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David Anez Saint Mary’s/Dalhousie University May 14, 2011

Measurement of the Coulomb quadrupole amplitude in the γ * p → Δ (1232) reaction in the low momentum transfer region. David Anez Saint Mary’s/Dalhousie University May 14, 2011. Introduction. Took measurements of the p ( e , e ′ p ) π 0 (pion electroproduction) reaction

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David Anez Saint Mary’s/Dalhousie University May 14, 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 David Anez Saint Mary’s/Dalhousie University May 14, 2011

  2. Introduction • Took measurements of the p(e,e′p)π0 (pion electroproduction) reaction • In the low Q2 region where the pion cloud is expected to dominate • With center-of-mass energies near the Δ resonance to look at the transition amplitudes between the nucleon and the delta • To better understand the Coulomb quadrupole transition amplitude behavior in this region and how it affects nucleon deformation David Anez – May 17th, 2011 2/15

  3. World Data and Models David Anez – May 17th, 2011 3/15

  4. World Data and Models David Anez – May 17th, 2011 4/15

  5. World Data and Models David Anez – May 17th, 2011 5/56

  6. World Data and Models • Q2 = 0.045 (GeV/c)2 • New lowest CMR value • θe = 12.5° David Anez – May 17th, 2011 5/15

  7. 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 David Anez – May 17th, 2011 5/15

  8. 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 David Anez – May 17th, 2011 5/15

  9. 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 David Anez – May 17th, 2011 6/15

  10. High Resolution Spectrometers • Vertical drift chambers • Particle tracking • Scintillators • Timing information • Triggering DAQ • Gas Cerenkov detectors • Particle identification • Lead glass showers • Particle identification David Anez – May 17th, 2011 7/15

  11. Original Kinematic Settings David Anez – May 17th, 2011 8/15

  12. Revised Kinematic Settings David Anez – May 17th, 2011 9/15

  13. Actual Kinematic Settings David Anez – May 17th, 2011 10/15

  14. Response Functions • Unpolarized cross section made up of four independent partial cross sections David Anez – May 17th, 2011 11/15

  15. Response Functions David Anez – May 17th, 2011 12/15

  16. Multipole Amplitudes David Anez – May 17th, 2011 13/15

  17. Response Functions David Anez – May 17th, 2011 12/15

  18. Response Functions • Truncated Multipole Expansion • Model Dependent Extraction • Fit theoretical model to existing data • Insert model values for background amplitudes David Anez – May 17th, 2011 14/15

  19. Work Still to Do • Calibration Analysis: May 2011 • Data Analysis: January 2012 • Doctoral Thesis: December 2012 • Published Paper: October 2015 David Anez – May 17th, 2011 15/15

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