Timeline of particle discoveries

Last updated

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:

1800 William Herschel discovers "heat rays" (now known as infrared)
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 (both of which were later determined to be photons). 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. [1]
1895Discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet (later identified as photons) because it is strongly absorbed by air, by the German physicist Victor Schumann [2]
1895 X-ray produced by Wilhelm Röntgen (later identified as photons) [3]
1897 Electron discovered by J. J. Thomson [4]
1899 Alpha particle discovered by Ernest Rutherford in uranium radiation [5]
1900 Gamma ray (a high-energy photon) discovered by Paul Villard in uranium decay [6]
1911 Atomic nucleus identified by Ernest Rutherford, based on scattering observed by Hans Geiger and Ernest Marsden [7]
1919 Proton discovered by Ernest Rutherford [8]
1931 Deuteron discovered by Harold Urey [9] [10] (predicted by Rutherford in 1920 [11] )
1932 Neutron discovered by James Chadwick [12] (predicted by Rutherford in 1920 [11] )
1932 Antielectron (or positron), the first antiparticle, discovered by Carl D. Anderson [13] (proposed by Paul Dirac in 1927 and by Ettore Majorana in 1928)
1937 Muon (or mu lepton) discovered by Seth Neddermeyer, Carl D. Anderson, J.C. Street, and E.C. Stevenson, using cloud chamber measurements of cosmic rays [14] (it was mistaken for the pion until 1947 [15] )
1947 Pion (or pi meson) discovered by C. F. Powell's group, including César Lattes (first author) and Giuseppe Occhialini (predicted by Hideki Yukawa in 1935 [16] )
1947 Kaon (or K meson), the first strange particle, discovered by George Dixon Rochester and Clifford Charles Butler [17]
(or lambda baryon) discovered during a study of cosmic-ray interactions [18]
1955 Antiproton discovered by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis [19]
1956 Electron neutrino detected by Frederick Reines and Clyde Cowan (proposed by Wolfgang Pauli in 1930 to explain the apparent violation of conservation of energy in beta decay) [20] At the time it was simply referred to as neutrino since there was only one known neutrino.
1962 Muon neutrino (or mu neutrino) shown to be distinct from the electron neutrino by a group headed by Leon Lederman [21]
1964 Omega baryon [22] and Xi baryon discovery at Brookhaven National Laboratory [23]
1969 Partons (internal constituents of hadrons) observed in deep inelastic scattering experiments between protons and electrons at SLAC; [24] [25] this was eventually associated with the quark model (predicted by Murray Gell-Mann and George Zweig in 1964) 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 [26] [27] (proposed by James Bjorken and Sheldon Glashow in 1964 [28] )
1975 Tau discovered by a group headed by Martin Perl [29]
1977 Upsilon meson discovered at Fermilab, demonstrating the existence of the bottom quark [30] (proposed by Kobayashi and Maskawa in 1973)
1979 Gluon observed indirectly in three-jet events at DESY [31]
1983 W and Z bosons discovered by Carlo Rubbia, Simon van der Meer, and the CERN UA1 collaboration [32] [33] (predicted in detail by Sheldon Glashow, Mohammad Abdus Salam, and Steven Weinberg)
1995 Top quark discovered at Fermilab [34] [35]
1995 Antihydrogen produced and measured by the LEAR experiment at CERN [36]
2000 Quark-gluon fireball discovered at CERN [37]
2000 Tau neutrino first observed directly at Fermilab [38]
2011 Antihelium-4 produced and measured by the STAR detector; the first particle to be discovered by the experiment
2012A 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 [39]

See also

Related Research Articles

<span class="mw-page-title-main">Standard Model</span> Theory of forces and subatomic particles

The Standard Model of particle physics is the theory describing three of the four known fundamental forces in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.

<span class="mw-page-title-main">Omega baryon</span>

The omega baryons are a family of subatomic hadron particles that are represented by the symbol
and are either neutral or have a +2, +1 or −1 elementary charge. They are baryons containing no up or down quarks. Omega baryons containing top quarks are not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s, which is about a twentieth of the timescale for strong interactions, and therefore that they do not form hadrons.

