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SpinAsymmetries of the NucleonExperiment( E07-003)
Anusha LiyanageHall C Users Meeting
January 23, 2010
Measurement Of the Proton Form Factor Ratio
at High Q2 by Using The
Double Spin Asymmetries
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CONTENTS
Physics Motivation & HMS KinematicSANE LayoutAnalysis StatusSIMC SimulationWork Status
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Dramatic discrepancy !
between Rosenbluth and recoil polarization technique.
Physics Motivation & HMS Kinematic For Proton E Beam
GeV4.725 5.891
PGeV/C
3.585 4.170
Θ(Deg)
22.30 22.00
Q2
(GeV/C)2
5.170 6.259
# of Total runs
~44 ~135
e-p Events
~153 ~948
RSS (Jlab)Q2 = 1.5 (GeV/c)2
M. Jones et al., PRC74 (2006) 035201
GeP-III, Hall C
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SANE LayoutBETA
(40°)HMS (14°- 48°)
BigCal
Lucite Hodoscope
Gas Cherenkov
Forward Hodosco
pe
B at 80° OR 180°
Polarized Target
Target Beamposition monitor
Beam Line
e-P
Θ PΘe
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From The Experiment
The raw asymmetry,
The elastic asymmetry,
The beam-target
asymmetry,
Here,
The calculated asymmetry vs μGE/GM
Am = N+ - N- N+ + N-
AP = + Nc Am
f PBPT
Ap = - br SinΘ*CosФ* - aCosΘ* r2 + c
r = GE /GM
a, b, c = kinematic factorsΘ*,Ф* = pol. and azi. Angles between q and S
PB,PT = Beam & Target Pol. f = Dilution Factor Nc = A Correction Term
N+= Helicity + CountsN- = Helicity - Counts
At Q2=6.259 (GeV/C)2
Θ*≈ 102° and Ф* = 0From the HMS kinematics, r2 << c
Ap = - bSinΘ*CosФ* r - aCosΘ* c c
PT + = ~71.0% , PT - = ~-65.0%, PB = ~73.0%,
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Error Propagation From The Experiment…..
Ap = - bSinΘ*CosФ* r - aCosΘ* c c
∆Ap = bSinΘ*CosФ* ∆r c
Using the experiment data at Q2=6.259 (GeV/C)2,
∆r = 0.118 μ ∆r = 2.79 x 0.118 μ ∆r = 0.3Where , μ – Magnetic Moment of the Proton The error on the μ ∆r
from the experimental data with total ep events ~1000, μ ∆r = 0.3
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Analysis Status
HMS Detector Calibration is Completed.Detector Efficiency.
Modification of the DC tracking efficiency algorithm is done.
(The tracking efficiency is increased by 15%-20%)
Extracted the elastic events. Correlation corrections are
completed.
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Tracking Efficiency Corrections
Used 4/6 DC hits instead of 5/6 DC hits.
Used the tracks which have stubs only on one of the DC’s as good tracks.
Tracking Efficiency Vs Run Number
Drift Chamber hits Vs x focal plane
Ch1 Vs hsxfp
Ch2 Vs hsxfp
Ch1 Vs hsxfp
Ch2 Vs hsxfp
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Tracking Efficiency CorrectionTracking Efficiency Vs x-focal plane
Use the Tracking Efficiency as a function of hsxfp to correct data.
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Extracted the elastic eventsMomentum Difference , dPel_hms
HMS
COIN
HMS – abs(dPel_hms ) < 0.02 abs(hsdelta) < 8 hcer_npe < 0.2 hsshtrk/hse > 0.01
COIN - abs(EHMS-eclust+0.37) <1 abs(XHMS-xclust-0.15) < 5 abs(YHMS-yclust+0.41) < 10
dPel_hms = PHMS – Pcal
Pcent
Q2 = 4M2E2cos2Θ M2+2ME+E2sin2Θ ν = Q2
2MPcal = Sqrt(ν2 + 2Mν)
Elliptic cut
yi = variable ai = offset σi = cut
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X/Y position differenceX position Difference
HMS cuts
COIN cuts
X/Y_HMS – Predicted X/Y positions (Target Mag. Field Corrected)on the BigCal using the HMS kinematicsX/Yclust - Measured X/Y positions on the BigCal
X_HMS - Xclust
Y position Difference
Y_HMS - Yclust
HMS cuts
COIN cuts
Y_HMS - Yclust
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Correlation Corrections for ….
The dPel_hms vs srast_y ....
The Y position difference Vs srast _y ….
dPel_hms vs srast_y
dPe_hms vs srast_y
Corrected dPel_hms vs srast_y
Ydiff Vs srast_y
Corrected Ydiff Vs srast_y
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SIMC Simulation
HMS Single Arm Variables HMS Coincidence with BigCalVariables
SIMC SimulationExperimental Data
σ = 0.79σ = 1.69
σ = 2.98σ = 4.21
σ = 0.0041σ = 0.0055
SIMC Counts = 1696Data = 950• Target Magnetic Field is corrected
• Normalized to Charge, Tracking Efff. and Comp. L.T.
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Work StatusHMS Calibration – completedPreliminary elastic event selection – completed
To Do …..Improve the SIMC simulation
Use the Data which are corrected with the new Tracking Efficiency correction function.(with hsxfp)
Include the new tracking algorithm to the simulationUse the Efficiency CorrectionsExtract the Asymmetry and the GE/GM Ratio