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2.2: A Timeline of Particle Physics

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  • Page ID

    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)