Timeline of particle discoveries
This is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary 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 that have so far been observed. The Standard Model is the most comprehensive existing model of particle behavior. All Standard Model particles including 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 antiproton. 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.
| Time | Event |
| 1800 | William Herschel discovers "heat rays" |
| 1801 | Johann Wilhelm Ritter made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum were especially effective at lightening silver chloride-soaked paper. He called them "de-oxidizing rays" to emphasize chemical reactivity and to distinguish them from "heat rays" at the other end of the invisible spectrum. The more general term "chemical rays" was adopted shortly thereafter to describe the oxidizing rays, and it remained popular throughout the 19th century. The terms chemical and heat rays were eventually dropped in favor of ultraviolet and infrared radiation, respectively. |
| 1895 | Discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is strongly absorbed by air, by the German physicist Victor Schumann |
| 1895 | X-ray produced by Wilhelm Röntgen |
| 1897 | Electron discovered by J. J. Thomson |
| 1899 | Alpha particle discovered by Ernest Rutherford in uranium radiation |
| 1900 | Gamma ray discovered by Paul Villard in uranium decay |
| 1911 | Atomic nucleus identified by Ernest Rutherford, based on scattering observed by Hans Geiger and Ernest Marsden |
| 1919 | Proton discovered by Ernest Rutherford |
| 1931 | Deuteron discovered by Harold Urey |
| 1932 | Neutron discovered by James Chadwick |
| 1932 | Antielectron, the first antiparticle, discovered by Carl D. Anderson |
| 1937 | Muon discovered by Seth Neddermeyer, Carl D. Anderson, J.C. Street, and E.C. Stevenson, using cloud chamber measurements of cosmic rays |
| 1947 | Pion discovered by C. F. Powell's group, including César Lattes and Giuseppe Occhialini |
| 1947 | Kaon, the first strange particle, discovered by George Dixon Rochester and Clifford Charles Butler |
| 1950 | Lambda baryon| discovered during a study of cosmic-ray interactions |
| 1955 | Antiproton discovered by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis |
| 1956 | Electron neutrino detected by Frederick Reines and Clyde Cowan At the time it was simply referred to as neutrino since there was only one known neutrino. |
| 1962 | Muon neutrino shown to be distinct from the electron neutrino by a group headed by Leon Lederman |
| 1964 | Xi baryon discovery at Brookhaven National Laboratory |
| 1969 | Partons observed in deep inelastic scattering experiments between protons and electrons at SLAC; this was eventually associated with the quark model and thus constitutes the discovery of the up quark, down quark, and strange quark. |
| 1974 | J/ψ meson discovered by groups headed by Burton Richter and Samuel Ting, demonstrating the existence of the charm quark |
| 1975 | Tau discovered by a group headed by Martin Perl |
| 1977 | Upsilon meson discovered at Fermilab, demonstrating the existence of the bottom quark |
| 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 UA1 collaboration |
| 1995 | Top quark discovered at Fermilab |
| 1995 | Antihydrogen produced and measured by the LEAR experiment at CERN |
| 2000 | Quark-gluon fireball discovered at CERN |
| 2000 | Tau neutrino first observed directly at Fermilab |
| 2011 | Antihelium-4 produced and measured by the STAR detector; the first particle to be discovered by the experiment |
| 2012 | A particle exhibiting most of the predicted characteristics of the Higgs boson discovered by researchers conducting the Compact Muon Solenoid and ATLAS experiments at CERN's Large Hadron Collider |