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Presentation by David Anez Presented by Douglas Higinbotham 15 December 2011

Measurement of the Coulomb quadrupole amplitude in the γ * p → Δ (1232) reaction in the low momentum transfer region. Presentation by David Anez Presented by Douglas Higinbotham 15 December 2011. Introduction. Took measurements of the p ( e , e ′ p ) π 0 reaction low Q 2 region

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Presentation by David Anez Presented by Douglas Higinbotham 15 December 2011

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  1. Measurement of the Coulomb quadrupole amplitude in the γ*p→Δ(1232) reaction in the low momentum transfer region Presentation by David Anez Presented by Douglas Higinbotham 15 December 2011

  2. Introduction • Took measurements of the p(e,e′p)π0 reaction • low Q2 region • center-of-mass energies near the Δ resonance to look at the transition amplitudes between the nucleon and the delta • to better understand the structure of the proton December 15, 2011

  3. Motivation: Constituent Quark Model • Magnetic Dipole (M1 / ) • Spin-flip • Dominant December 15, 2011

  4. Motivation: Constituent Quark Model • Electric quadrupole (E2 / ) • Coulomb quadrupole (C2 / ) December 15, 2011

  5. Multipole Amplitudes • E1+ and S1+ (E2 & C2) are relatively small • Determine the ratio to dominant M1+ • EMR = • CMR = December 15, 2011

  6. World Data and Models • Q2 = 0.045 (GeV/c)2 • New lowest CMR value • θe = 12.5° • Q2 = 0.125 (GeV/c)2 • Validate previous measurements • Q2 = 0.090 (GeV/c)2 • Bridge previous measurements December 15, 2011

  7. The Experiment • Jefferson Lab, Hall A • February 27th – March 8th, 2011 • 1160 MeV e− beam • 4 & 15 cm LH2 target • Two high resolution spectrometers • HRSe and HRSh December 15, 2011

  8. High Resolution Spectrometers • Vertical drift chambers • Particle tracking • Scintillators • Timing information • Triggering DAQ • Gas Cerenkov detectors • Particle identification • Lead glass showers • Particle identification December 15, 2011

  9. Response Functions • Unpolarized cross section made up of four independent partial cross sections December 15, 2011

  10. Response Functions December 15, 2011

  11. Response Functions • Truncated Multipole Expansion • Model Dependent Extraction • Fit theoretical model to existing data • Insert model values for background amplitudes December 15, 2011

  12. Kinematic Settings December 15, 2011

  13. Actual Kinematic Settings 85% 85% December 15, 2011

  14. Revised Phase Space PlotsQ2 = 0.045 (GeV/c)2 (θpq* = 33°) W vs θpq* W vs Q2 Q2 vs θpq* Q2 vs θpq* W± 5MeV

  15. Work Ongoing (i.e. David’s Promises) • Calibration and Data Analysis • Doctoral Thesis: May 2013 • Paper Submission (required for graduation): 2013 • Has promised some analysis results for the summer Hall A meeting! December 15, 2011

  16. Motivation: Constituent Quark Model • Wave functions created December 15, 2011

  17. Multipole Amplitudes December 15, 2011

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