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

CONTENTS

Physics Motivation & HMS KinematicSANE LayoutAnalysis StatusSIMC SimulationWork Status

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

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

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%,

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

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.

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

Tracking Efficiency CorrectionTracking Efficiency Vs x-focal plane

Use the Tracking Efficiency as a function of hsxfp to correct data.

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

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

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

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.

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