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Seoul National University
Coulomb Sum Rule Experiment
Precision Measurement of RL and RT of Quasi-Elastic Electron Scattering
Seonho Choi
MENU2010 ConferenceJune 2, 2010
Williamsburg, USA
Seoul National University
PeopleKalyan Allada, Korand Aniol, John Arrington, Todd Averett, Herat Bandara, Werner Boeglin,
Alexandre Camsonne, Mustafa Canan, Jian-Ping Chen, Wei Chen, Khem Chirapatpimol, Seonho Choi, Eugene Chudakov, Evaristo Cisbani, Francesco Cusanno, Raffaele De Leo,
Chiranjib Dutta, Cesar Fernandez-Ramirez, Salvatore Frullani, Haiyan Gao, Franco Garibaldi, Ronald Gilman, Oleksandr Glamazdin, Brian Hahn, Ole Hansen, Douglas
Higinbotham, Tim Holmstrom, Bitao Hu, Jin Huang, Florian Itard, Liyang Jiang, Xiaodong Jiang, Hoyoung Kang, Joe KatichMina Katramatou, Aidan Kelleher, Elena Khrosinkova,
Gerfried Kumbartzki, John LeRose, Xiaomei Li, Richard Lindgren, Nilanga Liyanage, Joaquin Lopez Herraiz, Lagamba Luigi, Alexandre Lukhanin, Maria Martinez Perez, Dustin McNulty,
Zein-Eddine Meziani, Robert Michaels, Miha Mihovilovic, Joseph Morgenstern, Blaine Norum, Yoomin Oh, Michael Olson, Makis Petratos, Milan Potokar, Xin Qian, Yi Qiang, Arun Saha, Brad Sawatzky, Elaine Schulte, Mitra Shabestari, Simon Sirca, Patricia Solvignon, Jeongseog Song, Nikolaos Sparveris, Ramesh Subedi, Vincent Sulkosky, Jose Udias, Javier Vignote, Eric Voutier, Youcai Wang, John Watson, Yunxiu Ye, Xinhu Yan, Huan Yao,
Zhihong Ye, Xiaohui Zhan, Yi Zhang, Xiaochao Zheng, Lingyan Zhu
and
Hall-A Collaboration
Seoul National University
Outline
• Motivation
• Previous Results
• New Experiment at JLab
• A few preliminary results
• Summary
Seoul National University
Electron Scattering on Nucleons
• Excellent tool to study properties of nucleons, nuclei etc.
• Charge distribution of various nucleus
• Elastic form factors of nucleons
• Goal: Study of the nucleon properties inside the nucleus
• How? - Comparison of
• Elastic scattering on a free nucleon and
• Quasi-elastic scattering from a bound nucleon
• Especially interested in the electric form factor of the proton
Seoul National University
Elastic Scattering of Electrons
• Elastic cross section of eN scattering
• Form Factors
• GE: Charge distribution
• GM: Magnetization distribution
Seoul National University
Quasi-Elastic Scattering
• Almost elastic scattering on moving nucleons inside the nucleus
• Roughly, RL corresponds to GE,RT corresponds to GM
Seoul National University
Coulomb Sum
• Integral of RL at constant q
• Denominator: contribution from electric form factors of protons and neutrons
Seoul National University
Saturation/Quenching of the Coulomb Sum
• Coulomb Sum Rule
• at sufficiently large q
• Deviation from the unity
• at small q
• Pauli blocking
• NN long-range correlations
• at large q
• Short range correlations(small, ~ 10% at most)
• Modification of nucleon properties in the nuclear medium
S(q)
1
q2kF
Seoul National University
200 400 600 800 1000 1200qeff (MeV/c)
0.4
0.6
0.8
1.0
S L (q
eff)
3He 40Ca 56Fe 208Pb 56Fe 56Fe
Previous Measurements• For the past 20 years, a
large experimental program at Bates, Saclay and SLAC
• Saturation of the Coulomb sum still controversial
• Limited kinematic coverage in q and ω
The figure does NOT include all the existing data.Especially, MIT Bates results are not included
Seoul National University
Controversy on CSR• Early data shows significant quenching.
• With the addition of forward angle data, Bates claims NO significant quenching.
• Saclay new analysis claims that quenching persists.
