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The PAX experiment P.F.Dalpiaz Ferrara

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. Transversity. Drell-Yan. Direct mesurament. The most direct probe. valence quarks.

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The PAX experiment P.F.Dalpiaz Ferrara

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  1. 2 workshop on the QCD structure of the nucleon 12-16 june 2006 Monte Porzio Catone PolarizedAntiproton at FAIR The PAXexperiment P.F.Dalpiaz Ferrara 16 june 2006

  2. Transversity 16 june 2006

  3. Drell-Yan Direct mesurament 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 16 june 2006

  4. The measurament in polarized proton-antiproton scattering valence quarks sea quarks At GSI-FAIR very large asymmetry expected 16 june 2006

  5. Intense beam of never produced Polarized Antiprotons 16 june 2006

  6. Theorethical, never tested 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 16 june 2006

  7. How polarize antiproton? 2006 The Spin Filter Method Experimentally tested in 1992 P.L.Csonka,1968, NIM 63 (1968) 247 16 june 2006

  8. Principle of spin filter method Multiple passage of a stored beam in a Polarized Internal Target (PIT) 16 june 2006

  9. An unpolarized beam has an equal population of spin  longitudinal case transverse case “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 16 june 2006

  10. Polarized anti-p beam Unpolarized anti-p beam Principle of spin filter method Polarized H target 16 june 2006 Polarization Staging Signals Timeline

  11. The filter 16 june 2006

  12. gas polarized hydrogen target a short review 16 june 2006

  13. |1> e- p 1 |1> mj = +1/2 mi=+1/2 |2> mi=-1/2 mi=-1/2 |3> mj = -1/2 mi=+1/2 |4> ABS Atomic Beam Source Pz+ = |1> + |4> Pz- = |2> + |3> Pe+ = |1> + |2> Pe- = |3> + |4> 16 june 2006

  14. Hydrogen gas targets: densities • 1970 • 1985, Novosibirsk,Zurig • 1998,HERMES • 2004,RHIC • 1965 - • 1984,W.Haeberli accumulation cell 16 june 2006

  15. The storage cell • Material:75 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) 16 june 2006

  16. Longitudinal Field (B=335 mT) Dz PT = 0.845 ± 0.028 H Fast reorientation in a weak field (x,y,z) Dzz HERMES H PT = 0.795  0.033 HERMES Performance of Polarized Internal Targets HERMES: Stored Positrons PINTEX: Stored Protons Transverse Field (B=297 mT) Targets work very reliably (months of stable operation) 16 june 2006 Polarization Staging Signals Timeline Polarization Staging Signals Timeline

  17. Test experiment on the filter method The TSR experiment with protons 1992 16 june 2006

  18. Experimental Setup at TSR (1992) 16 june 2006

  19. |1> e- p 1 |1> mj = +1/2 mi=+1/2 |2> mi=-1/2 mi=-1/2 |3> mj = -1/2 mi=+1/2 |4> The FILTEX experiment has runned with state 1 hydrogen ~80% of electronic polarization ~80% of nuclear polarization Transverse target polarization 16 june 2006

  20. 1992 Filter Test at TSR with protons, T=23 MeV Experimental Setup Results F. Rathmann. et al., PRL 71, 1379 (1993) 16 june 2006

  21. SPIN filtering works! but how? 16 june 2006

  22. FILTEX RESULTS Revolution frequency PIT areal thickness PIT polarization Observedcross-section Observedpolarization build-up: 16 june 2006

  23. Two interpretations of FILTEX result 1994. Meyer and Horowitz: three distinct effects • Selective removal through scattering beyond θacc=4.4 mrad (σR=83 mb) • Small angle scattering of target prot. into ring acceptance (σS=52 mb) • Spin-transfer from pol. el. of target atoms to stored prot. (σE=-70 mb) σ1= σR+ σS + σE = 65 mb 2005. Milstein & Strakhovenko + Nikolaev & Pavlov: only one effect • Selective removal through scattering beyond θacc=4.4 mrad (σR=85.6 mb) No contribution from other two effects (cancellation between scattering and transmission) σ1 = 85.6mb 16 june 2006

