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 E 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 E covered region from 0.1 to 0.9 GeV 2 Finalizing systematic uncertainties and first publication

Neutron Spin Polarizabilities

Experiment E 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, (2002)

Kinematic Coverage

Current Work Waiting on final target polarization (J. Singh) Elastic 3 He 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)

Elastic Asymmetry Analysis Work by V. Laine`

3 He Elastic Acceptance Delta y tg W-M

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

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

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

Variation of Acceptance Cuts Varying acceptance cuts does not help

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

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

Summary Work is progressing though slowly Hope to wrap up acceptance analysis soon Major 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 in progress (75% complete) and expect to be internally available this month

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

Systematic Uncertainties

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.)

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

Delta Acceptance E E Flat region of  -acceptance is much smaller with Septum Simulation is not perfect on the falling edges

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