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Marco Contalbrigo – INFN and Università di Ferrara - ITALY

PAX project at FAIR. http://www.fz-juelich.de/ikp/pax. Marco Contalbrigo – INFN and Università di Ferrara - ITALY. Tbilisi, 5 September 2006. Physics Program. Nucleon structure: polarized reactions. Cerenkov. pbar-p elastic. Fixed target experiment (√s<2 GeV):

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Marco Contalbrigo – INFN and Università di Ferrara - ITALY

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  1. PAX project at FAIR http://www.fz-juelich.de/ikp/pax Marco Contalbrigo – INFN and Università di Ferrara - ITALY Tbilisi, 5 September 2006 PAX Polarized Antiproton Experiments

  2. Physics Program PAX Polarized Antiproton Experiments

  3. Nucleon structure: polarized reactions Cerenkov pbar-p elastic Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target Polarized Antiproton eXperiments PAX Polarized Antiproton Experiments

  4. Low-E pp, pd at AD Similar studies in pp elastic scattering Elastic Scattering Polarization build-up studies T=10.85 GeV High-t pp from ZGS, AGS Spin-dependence at large-P (90°cm): Hard scattering takes place only with spins . D.G. Crabb et al., PRL 41, 1257 (1978) PAX Polarized Antiproton Experiments

  5. Cerenkov Proton EFFs Polarized Antiproton eXperiments Nucleon structure: polarized reactions pbar-p elastic Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target PAX Polarized Antiproton Experiments

  6. TWO DIFFERENTS METHODS TWO DIFFERENTS RESULTS JLab PT data SLAC RS data (Phys. Rev.C 68 (2003) 034325) Proton Electromagnetic Formfactors COMPARISON BETWEEN ROSENBLUTH SEPARATION AND POLARIZATION TRANSFER TECNIQUES PAX Polarized Antiproton Experiments

  7. Proton Electromagnetic Formfactors • Double-spin asymmetry in pp → e+e- • independent GE-Gm separation • test of Rosenbluth separation in the time-like region • Single-spin asymmetry in pp → e+e- • Measurement of relative phases of magnetic and electric FF in the time-like region S. Brodsky et al., Phys. Rev. D69 (2004) PAX Polarized Antiproton Experiments

  8. Parton distribution: transversity Cerenkov Drell-Yan Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Polarized Antiproton eXperiments Nucleon structure: polarized reactions pbar-p elastic Proton EFFs Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target PAX Polarized Antiproton Experiments

  9. Leading Twist Distribution Functions L R L R L R L R quark quark’ 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 proton proton’ R L 1/2 -1/2     -     Probabilistic interpretation in helicity base: + f1(x) q(x) spin averaged (well known) - Dq(x) helicity diff. (known) g1(x) No probabilistic interpretation in the helicity base (off diagonal) h1(x) u = 1/2(uR + uL) u = 1/2(uR - uL) Transversity base dq(x) helicity flip (unknown) PAX Polarized Antiproton Experiments

  10. Transversity • Probes relativistic nature of quarks • No gluon analog for spin-1/2 nucleon • Different Q2 evolution than Dq • Sensitive to valence quark polarization Properties: See talk by M. Anselmino Chiral-odd: requires another chiral-odd partner epe’X epe’hX ppe+e-X Indirect Measurement: convolution with unknown fragment. fct. Direct Measurement Impossible in DIS h1 must couple to another chiral-odd function h1 x h1 h1 x Collins function PAX Polarized Antiproton Experiments

  11. Drell-Yan process M invariant Mass of lepton pair Elementary LO interaction: PAX Polarized Antiproton Experiments Plenty of single and double spin effects

  12. ≠ h1q (x ,Q2) h1q (x, Q2) - h1q (x, Q2)small and with much slower evolution than Δq(x, Q2)and q(x, Q2)at small x 1 2 h1 from p-p Drell-Yan Barone, Calarco, Drago Martin, Schäfer, Stratmann, Vogelsang RHIC: M2/s=x1x2~10-3 → sea quarks(ATT ~ 0.01) JPARC/U70: M2/s=x1x2~10-1-10-2 → valence and sea(ATT ~ 0.1) PAX:M2/s=x1x2~10-1-10-2 → valence and sea (ATT ~ 0.1) PAX Polarized Antiproton Experiments

