Particle Physics

Particle physics studies the fundamental constituents of matter and radiation and the forces through which they interact. Its roots lie in the late nineteenth century discovery that the atom is not indivisible: J.J. Thomson's 1897 cathode-ray experiments identified the electron, a particle far lighter than any atom, and Ernest Rutherford's 1911 gold foil experiments showed that an atom's mass and positive charge are concentrated in a tiny central nucleus. Through the early twentieth century the field grew alongside nuclear physics, cosmic-ray research and quantum field theory, discovering the proton, neutron and positron, before large particle accelerators built after the Second World War let physicists probe matter at ever smaller scales and higher energies. In 1964 Murray Gell-Mann and George Zweig independently proposed that protons and neutrons are themselves built from smaller constituents Gell-Mann named quarks, a model confirmed experimentally at the Stanford Linear Accelerator Center in 1968. International laboratories, above all CERN, founded in 1954, became the field's central experimental sites, culminating in the 2012 discovery of the Higgs boson. Historians of science do not agree on a single founding moment for particle physics as a distinct discipline, since it emerged gradually from several converging research traditions rather than one act of founding.