E97-110: Small Angle GDH Experimental Status Report

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 December 10th, 2012

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 • Finalize acceptance (V. Sulkosky) • Radiative Corrections • Preliminary work done by J. Singh • Work on going by Tim Holmstrom • Final NMR and EPR polarizations confirmed(J. Singh) • Elastic 3He analysis (V. Laine) • 2.1 GeV asymmetry and cross section completed • Now working on the other 3 data sets • Estimation of QE contribution to neutron results (V. Sulkosky)

6. 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 tightacceptance cuts improve the issues Septum Mistuned 5-10% uncertainty

7. 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

8. 3He Cross Sections Applied very tight acceptance cuts on angles with P. Bosted’s 2009 model

9. Acceptance Cut Study Acceptance shows sensitivity to loose θtgcuts

10. Acceptance Cut Study Acceptance shows sensitivity to loose φtgcuts, especially on the negative side

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

12. Acceptance Cut Study Cut na4: chosen as the reference cut to compare others against Cross section angular differences corrected using P. Bosted’s model

13. 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

14. Summary • Work is progressing • Acceptance analysis mostly completed; currently checking other energies and yield stability • More 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

15. Back-up slides

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

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

22. 6o Acceptance Solutions • ||  3.6% • Removed edge bins with a secondary process • Corrected remaining edge imperfections with • a secondary acceptance correction

23. 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

24. 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. • Carbon cross section analysis to verify the absolute • normalization of the data.

25. Radiative Tail & Finite Acceptance

26. Carbon Cross Section 2.007 GeV/c

27. Elastic Asymmetry Analysis Work by V. Laine`

28. 3He Elastic Acceptance Delta ytg W-M

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

30. Kinematic Coverage