300 400 500q (MeV/c)
0.4
0.6
0.8
1.0
YLAB
EL
40Ca Bates 40Ca Saclay
300 400 500q (MeV/c)
238U Bates 208Pb Saclay
Seoul National University
New Experiment at JLab
• Beam: 16 energies from 0.4 to 4.0 GeV
• Scattering angles: 15o, 60o, 90o, 120o
• Targets: 4He, 12C, 56Fe, 208Pb
• Spectrometer momenta range from 4 GeV down to 100 MeV
• Covers q from 550 to 1000 MeV/c
Seoul National University
Coverage at 15o
0 200 400 600 800 1000
! (MeV)
0.4
0.6
0.8
1
1.2
1.4
q (
GeV
/c)
1.256 GeV
1.645 GeV
2.139 GeV
2.445 GeV
2.839 GeV
3.245 GeV
3.683 GeV
4.045 GeV
15o
Seoul National University
Coverage at 120o
0 200 400 600 800 1000
! (MeV)
0.4
0.6
0.8
1
1.2
1.4
q (
GeV
/c)
0.400 GeV
0.528 GeV
0.645 GeV
0.739 GeV
0.845 GeV
0.959 GeV
120o
Seoul National University
Lever Arm for Rosenbluth Separation
0 200 400 600 800 1000 (MeV)
0.0
0.2
0.4
0.6
0.8
1.0
|q| = 550 MeV/c|q| = 750 MeV/c|q| = 900 MeV/c
Seoul National University
What’s New?• Comfortable high values of q
• From 550 MeV/c to 1000 MeV/c
• High enough for clean observation of CSR
• Previously unexplored region
• Comprehensive single experiment
• Largest lever arm
• Measurement at 4 angles
• Better control of background with NaI detector
Seoul National University
CSRCollaborationMeeting
X. Yan
NaI Detector
Data QualityCheck
Bcm
Preshower and
Shower
Left Arm Cerenkov
Detector
Right Arm Cerenkov
Detector
logoRun4271 E=2845MeV P0=2656MeV/c 15!
carbon
h0Entries 30089
Mean 2532
RMS 238.3
Ep(MeV)0 1000 2000 3000 4000 5000
-410
-310
-210
-110
h0Entries 30089
Mean 2532
RMS 238.3
h0Entries 30089
Mean 2532
RMS 238.3
Red:No Ref(9088)
Purple: D1 Ref(2)
Blue: Q3 Ref(53)
Black: Data(30089)
middle box
Figure 19: comparison between simulation and our data for high
energy
Detector Performance• NaI Detector
• Independent measurement of the electron energy
• Control of low energy scattered electrons
• Simulation
• Electrons reflected inside the spectrometer
• Comparison of low energy tail
Seoul National University
Acceptance
Database Optics Detector efficiency Acceptance Cross Section To do list
21908 Acceptance
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.080
100
200
300
400
500
600
tg! h1_Data_Tg_MoreBins_0
Entries 34046
Mean 0.0003542RMS 0.02985
tg!
-0.03 -0.02 -0.01 0 0.01 0.02 0.030
100
200
300
400
500
600
700
tg" h1_Data_Tg_MoreBins_1
Entries 34046
Mean -0.0004368RMS 0.01281
tg"
-0.01 -0.005 0 0.005 0.01 0.015 0.020
200
400
600
800
1000
1200
(m)tg
y h1_Data_Tg_MoreBins_2
Entries 34046
Mean 0.006687RMS 0.004099
(m)tg
y
-0.06 -0.04 -0.02 0 0.02 0.04 0.060
100
200
300
400
500
600
700
dp h1_Data_Tg_MoreBins_3
Entries 34046
Mean -0.002811RMS 0.02465
dp
-0.01 -0.005 0 0.005 0.01 0.015 0.02 0.0250
200
400
600
800
1000
1200
ReactZ (m) h1_Data_Tg_MoreBins_4
Entries 34046
Mean 0.006189RMS 0.004797
ReactZ (m)
0 0.005 0.01 0.015 0.02 0.025 0.03 0.0350
100
200
300
400
500
600
700
800
RValue h1_Data_Tg_MoreBins_5
Entries 34046
Mean 0.01545RMS 0.006779
RValue
Figure: 21908 Acceptance ( Black: Data Red: Simulation Blue:
Simulation Generator
21 / 28
Subatomic Physics Group at Temple University
Seoul National University
Preliminary Cross Section ComparisonComparison
(MeV)
0 50 100 150 200 250 300 350 400 450
0
0.2
0.4
0.6
0.8
1
1.2
1.4 E0 = 646 MeV
° = 60
Raw data
Elastic tail
Tail subtracted
(MeV)
50 100 150 200 250 300 350 400 450
0
0.2
0.4
0.6
0.8
1
1.2
1.4E0 = 646 MeV
° = 60
Raw data
Elastic tail
Tail subtracted
Zghiche et al. Nucl. Phys. A572(513)
• 4He target
• JLab: 646 MeV, 60o
• Blue cross: No radiative corrections yet
• Saclay: 640 MeV, 60o
• Filled circle: without radiative corrections
• Open circle: after the radiative corrections
PRELIMINARY
Seoul National University
Summary• Precision measurement of RL and RT over QE scattering range
• Momentum transfer: 550 MeV/c to 1000 MeV/c
• On four nuclei: 4He, 12C, 56Fe, 208Pb
• Experiment completed successfully
• A few new features compared to previous measurements
• Analysis in the final stage
• Preliminary cross sections obtained
• Radiative corrections in progress
• Hope to resolve the controversy on the Coulomb Sum Rule
Seoul National University
Expected Error
200 400 600 800 1000 1200qeff (MeV/c)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
S L (q
eff)
3He 40Ca 56Fe 208Pb 56Fe 56Fe Expected Error on 56Fe