Elementary Particles

Elementary Particles

For each of these particles, except the photon, gluon, and Z-boson, there is an antiparticle with the same mass and opposite charge. In most cases the antiparticle is denoted by an overbar over the particle symbol (e.g., the symbol for the antiproton is p.  Because quarks cannot be isolated, the masses given for them are approximate.

Elementary Particles

Leptons Particle Symbol Mass (MeV/c 2 ) Electric Charge electron e - 0.511 -1 muon μ - 105.7 -1 tau τ 1784.1 -1 electron neutrino ν e <7.3×10 -6 0 muon neutrino ν μ <0.27 0 tau neutrino ν τ <35 0

Quarks down d 5-15 - 1/3 up u 2-8 2/3 strange s 100-300 - 1/3 charm c 1300-1700 2/3 bottom b 4700-5300 - 1/3 top t >91,000 2/3

Gauge Bosons photon γ 0 0 gluon g 0 0 W-boson W 80,200 1 Z-boson Z 91,170 0

Some Sample Hadrons Particle Symbol Mass (MeV/c 2 ) Electric Charge Quark Content positive pion π + 139.6 1 ud positive kaon K + 493.7 1 us proton p 938.3 1 uud neutron n 939.6 0 udd lambda Λ 1115.6 0 uds

elementary particle In physics, a subatomic particle that cannot be subdivided. Such particles are the basic constituents of matter. There are three groups of elementary particles: quarks, leptons (light particles), and gauge bosons (messenger particles). All elementary particles have an associated antiparticle which make up antimatter.

elementary particle A fundamental constituent of matter; also known as a subatomic particle. Elementary particles are divided into two main classes: hadrons, which themselves consist of units called quarks; and leptons, which are not composed of quarks and seem to have no internal structure. Hadrons which consist of three quarks are also known as baryons; examples are the proton and the neutron. Hadrons which consist of two quarks are known as mesons. Leptons include the electron, muon, and neutrino. Elementary particles have properties of charge, spin, and rest mass. They can be classified by the interactions they take part in. Hadrons participate in strong interactions, weak interactions, and, if they carry charge, electromagnetic interactions. Leptons do not participate in strong interactions. About 200 different elementary particles are thought to exist.