1. The quark model
FK7003

2. The quark model
FK7003

3. Forming hadrons
FK7003

4. Combining particles (1) – angular momentum
FK7003

5. Quarks and isospin
FK7003

6. Isospin of antiquarks (not for lecture or exam)
FK7003

7. Combining particles (2) – isospin
FK7003

8. Combining particles (3) – colour
FK7003

9. Can we describe the observed mesons r- r0 r+
w ?
FK7003

10. Meson wave functions Lq 2 q 1 q Lq
FK7003

11. Baryons
FK7003

12. FK7003

13. Baryons
FK7003

14. Combining colour
FK7003

15. Baryon wave function
FK7003

16. Can we describe the observed baryons
-1/ /2 D- D0 D+
D++
-3/ / / /2
FK7003

17. Test the quark model – Spin 3/2 baryon 
FK7003

18. Test the quark model – spin-1/2 baryons
Left as an exercise….
FK7003

19. So far so good
Can understand the existence and properties of multiplets the very lightest hadrons with SU(2)-isospin symmetry.
SU(2) symmetry is ”good” - all hadrons in an isospin multiplet have similar masses since u,d have similar masses.
FK7003

20. Extending the model ½ -½ ½ -½ I3 I3 +1 -1 +1 -1 Meson nonet (spin 0)
Baryon decuplet
(spin 1/2)
Baryon decuplet
(spin 3/2)
FK7003

21. Extending the quark model
FK7003

22. Combining quarks (3) - flavour
Isospin multiplets form part of pattern.
Meson nonet
(octet+singlet)
(spin 0) -1 +1 -½ I3
FK7003

23. Identifying the states
FK7003

24. SU(3) Flavour – mesons of spin 1 (vector)
FK7003

25. Meson wave functions
FK7003

26. Baryons
-3/ / / /2
FK7003

27. FK7003
/ /

28. FK7003

29. Test the quark model – decuplet 
FK7003

30. The quark model works
Possible mutliplets of ground state baryons with similar properties
Observed in nature ?
Predicted to exist by the quark model
Comments
Spin 1/2 octet 
Spin 3/2 octet X
Spin 1/2 singlet
Spin 3/2 singlet
Spin 1/2 decuplet
Spin 3/2 decuplet
FK7003

31. Success of SU(3)
With SU(3) symmetry and u,d,s quark model can understand the existence and basic properties of all light ground state hadrons
SU(2) symmetry is ”good” - all hadrons in an isospin multiplet have similar masses since u,d have similar masses.
SU(3) symmetry is ”approximate” – larger mass differences owing to difference of s and u,d, masses.
To include charm, use SU(4) symmetry – useful to enumerate states but a poor symmetry owing to the heavy charm mass.
FK7003

32. A historical note
FK7003

33. Baryon magnetic moments
FK7003

34. Baryon magnetic moments
Prediction
Experiment p
2.79
2.793 n
-1.86
1.913 L
-0.58
-0.61 S+
2.68
2.33 +/- 0.13 S0
0.82
No measurement S-
-1.05
/- 0.25
-1.40 /
-0.47
/- 0.04
FK7003

35. Summary Hadrons with similar properties occur in multiplets in nature
The quark model is based on a few simple postulates
The quark model successfully describes the observed multiplet structure
Still to show evidence that ”quarks” are physical objects (next lecture)
FK7003