Vincent Sulkosky

University of Virginia

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

Hall A Collaboration Meeting

January 20th, 2013

E97-110: Small Angle GDH

Experimental Status Report

1

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

2

Experiment E97-110

Inclusive experiment:

Scattering angles of 6◦ and 9◦

with superconducting septum

magnet (RHRS only)

Polarized electron beam:

Average Pbeam = 75%

Pol. 3He target (para & perp):

Average Ptarg = 40%

Measured polarized cross-

section differences

Xee )',(He3

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

3

Kinematic Coverage

4

Horizontal lines: at constant Q2

Kinematic Coverage,

including E94-010

5

Work in Progress (2013) Pertains only to second run period.

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 completed

Asymmetry analysis of the other three elastic data sets completed

Finalize acceptance (V. Sulkosky)

Systematic uncertainty determination in progress

Cross section consistency checks in progress

Radiative Corrections

Preliminary work done by J. Singh

Work continued by T. Holmstrom (Longwood)

Work on going by R. Zielinski for g2p (UNH)

Estimation of QE contribution to neutron results (V. Sulkosky)6

2016 Update

New collaborators:

Chao Peng (Duke): analysis on the 3He moments

Nguyen Ton (UVA): first period analysis

Finalized acceptance (V. Sulkosky)

Systematic uncertainty determination

Cross section consistency checks

Radiative Corrections in progress

Preliminary work done by J. Singh

Work continued by T. Holmstrom (Longwood), M.

Meziane (Duke) and C. Peng

Work on going by R. Zielinski for g2p (UNH)

Estimation of QE contribution to neutron results (V.

Sulkosky) 7

Acceptance Systematics

8

• The acceptance systematic uncertainty has

three main components:

a) General normalization uncertainty determined

either from the geometric shape or a cut study

from simulation. Uncertainty ~ 1-2%.

b) Secondary acceptance corrections due to adjacent

momentum setting discontinuities caused by

inadequate coverage of the 𝛿 acceptance for the

optics calibration. Uncertainty ~ 1-2%.

c) Finite acceptance and bin-centering corrections.

Residual Point-to-Point Systematic

9

• Loose acceptance cuts result in a bow affect, which is

largely removed with tighter cuts.

• Residual effect near edge of 𝛿𝑝 acceptance.

2.845 GeV, Residual Corrections

10

Before Corrections After Corrections

2.845 GeV, 6 degrees

11

Regions where momentum settings overlap agree well,

after secondary acceptance corrections are applied.

Cross Section Experimental

Systematics (3He + Nitrogen)

Energy

[MeV]

Angle

[deg]

Normalization

[%]

Point-to-point

[%]

2135 6 2.7 1.8

2845 6 2.9 1.2-2.0

4209 6 3.1 1.6-1.8

1147 9 3.0 1.5

2234 9 2.8 0.4-1.5

3319 9 2.8 1.2-1.3

3775 9 3.4 1.4-2.1

4404 9 3.0 1.2-1.412

The nitrogen subtraction contributes a small amount,

but less than 1%.

Cross Section Smoothing

13Plots from Chao Peng

First Period Target Polarimetry

1. Cell characteristics are available from UVA:

• Window and wall thicknesses, nominal densities

• https://userweb.jlab.org/~singhj/runsummary/

2. Junhao Chen analyzed the calibration data for NMR

and EPR with septum magnet off

3. Junhao is now a graduate student at W&M and plans

on finishing the work with the septum magnet on.

Information from Feb. 5, 2014

14

Polarimetry C Stat. Syst.

NMR-EPR 15.224 0.020 0.580

NMR-water 14.304 0.178 0.515

NMR-water

w/o Apr7,4

14.345 0.191 0.516

Focal plane phi and y

First Period Acceptance

15Plots from Nguyen Ton

Optics/Acceptance

Procedure from Nilanga Liyanage:

1. By fitting the first period sieve slit data, a set of forward matrix

elements was obtained.

