leptons do not possess any strong interactions and are also called as fundamental particles as they are the basic structures and can't be broken into smaller ones. Leptons unlike quarks are solitary particles. Electron is the lightest Lepton and has a mass of only 1/1,840 of a proton. Muons are 200 times heavier than electrons whereas Taus are approx 3700 times heavier than electrons. If there are charged particles, there are neutral Lepton particles to associate with each charged particle. These are the neutrinos which have no distinct mass and electric charge. Lepton is also known to have a corresponding anti-lepton/antiparticles. In this case although the mass of antiparticles or anti-lepton is similar to the Lepton the various other properties are the exactly opposite. One of the most interesting features of Leptons is the internal spin or angular momentum.
Fermions are a big group of subatomic particles from where Lepton is classified. The main characteristics of this group are that it spins in half integer values. Whenever any particle reaction takes place the number of Lepton instead of deviating remain constant. A conservation number law is known to exist in between each type of Leptons. For example, the electrons and electron-neutrinos are conserved in separate numbers from the muons and muon neutrinos numbers. Usually this law is not violated and the chances of violation o f this conservation law has been found to be only one part/million.
Although muon or the tau are heaviest leptons, they are not present as ordinary matter in the universe as whenever they are formed they instantly get decayed or transform themselves into Lepton of lighter version. The tau Lepton many times gets decayed into an antiquark, tau neutrino or a quark. The other types of Lepton are stable and those are always found present in the universe. Although some of the Leptons decay and some do not they remain loyal to their families and the law of conservation and always remain constant in number and complement each other.