Happex Status Report

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Happex Status Report
Ryan Snyder University of Virginia
Hall A Collaboration Meeting University of
Virginia June 23, 2005
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Looking forward to 05
Suggestions of positive GMs from 2004 data set
will be well tested by final HAPPEX-II result
He nucl-ex/0506010 H nucl-ex/0506011
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Timeline
June 8-22 Helium June 24 - July 26
Hydrogen August 2004 He results
(prelim) October 2004 Hyd. results
(prelim) March 25, 2005 Final results
presented 2005 run starting July 2005
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The experiment (basic idea)

• 3 GeV beam
• LH2 , He target
• 6 º scattering angle (lab frame)
• Q2 0.1 GeV2

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How is the PV Asymmetry Measured?
1 ppm 5 measurement gt 4x1014 counts
Beam Helicity - 30 Hz
PV asymmetry between window pair is measured 30
M times to achieve full precision
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Beam Asymmetries
Araw Adet - AQ ??E ??i?xi

• natural beam jitter (regression)
• beam modulation (dithering)

Slopes from
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Beam Asymmetries
Five l/2 waveplate reversals (slugs)
AI-0.1/-0.3 ppm
AE-5.7/-2.6 ppb
DX8.5/-2.9 nm
Dq-10.5/-7.2 nrad
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Superlattice vs. strained GaAs
Superlattice Pe86 !
Presently, tests indicate superlattice has good
lifetime.
-Will be installed on gun 3 on July 1st
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COMPTON POLARIMETRY
Hall A
e- detector
Compton Int. Point
g detector

• Most important for Helium (cant run without)
• Hyd. will run first if not working

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Septum Heating
8
6
4
-20 minutes
-40 minutes
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Sweeper Magnet

• Used to bend Moller flux away from acceptance of
  Septum

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Focal Plane Detectors
Two segment L-shape covers hydrogen elastic
peak Smaller 4He elastic peak requires only ½
single-segment detector
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Cavity Monitors

• Electronics work
• Yet to be used reliably but there are encouraging
  signs
• Could still help us

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Other improvements

• Integrating Compton (H. Benoaum)
• Online Software (B. Moffit)
• S0 trigger (B. Moffit)
• Streamlined Source Setup - He (R.
  Snyder)

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Shifts
Sign up here http//hallaweb.jlab.org/e
xperiment/HAPPEX/
Special training needed for He target
- connected to CHL
We need 800 shift workers
Asking that all authors take 8 shifts