1. 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

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
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3. World Data and Models
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4. World Data and Models
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5. World Data and Models
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6. World Data and Models Q2 = 0.045 (GeV/c)2 New lowest CMR value
David Anez – May 17th, 2011
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7. World Data and Models Q2 = 0.045 (GeV/c)2 Q2 = 0.125 (GeV/c)2
New lowest CMR value
θe = 12.5°
Q2 = (GeV/c)2
Validate previous measurements
David Anez – May 17th, 2011
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8. World Data and Models Q2 = 0.045 (GeV/c)2 Q2 = 0.125 (GeV/c)2
New lowest CMR value
θe = 12.5°
Q2 = (GeV/c)2
Validate previous measurements
Q2 = (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
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10. 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
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11. 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
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12. 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
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13. 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
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14. Response Functions
Unpolarized cross section made up of four independent partial cross sections
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15. Response Functions
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16. 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
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17. Response Functions
David Anez – May 17th, 2011
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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
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19. Work Still to Do Calibration Analysis: May 2011
Data Analysis: January 2012
Doctoral Thesis: December 2012
Published Paper: October 2015
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