  13. h1 from pbar-p Drell-Yan M2 > 4 GeV2 Anselmino et al. PLB 594,97 (2004) Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004) PAX : M2/s=x1x2~0.02-0.3→valence quarks(ATTlarge ~ 0.2-0.4) PAX Polarized Antiproton Experiments

  14. p-pbar p-p DY events distribution M2/s = x1x2 ~ 0.02-0.3 At x1=x2ATT ~ h1u2 Extraction of h1u for x<0.2 Direct measurement of h1u for 0.05<x<0.5 pbarp+pp complete mapping of transversity PAX Polarized Antiproton Experiments

  15. Parton distribution: transversity Cerenkov Drell-Yan SSA Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Polarized Antiproton eXperiments Nucleon structure: polarized reactions pbar-p elastic Proton EFFs Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target PAX Polarized Antiproton Experiments

  16. Single Spin Asymmetries(and their partonic origin) π Pq k┴ Collins effect = fragmentation of polarized quark depends onPq· (pqx k┴) pq q P k┴ Sivers effect = number of partons in polarized proton depends onP· (p x k┴) p Pq q Boer-Mulders effect = polarization of partons in unpolarized proton depends onPq· (p x k┴) k┴ p Collins: chiral-odd Sivers: chiral-even Boer-Mulders: chiral-odd These effects may generate SSA See talk by O. Ivanov, M. Anselmino, O.Shevchenko PAX Polarized Antiproton Experiments

  17. BNL-AGS √s = 6.6 GeV 0.6 < pT < 1.2 p↑p E704 √s = 20 GeV 0.7 < pT < 2.0 p↑p STAR-RHIC √s = 200 GeV 1.1 < pT < 2.5 p↑p E704 √s = 20 GeV 0.7 < pT < 2.0 p↑p SSA, pp → πX PAX Polarized Antiproton Experiments

  18. HERMES Sivers Collins See talk by L. Pappalardo SSA, SIDIS PAX Polarized Antiproton Experiments

  19. Parton distribution: transversity Cerenkov Drell-Yan SSA Charmonium Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Polarized Antiproton eXperiments Nucleon structure: polarized reactions pbar-p elastic Proton EFFs Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target PAX Polarized Antiproton Experiments

  20. Fermilab E866 800 GeV/c "safe region" Usually taken as Kinematics for Drell-Yan processes CERN NA51 450 GeV/c Q2>4 GeV2 QCD corrections might be very large at smaller values of M, for cross-sections, not for ATT: K-factor almost spin-independent H. Shimizu, G. Sterman, W. Vogelsang and H. Yokoya, hep-ph/0503270 V. Barone et al., in preparation PAX Polarized Antiproton Experiments

  21. l+ l+ q q J/ψ l– l– q q all vector couplings, same spinor structure and, at large x1, x2 measure ATTalsoin J/ψ resonance region M. A., V. Barone, A. Drago and N. Nikolaev PAX Polarized Antiproton Experiments

  22. The FAIR project PAX Polarized Antiproton Experiments

  23. Facilty for Antiproton and Ion Research (GSI, Darmstadt, Germany) • Proton linac (injector) • 2 synchrotons (30 GeV p) • A number of storage rings •  Parallel beams operation PAX Polarized Antiproton Experiments

  24. PAX Accelerator Setup • APR: Antiproton Polarizer Ring (Ppbar>0.2) • CSR: Cooled Synchrotron Ring (p<3.5 GeV/c) • HESR: High Energy Synchrotron Ring (p<15 GeV/c) PAX Polarized Antiproton Experiments

  25. PAX Detector Concept GEANT simulation (200 mm) (20 mm) Designed for Collider but compatible with fixed target PAX Polarized Antiproton Experiments

  26. Polarized Antiproton eXperiments Phase I: Proton time-like FFs Hard pbar-p elastic scatt. Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target From few hours to few weeks measurements PAX Polarized Antiproton Experiments

  27. Polarized Antiproton eXperiments Phase II: Transversity Distribution Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) 1 year of run 10 % precision on the h1u(x) in the valence region PAX Polarized Antiproton Experiments

  28. RINGS SETUP Asymmetric collider Luminosity up to 1031 cm-2s-1 See talk by Y. Shatunov, D. Prasuhn, A. Garishvili, A. Smirnov PAX Polarized Antiproton Experiments

