Like all good physics programs, particle physics has kept several different generations of physicists employed. To remain employed, one must succumb to the publish or perish disease currently infesting physics. And of course, to publish, one must discover.
Here, I present a list of particles discovered by physicists, along with some useful information about the particles. This list is not intended to be exhaustive, as there are more particles in nature than useful politicians in Congress. One thing to note is that I only discuss the list of elementary particles discovered, to list all the baryons and mesons made from them is going to have to wait for another blog post.
| Particle | Year | Mass (MeV/c2) | Spin | Antiparticle | Comments |
| Electron | 1897 | 0.511 | 1/2 | Positron | Also known as beta ray |
| Alpha particle | 1899 | big | 0 | anti-helium | A doubly ionized Helium nucleus |
| Photon | 1900 | 0 | 1 | self | 1 |
| Proton | 1919 | 938.272 | 1/2 | anti-proton | |
| Neutron | 1932 | 939.566 | 1/2 | anti-neutron | |
| Anti-electron | 1932 | 0.511 | 1/2 | electron | 2 |
| Muon | 1937 | 105.7 | 1/2 | anti-muon | 3 |
| Pion | 1947 | 134.98 | 0 | Self | Predicted in 1935 by Yukawa |
| Kaon | 1947 | 497.65 | 0 | Self | First strange particle discovered |
| Anti-proton | 1955 | 938.272 | 1/2 | Proton | |
| Electron neutrino | 1956 | under 2.2×10-6 | 0 | Anti-electron neutrino | 4 |
| Up, Down, and Strange Quark | 1969 | 1.5, 3.5, and 70 | 1/2 for all | Anti-up, anti-down, anti-strange | Deep elastic scattering in protons led to this discovery |
| J/Psi meson | 1974 | 3096.916 | 1 | self | Showed existence of charm quark |
| Upsilon meson | 1977 | 9460 | 1 | self | 5 |
| Gluons | 1979 | 0 | 1 | self | Gluons mediate strong force, and confine quarks. |
| W and Z bosons | 1983 | 8039.8 (2.3), 9118.76 (21) | 1 | self | Mediate weak force. W bosons violate parity. |
| Top quark | 1995 | 1731 (13) | 1/2 | top antiquark | 6 |
Footnotes
- 1 Also known as gamma radiation, it was originally discovered in 1895 as X-rays, but was only successfully identified as electromagnetic radiation in 1900.
- 2 Dirac’s relativistic quantum equation predicted this particle would appear, and have the same mass as the electron, but opposite charge. Dirac reasoned it was actually the proton it was predicting, however, the anti-electron was found experimentally in 1932. Despite not predicting it, Dirac still shared in the Nobel prize awarded for its discovery.
- 3 With a long half-life, the muon can form chemical bonds in atoms.
- 4 The neutrino was proposed by Wolfgang Pauli in 1931 to save the idea of conservation of energy, one of the most fundamental tenents in physics. During beta decay, it was found that some energy was escaping in an unknown form, so Pauli proposed the neutrino, an unknown particle with no mass and no charge, but containing energy. Neils Bohr favored the idea of getting rid of the conservation of energy instead. Luckily for physics, the neutrino was found, allowing us to keep the conservation of energy intact.
- 5 Showed bottom quark properties. Feynman immediately predicted top quark existed.
- 6 This particle is heavier than gold, and the last discovered quark. Some beyond-the-standard-model models predict a fourth generation of quarks, but none have been discovered.
) to form a muon and a muon neutrino. The muon then decays to a positron, electron neutrino, and a muon antineutrino.
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