Vincent Sulkosky Massachusetts Institute of Technology Spokespeople: J.-P. Chen, A. Deur, F. Garibaldi Hall A Collaboration Meeting December 10 th, 2012 E97-110: Small Angle GDH Experimental Status Report

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

E 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)

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 3 He 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)

9 o Acceptance Septum Mistuned 5-10% uncertainty 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

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: ◦ Elastic radiative tail removed using Rosetail averaged over the solid angle acceptance of E97-110

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

Acceptance Cut Study Acceptance shows sensitivity to loose θ tg cuts

Acceptance Cut Study Acceptance shows sensitivity to loose φ tg cuts, especially on the negative side

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

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

Summary of Cut Study Cut  sc [deg]  tg [mrad]  tg [mrad] Y tg [cm] Pdiff [%]  [%] Na 88 33 4 Na  15 33 4 Na  30 33 4 Na  15 66 44 --- Na  15  12 4 Na  ,8 4 Na78.67  ,8 4 Na  15 -6,12 4 Na  15 -6,15 4 Na  15 66 8 Na  20 66 8 Cross section cut sensitivity is typically less than 2%, as long as  tg is kept away from the small angle acceptance side

Summary Work is progressing Acceptance analysis mostly completed; currently checking other energies and yield stability More work needs to go into radiative corrections: 1.Smoothing of the data completed (T. Holmstrom) 2.Elastic tail subtraction with acceptance and collimator effects included 3.Model for the two lowest energies Draft of first paper completed and internally circulated

Back-up slides

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

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

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

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

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

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

Radiative Tail & Finite Acceptance

Carbon Cross Section GeV/c

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

Kinematic Coverage