The PAX experiment

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2 workshop on the QCD structure of the
nucleon 12-16 june 2006 Monte Porzio Catone
Polarized Antiproton at FAIR

• The PAX experiment
• P.F.Dalpiaz
• Ferrara

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Transversity
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The most direct probe
valence quarks
J. Ralston and D.Soper, 1979 J. Cortes, B. Pire,
J. Ralston, 1992
Why it works
Elementary LO interaction
LO interaction has no initial gluons
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The measurament
sea quarks
At GSI-FAIR very large asymmetry expected
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Polarized Antiprotons
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How polarize antiproton?
2006

• Polarized pbar from antilambda decay (1987-90)
• Pbar scattering off liquid H2 target (1995)
• (Niinikoscki and Rossmanith 1985) Stern-Gerlach
  separation of a stored beam
• Very recently (Th. Walcher et al) polarized
  electron beam

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How polarize antiproton?
2006
The Spin Filter Method
Experimentally tested in 1992
P.L.Csonka,1968, NIM 63 (1968) 247
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Principle of spin filter method

• Multiple passage of a stored beam in a Polarized
  Internal Target (PIT)

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parallel spin scatter more often then
antiparallel spin, resulting in a polarized
(less intense )beam,after passages in a polarized
target
Total cross section
Low energy scattering
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Principle of spin filter method
Polarized H target
Polarization Staging Signals Timeline
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The filter
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gas polarized hydrogen target

• a short review

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ABS
Atomic Beam Source
Pz 1gt 4gt Pz- 2gt 3gt
Pe 1gt 2gt Pe- 3gt 4gt
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Hydrogen gas targets densities

• 1970
• 1985, Novosibirsk,Zurig
• 1998,HERMES
• 2004,RHIC
• 1965 -
• 1984,W.Haeberli

accumulation cell
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The storage cell

• Material75 mm Al with Drifilm coating
• Size length 400mm, elliptical cross section (21
  mm x 8.9 mm)
• Working temperature 100 K ( variable 35 K 300
  K)

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Performance of Polarized Internal Targets
HERMES Stored Positrons
PINTEX Stored Protons
Transverse Field (B297 mT)
Targets work very reliably (months of stable
operation)
Polarization Staging Signals Timeline
Polarization Staging Signals Timeline
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Test experiment on the filter method

• The TSR experiment with protons 1992

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Experimental Setup at TSR (1992)
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The FILTEX experiment has runned with state 1
hydrogen 80 of electronic polarization 80 of
nuclear polarization
Transverse target polarization
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1992 Filter Test at TSR with protons, T23 MeV
F. Rathmann. et al., PRL 71, 1379 (1993)
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SPIN filtering works! but how?
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FILTEX RESULTS
Observed polarization build-up
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Two interpretations of FILTEX result

• 1994. Meyer and Horowitz three distinct effects
• Selective removal through scattering beyond
  ?acc4.4 mrad (sR?83 mb)
• Small angle scattering of target prot. into ring
  acceptance (sS?52 mb)
• Spin-transfer from pol. el. of target atoms to
  stored prot. (sE?-70 mb)
• s1 sR? sS? sE? 65 mb

• 2005. Milstein Strakhovenko Nikolaev
  Pavlov only one effect
• Selective removal through scattering beyond
  ?acc4.4 mrad (sR?85.6 mb)
• No contribution from other two effects
• (cancellation between scattering and
  transmission)
• s1 85.6 mb

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Spin-filtering Present situation
Spin filtering works, but

• controversial interpretations of TSR result

• no experimental basis for antiprotons

Experimental tests - Protons (40-800 MeV)
(COSY) - Antiprotons (5MeV-3GeV)(AD)
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How to disentangle
hadronic and electromagnetic contributions?
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Polarizing cross-section for the two models
TSR
A measurement of s with 10 precision is needed.
Polarization measurement with DP/P 10
requested.
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How to disentangle had. and elm contributions?
1 Injection of different combination of
hyperfine states
Different combinations of elm. and hadronic
contributions
Null experiment (elm. component 0) possible in
strong holding field
Inj. states Pe Pz Interaction Holding field Holding field
1gt 1 1 Elm. had. Transv. Long. Weak (20 G)
1gt4gt 0 1 Only had. Long. Strong. (3kG)
1gt2gt 1 0 Only elm Long. Strong. (3kG)
Experiment at AD will require both transverse and
longitudinal (weak)field.
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How to disentangle had. and elm contributions?
2 Use of different energy dependence of the
processes Measurement at different energies
Spin-transfer
Hadronic
100
10
selm? (mbarn)
1
10
100
1000
T (MeV)
(Transverse case)
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Spin-filtering studies at COSY

• Goal deeper understanding spin-filtering
  mechanism
• Disentangle between two interpretations of TSR
  result.
• Electromagnetic hadronic contributions

(20-120MeV 175-2880 MeV)
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Experimental setup

