Search results
Results from the WOW.Com Content Network
In particle physics, a lepton is an elementary particle of half-integer spin (spin 1 / 2 ) that does not undergo strong interactions. [1] 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.
A hadron is a composite subatomic particle.Every hadron must fall into one of the two fundamental classes of particle, bosons and fermions. In particle physics, a hadron (/ ˈ h æ d r ɒ n / ⓘ; from Ancient Greek ἁδρός (hadrós) 'stout, thick') is a composite subatomic particle made of two or more quarks held together by the strong interaction.
There are six leptons in total; the three charged leptons are called "electron-like leptons", while the neutral leptons are called "neutrinos". Neutrinos are known to oscillate, so that neutrinos of definite flavor do not have definite mass: Instead, they exist in a superposition of mass eigenstates.
Leptons, on the other hand, are not composed of quarks and as such do not participate in the strong interaction. The best known baryons are protons and neutrons, which make up most of the mass of the visible matter in the universe, whereas electrons, the other major component of atoms, are leptons.
The Standard Model recognizes two types of elementary fermions: quarks and leptons. In all, the model distinguishes 24 different fermions. In all, the model distinguishes 24 different fermions. There are six quarks ( up , down , strange , charm , bottom and top ), and six leptons ( electron , electron neutrino , muon , muon neutrino , tauon and ...
Half of the fermions are leptons, three of which have an electric charge of −1 e, called the electron (e −), the muon (μ −), and the tau (τ −); the other three leptons are neutrinos (ν e, ν μ, ν τ), which are the only elementary fermions with neither electric nor color charge. The remaining six particles are quarks (discussed below).
Owing to a phenomenon known as color confinement, quarks are never found in isolation; they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons, or in quark–gluon plasmas. [2] [3] [nb 1] For this reason, much of what is known about quarks has been drawn from observations of hadrons.
All leptons carry a lepton number L = 1. In addition, leptons carry weak isospin, T 3, which is − 1 / 2 for the three charged leptons (i.e. electron, muon and tau) and + 1 / 2 for the three associated neutrinos. Each doublet of a charged lepton and a neutrino consisting of opposite T 3 are said to constitute one generation of ...