<span class="mw-page-title-main">Charm quark</span> Type of quark

The charm quark, charmed quark, or c quark is an elementary particle of the second generation. It is the third-most-massive quark with a mass of 1.27±0.02 GeV/c2 as measured in 2022 and a charge of +2/3e. It carries charm, a quantum number. Charm quarks are found in hadrons such as the J/psi meson and the charmed baryons. Several bosons, including the W and Z bosons and the Higgs boson, can decay into charm quarks.

<span class="mw-page-title-main">Top quark</span> Type of quark

The top quark, sometimes also referred to as the truth quark, is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs Boson. This coupling is very close to unity; in the Standard Model of particle physics, it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the CDF and DØ experiments at Fermilab.

<span class="mw-page-title-main">Samuel C. C. Ting</span> Nobel prize winning physicist

Samuel Chao Chung Ting is an American physicist who, with Burton Richter, received the Nobel Prize in 1976 for discovering the subatomic J/ψ particle. More recently he has been the principal investigator in research conducted with the Alpha Magnetic Spectrometer, a device installed on the International Space Station in 2011.

<span class="mw-page-title-main">Tetraquark</span> Exotic meson composed of four valence quarks

A tetraquark, in particle physics, is an exotic meson composed of four valence quarks. A tetraquark state has long been suspected to be allowed by quantum chromodynamics, the modern theory of strong interactions. A tetraquark state is an example of an exotic hadron which lies outside the conventional quark model classification. A number of different types of tetraquark have been observed.

The tau neutrino or tauon neutrino is an elementary particle which has the symbol
and zero electric charge. Together with the tau , it forms the third generation of leptons, hence the name tau neutrino. Its existence was immediately implied after the tau particle was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC–LBL group. The discovery of the tau neutrino was announced in July 2000 by the DONUT collaboration.

<span class="mw-page-title-main">Upsilon meson</span>

The Upsilon meson is a quarkonium state formed from a bottom quark and its antiparticle. It was discovered by the E288 experiment team, headed by Leon Lederman, at Fermilab in 1977, and was the first particle containing a bottom quark to be discovered because it is the lightest that can be produced without additional massive particles. It has a lifetime of 1.21×10−20 s and a mass about 9.46 GeV/c2 in the ground state.

Sterile neutrinos are hypothetical particles that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term sterile neutrino is used to distinguish them from the known, ordinary active neutrinos in the Standard Model, which carry an isospin charge of ±+1/ 2  and engage in the weak interaction. The term typically refers to neutrinos with right-handed chirality, which may be inserted into the Standard Model. Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang nucleosynthesis are often called neutral heavy leptons (NHLs) or heavy neutral leptons (HNLs).

<span class="mw-page-title-main">MiniBooNE</span> Neutrino physics experiment

MiniBooNE is a Cherenkov detector experiment at Fermilab designed to observe neutrino oscillations. A neutrino beam consisting primarily of muon neutrinos is directed at a detector filled with 800 tons of mineral oil and lined with 1,280 photomultiplier tubes. An excess of electron neutrino events in the detector would support the neutrino oscillation interpretation of the LSND result.

<span class="mw-page-title-main">Oops-Leon</span>

Oops-Leon is the name given by particle physicists to what was thought to be a new subatomic particle "discovered" at Fermilab in 1976. The E288 experiment team, a group of physicists led by Leon Lederman who worked on the E288 particle detector, announced that a particle with a mass of about 6.0 GeV, which decayed into an electron and a positron, was being produced by the Fermilab particle accelerator. The particle's initial name was the greek letter Upsilon. After taking further data, the group discovered that this particle did not actually exist, and the "discovery" was named "Oops-Leon" as a pun on the original name and the first name of the E288 collaboration leader.

<span class="mw-page-title-main">MINOS</span> Particle physics experiment

Main injector neutrino oscillation search (MINOS) was a particle physics experiment designed to study the phenomena of neutrino oscillations, first discovered by a Super-Kamiokande (Super-K) experiment in 1998. Neutrinos produced by the NuMI beamline at Fermilab near Chicago are observed at two detectors, one very close to where the beam is produced, and another much larger detector 735 km away in northern Minnesota.

