e97-110: small angle gdh experimental status report

Vincent SulkoskyMassachusetts Institute of Technology

Spokespeople: J.-P. Chen, A. Deur, F. Garibaldi

Hall A Collaboration MeetingJune 13th, 2013

E97-110: Small Angle GDHExperimental Status Report

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

E97-110 Spin Polarizabilities

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

Xee )',(He3

M. Amarian et al., PRL 89, 242301 (2002)

Work in Progress Finalized target analysis:

Density and NMR/EPR polarizations (J. Singh)Target polarization uncertainties (V. Sulkosky)

Elastic 3He analysis (V. Laine) 2.1 GeV asymmetry and cross section completedAnalysis 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. SinghWork 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 degrees113 runs for Priapus at 9 degrees

Calib. Source Penelope 6 degs

Priapus 6 degs Priapus 9 degs

Water NMR 6.8% 6.7% 6.7%EPR-NMR 3.9% 4.4% 4.0%

EPR 2.2% 2.2% 2.2%

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.

Period Total UncertaintyPenelope 2.9%

Priapus 6 degs w/ EPR 3.0%Priapus 6 degs w/o EPR 5.1%Priapus 9 degs w/ EPR 2.9%Priapus 9 degs w/o EPR 4.8%

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 included3. Model for the two lowest energies

Draft of first paper completed and internally circulated

Back-up slides

Stability of Cross SectionsProblematic beam trip cuts Good beam trip cuts

Axial Anomaly and the LT Puzzle

N. Kochelev and Y. Oh; arXiv:1103.4891v1

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

9o Acceptance

Septum Mistuned5-10% 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: https://userweb.jlab.org/~bosted/F1F209.f

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

3He Cross SectionsApplied very tight acceptance cuts on angles

with P. Bosted’s 2009 model

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

Summary of Cut StudyCut sc

[deg]tg

[mrad]

tg

[mrad]

Ytg

[cm]Pdiff [%]

[%]

Na1 9.002 8 3 4 -1.3 3.1

Na2 9.019 15 3 4 0.1 2.3

Na3 9.056 30 3 4 1.1 2.1

Na4 8.986 15 6 4 --- ---

Na5 8.920 15 12 4 -1.3 2.0

Na6 8.789 15 -18,8 4 2.0 4.1

Na7 8.67 15 -12,8 4 1.3 2.0

Na8 8.987 15 -6,12 4 -4.2 1.5

Na9 8.996 15 -6,15 4 -7.1 2.1

Na10 8.994 15 6 8 -2.1 1.5

Na11 9.249 20 6 8 -1.6 1.8Cross section cut sensitivity is typically less than 2%,

as long as tg is kept away from the small angle acceptance side

Updated SAMC CodeWork done by V. Laine`SAMC rewritten in C++ from FortranImproved implementation of target

collimator cutsRaster correction by calculating electron’s

travel length through the cellRadiative 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

E94-010

E97-110

• Flat region of -acceptance is much smaller with Septum• Simulation is not perfect on the falling edges

3He Elastic AcceptanceDelta

ytg W-M

tg tg

Kinematic Coverage