Forschungszentrum Jlich

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Towards Polarized Antiprotons
Hans Ströher (IKP, FZ-Jülich, Jülich, Germany)
Inaugural Meeting VIQCD Nov. 30, 2007 FZ-Jülich
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Motivation
FAIR at GSI, Darmstadt
HESR High Energy Storage Ring
Antiproton Beams
PANDA Internal Detector Hadron Physics
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Motivation
FAIR at GSI, Darmstadt
PAX What about
polarized antiprotons?
HESR High Energy Storage Ring
Antiproton Beams
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A New Initiative
Antiproton Polarizer (AP), Experimental Storage
Ring (ESR)
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Historical Remark
LEAR Proposal (1985)
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Overview

• Why Polarization?
• Polarization of Matter Particles ?
• How to polarize Antiprotons?
• FILTEX Experiment
• Road to Polarized Antiprotons
• Physics Case
• Summary and Outlook

Paolo Lenisa
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Polarization
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Polarization of Stable Particles e
Electron polarization buildup in synchroton
Sokolov-Ternov effect self-polarization via
synchrotron radiation
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Polarization of Stable Particles p
(Anti-)proton polarization buildup in a storage
ring Self-polarization via Stern-Gerlach effect
(Spin Splitting)
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Polarization of Stable Particles p
EPAC 1988
(Anti-)proton polarization buildup in a storage
ring Self-polarization via Stern-Gerlach effect
(Spin Splitting)
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Spin Filtering
Interaction with polarized nuclei

• is the only successfully tested method
  to effectively polarize
  antiprotons

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Spin Filtering

• (Spin-dependent) interaction of beam particles
  with polarized target nuclei (transverse case)
• Polarization buildup of a beam in a storage ring
• ? optimize achieved polarization against
  particle loss
• via filtering time
• ? Example FILTEX

s0 spin-independent, s spin-dependent
cross-section Q target polarization
dt target thickness, frev revolution frequency
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FILTEX (1992)
FILTEX Setup at TSR (MPI-KH Heidelberg)
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FILTEX (1992)
FILTEX Setup at TSR (MPI-KH Heidelberg)
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FILTEX (1992)
FILTEX Setup at TSR (MPI-KH Heidelberg) Proof-of-p
rinciple of spin filtering
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FILTEX (1992)
FILTEX Result (F. Rathmann. et al., PRL 71, 1379
(1993)) Observation of polarization build-up
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How does Spin Filtering work ?
a) Nucleon-nucleon interaction ?
different for proton and antiproton b)
Electron-nucleon interaction ? QED at work,
i.e. e-p identical to ep c) both a)
and b)
? Clarification of this question is the most
important/urgent issue!
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FILTEX (1992)
hadronic only em hadronic
Exp
Meyer, Horowitz (1995) Milstein, Strakhovenko
Nikolaev, Pavlov (2005) FILTEX does not
provide the answer
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The Road to p
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Steps towards Polarized Antiprotons

• Step 1 Depolarization of polarized protons in
  electron
• cooler
• Step 2 Spin filtering with a proton beam
• (FILTEX at higher p-energy)
• ? at COSY
• Step 3 Spin filtering with an antiproton beam
• ? at CERN/AD
• ? Parameters of an antiproton polarizer ring
  (APR)

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Step 1

• Depolarization studies

Polarimetry w/ STT
? Inverse process Unpolarized electrons Polarized
protons
Set-up ready first test measurement performed in
Nov.07
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Step 1

• Depolarization studies

Set-up ready first test measurement performed in
Nov.07 Beamtime for measurement in I/2008
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Step 2

• Proton spin filtering

WASA
Design and construction of low-b section in
COSY started experiments foreseen in
2009/10
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Step 3

• Antiproton spin filtering

Target
Snake
E-Cooler
Design and construction of set-up started
experiments foreseen in 2010/11
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and then The APR
APR
Large acceptance needed!
Sketch of the APR/HESR facility (F. Rathmann et
al., PRL 94, 014801 (2005))
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and finally HESR-CSR-APR Complex
Stand-alone Collider
Sketch of the HESR-CSR-APR complex (From
PAX-Proposal)
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• Summary and Outlook
• Polarized antiprotons will be a unique
  opportunity for FAIR !
• Physics case is outstanding (Transversity)
• Major technological challenges (foremost HOW?)
• Spin-filtering is only viable method yet
• Necessity of preparatory tests (w/ p and p )
• PAX-collaboration is committed to tests, design
  and physics
• program (long term project ? FAIR upgrade)

A one-time opportunity (now and here or never) !
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• The End
• -
• Thank you very much
• for your attention
• Good luck for VIQCD !