coulomb sum rule experiment - paralle… · seoul national university electron scattering on...

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


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


Outline

• Motivation

• Previous Results

• New Experiment at JLab

• A few preliminary results

• Summary


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


Elastic Scattering of Electrons

• Elastic cross section of eN scattering

• Form Factors

• GE: Charge distribution

• GM: Magnetization distribution


Quasi-Elastic Scattering

• Almost elastic scattering on moving nucleons inside the nucleus

• Roughly, RL corresponds to GE,RT corresponds to GM


Coulomb Sum

• Integral of RL at constant q

• Denominator: contribution from electric form factors of protons and neutrons


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


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


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


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


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


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


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


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


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


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


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


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


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

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