E97-110: Small Angle GDH Experimental Status Report · 2016. 1. 20. · Motivation Precision...
Transcript of E97-110: Small Angle GDH Experimental Status Report · 2016. 1. 20. · Motivation Precision...
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
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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
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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)
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Kinematic Coverage
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Horizontal lines: at constant Q2
Kinematic Coverage,
including E94-010
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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
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• 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
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• 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
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Before Corrections After Corrections
2.845 GeV, 6 degrees
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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
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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.
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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
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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
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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
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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
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Back-up slides
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2.234 GeV, 9 degrees, Nitrogen
Subtraction
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3.319 GeV, 9 degrees, Elastic Tail
Subtraction
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3.775 GeV, 9 degrees, Elastic Tail
Subtraction
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Stability of Cross Sections
Problematic beam trip cuts Good beam trip cuts
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Axial Anomaly and the LT Puzzle
N. Kochelev and Y. Oh; arXiv:1103.4891v1
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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%
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Systematic Uncertainties
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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
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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
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Acceptance shape from SAMC
9 Degree Angular Acceptance
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Acceptance shape from SAMC
Faddeev Calculations
from A. Deltuva
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• 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
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