Vincent Sulkosky Massachusetts Institute of Technology Spokespeople: J.-P. Chen, A. Deur, F. Garibaldi Hall A Collaboration Meeting June 13 th, 2013 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  Finalized target analysis:  Density and NMR/EPR polarizations (J. Singh)  Target polarization uncertainties (V. Sulkosky)  Elastic 3 He analysis (V. Laine)  2.1 GeV asymmetry and cross section completed  Analysis of the other three elastic data sets in progress  Finalize acceptance (V. Sulkosky)  Fine tuning beam trip cuts for cross section and asymmetry consistency checks  Radiative Corrections  Preliminary work done by J. Singh  Work on going by Tim Holmstrom  Estimation of QE contribution to neutron results (V. Sulkosky)

“Final” Target Polarizations Analysis by J. Singh 6.6%

Run-by-Run Polarizations Significant Drop in Polarization

Polarization Ratios

Re-averaging of Polarizations  Used the total errors, statistical and systematic in a weighted average of polarizations.  EPR polarizations were excluded for 128 runs:  15 runs for Priapus at 6 degrees  113 runs for Priapus at 9 degrees Calib. SourcePenelope 6 degsPriapus 6 degsPriapus 9 degs Water NMR6.8%6.7% EPR-NMR3.9%4.4%4.0% EPR2.2%

Polarization Uncertainties  When EPR is available, the averages are dominated by EPR and NMR calibrated by EPR.  When EPR is unavailable, the averages are dominated by NMR calibrated by EPR and to a lesser extent NMR calibrated by water. PeriodTotal Uncertainty Penelope2.9% Priapus 6 degs w/ EPR3.0% Priapus 6 degs w/o EPR5.1% Priapus 9 degs w/ EPR2.9% Priapus 9 degs w/o EPR4.8%

Penelope at 6 Degrees

Priapus at 9 Degrees

Elastic Asymmetry Analysis Work by V. Laine`

Elastic Asymmetry Analysis Work by V. Laine` Preliminary

Summary  Work is progressing  Target polarizations and uncertainties finalized  Acceptance analysis mostly completed; currently finalizing beam trip cuts and then checking cross section stability  Additional 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

Stability of Cross Sections Problematic beam trip cutsGood beam trip cuts

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

NMR Systematics 1% Reduces systematics from 8.2% to 6.6%

Priapus at 9 Degrees

4.4 GeV Drop in Polarization Significant Drop in Polarization 3.14 GeV/c

4.4 GeV Asymmetries 3.14 GeV/c

Charge Normalized Asymmetries Corrected for Charge and livetime

Systematic Uncertainties

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

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

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

3 He Elastic Acceptance Delta y tg W-M

Kinematic Coverage