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E97-110: Small Angle GDH Experimental Status Report

E97-110: Small Angle GDH Experimental Status Report. Vincent Sulkosky Massachusetts Institute of Technology Spokespeople : J.-P. Chen, A. Deur , F. Garibaldi Hall A Collaboration Meeting June 13 th , 2013. Motivation.

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E97-110: Small Angle GDH Experimental Status Report

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  1. E97-110: Small Angle GDHExperimental Status Report Vincent Sulkosky Massachusetts Institute of Technology Spokespeople: J.-P. Chen, A. Deur, F. Garibaldi Hall A Collaboration Meeting June 13th, 2013

  2. 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

  3. E97-110 Spin Polarizabilities

  4. 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 M. Amarianet al., PRL 89, 242301 (2002)

  5. 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 completed • Analysis 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. Singh • Work on going by Tim Holmstrom • Estimation of QE contribution to neutron results (V. Sulkosky)

  6. “Final” Target Polarizations 6.6% Analysis by J. Singh

  7. Run-by-Run Polarizations Significant Drop in Polarization

  8. Polarization Ratios

  9. 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 degrees • 113 runs for Priapus at 9 degrees

  10. 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.

  11. Penelope at 6 Degrees

  12. Priapus at 9 Degrees

  13. Elastic Asymmetry Analysis Work by V. Laine`

  14. Elastic Asymmetry Analysis Preliminary Work by V. Laine`

  15. 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: • Smoothing of the data completed (T. Holmstrom) • Elastic tail subtraction with acceptance and collimator effects included • Model for the two lowest energies • Draft of first paper completed and internally circulated

  16. Back-up slides

  17. Stability of Cross Sections Problematic beam trip cuts Good beam trip cuts

  18. Axial Anomaly and the LTPuzzle N. Kochelev and Y. Oh; arXiv:1103.4891v1

  19. NMR Systematics 1% Reduces systematics from 8.2% to 6.6%

  20. Priapus at 9 Degrees

  21. 4.4 GeV Drop in Polarization 3.14 GeV/c Significant Drop in Polarization

  22. 4.4 GeV Asymmetries 3.14 GeV/c

  23. Charge Normalized Asymmetries Corrected for Charge and livetime

  24. Systematic Uncertainties

  25. 9o Acceptance • 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 Septum Mistuned 5-10% uncertainty

  26. 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

  27. 3He Cross Sections Applied very tight acceptance cuts on angles with P. Bosted’s 2009 model

  28. Acceptance Cut Study Cut na4: chosen as the reference cut to compare others against

  29. Summary of Cut Study Cross section cut sensitivity is typically less than 2%, as long as tg is kept away from the small angle acceptance side

  30. Updated SAMC Code • Work done by V. Laine` • SAMC rewritten in C++ from Fortran • Improved implementation of target collimator cuts • Raster correction by calculating electron’s travel length through the cell • Radiative 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

  31. Delta Acceptance E94-010 • Flat region of • -acceptance • is much smaller • with Septum • Simulation is • notperfect on • the falling edges E97-110

  32. 3He Elastic Acceptance Delta ytg W-M

  33. Kinematic Coverage

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