Skip to main content
\(\require{cancel}\)
Physics LibreTexts

2.2: A Timeline of Particle Physics

  • Page ID
    14997
  • Year Experiment Theory
    1927 \(\beta\) decay discovered
    1928 Paul Dirac: Wave equation for electron
    1930 Wolfgang Pauli suggests existence of neutrino
    1931 Positron discovered
    1931 Paul Dirac realises that positrons are part of his equation
    1931 Chadwick discovers neutron
    1933/4 Fermi introduces theory for \(\beta\) decay
    1933/4 Hideki Yukawa discusses nuclear binding in terms of pions
    1937 \(\mu\) discovered in cosmic rays
    1938 Baryon number conservation
    1946 \(\mu\) is not Yukawa’s particle
    1947 \(\pi^{+}\) discovered in cosmic rays
    1946-50 Tomonaga, Schwinger and Feynman develop QED
    1948 First artificial \(\pi\)’s
    1949 \(K^{+}\) discovered
    1950 \(\pi^{0}\rightarrow \gamma\gamma\)
    1951 ”V-particles” \(\Lambda^{0}\) and \(K^{0}\)
    1952 \(\Delta\): excited state of nucleon
    1954 Yang and Mills: Gauge theories
    1956 Lee and Yang: Weak force might break parity!
    1956 CS Wu and Ambler: Yes it does.
    1961 Eightfold way as organising principle
    1962 \(\nu_{\mu}\) and \(\nu_{e}\)
    1964 Quarks (Gell-man and Zweig) \(u,d,s\)
    1964 Fourth quark suggested (\(c\))
    1965 Colour charge all particles are colour neutral!
    1967 Glashow-Salam-Weinberg unification of electromagnetic and weak interactions. Predict Higgs boson.
    1968-69 DIS at SLAC constituents of proton seen!
    1973 QCD as the theory of coloured interactions. Gluons.
    1973 Asymptotic freedom
    1974 \(J/\psi\) (\(c\bar c\)) meson
    1976 \(D0\) meson (\(\bar u c\)) confirms theory.
    1976 \(\tau\) lepton!
    1977 b (bottom quark). Where is top?
    1978 Parity violating neutral weak interaction seen
    1979 Gluon signature at PETRA
    1983 \(W^{\pm}\) and \(Z^{0}\) seen at CERN
    1989 SLAC suggests only three generations of (light!) neutrinos
    1995 t (top) at 175 GeV mass
    1997 New physics at HERA (200 GeV)