1. Hadron physics Hadron physics Challenges and Achievements Mikhail Bashkanov University of Edinburgh UK Nuclear Physics Summer School I

2. OUTLINE OF THE COURSE Lecture 1: Hadron Physics. Experiments: new toys – new knowledge (progress in particle detector systems). Research areas: Hadron spectroscopy, meson rare decays (physics beyond SM), structure of hadrons. Lecture 2: Baryon spectroscopy, naïve quark model and beyond, molecular states, new horizons with precise measurements. Lecture 3: Using EM probes to learn about the nucleon. Nucleon form factors. Radius of the proton. 2

3. HADRON PHYSICS 3

4. ELECTROMAGNETIC INTERACTIONS 4 Ze

5. ELECTROMAGNETIC INTERACTIONS 5 Ze 2

6. EM -> STRONG INTERACTIONS 6 2 qq q q g

7. QUARKS 7

8. ENERGY DEPENDENCE OF THE COUPLING CONSTANT 8 q Bare quark

9. ENERGY DEPENDENCE OF THE COUPLING CONSTANT 9 q Dressed quark

10. ENERGY DEPENDENCE OF THE COUPLING CONSTANT 10 q Dressed quark Low energy probe

11. ENERGY DEPENDENCE OF THE COUPLING CONSTANT 11 q Dressed quark High energy probe

12. ELECTRON MICROSCOPY de Broglie wavelength of probe particle must be ~size of the object you wish to study 12

13. STRONG COUPLING CONSTANT 13

14. STRONG COUPLING CONSTANT Perturbative QCD Particle Physics Nonperturbative QCD Nuclear Physics 14

15. NUCLEAR VS PARTICLE PHYSICS Nuclear PhysicsParticle Physics Below charm thresholdAbove charm threshold Nucleon structureMesons with mass > 1.2 GeV Light quark baryons (without c/b quarks) 15 anticolor Meson Baryon color

16. MAJOR DIRECTIONS 16

17. RECENT PROGRESS IN NUCLEAR PHYSICS 17

18. BUBBLE CHAMBERS Gargamelle Bubble Chamber 18

19. MAGNETIC SPECTROMETERS 19 Time Of Flight->velocity

20. MODERN DETECTORS Large acceptance (close to 4  coverage) Charge and neutral particles Magnetic field, drift chambers Calorimeters High luminosity High rate, fast triggering Polarized beams/targets Polarimeters 20

21. MODERN DETECTORS KLOE WASA 21

22. PHOTONS Basics 22

23. WHY DO WE USE E/M PROBES? Pros: Interaction is understood (QCD) Beams are clean Beams can be polarized Targets can be polarized and dense Cons: Cross-sections are small Photon beams were(!) challenging Polarized targets are challenging Nucleon polarimetry is complicated 23

24. TYPES OF PHOTON POLARIZATION Linear polarization: (Electric field vector oscillates in plane) Circular polarization: (Electric field rotates Clockwise or anticlockwise) Both real and virtual photons can have polarization Determining azimuthal distribution of reaction products around these polarization directions gives powerful information. 24

25. HOW DO WE GENERATE INTENSE ELECTRON BEAMS Microtron: (MAMI, JLab) Electron beam accelerated by RF cavities. Tune magnetic field to ensure path through magnets multiple of Wavelength of accelerating field - electrons arrive back in phase with the accelerating field. Gives “continuous” beam (high duty factor) Stretcher ring: (ELSA, Spring8) Electron beams fed in from linac. Then accelerated and stored in ring. Useable beam bled off slowly Many stretcher rings built for synchrotron radiation – can exploit infrastructure for multiuse (e.g. Spring8) Tend to have poorer duty factors, less stable operation and poorer beam properties than microtrons. 25

26. REAL PHOTON BEAMS FROM ELECTRON BEAMS Wide range of photon energies Good time/position resolution for the tagger Small radiator-target distance Bremsstrahlung spectra 26

27. POLARIZATION IN REAL PHOTON BEAM Linear polarization: crystalline radiator, e.g. thin diamond. orient diamond to give polarised photons in certain photon energy ranges. Circular polarization: helicity polarised electrons. bremsstrahlung in amorphous radiator, e.g. copper. 27

28. COHERENT BREMSSTRAHLUNG 28

29. LINEAR POLARIZATION 29

30. COHERENT BREMSSTRAHLUNG 30

31. FROZEN SPIN TARGET 31

32. THE POLARIZED TARGET 32

33. NUCLEON POLARIMETER Polar angle distribution for unpolarized nucleons Analysing power Polarization 33

34. HADRON SPECTROSCOPY 34

35. REAL EXPERIMENT Diamond Target Polarimeter 35

36. INTERFERENCE 36

37. DECAY WIDTH 37 Decay width

38. NUCLEON EXCITED STATES 38

39. DOUBLE POLARIZATION EXPERIMENTS 39

40. POLARIZATION OBSERVABLES 40

41. RESONANCE HUNTING 41

42. MESON PHOTOPRODUCTION CROSS SECTIONS 42

43. RARE EVENTS The Standard Model and beyond 43

44. PRECISION IS POWER Testing Standard Model with precise measurements 44

45. ELECTRIC DIPOLE MOMENT 45

46. NEUTRON EDM 46

47. NEUTRON EDM SM SUSY 47

48. RARE DECAYS 48

49. 49

50. UNIVERSE CONTENT 50

51. SEARCH FOR DARK PHOTON Dark force: Dark photon 51

52. CONCLUSION Enormous progress in nuclear physics Precision is a new motto Acceptance Luminosity Polarization Photons are the best Experimentally clean Well understood theoretically 52