Particle Physics - FSU Physics Department

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Brief History of the Standard Model Late 1920’s - early 1930’s: Dirac, Heisenberg, Pauli, & others extend Maxwell’s theory of EM to include Special Relativity & QM (QED) - but it only works to lowest order! 1933: Enrico Fermi introduces 1st theory of weak interactions, analogous to QED, to explain β decay. 1935: Hideki Yukawa predicts the pion as carrier of a new, strong force to explain recently observed hadronic resonances. 1937: muon is observed in cosmic rays – first mistaken for Yukawa’s particle 1938: heavy W as mediator of weak interactions? (Klein) 1947: pion is observed in cosmic rays 1949: Dyson, Feynman, Schwinger, and Tomonaga introduce renormalization into QED - most accurate theory to date! 1954: Yang and Mills develop Gauge Theories 1950’s - early 1960’s: more than 100 hadronic “resonances” have been observed ! 1962 two neutrinos! 1964: Gell-Mann & Zweig propose a scheme whereby resonances are interpreted as composites of 3 “quarks”. (up, down, strange) 40
Brief History of the Standard Model - 2 1970: Glashow, Iliopoulos, Maiani: 4th quark (charm) explains suppression of K decay into μμ 1964-1967: spontaneous symmetry breaking (Higgs, Kibble) 1967: Weinberg & Salam propose a unified Gauge Theory of electroweak interactions, introducing the W ± ,Z as force carriers and the Higgs field to provide the symmetry breaking mechanism. 1967: deep inelastic scattering shows “Bjorken scaling” 1969: “parton” picture (Feynman, Bjorken) 1971-1972: Gauge theories are renormalizable (even when symmetry is spontaneoulsy broken) (t’Hooft, Veltman, Lee, Zinn-Justin..) 1972: high p t pions observed at the CERN ISR 1973: Quantum Chromodynamics (Gross, Wilczek, Politzer, Gell-Mann & Fritzsch) : quarks are held together by a Gauge-Field whose quanta, gluons, mediate the strong force 1973: “neutral currents” observed (Gargamelle bubble chamber at CERN) 41
Page 1 and 2: Particle Physics Particle physics
Page 3 and 4: About Units Energy - electron-volt
Page 5 and 6: Sizes and distance scales Molecule
Page 7 and 8: Contemporary Physics Education 7 Pr
Page 9 and 10: Issues of High Energy Physics Issue
Page 12 and 13: Positron Positron (anti-electron)
Page 14 and 15: Neutron Bothe + Becker (1930): •
Page 16 and 17: Nuclear force - field quantum phot
Page 18 and 19: Discovery of pion in 1947, Lattes,
Page 20 and 21: “Strange particles” Kaon: disc
Page 22 and 23: Particle Zoo 1940’s to 1960’s
Page 24 and 25: Particle nomenclature by mass: •
Page 26 and 27: Towards the standard model Quark M
Page 28 and 29: color charge problem with quark mo
Page 30 and 31: Standard Model A theoretical model
Page 33 and 34: From Contemporary Physics Education
Page 36 and 37: From Contemporary Physics Education
Page 38 and 39: Electroweak interactions leptons (
Page 42 and 43: Brief History of the Standard Model
Page 44 and 45: Present scenario Most of what’s
Page 46 and 47: Homework set 5 HW 5.1 • go to Pa

Particle Physics - FSU Physics Department

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