Leptons

A neutrino ( ; denoted by the Greek letter Nu (letter)|) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles (excluding massless particles).

The positron or antielectron is the particle with an electric charge of +1e, a spin of 1/2 ħ (the same as the electron), and the same mass as an electron. It is the antiparticle (antimatter counterpart) of the electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more photons.

In particle physics, a lepton is an elementary particle of half-integer spin (spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), including the electron, muon, and tauon, and neutral leptons, better known as neutrinos. Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed. The best known of all leptons is the electron.

A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 e and a spin of  ħ, but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not thought to be composed of any constituent particles.

heavy, negatively charged subatomic particle

neutral subatomic elementary particle of first generation of leptons

neutral subatomic elementary particle

neutral subatomic elementary particle

conserved quantum number representing the number of leptons minus the number of antileptons in an elementary particle reaction

3×3 unitary mixing matrix that relates the flavor basis of the neutrinos to the mass eigenbasis

unexplained empirical equation in particle physics