The Xi baryons or cascade particles are a family of subatomic hadron particles which have the symbol Ξ and may have an electric charge of +2 e, +1 e, 0, or −1 e, where e is the elementary charge.

<span class="mw-page-title-main">PS210 experiment</span> Scientific experiment

The PS210 experiment was the first experiment that led to the observation of antihydrogen atoms produced at the Low Energy Antiproton Ring (LEAR) at CERN in 1995. The antihydrogen atoms were produced in flight and moved at nearly the speed of light. They made unique electrical signals in detectors that destroyed them almost immediately after they formed by matter–antimatter annihilation.

is a meson composed of a bottom antiquark and a strange quark. Its antiparticle is the
, composed of a bottom quark and a strange antiquark.

The timeline of particle physics lists the sequence of particle physics theories and discoveries in chronological order. The most modern developments follow the scientific development of the discipline of particle physics.

In particle physics, B mesons are mesons composed of a bottom antiquark and either an up, down, strange or charm quark. The combination of a bottom antiquark and a top quark is not thought to be possible because of the top quark's short lifetime. The combination of a bottom antiquark and a bottom quark is not a B meson, but rather bottomonium, which is something else entirely.

<span class="mw-page-title-main">Modern searches for Lorentz violation</span> Overview about the modern searches for Lorentz violation

Modern searches for Lorentz violation are scientific studies that look for deviations from Lorentz invariance or symmetry, a set of fundamental frameworks that underpin modern science and fundamental physics in particular. These studies try to determine whether violations or exceptions might exist for well-known physical laws such as special relativity and CPT symmetry, as predicted by some variations of quantum gravity, string theory, and some alternatives to general relativity.

<span class="mw-page-title-main">Kam-Biu Luk</span>

Kam-Biu Luk is a professor of physics, with a focus on particle physics, at UC Berkeley and a senior faculty scientist in the Lawrence Berkeley National Laboratory's physics division. Luk has conducted research on neutrino oscillation and CP violation. Luk and his collaborator Yifang Wang were awarded the 2014 Panofsky Prize “for their leadership of the Daya Bay experiment, which produced the first definitive measurement of θ13 angle of the neutrino mixing matrix.” His work on neutrino oscillation also received 2016 Breakthrough Prize in Fundamental Physics shared with other teams. He also received a Doctor of Science honoris causa from the Hong Kong University of Science and Technology in 2016. Luk is a fellow of the American Physical Society, and the American Academy of Arts and Sciences.

<span class="mw-page-title-main">David B. Cline</span> American particle physicist



