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strong interactions

lecture 5. strong interactions. Q C D. quantum chromodynamics. -. quarks: triplets of SU(3). -. proton: ( u u d ) neutron: ( d d u ). -. problems of the quark model. s. s. s. Omega Minus: symmetric wave function. -. three s – quarks in the ground state:

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strong interactions

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  1. lecture 5 strong interactions QCD quantum chromodynamics

  2. - quarks: triplets of SU(3)

  3. - proton: ( u u d ) neutron: ( d d u )

  4. - problems of the quark model

  5. s s s Omega Minus: symmetric wave function

  6. - • three s – quarks in the • ground state: • - spins aligned - • space wave function symmetric - problem: Pauli statistics

  7. - 1964 O. Greenberg quarks ==> parastatistics of rank 3

  8. - 1965 Han and Nambu quarks ==> integral charges

  9. - broken

  10. - 1971 color Fritzsch Gell-Mann q=> q q q SU(3,c)

  11. - broken exact

  12. meson:

  13. baryons: (antisymmetric in color index) Hadrons: color singlets “white states”

  14. - - Hadrons - white states

  15. b r g

  16. Omega Minus

  17. antisymmetric in color

  18. no problem with Pauli statistics antisymmetric in color

  19. forces between the quarks: 1972: F., Gell-Mann 1973: F., Gell-Mann, Leutwyler gauge theory in color space ==> QCD

  20. Lagrange function : ==> QED

  21. - QED: photon - QCD: gluons

  22. 8 gluons

  23. Q E D photon e e

  24. gluon g g

  25. QED photon electron

  26. QCD gluon quark

  27. gluon field strength self-interaction

  28. QCD

  29. g new quark 3-gluon interactions

  30. 2 g 4-gluon interactions

  31. Quantum Field Theory: Finestructure constant becomes function of energy or scale due to quantum fluctuations of electron-positron pairs => partial screening of bare charge of the electron at distances less than the compton wavelength of the electron M. Gell-Mann, F. Low 1955

  32. partial screening + - + + - - - -

  33. - renormalization group M. Gell-Mann, F. Low - 1954

  34. ALEPH L3 OPAL DELPHI LEP

  35. - LEP: ~ 1/127

  36. QCD: asymptotically free coupling at high energies ==> 0 Khriplovich t Hooft Gross, Wilczek Politzer

  37. QED - QCD negativ!!!

  38. as in QED const. = +5 const. = -16 -

  39. QCD as

  40. 3 Quarks: u,d,s coupling ==>0

  41. - infrared slavery

  42. infrared slavery ==> Confinement

  43. Effective potential between quark and antiquark:

  44. * * small distances: Coulomb potential

  45. Large distance:linear term

  46. lattice calculations

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