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Size and Structure Mikhail Bashkanov University of Edinburgh UK Nuclear Physics Summer School III Slide 2 Outline Electron scattering Proton form factors Proton size puzzle 2 Slide 3 Electron microscopy de Broglie wavelength of probe particle must be ~size of the object you wish to study 3 Slide 4 Electrons as waves Scattering process is quantum mechanical 4 Slide 5 Classical Fraunhofer Diffraction 5 Slide 6 6 Slide 7 Electron scattering. Experiment 7 Slide 8 Electron scattering Plane wave approximation for incoming and outgoing electrons Born approximation: interact only once 8 Slide 9 Form Factor and charge distribution 9 Slide 10 Form Factor and cross-section 10 Slide 11 Experiment 11 Slide 12 Probing the proton Sachs form factors 12 Slide 13 Rosenbluth separation 13 Slide 14 Dipole form factor 14 Slide 15 Results 15 Slide 16 New technique: polarization transfer Longitudinally polarized electron+ Recoil polarimetry Longitudinally polarized electron+ Polarized target 16 Slide 17 Data extracted using Rosenbluth separation only 17 Slide 18 B Data extracted using polarization transfer only 18 Slide 19 All data 19 Slide 20 Radiative corrections to single photon exchange 20 Slide 21 21 Slide 22 Dipole form factor proton radius 22 Slide 23 Proton Charge radius 23 Slide 24 Bohrs atom 24 Slide 25 Hydrogen atom 25 Slide 26 Proton radius from hydrogen spectroscopy 26 Slide 27 Proton Charge radius 27 Slide 28 Proton Charge radius 28 Slide 29 Proton Charge radius puzzle 29 Slide 30 Lamb shift: status of known corrections VP: vacuum polarization SE: self energy 30 Slide 31 Proton radius puzzle: new physics? 31 Slide 32 Proton radius puzzle: whats next? 32 Slide 33 Proton 33 Slide 34 Nucleon internal structure 34 Valence quarks Sea quarks Gluons Slide 35 Valence quarks 35 Slide 36 Sea quarks 36 Slide 37 Gluons 37 Slide 38 What is inside? 38 Slide 39 Proton spin puzzle Proton spin quarks angular momentum gluon spin gluons angular momentum quarks spin Nave quark model: Reality: 39 Slide 40 Conclusion Nucleon structure is complex and complicated A lot of puzzles and a lot of progress New tools, high precision, high accuracy, polarization 40