Extraction of G E n at Q 2 =1 (GeV/c) 2 by Measurements of

transcript

Extraction of GEn at Q2=1 (GeV/c)2 by

Measurements of

June 9, 2011

Ge JinUniversity of Virginia

)'e,e(He3

Abstract

GEn was extracted for the first time by inclusive polarized

measurements of Getting the ratio of asymmetries in longitudinal and

transverse target polarization; separating the electric and magnetic form factor contributions

Proton and neutron contributions calculated in PWIA New technique, confirms previous measurements;

uncertainty: ~18%, largely statistical

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Previous measurements and extraction of GE

Rosenbluth separation Polarization transfer d(e,e’n)p Polarized scattering, neutron tagging Polarized inclusive quasi-elastic

scattering

)n'e,e(He3

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Previous extractions of GE by

Uncertainties comparable to measured quantity

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Detectors and kinematics of this measurement Detectors:

HRS-R: detect electrons, placed at 170

Kinematics: Beam energy: 3.6 GeV Q2: 1 (GeV/c)2

Polarized 3He target

Room-temperature gaseous (10 atm) target

Rb-K hybrid optical pumping and spin exchange

Average polarization ~55%

Analysis of asymmetries

Beam polarization: by Hall A Möller measurements Target polarization: by run-by-run NMR calibration Dilution factor: by N2 pressure curve Radiative correction: by formalism of Mo and Tsai, peaking

approximation of Steil, et al. Code used in JLab E94010 for inelastic 3He scattering

Transverse-longitudinal asymmetry ATL’

(target polarization perpendicular to q)

Near quasi-elastic peak 0.9<xBj<1.1,

ATL’=(-0.55±0.09 (stat)±0.04 (syst))%

Transverse asymmetry AT’

(target polarization parallel to q)

Near quasi-elastic peak 0.9<xBj<1.1,

AT’ =(3.12±0.10 (stat)±0.21 (syst))%

Helicity asymmetry in electron scattering

RvRvA 33

'''' *cos*cos*sin

where R’s are response functions and v’s are kinematics factors

T. D. Donnelly and A. S. Raskin, Ann. Phys 169, 247 (1986)

Ratio of asymmetries

asymmetry allongitudin-e transvers,0* and 2/*when

asymmetry se transver,0*when

3He inclusive response functions near quasi-elastic peak in PWIA

Transverse-

longitudinal:

Transverse:

where H’s are calculated by momentum distribution and nucleon polarization in 3He

A. Kievsky, E. Pace, G. Salme’ and M. Viviani, PRC 56 (1997) p.64

Neutron: HnProton: Hp

Proton: HpTL’

])()(2[2

HGHGqM

HGGHGGR

3He spin structure

Spin-1/2 particle, 3 spin-1/2 nucleons (protons and neutron)

Angular Momentum l=0 l=0 l=2 ~90% ~1-2% ~8%

EffectiveNeutronTarget

The ratio of asymmetries as functions of form factors

]))()(2[2

])2[2(

HGHGqMQ

HGGHGGv

By measuring ATL’/AT’ and using GEp, GM

n, and GMn

as known parameters can one extract GEn

Final result of GEn at Q2=0.95 (GeV/c)2

Results: GE

n/GD=0.226±0.041 (stat)±0.016 (syst)

GEn=0.0414±0.0077 (stat)±0.0032 (syst)

Conclusion Our unprecedented method of measuring GE

n (ratio of asymmetries in ) gave results in agreement with world data

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Comments and Outlook

Further theoretical support (near quasi-elastic peak)

Advantages: Single arm (HRS) detector calibration At higher Q2, GE

n contributes more strongly to ATL’ than the other form factors.

Big saving of beam time: 18% accuracy in 3-day run Ratio-of-asymmetry method insensitive to systematic

error (beam and target polarization, dilution factor, radiative correction partly cancel)

Graduate StudentsG. Jin, University of Virginia

E. Long, Kent State UniversityM. Mihovilovič, Jožef Stefan Institute

Y. Zhang, Lanzhou University

Run CoordinatorsA. Camsonne, Jefferson Lab

P. Monaghan, Hampton UniversityS. Riordan, University of VirginiaB. Sawatzky, Temple UniversityR. Subedi, University of Virginia

V. Sulkosky, MITY. Qiang, Duke University

B. Zhao, College of William and Mary

S. Golge

O. Hansen

T. Holmstrom

J. Huang

H. Ibrahim

E. Jensen

M. Jones

H. Kang

J. Katich

C. W. Kees

P. King

J. LeRose

R. Lindgren

W. Luo

K. Allada

B. Anderson

J. R. M. Annand

W. Boeglin

P. Bradshaw

M. Canan

C. Chen

R. De Leo

X. Deng

A. Deur

C. Dutta

L. El Fassi

D. Flay

F. Garibaldi

H. Gao

R. Gilman

P. Markowitz

M. Meziane

R. Michaels

B. Moffit

N. Muangma

H. P. Khanal

K. Pan

D. Parno

E. Piasetzky

M. Posik

A. J. R. Puckett

X. Qian

X. Qui

A. Saha

Thanks to the Hall A Quasi-Elastic

Family ExperimentsSpokespersons

T. Averett, College of William and Mary (E05-015, E08-05)

J. P. Chen, Jefferson Lab (E05-015)

S. Gilad, MIT (E05-102)

D. Higinbotham, Jefferson Lab (E05-102, E08-005)

X. Jiang, Rutgers University (E05-015)

W. Korsch, University of Kentucky (E05-102)

B. E. Norum, University of Virginia (E05-102)

S. Sirca, University of Ljubljana (E05-102)

V. Sulkosky, MIT (E08-005)

E05-015,E08-005,and E05-102

CollaborationF. Salvatore

M. ShabestariA. ShahinyanB. Shoenrock

J. St. JohnA. Tobias

W. TiremanG. M. Urciuoli

D. WangK. WangJ. Watson

B. WojtsekhowskiZ. Ye

X. ZhanX. Zheng

L. Zhu

Four nucleon form factors

J. J. Kelly, PRC 068202, 2004

Ratio of Inclusive Asymmetry ATL’/AT’

Longitudinal:

Transverse:

Asymmetry ratio:

Where v’s are kinematics factors

By measuring ATL’/AT’ and using GEp , GM

n , GMn

as known parameters can one extract GEn

ctiond_cross_seunpolarize

)*cos*cos*(sin

]))()(2[2

])2[2(

ctiond_cross_seunpolarize

TLMottTL

TMottT

TLMottTL

HGHGqMQ

HGGHGGv

Asymmetry Results

Kinematics: 3 pass beam, HRS-R 170, Q2=0.95 GeV2

Analysis: Asymmetry in 0.9<x<1.1 Yawei Zhang’s target and dilution factor

analysis Karl Slifer’s radiative correction code radcor.f

Results: ATL’=-0.55±0.09(stat)±0.04(syst)% AT’ =3.12±0.10(stat)±0.21(syst)%

Error: Stat error dominates ATL’ Syst error contributed by beam and target

polarization, and dilution factor

Analysis on the ratio of asymmetries Ratio:

ATL’/AT’ =-0.18±0.03(stat)±0.01(syst)

Statistical uncertainty dominates Systematic

Beam polarization: <3% Dilution factor cancels Target polarization: ~0.6% contributed by the frequency reading

Δν in EPR calibration Radiative correction: <5%

Extraction of G E n at Q 2 =1 (GeV/c) 2 by Measurements of

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