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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 Hall A Collaboration Meeting June 9 th , 2011. Introduction E97-110.

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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 Hall A Collaboration Meeting June 9th, 2011

  2. Introduction E97-110 • 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. Neutron 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. Kinematic Coverage

  6. Current Work • Waiting on final target polarization (J. Singh) • Elastic 3He analysis (V. Laine) • 2.1 GeV asymmetry and cross section complete • Now working on 2.8 GeV data set • Finalize acceptance (V. Sulkosky) • Radiative Corrections • Preliminary done by J. Singh; code now available • Tim Holmstrom working on it • Estimation of QE contribution to neutron results (V. Sulkosky)

  7. Elastic Asymmetry Analysis Work by V. Laine`

  8. 3He Elastic Acceptance Delta ytg W-M

  9. Elastic Cross Section Analysis Average 10 A; VDC 19% multi-tracks Work by V. Laine`

  10. 6o Acceptance Solutions • ||  3.6% • Removed edge bins with a secondary process • Corrected remaining edge imperfections with • a secondary acceptance correction

  11. 9o Acceptance • More painful: • Saturation effect is present • A few settings were mistuned with the septum magnet • tg-acceptance appears squeezed at the highest field settings Septum Mistuned 15% uncertainty

  12. Variation of Acceptance Cuts Varying acceptance cuts does not help

  13. Interpolation • ||  3.6% • Removed edge bins with a secondary process • Corrected remaining edge imperfections with • a secondary acceptance correction • The interpolation method works, but there is a concern • about the adjacent momentum settings. • Currently working on Carbon cross section analysis to • verify the absolute normalization of the data.

  14. Cross Section Smoothing 3.319 GeV, 9o Work by T. Holmstrom 4.404 GeV, 9o

  15. Summary • Work is progressing though slowly • Hope to wrap up acceptance analysis soon • Major work needs to go into radiative corrections: • Smoothing of the data completed (T. Holmstrom) • Finite acceptance for elastic tail subtraction • Model for the two lowest energies • Draft of first paper in progress (75% complete) and expect to be internally available this month

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

  17. Systematic Uncertainties

  18. Analysis Status • Preliminary results for the moments have been extracted at constant Q2. • Collimator background is mostly from polarized 3He • Need to estimate size of leakage into physics asymmetry • Issues and analysis still in progress: • Almost final target polarizations (J. Singh) Waiting to receive final numbers very soon. • Elastic analysis as a cross check of systematics (V. Laine) • 2.1 GeV completed; working on other energies now • Acceptance: very messy but making steady progress • Finalize radiative corrections (J. Singh, T. Holmstrom& V. S.)

  19. 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

  20. Delta Acceptance E94-010 • Flat region of • -acceptance • is much smaller • with Septum • Simulation is not • perfect on the • falling edges E97-110

  21. 9-Degree Acceptance • More painful: • Saturation effect is present • A few settings were mistuned with the septum magnet • tg-acceptance appears squeezed at the highest field settings

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