1. Shapes of proton, spin of proton
Light Front Calculations of Nucleon Form Factors - shapes of the proton G A Miller, UW
Experimental progress JLAB
Model: relativistic quarks, π cloud, symmetry-aided phenomenology
Electromagnetic form factors
Shapes of proton, spin of proton
Connect with lattice QCD

2. Definitions

3. Expectations- Pre Jlab
QF2 /F1
GE/GM
QF2/F1
GE/GM Q2 Q2

4. Implement Relativity

5. Impulse Approximation

7. Wave function

8. 1995 Frank, Jennings, Miller

9. Ratio of Pauli to Dirac Form Factors 1995

10. Relativistic Explanation

12. Neutron Electric Form Factor

13. Ratio of Pauli to Dirac Form Factors 2003

14. Two More Form Factors Needed

15. Model exists Lower components OAM Shape of proton
Spin dependent densities SDD non-rel
Relativistic SDD H atom
Proton

19. Shapes of the proton

20. Spin density operator: d(r-rp) s . n
PRB65,
Canted ferromagnetic structure of UNiGe high magnetic fields
Neutron magnetic scattering
Neutron, B, crystal

24. LFCBM and LATTICE FORM FACTORS
H. H. Matevosyan, GAM, AW Thomas
Lattice results described using LFCBM with parameters taken as analytic functions of lattice quark mass
Extrapolate back to physical regime
Form factors look like data
First attempt to relate lattice QCD with
form factors that depend on Q2

25. Reproduce Lattice QCDSF data

26. Extrapolate to physical, predict

27. Summary
Phenomenological model –three quark plus pion cloud- of nucleon respects Lorentz invariance and chiral
symmetry
Describes form factor data pretty well
Has some connection with lattice/fundamental theory

28. Extras follow

29. High Q2

30. How proton holds together
pQCD
Feynman
Non perturbative ∞ gluon exch

31. Compton scattering same model Relativistic Massive Quarks