These matrix elements work only within the momentum range

of -0.7% to 2.5%; this cut should always be used with data and

simulation for these runs.

2. Using the forward matrix elements, the focal plane variables y

and 𝜑 are reconstructed in the simulation; a set of cuts

enclosing the acceptance volume for the broken septum case

is determined in the yfp and 𝜑fp and 𝛿 space.

3. By running the simulation (SAMC) one can get the phase

space acceptance within this volume.

16

Acceptance Procedure and Progress

1. Calculate the carbon elastic cross section for the first period runs (using the proper cuts and the phase-space from the simulation). Compare the experimental cross sections to simulation.

2. Then calculate 3He elastic cross-section and compare to simulation.

3. Hai-jiang Lu started this study:

a) Preliminary elastic asymmetries and cross sections were calculated (2009)

b) Initial comparison with simulation started (2011)

4. Nguyen Ton has resumed work on this task (2015):

a) Started with first period data

b) Now working on second period carbon data to test the procedure on a well known acceptance

17

1C 1D

2C 2D

SA=86*E-6 [sr]SA=99*E-6 [sr]

~17%

Sieve surveySimulation

First Period Carbon Cross Section

18Plots from Nguyen Ton

19

Faddeev Calculations

• Received Faddeev calculations from A. Deltuva

(Hannover group) for cross sections and asymmetries

for all first and second period kinematics versus ν.

χpt – Chiral Perturbation Theory20

First Moment of g1

χpt – Chiral Perturbation Theory21

First Moment of g1

E97-110 Spin Polarizabilities

22

Summary

Work is nearing completion for the second period

New collaborators working on 3He and first period analyses

Acceptance analysis completed; need to apply bin-centering corrections

Radiative corrections in the process of being finalized:1. 3He Elastic tail subtraction with finite acceptance and

collimator effects included (V. Sulkosky)

2. Smoothing of the data completed (T. Holmstrom, M. Meziane and C. Peng)

3. Model for the two lowest energies

4. Determine systematics

Draft of first paper completed and internally circulated

23

Back-up slides

24

2.234 GeV, 9 degrees, Nitrogen

Subtraction

25

3.319 GeV, 9 degrees, Elastic Tail

Subtraction

26

3.775 GeV, 9 degrees, Elastic Tail

Subtraction

27

Stability of Cross Sections

Problematic beam trip cuts Good beam trip cuts

28

Axial Anomaly and the LT Puzzle

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

29

Target 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 Uncertainty

Penelope 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%

30

Systematic Uncertainties

31

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

32

Rosetail Updates

1. Updated the 3He form factor parametrization to use Amroun et al., only affects the version of rtails used for the punch-through effect.

2. Updated the physical constants, radiation lengths, formulas used by Stein, and the values for the collisional thickness and losses as determined by Jaideep.

3. Updated the code to calculate the tails for ∆𝜎‖, ⊥

, since the punch-through version of rtails did not produce tails for these quantities.

4. Technical report “Update on Corrections to Radiative Tails for E97-110”:

http://hallaweb.jlab.org/experiment/E97-110/tech/punchthru_update.pdf

6 Degree Angular Acceptance

34

Acceptance shape from SAMC

9 Degree Angular Acceptance

35

Acceptance shape from SAMC

Faddeev Calculations

from A. Deltuva

36

• Received Faddeev calculations from Hannover group

for cross sections and asymmetries for both first and

second period kinematics versus ν.

1. At the low-energy end, if nonrelativistic 3N c.m. excitation

energy is below 5.5 MeV, the breakup is not allowed.

2. At the high energy end, if excitation energy > 200 MeV, the

calculations are not reliable since in that regime there are

structures in the N-Delta potential that are not realistic

and are not carefully treated numerically.

3. Calculations should not be shown beyond our group

until we share the comparisons with Arnas.

Delta Acceptance

E94-010

E97-110

• Flat region of

-acceptance

is much smaller

with Septum

• Simulation is

not perfect on

the falling edges

37