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Transcript of Particle physics
proton, neutron, mezons
And God said, Let there be light: and there was light.
electron diffraction experiment
spectrum of hydrogen
trace of positron in the Wilson/cloud chamber through lead lamina (the speed is decreasing and the radius decreasing too)
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964.
elementary particle and a fundamental constituent of matter
they can only be found within baryons or mesons
six types of quarks
properties: electric charge, color charge, mass, and spin
experience all four fundamental interactions
quarks are spin 1⁄2 particles, implying that they are fermions
they are subject to the Pauli exclusion principle
insert for A level physics
two main classes: charged leptons and neutral leptons (neutrinos)
electrons are stable and the most common charged lepton in the universe, whereas muons and taus can only be produced in high energy collisions
properties: electric charge, spin, mass, lepton number
leptons are not subject to the strong interaction
electron, muon, tau: subject to gravitation, weak interaction, electromagnetism
neutrinos: subject to gravitation, weak interaction
insert for A level physics
Early in human history, people thought that all matter was composed of 4 main elements: Earth, Wind, Water, and Fire.
Demokritus (ca. 460 BC – ca. 370 BC) was an Ancient Greek philosopher.
The theory of Democritus and Leucippus held that everything is composed of "atoms",
which are indivisible.
The name atom comes from the Greek (atomos, "indivisible")
Newton (1642 – 1727): light is composed of particles.
Huygens (1629 – 1695): light consists of waves
In the early 19th century, the double-slit experiments by Young and Fresnel provided evidence for Huygens' wave theories.
In the late 19th century, James Clerk Maxwell explained light as the propagation of electromagnetic waves.
1874 – George Johnstone Stoney hypothesizes a minimum unit of electric charge. In 1891, he coins the word electron for it;
experiment by Heinrich Hertz in 1887, and the wave theory became widely accepted
1896 Wilhelm Conrad Röntgen discovers the X-rays
1897 J.J. Thomson discovers the electron
In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for cathode rays.
1900 – Paul Villard discovered the Gamma ray in uranium decay.
In 1905, Albert Einstein provided an explanation of the photoelectric effect:
existence of photons, quanta of light energy
Rutherford model in 1911: atom like Solar system
1913 Niels Bohr presents his quantum model of the atom
1919 – Ernest Rutherford discovered the proton (uud);
1924 Pauli: no two electrons could exist in the same quantum state
1924 Louis de Broglie suggests that electrons may have wavelike properties in addition to their 'particle' properties; the wave-particle duality has been later extended to all fermions and bosons.
In 1926, Erwin Schrödinger used this idea to develop a mathematical model of the atom that described the electrons as three-dimensional waveforms rather than point particles.
1927 Clinton Davisson, Lester Germer, and George Paget Thomson confirm the wavelike nature of electrons.
1932 James Chadwick discovers the neutron (udd)
1932 Carl D. Anderson discovers the positron (antielectron).
1936 – Carl D. Anderson discovered the muon while he studied cosmic radiation;
1947 – George Dixon Rochester and Clifford Charles Butler discovered the Kaon, the first strange particle;
1947 – Cecil Powell, César Lattes and Giuseppe Occhialini discovered the pion;
1955 – Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis discovered the Antiproton;
1956 – Clyde Cowan and Frederick Reines discovered the neutrino;
1962 – Leon M. Lederman, Melvin Schwartz and Jack Steinberger discovered the muon neutrino;
1977 – Upsilon particle discovered at Fermilab, demonstrating the existence of the bottom quark;
1977 – Martin Lewis Perl discovered the Tau lepton after a series of experiments;
1979 – Gluon observed indirectly;
1983 – Carlo Rubbia and Simon van der Meer discovered the W and Z bosons;
1995 – Top quark discovered at Fermilab;
2000 – Tau neutrino proved distinct from other neutrinos at Fermilab.
2??? Higgs boson
Large Hadron Collider