• Low-beta section
• Polarized target (HERMES)
• Detector
• Snake
• Commissioning of AD setu-up

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Low beta section

• bx,ynew0.3 -gt increase a factor 30 in density
  respect ANKE
• Lower buildup time, higher rates
• Higher polarization buildup-rate due to higher
  acceptance
• Use of HERMES target (in Jülich since March 2006)

S.C. quadrupole development applicable to AD
experiment
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Detector concept

• Reaction
• p-p elastic (COSY)
• p-pbar elastic (AD)
• Good azimuthal resolution (up/down left/right
  asymmetries)
• Low energy recoil (lt8 MeV)
• Teflon cell requested

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Teflon cell (IUCF 2002)
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Detector concept

• Reaction
• p-p elastic (COSY)
• p-pbar elastic (AD)
• Good azimuthal resolution (up/down asymmetries)
• Low energy recoil (lt8 MeV)
• Teflon cell
• Silicon tracking telescope

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The ANKE silicon tracking telescope
cluster beam
COSY beam
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Detector concept

• Reaction
• p-p elastic (COSY)
• p-pbar elastic (AD)
• Good azimuthal resolution (up/down asymmetries)
• Low energy recoil (lt8 MeV)
• Teflon cell
• Silicon tracking telescope
• Angular resolution on the forward particle for
  p-pbar
• AD experiment will require an opening-cell

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ANKE vs new interaction point
Cross sections
Lifetimes
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ANKE vs new interaction point
Polarization
T40 MeV Ninj1.5x1010
PIT Filter. time Polar. Total rate Meas. Time (DP/P10)
ANKE 2t 16 h 1.2 7.5x102 s-1 44 min
ANKE 5t 42 h 3.5 5x10 s-1 26 min
New IP 2t 5 h 16 2.2x104 s-1 1 s
New IP 5t 13 h 42 1.5x103 s-1 lt 1 s
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Antiproton polarization build-up

• Test at AD

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ANKE
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Commissioning of ANKE PIT
Propedeutical studies to spin-filtering
experiments
Goal installation of a storage cell with a
polarized target in COSY Electron-cooling at
injection with storage cell Stochastic cooling
at 700 MeV Cooler stacking to increase particles
in the ring
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Storage Cell Setup (coll. Ferrara FZJ)
XY-table
Frame with storage cell and aperture
Target chamber
400mm
COSY beam
Feeding tube l 120 mm, Ø 10
mm Extraction tube l 230 mm, Ø 10
mm Beam tube l 400 mm, 20x20 mm2
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Storage cell and stochastically cooled beam
Cooling off
Tp831 MeV
Cooling on
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Target Thickness (from pp?dp)
Storage Cell
Jet
Method Jet atoms/cm2 Storage Cell atoms/cm2
ABS flux ( cell geometry) (1.60.1)1011 (1.90.1)1013
Rates (pp?dp) (1.50.1)1011 (2.10.1)1013
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Cooler Stacking into the Storage Cell

• 28 stacks followed by
• 2s electron cooling
• after 58s acceleration toTp600 MeV

Cooler Stacking allows for higher polarized beam
intensities with cell. 2.51010 protons have
been injected in the ring
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Ferrara is building an ion-deflector
Next step Installation of the Lamb-shift
polarimeter
October 2006
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Antiproton polarization build-up

• AD

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Measurements at AD at CERN (2009-2010)
study of spin-filtering in pp scattering
T5 MeV2.8 GeV Np 3107
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Timeline

• Fall 2006 Submission of Technical Proposal
  for COSY
• Spring 2007 Submission of Technical Proposal for
  AD
• 2006-08 Design and construction phase COSY
• 2008 Spin-filtering studies at COSY
• Commissioning of AD
  experiment
• 2009 Installation at AD
• 2009-2010 Spin-filtering studies at AD

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VERY PRELIMINARY

• Polarization build-up implemantation at HESR,FAIR

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PAX ACCELERATOR SETUP
preliminary!
Valence region xgt0.5 4ltQ2lt100GeV2 ATTgt0.3 L?2x1030
1000 events by day
Physics Transversity
EXPERIMENT Asymmetric collider s210GeV2
polarized antiprotons in HESR (p15 GeV/c)
polarized protons in CSR (p3.5 GeV/c)
Internal polarized target with 22 GeV/c
polarized antiproton beam.
s30GeV2
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http//www.fz-juelich.de/ikp/pax
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THE END
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Electron Transfer Polarization
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Filter Test T 23 MeV ?acc 4.4 mrad
Polarization Staging Signals Timeline
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Polarization with hadronic pbar-p interaction
Model A T. Hippchen et al. Phys. Rev. C 44, 1323
(1991)
P
Kinetic energy (MeV)
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pp Elastic Scattering from ZGS
Spin-dependence at large-P? (90cm) Hard
scattering takes place only with spins ??.
D.G. Crabb et al., PRL 41, 1257 (1978)
T10.85 GeV
Similar studies in pbar p elastic scattering
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