  24. 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) 16 june 2006

  25. How to disentangle hadronic and electromagnetic contributions? 16 june 2006

  26. Polarizing cross-section for the two models … only had - elm. + had. TSR A measurement of s with 10 % precision is needed. Polarization measurement with DP/P = 10% requested. 16 june 2006

  27. Strong field can be applied only longitudinally (minimal beam interference) Target polarimetry difficult for pure electron polarization. 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 Experiment at AD will require both transverse and longitudinal (weak)field. 16 june 2006

  28. 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) 16 june 2006

  29. 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) 16 june 2006

  30. Experimental setup • Low-beta section • Polarized target (HERMES) • Detector • Snake • Commissioning of AD setu-up 16 june 2006

  31. Low beta section • bx,ynew=0.3 -> 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 16 june 2006

  32. Detector concept • Reaction: • p-p elastic (COSY) • p-pbar elastic (AD) • Good azimuthal resolution (up/down + left/right asymmetries) • Low energy recoil (<8 MeV) • Teflon cell requested 16 june 2006

  33. Teflon cell (IUCF – 2002) 16 june 2006

  34. Detector concept • Reaction: • p-p elastic (COSY) • p-pbar elastic (AD) • Good azimuthal resolution (up/down asymmetries) • Low energy recoil (<8 MeV) • Teflon cell • Silicon tracking telescope 16 june 2006

  35. 3 silicon detector layers • 69 µm silicon • 300/500 µm silicon 128 x 151 segments 51 x 66 mm (≈400 µm pitch) • >5 mmSi(Li) 96 x 96 strip 64 x 64 mm (≈666 µm Pitch) The ANKE silicon tracking telescope cluster beam COSY beam 35 16 june 2006

  36. Detector concept • Reaction: • p-p elastic (COSY) • p-pbar elastic (AD) • Good azimuthal resolution (up/down asymmetries) • Low energy recoil (<8 MeV) • Teflon cell • Silicon tracking telescope • Angular resolution on the forward particle for p-pbar • AD experiment will require an opening-cell 16 june 2006

  37. … elm + had - only had. Acceptance @ ANKE Acceptance @ new-IP ANKE vs new interaction point Cross sections Lifetimes 16 june 2006

  38. New IP ANKE ANKE vs new interaction point Polarization T=40 MeV Ninj=1.5x1010 16 june 2006

  39. Antiproton polarization build-up Test at AD 16 june 2006

  40. ANKE 16 june 2006

  41. 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 16 june 2006

  42. Storage Cell Setup (coll. Ferrara – FZJ) XY-table Target chamber Frame with storage cell and aperture 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 16 june 2006

  43. Storage cell and stochastically cooled beam Cooling off Tp=831 MeV Cooling on 16 june 2006

  44. Target Thickness (from pp→dπ+) Storage Cell Jet 16 june 2006

  45. Cooler Stacking into the Storage Cell • 28 stacks followed by • 2s electron cooling • after 58s acceleration toTp=600 MeV Cooler Stacking allows for higher polarized beam intensities with cell. 2.5·1010 protons have been injected in the ring 16 june 2006

  46. Next step: Installation of the Lamb-shift polarimeter Ferrara is building an ion-deflector October 2006 16 june 2006

  47. Antiproton polarization build-up AD 16 june 2006

  48. Target Snake E-cooler Measurement of effective polarization cross-section. Both transverse and longitudinal. Variable ring acceptance. First measurement at all for spin correlations in pp (not pure text experiment!) Measurements at AD at CERN (2009-2010) study of spin-filtering in pp scattering T:5 MeV÷2.8 GeV Np = 3·107 16 june 2006

  49. 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 16 june 2006

  50. VERY PRELIMINARY Polarization build-up implemantation at HESR,FAIR 16 june 2006

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