  1. Hockberger, P. E. (2002). "A history of ultraviolet photobiology for humans, animals and microorganisms". Photochem. Photobiol. 76 (6): 561–579. doi:10.1562/0031-8655(2002)0760561AHOUPF2.0.CO2. ISSN   0031-8655. PMID   12511035. S2CID   222100404.
  2. The ozone layer protects humans from this. Lyman, T. (1914). "Victor Schumann". Astrophysical Journal. 38: 1–4. Bibcode:1914ApJ....39....1L. doi: 10.1086/142050 .
  3. W.C. Röntgen (1895). "Über ein neue Art von Strahlen. Vorlaufige Mitteilung". Sitzber. Physik. Med. Ges. 137: 1. as translated in A. Stanton (1896). "On a New Kind of Rays". Nature . 53 (1369): 274–276. Bibcode:1896Natur..53R.274.. doi: 10.1038/053274b0 .
  4. J.J. Thomson (1897). "Cathode Rays". Philosophical Magazine . 44 (269): 293–316. doi:10.1080/14786449708621070.
  5. E. Rutherford (1899). "Uranium Radiation and the Electrical Conduction Produced by it". Philosophical Magazine . 47 (284): 109–163. doi:10.1080/14786449908621245.
  6. P. Villard (1900). "Sur la Réflexion et la Réfraction des Rayons Cathodiques et des Rayons Déviables du Radium". Comptes Rendus de l'Académie des Sciences . 130: 1010.
  7. E. Rutherford (1911). "The Scattering of α- and β- Particles by Matter and the Structure of the Atom". Philosophical Magazine . 21 (125): 669–688. doi:10.1080/14786440508637080.
  8. E. Rutherford (1919). "Collision of α Particles with Light Atoms IV. An Anomalous Effect in Nitrogen". Philosophical Magazine . 37: 581.
  9. Brickwedde, Ferdinand G. (1982). "Harold Urey and the discovery of deuterium". Physics Today. 35 (9): 34. Bibcode:1982PhT....35i..34B. doi:10.1063/1.2915259.
  10. Urey, Harold; Brickwedde, F.; Murphy, G. (1932). "A Hydrogen Isotope of Mass 2". Physical Review. 39 (1): 164–165. Bibcode:1932PhRv...39..164U. doi: 10.1103/PhysRev.39.164 .
  11. 1 2 E. Rutherford (1920). "Nuclear Constitution of Atoms". Proceedings of the Royal Society A . 97 (686): 374–400. Bibcode:1920RSPSA..97..374R. doi: 10.1098/rspa.1920.0040 .
  12. J. Chadwick (1932). "Possible Existence of a Neutron". Nature . 129 (3252): 312. Bibcode:1932Natur.129Q.312C. doi: 10.1038/129312a0 . S2CID   4076465.
  13. C.D. Anderson (1932). "The Apparent Existence of Easily Deflectable Positives". Science . 76 (1967): 238–9. Bibcode:1932Sci....76..238A. doi:10.1126/science.76.1967.238. PMID   17731542.
  14. S.H. Neddermeyer; C.D. Anderson (1937). "Note on the nature of Cosmic-Ray Particles" (PDF). Physical Review . 51 (10): 884–886. Bibcode:1937PhRv...51..884N. doi:10.1103/PhysRev.51.884.
  15. M. Conversi; E. Pancini; O. Piccioni (1947). "On the Disintegration of Negative Muons". Physical Review . 71 (3): 209–210. Bibcode:1947PhRv...71..209C. doi:10.1103/PhysRev.71.209.
  16. H. Yukawa (1935). "On the Interaction of Elementary Particles". Proceedings of the Physico-Mathematical Society of Japan . 17: 48.
  17. G.D. Rochester; C.C. Butler (1947). "Evidence for the Existence of New Unstable Elementary Particles". Nature . 160 (4077): 855–857. Bibcode:1947Natur.160..855R. doi:10.1038/160855a0. PMID   18917296. S2CID   33881752.
  18. The Strange Quark
  19. O. Chamberlain; E. Segrè; C. Wiegand; T. Ypsilantis (1955). "Observation of Antiprotons" (PDF). Physical Review . 100 (3): 947–950. Bibcode:1955PhRv..100..947C. doi:10.1103/PhysRev.100.947.
  20. F. Reines; C.L. Cowan (1956). "The Neutrino". Nature . 178 (4531): 446–449. Bibcode:1956Natur.178..446R. doi:10.1038/178446a0. S2CID   4293703.
  21. G. Danby; et al. (1962). "Observation of High-Energy Neutrino Reactions and the Existence of Two Kinds of Neutrinos". Physical Review Letters . 9 (1): 36–44. Bibcode:1962PhRvL...9...36D. doi:10.1103/PhysRevLett.9.36.
