- Fermion - Text by M. Alan Kazlev
Subatomic particle with half integer spin. The Pauli Exclusion Principle prevents more than one fermion occupying a particular quantum state. This means matter is conserved during particle interactions (i.e. that the net amount of fermions is a constant). The electron is considered a typical fermion, and it is because of its half-spin quality that electrons form into "shells" providing the outer valence electrons that make chemistry work, as well as making life and atoms as we know them possible. Contrast with the boson. [after physicist Enrico Fermi]
- Hadron - Text by Anders Sandberg
Matter particle consisting of quarks or antiquarks. Hadrons are divided into mesons, composed of a quark and an antiquark, and baryons, composed of three quarks or three antiquarks.
- Lepton - Text by M. Alan Kazlev
Subatomic particle that is susceptible to the weak nuclear force but not the strong force (the force that binds an atomic nucleus together). There are six leptons: the electron, muon, tau, electron neutrino, muon neutrino, and tau neutrino.
- Meson - Text by M. Alan Kazlev
Particles composed of a quark and an antiquark; the lowest mass mesons (the pi and K mesons) have masses intermediate between leptons and baryons. All mesons are unstable.
- Neutron - Text by M. Alan Kazlev
Uncharged atomic nuclear particle. It has a mass slightly greater than a proton. In beta decay, a neutron decays into a proton, an electron, and an anti-neutrino.
- Pi-zero Meson - Text by Richard Baker
Meson with neutral electric charge. Pi-zero mesons can be produced by electron-positron collisions and can decay back into an electron-positron pair, but they are not a bound state of an electron and a positron. The electron and positron annihilate to form a virtual photon and that then decays into a quark and antiquark, which form the meson.
- Proton - Text by M. Alan Kazlev
One of the two basic elementary particles found the atomic nucleus, the other being the neutron. It has a positive charge equal and opposite that of the electron, and a mass similar to the neutron. Protons have a mass of 1.007276 daltons, or 1.6726 = 10-27 kg.