Timeline of particle discoveries
From Wikipedia, the free encyclopedia
This is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary (that is, indivisible) given the best available evidence. It also includes the discovery of composite particles and antiparticles that were of particular historical importance.
More specifically, the inclusion criteria are:
- Elementary particles from the Standard Model of particle physics which have so far been observed. The Standard Model is the most comprehensive existing model of particle behavior; no substantial contradictions have been discovered thus far. All Standard Model particles except the Higgs boson have been verified, and all other observed particles are combinations of two or more Standard Model particles.
- Antiparticles which were historically important to the development of particle physics, specifically the positron and anti-proton. The discovery of these particles required very different experimental methods from that of their ordinary matter counterparts, and provided evidence that all particles had antiparticles—an idea that is fundamental to quantum field theory, the modern mathematical framework for particle physics. In the case of most subsequent particle discoveries, the particle and its anti-particle were discovered essentially simultaneously.
- Composite particles which were the first particle discovered containing a particular elementary constituent, or whose discovery was critical to the understanding of particle physics.
Note that there are have been many, many other composite particles discovered; see list of mesons and list of baryons. See List of particles for a more general list of particles, including hypothetical particles.
- 1895 - X-rays produced by Wilhelm Röntgen (later identified as photons)[1]
- 1897 - Electron discovered by J. J. Thomson[2]
- 1899 - Alpha particle discovered by Ernest Rutherford in uranium radiation[3]
- 1900 - Gamma ray (high-energy photon) discovered by Paul Villard in uranium decay.[4]
- 1911 - Atomic nucleus identified by Ernest Rutherford, based on scattering observed by Hans Geiger and Ernest Marsden.[5]
- 1919 - Proton discovered by Ernest Rutherford[6]
- 1932 - Neutron discovered by James Chadwick[7] (predicted by Rutherford in 1920[8])
- 1932 - Positron, the first antiparticle, discovered by Carl D. Anderson[9] (proposed by Paul Dirac in 1927)
- 1937 - Muon discovered by Seth Neddermeyer, Carl Anderson, J.C. Street, and E.C. Stevenson, using cloud chamber measurements of cosmic rays.[10] (It was mistaken for the pion until 1947.[11])
- 1947 - Pion discovered by Cecil Powell (predicted by Hideki Yukawa in 1935[12])
- 1947 - Kaon, the first strange particle, discovered by G.D. Rochester and C.C. Butler[13]
- 1955 - Antiproton discovered by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis
- 1956 - Neutrino detected by Frederick Reines and Clyde Cowan (proposed by Wolfgang Pauli in 1931 to explain the apparent violation of energy conservation in beta decay)
- 1962 - Muon neutrino shown to be distinct from electron neutrino by group headed by Leon Lederman
- 1969 - Partons (internal constituents of hadrons) observed in deep inelastic scattering experiments between protons and electrons at SLAC; this was eventually associated with the quark model (predicted by Murray Gell-Mann and George Zweig in 1963) and thus constitutes the discovery of the up quark, down quark, and strange quark.
- 1974 - J/ψ particle discovered by groups headed by Burton Richter and Samuel Ting, demonstrating the existence of the charm quark (proposed by Sheldon Glashow, John Iliopoulos, and Luciano Maiani in 1970)
- 1975 - Tau lepton discovered by group headed by Martin Perl
- 1977 - Upsilon particle discovered at Fermilab, demonstrating the existence of the bottom quark (proposed by Kobayashi and Maskawa in 1973)
- 1979 - Gluon observed indirectly in three jet events at DESY
- 1983 - W and Z bosons discovered by Carlo Rubbia, Simon van der Meer, and the CERN UA-1 collaboration (predicted in detail by Sheldon Glashow, Abdus Salam, and Steven Weinberg in the 1960s)
- 1995 - Top quark discovered at Fermilab[14][15]
- 2000 - Tau neutrino shown to be distinct from other neutrinos at Fermilab
[edit] References
- ^ W.C. Röntgen (1895). "Über ein neue Art von Strahlen. Vorlaufige Mitteilung". Sitzber. Physik. Med. Ges. 137: 1.
- ^ J. J. Thomson (1897). "Cathode Rays". Philosophical Magazine 44: 293.
- ^ E. Rutherford (1899). "Uranium Radiation and the Electrical Conduction Produced by it". Philosophical Magazine 47: 109.
- ^ P. Villard (1900). "Sur la Réflexion et la Réfraction des Rayons Cathodiques et des Rayons Déviables du Radium". Compt. Ren. 130: 1010.
- ^ E. Rutherford (1911). "The Scattering of α- and β- Particles by Matter and the Structure of the Atom". Philosophical Magazine 21: 669.
- ^ E. Rutherford (1919). "Collision of α Particles with Light Atoms IV. An Anomalous Effect in Nitrogen". Philosophical Magazine 37: 581.
- ^ J. Chadwick (129). "Possible Existence of a Neutron". Nature 1932: 312.
- ^ E. Rutherford (1920). "Nuclear Constitution of Atoms". Proc. Roy. Soc. A97: 324.
- ^ C.D. Anderson (1932). "The Apparent Existence of Easily Deflectable Positives". Science 76: 238. doi:.
- ^ S.H. Neddermeyer, C.D. Anderson (1937). "Note on the nature of Cosmic-Ray Particles". Phys. Rev. 51: 884. doi:.
- ^ M. Conversi, E. Pancini, O. Piccioni (1947). "On the Disintegration of Negative Muons". Phys. Rev. 71: 209.
- ^ C.D. Anderson (1935). "On the Interaction of Elementary Particles". Proc. Phys. Math. Soc. Jap. 17: 48.
- ^ G.D. Rochester, C.C. Butler (1947). "Evidence for the Existence of New Unstable Elementary Particles". Nature 160: 855.
- ^ F. Abe et al. (CDF collaboration) (1995). "Observation of Top quark production in
Collisions with the Collider Detector at Fermilab". Phys. Rev. Lett. 74: 2626. - ^ S. Arabuchi et al. (D0 collaboration) (1995). "Observation of the Top quark". Phys. Rev. Lett. 74: 2632.
- V.V. Ezhela et al. (1996). Particle Physics: One Hundred Years of Discoveries: An Annotated Chronological Bibliography. Springer-Verlag New York. ISBN 1-56396-642-5.
