Future activities of the COMPASS polarized target

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Future activitiesof the COMPASS polarized target

• N. Doshita
• University of Bochum, Germany

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Contents
The COMPASS experiment
The Polarized Target 2002-2004
Upgrade for 2006
Summary
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CERN and COMPASS
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The COMPASS experiment
Physics data taking started in 2002

• Muon program
• -Nucleon spin structure --- gluon
  contribution
• -Polarized muon beam and polarized nucleon
  target
• Hadron program
• -Meson spectroscopy
• -hadron beam and Hydrogen, carbon target

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Gluon polarization measurement in the COMPASS
Experimentally measurable double spin cross
section asymmetry via PGF
PB Beam polarization PT Target polarization f
Dilution factor N Number of events
Direction of beam polarization
Dilution factor polarizable nucleon rate in
material
?
Direction of target polarization
Aphys ? Gluon polarization
(double spin asymmetry)
Extraction
What kinds of events can be approached to realize
PGF ?

• Open charm production events
• High-PT hadron production events

D0, D0
Low statistics
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Requirement of Polarized Target
Statistical accuracy
-High polarization -High dilution factor -Large
target
COMPASS polarized target

• - Target material 6LiD (high
  dilution factor), 350g
• - Magnetic field 2.5T
  superconducting magnet
• Temperature 60mK and 300mW at
  300mK
• by
  dilution refrigerator

?
Dynamic Nuclear Polarization with Microwave
Deuteron polarization more than 50
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COMPASS polarized target2002 2004
Still pumping line
Magnet 2.5 T solenoid 0.5 T
dipole
3He precooling line
µ beam
69 mrad
Twin target cells 60 cm 60 cm
Mixing chamber 6 L
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Dilution refrigerator
3He Pumping line
Magnet
Beam
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Upgrade for 2006
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Upgrade part 1
Large acceptance
- F 60cm
- 30 gain in statistics
2.5T Solenoid, 0.5T Dipole
- Solenoid lt 100 ppm homogeneity
- 25 L/hour Liq. He
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Upgrade part 2
3 target cells
To reduce false asymmetry
Large cavity
Fit on new magnet
talk of Y. Kisselev
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Upgraded PT system for 2006
Ready in next spring
Data taking June 14th
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COMPASS Oxford Danfysik magnet

• OD magnet assembly was finished at December 2004
  and has been tested in Saclay.
• It is almost finished to test the magnet and
  construct its instruments.
• The magnet is being delivered to CERN in the end
  of this month.

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COMPASS OD magnet
1st attempt to get uniform field (June 24th)
obtained less than 100 ppm homogeneity now
100 ppm
Request is 100 ppm
Target region 130cm
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Summary
- The COMPASS polarized target has been used
since 2002.
- The system is upgraded for 2006 .
- 3 target cells - New large acceptance magnet -
New microwave cavity
- Expect high statistics and high quality data in
2006