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Vincent SulkoskyMassachusetts Institute of Technology
Spokespeople: J.-P. Chen, A. Deur, F. Garibaldi
Hall A Collaboration MeetingJune 13th, 2013
E97-110: Small Angle GDHExperimental Status Report
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Motivation Precision measurement of the moments of spin
structure functions at low Q2, 0.02 to 0.24 GeV2 for the neutron (3He)
Covered an unmeasured region of kinematics to test theoretical calculations (Chiral Perturbation theory)
Complements data from experiment E94-010 covered region from 0.1 to 0.9 GeV2
Finalizing systematic uncertainties and first publication
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E97-110 Spin Polarizabilities
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Experiment E97-110
Inclusive experiment:Scattering angles of 6◦ and 9◦ Polarized electron beam: Avg. Pbeam = 75%Pol. 3He target (para & perp): Avg. Ptarg = 40%
Measured polarized cross-section differences
Xee )',(He3
M. Amarian et al., PRL 89, 242301 (2002)
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Work in Progress Finalized target analysis:
Density and NMR/EPR polarizations (J. Singh)Target polarization uncertainties (V. Sulkosky)
Elastic 3He analysis (V. Laine) 2.1 GeV asymmetry and cross section completedAnalysis of the other three elastic data sets in progress
Finalize acceptance (V. Sulkosky) Fine tuning beam trip cuts for cross section and asymmetry
consistency checks Radiative Corrections
Preliminary work done by J. SinghWork on going by Tim Holmstrom
Estimation of QE contribution to neutron results (V. Sulkosky)
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“Final” Target Polarizations
Analysis by J. Singh
6.6%
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Run-by-Run Polarizations
Significant Drop in Polarization
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Polarization Ratios
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Re-averaging of Polarizations
Used the total errors, statistical and systematic in a weighted average of polarizations.
EPR polarizations were excluded for 128 runs:15 runs for Priapus at 6 degrees113 runs for Priapus at 9 degrees
Calib. Source Penelope 6 degs
Priapus 6 degs Priapus 9 degs
Water NMR 6.8% 6.7% 6.7%EPR-NMR 3.9% 4.4% 4.0%
EPR 2.2% 2.2% 2.2%
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Polarization Uncertainties
When EPR is available, the averages are dominated by EPR and NMR calibrated by EPR.
When EPR is unavailable, the averages are dominated by NMR calibrated by EPR and to a lesser extent NMR calibrated by water.
Period Total UncertaintyPenelope 2.9%
Priapus 6 degs w/ EPR 3.0%Priapus 6 degs w/o EPR 5.1%Priapus 9 degs w/ EPR 2.9%Priapus 9 degs w/o EPR 4.8%
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Penelope at 6 Degrees
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Priapus at 9 Degrees
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Elastic Asymmetry Analysis
Work by V. Laine`
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Elastic Asymmetry Analysis
Work by V. Laine`
Preliminary
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Summary Work is progressing Target polarizations and uncertainties finalized Acceptance analysis mostly completed; currently
finalizing beam trip cuts and then checking cross section stability
Additional work needs to go into radiative corrections:1. Smoothing of the data completed (T. Holmstrom)2. Elastic tail subtraction with acceptance and collimator
effects included3. Model for the two lowest energies
Draft of first paper completed and internally circulated
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Back-up slides
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Stability of Cross SectionsProblematic beam trip cuts Good beam trip cuts
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Axial Anomaly and the LT Puzzle
N. Kochelev and Y. Oh; arXiv:1103.4891v1
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NMR Systematics
1%
Reduces systematics from 8.2% to 6.6%
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Priapus at 9 Degrees
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4.4 GeV Drop in Polarization
Significant Drop in Polarization
3.14 GeV/c
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4.4 GeV Asymmetries
3.14 GeV/c
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Charge Normalized Asymmetries
Corrected for Charge and livetime
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Systematic Uncertainties
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9o Acceptance
Septum Mistuned5-10% uncertainty
Difficulty:◦ Saturation effect is present◦ A few settings were
mistuned with the septum magnet
◦ tg-acceptance appears squeezed at the highest field settings
◦ Only tight acceptance cuts improve the issues
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Tools for Inelastic Cross Sections
Single Arm Monte-Carlo (SAMC) from A. Deur◦ Uses John LeRose transport functions at 9º and
apertures ◦ Updated septum magnet apertures with bore cooler◦ Program complied with QFS subroutines to perform
radiative corrections: internal and external◦ Program utilizes the parameterized cross section for
A> 2 from P. Bosted: https://userweb.jlab.org/~bosted/F1F209.f
◦ Elastic radiative tail removed using Rosetail averaged over the solid angle acceptance of E97-110
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3He Cross SectionsApplied very tight acceptance cuts on angles
with P. Bosted’s 2009 model
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Acceptance Cut StudyCut na4: chosen as the reference cut to compare others against
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Summary of Cut StudyCut sc
[deg]tg
[mrad]
tg
[mrad]
Ytg
[cm]Pdiff [%]
[%]
Na1 9.002 8 3 4 -1.3 3.1
Na2 9.019 15 3 4 0.1 2.3
Na3 9.056 30 3 4 1.1 2.1
Na4 8.986 15 6 4 --- ---
Na5 8.920 15 12 4 -1.3 2.0
Na6 8.789 15 -18,8 4 2.0 4.1
Na7 8.67 15 -12,8 4 1.3 2.0
Na8 8.987 15 -6,12 4 -4.2 1.5
Na9 8.996 15 -6,15 4 -7.1 2.1
Na10 8.994 15 6 8 -2.1 1.5
Na11 9.249 20 6 8 -1.6 1.8Cross section cut sensitivity is typically less than 2%,
as long as tg is kept away from the small angle acceptance side
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Updated SAMC CodeWork done by V. Laine`SAMC rewritten in C++ from FortranImproved implementation of target
collimator cutsRaster correction by calculating electron’s
travel length through the cellRadiative corrections made for each material
separately (previously done all at once)Default units now in meter, gram, GeV and
radian instead of cm and mrad
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Delta Acceptance
E94-010
E97-110
• Flat region of -acceptance is much smaller with Septum• Simulation is not perfect on the falling edges
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3He Elastic AcceptanceDelta
ytg W-M
tg tg
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Kinematic Coverage