1. 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 December 15 th, 2011

2. Motivation Precision measurement of the moments of spin structure functions at low Q 2, 0.02 to 0.24 GeV 2 for the neutron ( 3 He) 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 GeV 2 Finalizing systematic uncertainties and first publication

3. Neutron Spin Polarizabilities

4. E97-110 Spin Polarizabilities

5. Experiment E97-110 Inclusive experiment: ◦ Scattering angles of 6 ◦ and 9 ◦ ◦ Polarized electron beam: Avg. P beam = 75% ◦ Pol. 3 He target (para & perp): Avg. P targ = 40% Measured polarized cross- section differences M. Amarian et al., PRL 89, 242301 (2002)

6. Current Work Waiting on final target polarization (J. Singh) Elastic 3 He analysis (V. Laine) ◦ 2.1 GeV asymmetry and cross section completed ◦ 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. 9 o Acceptance Septum Mistuned 15% uncertainty Difficulty: ◦ Saturation effect is present ◦ A few settings were mistuned with the septum magnet ◦ tg -acceptance appears squeezed at the highest field settings ◦ Varying acceptance cuts does not help

8. Interpolation 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. |  |  3.6% Removed edge bins with a secondary process Corrected remaining edge imperfections with a secondary acceptance correction

9. Tools for Carbon Cross Sections Single carbon foil data were taken for each of the momentum settings for E = 3.775 GeV Single Arm Monte-Carlo (SAMC) from A. Deur ◦ Uses John LeRose transport functions at 9º and apertures ◦ 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.fhttps://userweb.jlab.org/~bosted/F1F209.f ◦ Elastic radiative tail was removed using Rosetail averaged over the solid angle acceptance of E97-110

10. Septum Entrance Apertures Shift large angle side by 7mm Shift small angle side by 5 mm

11. Carbon Cross Section 2.007 GeV/c

12. Carbon inelastic cross sections

13. Summary Work is progressing Acceptance analysis to be completed soon More work needs to go into radiative corrections: 1.Smoothing of the data completed (T. Holmstrom) 2.Finite acceptance for elastic tail subtraction 3.Model for the two lowest energies Draft of first paper completed and internally circulated

14. Radiative Tail & Finite Acceptance

15. Axial Anomaly and the  LT Puzzle N. Kochelev and Y. Oh; arXiv:1103.4891v1

16. Systematic Uncertainties

17. Analysis Status Preliminary results for the moments have been extracted at constant Q 2. Collimator background is mostly from polarized 3 He ◦ 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.)

18. 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

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

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

21. 6 o Acceptance Solutions |  |  3.6% Removed edge bins with a secondary process Corrected remaining edge imperfections with a secondary acceptance correction

22. 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

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

24. Elastic Asymmetry Analysis Work by V. Laine`

25. 3 He Elastic Acceptance Delta y tg W-M

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

27. Kinematic Coverage