The Second Generation HAPPEX Experiments

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The Second Generation HAPPEX Experiments

• Richard Holmes
• for
• The HAPPEX Collaboration
• California State University, Los Angeles -
  Syracuse University -
• DSM/DAPNIA/SPhN CEA Saclay - Thomas Jefferson
  National Accelerator
• Facility - INFN, Rome - INFN, Bari - Harvard -
  Indiana University -
• University of Virginia - University of
  Massachusetts - Florida
• International University - University of New
  Hampshire - Massachusetts
• Institute of Technology - College of William and
  Mary in Virginia
• Parity Violation and Hadronic Structure /
  Grenoble, 9 Jun 2004

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The HAPPEX Experiments

• A look back HAPPEX, ep Q20.5 (GeV/c)2
• HAPPEX-H ep, Q20.1 (GeV/c)2
• HAPPEX-He e4He, Q20.1 (GeV/c)2
• PREX ePb, Q20.01 (GeV/c)2

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PVES and strange form factors
For hydrogen
gt Measurement of APV yields linear combination
of GsE, GsM Related at Q20 to ?s, ?s.
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A look back HAPPEX

• Hall A Proton Parity Experiment (JLAB E91-0910)
• Using PVES to access strange quark contributions
  to vector form factors
• ep at Q20.5 (GeV/c)2, 12.3 degrees
• Phys. Rev. Lett. 821096-1100,1999
• Phys. Lett. B509211-216,2001
• Detailed paper accepted for PRC - arXiv
  nucl-ex/0402004

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HAPPEX results
APV -14.92 0.98 (stat) 0.56 (syst) ppm gt
(GsE 0.392GsM) 0.014 0.020 (exp) 0.010
(FF)
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The next step

• This is kind of small!
• No strange effects?
• Need better sensitivity?
• Accidental cancellation at this Q2?
• Extrapolation to Q20 to access ?s, ?s?
• Separation of GsE , GsM?
• gt Two new experiments at smaller Q2

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HAPPEX-H (JLAB E99-115)

• Polarized e- on 1H
• Q2 0.1 (GeV/c)2, 6?
• APV 1.6 ppm
• ?A 5 (stat) 2.5 (syst)

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HAPPEX-He (JLAB E00-114)

• Polarized e- on 4He
• Q2 0.1 (GeV/c)2, 6?
• APV 8.4 ppm
• ?A 2.2 (stat) 2.1 (syst)

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Helium and strange form factors
For helium
gt APV sensitive only to GsE Clean measurement of
?s.
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PREX (JLAB E00-003)
Pb Radius Experiment Use PVES to measure Rn/Rp

• Polarized e- on 208Pb
• Q2 0.01 (GeV/c)2, 6?
• APV 0.5 ppm
• ?A 3 (stat) 1.1 (syst)

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What's new

• New septum magnets
• New target cell
• Improved polarized source
• Improved polarimetry
• New Cerenkov detectors

• New luminosity monitor
• New profile scanner
• New beam monitors
• Improved DAQ

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Septum magnets

• Minimum scattering angle 12.5 -gt 6.0
• Installed and commissioned 2003-2004

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Target cells
"Beer can", as used in HAPPEX-I
New "race track" design
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Polarized source

• Two amplitude control systems (IA, PC)
• PZT mirror for position control
• IHWP for slow helicity reversal
• RHWP for control of position/intensity
  systematics
• Lens to image beam onto photocathode
• GaAs photocathode - 80 polarization, 100 ?A

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Beam Requirements
Property Nominal Jitter (30 Hz) Hel corr
(run) Energy 3.2 GeV lt 80 ppm lt 13
ppb Current 100 ?A lt 1000 ppm lt 600
ppb Position 0 lt 12 ?m lt 2 nm Angle 0 lt 12 ?rad lt
2 nrad Halo lt100 Hz/?A _at_ 3 mm
Thanks to hard work by the source group in
collaboration with HAPPEX personnel, we believe
these requirements will be achievable. See talk
by Gordon Cates for more.
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Polarimetry

• Møller Main uncertainty is foil polarization
  ?p/p 2 achievable
• Compton Added electron recoil detector since
  HAPPEX-I ?p/p 1 achievable at high energy

• Big challenge for PREX - high current, low
  energy. Plan to upgrade Compton with green laser
  gt 1 in 16 hours

Compton GEANT4 monte carlo
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HRS
HAPPEX-H detector
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HAPPEX-H Detector geometry
Cerenkov detectors overlap the elastic line
above the focal plane
Hydrogen geometry
L geometry design
Clean rejection of inelastic events
He detector (H detector) / 2 !
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Assembly at Saclay
PMT
Brass-quartz stack
Light guide
Filter box
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Profile scanners
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Position monitoring
Goal (30 Hz) ??xlt 1.2 ?m in each BPM
Existing stripline position monitor Resolution
1.8 ?m
New cavity position monitors
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Luminosity monitors

• Target boiling
• Beam parameters
• Electronics noise

Tested to 200 ppm resolution
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Experimental impact
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Lead target
Diamond has high thermal conductivity
40 watts disspated by 50 ?A
Active cooling by liquid helium
Scattering from 12C well-understood
Successfully tested in Hall A
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Schedule
4-7 June '04 Installation (target, detectors,
sieve slit) 8 June Optics commissioning 9-10
June Configuration change (sieve slit, target
work) 11-16 June HAPPEX-He 17-18
June Configuration change (detector change) 19
June - 2 July HAPPEX-H 3 - 7 July Down (Lab
holiday and maintenance) 8 July Restore 9 - 25
July HAPPEX-H summer '05 HAPPEX-H and HAPPEX-He
concluded
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Beam modulation
Aphysics Adet - AQ ??E ??i?xi
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A walk down the beamline
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A walk down the beamline
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A walk down the beamline
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A walk down the beamline
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A walk down the beamline