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)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

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

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

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

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

World Data and Models Q2 = 0.045 (GeV/c)2 Q2 = 0.125 (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

World Data and Models Q2 = 0.045 (GeV/c)2 Q2 = 0.125 (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

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

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

Original Kinematic Settings # Q2 (GeV/c)2 W (MeV) (MeV/c) I (µA) L (cm) Q (mC) Time (hrs) 1 0.041 1221 12.52 767.99 24.50 547.54 75 6 405 1.5 2 30 528.12 540 3 36.48 945 3.5 4 1260 12.96 716.42 21.08 614.44 5 0.090 1230 19.14 729.96 29.37 627.91 40 14.99 589.08 810 7 43.74 1215 4.5 8 0.125 1232 22.94 708.69 30.86 672.56 9 20.68 649.23 1890 10 41.03 11 55 596.43 12 49.19 13 1170 21.74 788.05 37.31 575.57 14 1200 22.29 750.16 34.06 622.63 Configuration changes 17 Calibrations Total: 72 David Anez – May 17th, 2011 8/15

Revised Kinematic Settings # Q2 (GeV/c)2 W (MeV) (MeV/c) I (µA) L (cm) Q (mC) Time (hrs) 1 0.045 1221 12.5 805 25.5 552 50 4 608 3.5 2 33 528 810 4.5 3 38.5 1418 8 1260 13 755 22 618 5 0.090 1230 18 770 30 626 15 162 6 45 13.5 576 324 7 46 486 0.125 1232 750 31.5 670 378 2.5 9 21 646 756 10 41.5 11 55 591 12 1170 20.5 826 37.5 574 14 1200 789 34.5 621 216 1.5 David Anez – May 17th, 2011 9/15

Actual Kinematic Settings # Q2 (GeV/c)2 W (MeV) (MeV/c) I (µA) L (cm) Q (mC) Time (hrs) 1 0.045 1221 12.5 805 25.5 552 15 4 636 19 2 33 528 849 18 3 38.5 20 1416 17 1260 13 755 22 618 50 5 0.090 1230 770 30 626 80 642 6 45 13.5 576 40 1296 10 7 46 1861 8 0.125 1232 750 31.5 670 80/40 4/15 914 9 21 646 652 41.5 758 11 14.5 606 55 1436 12 48 1365 1170 20.5 826 37.5 574 35 285 14 1200 789 34.5 621 220 David Anez – May 17th, 2011 10/15

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

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

Multipole Amplitudes David Anez – May 17th, 2011 13/15 γN-Multipoles Initial State Excited State Final State πN-Multipoles C, E, M N* I2I2J Δ Lℓ±, Eℓ±, Mℓ± C0 0+ 1⁄2+ P11 P31 1+ L1− C1,E1 1− 1⁄2− S11 S31 0− L0+, E0+ 3⁄2− D13 D33 2− L2−, E2− M1 M1− 3⁄2+ P13 P33 M1+ C2, E2 2+ L1+, E1+ 5⁄2+ F15 F35 3+ L3−, E3− M2 M2− 5⁄2− D15 D35 M2+ David Anez – May 17th, 2011 13/15

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

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

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