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Lecture 04 - Hadrons

Lecture 04 - Hadrons. Quarks multiplets Hadron decays Conservation laws Resonances. The fundamental forces. Different exchange particles mediate the forces:. electromagnetic. weak. strong. No quantum field theory yet for gravity. The quarks. Spin ½ particles. Hadrons.

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Lecture 04 - Hadrons

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  1. FK7003 Lecture 04 - Hadrons • Quarks multiplets • Hadron decays • Conservation laws • Resonances

  2. The fundamental forces Different exchange particles mediate the forces: electromagnetic weak strong No quantum field theory yet for gravity FK7003

  3. FK7003 The quarks Spin ½ particles

  4. FK7003 Hadrons Full particle listings from the Review of Particle Physics: http://pdg.lbl.gov/2008/listings/contents_listings.html

  5. FK7003 The quarks Spin ½ particles + antiparticles

  6. Hadron quantum numbers FK7003

  7. Hadron properties FK7003

  8. FK7003 Evidence for a new quantum number: colour (4.03)

  9. FK7003 Hadrons and the strong force q (R) q (G) Gluon (RG) q(R) q (G)

  10. FK7003 Colour combinations We have never seen a quark or gluon! Nature abhors naked colour. Every particle in nature is colourless/colour singlet

  11. FK7003 A strong reaction:

  12. FK7003 QCD Description of the Strong Nuclear Force Yukawa model proposed pion exchange Interaction results from internal gluon lines and quark exchange

  13. FK7003 Some words about decays

  14. FK7003 Strong decay p+ u d u r u d p- u u u p+ d r d p- u u

  15. FK7003 OZI rule fdecays preferentially to K+K- than p+ p0 p- even though it is less energetically favourable. Decays in which all gluon lines can be ”cut” are suppressed. Rule proposed by Okubo, Zweig and Iizuka in 1960s

  16. FK7003

  17. FK7003 Weak decays of hadrons L s d } p- u Strangeness (and the other flavour quantum numbers, C,B) are not conserved in weak decays.

  18. Conserved quantities/symmetries FK7003

  19. FK7003 Short-lived particles

  20. FK7003 - Breit Wigner Seen in decays of nuclear and atomic energy levels. Ndecay Nmax 0.5 Nmax

  21. Resonances Shape of excited state mass distribution follows Breit-Wigner distribution 770 MeV – ”nominal” mass FK7003

  22. FK7003 Summary • Hadrons introduced • Decays via em, weak and strong forces. • Conservation laws • Width of a resonance provides a lifetime

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