Min HuangDuke University, TUNL
For the Jefferson Lab Hall A E08-027 (g2p) collaboration
APS A il M i A il 16 h 2013APS April Meeting, April 16th, 2013
E08‐027E08‐027 g2p & the LT Spin Polarizabilityg2 p y Spokespeople
Alexandre Camsonne Graduate Students
Toby Badman Alexandre Camsonne(JLab)
Jian-Ping Chen (JLab)
Toby Badman Melissa Cummings Chao Gu
Don Crabb (UVA) Karl Slifer (UNH)
Post Docs
Min Huang Jie Liu
P ji Zh Post Docs Kalyan Allada James Maxwell
Pengjia Zhu Ryan Zielinski
James Maxwell Vince Sulkosky Jixie Zhang
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Outline Introduction
Physics Motivation
Experimental Setup
Status of Data AnalysisStatus of Data Analysis
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Electron Scattering I l i l i d diff ti l ti
Nevzat Guler’sTalk in G3
Inclusive polarized differential cross section
e (E,k) e’ (E’,k’)θ
( , )
* ( )γ* (ν,q)
P (M 0)W g1, g2: polarized nucleon
spin structure functionsP (M,0)
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How to Obtain gHow to Obtain g2e‐ e‐
e‐
e‐
measured by g2p experiment, essential contribution to g2 in this kinematic region
For the kinematic region not measure for
JLab Hall B EG42 2
2 2d d
d d
, JLab Hall B EG4 data will be combined 2 2
2 2' '
' '' '
td dd dE d dE Ad dE d dEd d
d dE d dE
Will measure both asymmetry and cross section5APS April Meeting 2013 Min Huang
Motivation Measure the proton spin structure function g2 in the low 2
Q2 region (0.02<Q2<0.2 GeV2) for the first time Extract δLT to be a benchmark test of χPT calculationsLT χ Unique opportunity to test the Burkhardt-Cottingham sum
rule Crucial inputs for hydrogen hyperfine splitting and proton
charge radius measurementsgJudith Mcgovern’stalk in Q5
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S i LT P l i bilitSpin LT Polarizability
Can be calculated via χPT δ it bl t t t th hi l δLT more suitable to test the chiral
dynamics of QCD (in comparison to the forward spin polarizabilityγ0)
Neutron data show large deviation Neutron data show large deviation from χPT calculations
No proton data yet
7APS April Meeting 2013 Min Huangplot courtesy of V. Sulkosky
lBC Sum Rule2 j t d
H. Burkhardt and W. N. Cottingham, Annals. Phys., 56(1970)453
P
g2p projected
BC satisfied within errors for Neutron
Inconsistency seen in proton data
Mostly unmeasured forN
Mostly unmeasured for proton
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Experimental SetupExperimental Setup Large Scale Installation in Hall A Large Scale Installation in Hall A
Transverse polarized NH3 target (2.5/5T field) Low beam current (<100 nA) > new beamline diagnostics
Septa
Low beam current (<100 nA) -> new beamline diagnostics Rasters
S t t
Hall A High Resolution
Septa Septum magnets
BCM Rasters Chicane BPM
L l
Hall A High Resolution Spectrometer (HRS)
LocalDump
Polarized NH3 Target
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Achievements DAQ rate is Hall A record Achievements 6~7 kHz/HRS with <30% deadtime
Polarized target performance has been outstanding <PT> >30% @ 2.5T <PT> >75% @ 5T T @
BCM Rasters Chicane BPM
Polarized NH3 TargetTarget Talk by
Melissa
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Cummings X15
kinematics Coveragerun concurrently with G prun concurrently with Ge
p
Mp < W < 2 GeV0.02 < Q2 < 0.2 GeV2
Beam E Target Energy /GeV
a geField /T
2 254 2 52.254 2.51.706 2.51.158 2.52.254 5.03.352 5.0
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ProjectionsProjections
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Status of AnalysisStatus of Analysis
courtesy K. Allada13APS April Meeting 2013 Min Huang
Status of AnalysisStatus of Analysis
Complete! Run Database
Optics Talk by Chao Gu X15u atabase
HRS optics w/o target field Detector calibrations
S l T T lk b
Chao Gu X15
Scalers Offline target polarization calibration
Underway
Target Talk by Melissa Cummings X15y
HRS optics with target field Systematic uncertainty study of target polarization
B iti & t lib ti Beam position & raster calibrations
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Online ResultsYield
Y
APS April Meeting 2013 Min Huang 15courtesy R. Zielinski
Online ResultsLongitudinal 5T Asymmetry at E=2.254 GeV
APS April Meeting 2013 Min Huang 16courtesy T. Badman
Summary The g2p experiment ran in spring of 2012 took data The g2p experiment, ran in spring of 2012, took data
covering Mp < W < 2 GeV, 0.02 < Q2 < 0.2 GeV2
A first pass replay of production data is now complete A first pass replay of production data is now complete, and data quality checks are underway!
Will provide a precision measurement of g p in the low Q2 Will provide a precision measurement of g2p in the low Q2
region for the first time Results will shed light on several physics puzzles Results will shed light on several physics puzzles
Thanks to the g2p and Hall A collaboration!Thanks to the g2p and Hall A collaboration!
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Backupp
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H d H fi St tHydrogen Hyperfine Structure Hydrogen hyperfine splitting in the ground state has been measuredHydrogen hyperfine splitting in the ground state has been measured
to a relative high accuracy of 10-13
∆S is the proton structure correction and has the largest uncertainty
6 ∆Z can be determined from elastic scattering, -41.0±0.5×10-6
∆pol involves contributions of the inelastic part (excited state), and can be extracted to 2 terms corresponding to 2 different spin-can be extracted to 2 terms corresponding to 2 different spindependent structure function of proton
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H d H fi St tHydrogen Hyperfine Structure
Integrand of ∆2
g2p Experiment
B2 is dominated by low Q2 part
g2p is unknown in this region, so there may be huge eg o , so e e ay be ugeerror when calculating ∆2
This experiment will provide a constrainta constraint
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