  22. "Home | CERN Teacher Programmes". teacher-programmes.web.cern.ch. Retrieved 20 April 2023.
  23. R. Nave. "The Xi Baryon". HyperPhysics . Retrieved 20 June 2009.
  24. E.D. Bloom; et al. (1969). "High-Energy Inelastic ep Scattering at 6° and 10°". Physical Review Letters. 23 (16): 930–934. Bibcode:1969PhRvL..23..930B. doi: 10.1103/PhysRevLett.23.930 .
  25. M. Breidenbach; et al. (1969). "Observed Behavior of Highly Inelastic Electron-Proton Scattering". Physical Review Letters . 23 (16): 935–939. Bibcode:1969PhRvL..23..935B. doi:10.1103/PhysRevLett.23.935. OSTI   1444731. S2CID   2575595.
  26. J.J. Aubert; et al. (1974). "Experimental Observation of a Heavy Particle J". Physical Review Letters . 33 (23): 1404–1406. Bibcode:1974PhRvL..33.1404A. doi: 10.1103/PhysRevLett.33.1404 .
  27. J.-E. Augustin; et al. (1974). "Discovery of a Narrow Resonance in e+e Annihilation". Physical Review Letters . 33 (23): 1406–1408. Bibcode:1974PhRvL..33.1406A. doi: 10.1103/PhysRevLett.33.1406 .
  28. B.J. Bjørken; S.L. Glashow (1964). "Elementary Particles and SU(4)". Physics Letters . 11 (3): 255–257. Bibcode:1964PhL....11..255B. doi:10.1016/0031-9163(64)90433-0.
  29. M.L. Perl; et al. (1975). "Evidence for Anomalous Lepton Production in e+e Annihilation". Physical Review Letters . 35 (22): 1489–1492. Bibcode:1975PhRvL..35.1489P. doi:10.1103/PhysRevLett.35.1489.
  30. S.W. Herb; et al. (1977). "Observation of a Dimuon Resonance at 9.5 GeV in 400-GeV Proton-Nucleus Collisions". Physical Review Letters . 39 (5): 252–255. Bibcode:1977PhRvL..39..252H. doi:10.1103/PhysRevLett.39.252. OSTI   1155396.
  31. D.P. Barber; et al. (1979). "Discovery of Three-Jet Events and a Test of Quantum Chromodynamics at PETRA". Physical Review Letters . 43 (12): 830–833. Bibcode:1979PhRvL..43..830B. doi:10.1103/PhysRevLett.43.830. S2CID   13903005.
  32. J.J. Aubert et al. (European Muon Collaboration) (1983). "The ratio of the nucleon structure functions F2N for iron and deuterium" (PDF). Physics Letters B . 123 (3–4): 275–278. Bibcode:1983PhLB..123..275A. doi:10.1016/0370-2693(83)90437-9.
  33. G. Arnison et al. (UA1 collaboration) (1983). "Experimental observation of lepton pairs of invariant mass around 95 GeV/c2 at the CERN SPS collider". Physics Letters B . 126 (5): 398–410. Bibcode:1983PhLB..126..398A. doi:10.1016/0370-2693(83)90188-0.
  34. F. Abe et al. (CDF collaboration) (1995). "Observation of Top quark production in p–p Collisions with the Collider Detector at Fermilab". Physical Review Letters . 74 (14): 2626–2631. arXiv: hep-ex/9503002 . Bibcode:1995PhRvL..74.2626A. doi:10.1103/PhysRevLett.74.2626. PMID   10057978. S2CID   119451328.
  35. S. Arabuchi et al. (D0 collaboration) (1995). "Observation of the Top Quark". Physical Review Letters . 74 (14): 2632–2637. arXiv: hep-ex/9503003 . Bibcode:1995PhRvL..74.2632A. doi:10.1103/PhysRevLett.74.2632. PMID   10057979. S2CID   42826202.
  36. G. Baur; et al. (1996). "Production of Antihydrogen". Physics Letters B . 368 (3): 251–258. Bibcode:1996PhLB..368..251B. CiteSeerX . doi:10.1016/0370-2693(96)00005-6.
  37. "New State of Matter created at CERN". CERN. Retrieved 22 May 2020.
  38. "Physicists Find First Direct Evidence for Tau Neutrino at Fermilab" (Press release). Fermilab. 20 July 2000. Retrieved 20 March 2010.
  39. Boyle, Alan (4 July 2012). "Milestone in Higgs quest: Scientists find new particle". MSNBC . MSNBC. Archived from the original on 7 July 2012. Retrieved 5 July 2012.