  29. Antiproton Polarization PAX Polarized Antiproton Experiments

  30. 1992 Filter Test at TSR with protons Results Experimental Setup T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993) Experimental Proof of Principle PAX Polarized Antiproton Experiments

  31. Spin-filtering: Present situation Spin filtering works, but: • controversial interpretations of TSR result • no experimental basis for antiprotons Experimental tests: - Protons (COSY at FZJ) - Antiprotons (AD at CERN) See talk by P. Lenisa PAX Polarized Antiproton Experiments

  32. P P 0.20 0.20 0.15 0.15 0.10 0.10 0.05 0.05 Model A: T. Hippchen et al., Phys. Rev. C 44, 1323 (1991) Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995) T (MeV) 100 200 50 150 T (MeV) 100 250 200 50 150 Filter Test: T = 23 MeV Ψacc= 4.4 mrad Hadronic Interaction in p-pbar: Longitudinal CaseBeam Polarization 3 beam lifetimes Ψacc=20 mrad 2 beam lifetimes Ψacc=10-50 mrad PAX Polarized Antiproton Experiments

  33. Summary • PAX project has an innovative spin physics program * transversity * SSA * EMFF * hard p-pbar scatterings * polarized charmonium production • A method to obtain an antiproton beam with high degree of polarization has to be optimized (APR) • PAX viable accelerator setup at FAIR provides fexible 2nd IP really matched to the physics items * lots of interesting QCD physics in PAX Phase-I * asymmetric collider ideal to map transversity (Phase-II) PAX Polarized Antiproton Experiments

  34. Timeline Fall 2006 Technical Proposal for COSY-ANKE 2007 Propedeutical studies at COSY-ANKE Technical Proposal for COSY-New IP 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 PAX Polarized Antiproton Experiments

  35. Drell-Yan process M invariant Mass of lepton pair Elementary LO interaction: PAX Polarized Antiproton Experiments Plenty of single and double spin effects

  36. Fermilab E866 800 GeV/c "safe region" Usually taken as Kinematics for Drell-Yan processes CERN NA51 450 GeV/c Q2>4 GeV2 QCD corrections might be very large at smaller values of M, for cross-sections, not for ATT: K-factor almost spin-independent H. Shimizu, G. Sterman, W. Vogelsang and H. Yokoya, hep-ph/0503270 V. Barone et al., in preparation PAX Polarized Antiproton Experiments

  37. s=45 GeV2 s=45 GeV2 s=210 GeV2 s=210 GeV2 Cross-section Asymmetry PAX Polarized Antiproton Experiments

  38. l+ l+ q q J/ψ l– l– q q all vector couplings, same spinor structure M. A., V. Barone, A. Drago and N. Nikolaev measure ATTalsoin J/ψ resonance region PAX Polarized Antiproton Experiments

  39. Parton distribution: transversity Cerenkov Drell-Yan Charmonium Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Polarized Antiproton eXperiments Nucleon structure: polarized reactions pbar-p elastic Proton EFFs Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target PAX Polarized Antiproton Experiments

  40. COMPASS SSA, SIDIS PAX Polarized Antiproton Experiments

  41. s=45 GeV2 s=45 GeV2 s=210 GeV2 s=210 GeV2 Cross-section Asymmetry PAX Polarized Antiproton Experiments

  42. Polarized antiprotons: present situation • Intense beam of polarized pbar never produced: • Conventional methods (ABS) not appliable • Polarized pbar from antilambda decay • I< 1.5∙105 s-1 (P ≈ 0.35) • Stern-Gerlach separation of a stored beam • (M. Conte and M. Pusterla) • Interaction with polarized electron beam • (Th. Walcher et al) • Spin-filteringis the only succesfully tested technique PAX Polarized Antiproton Experiments

  43. Principle of spin filter method P beam polarization Q target polarization k || beam direction σtot = σ0 + σ·P·Q + σ||·(P·k)(Q·k) For initially equally populated spin states:  (m=+½) and  (m=-½) transverse case: longitudinal case: Unpolarized anti-p beam Polarized H target PAX Polarized Antiproton Experiments

  44. Polarized atomic beam source |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> Atoms with mj=+½ focused in sextupole magnets. RF transitions select HFS. PAX Polarized Antiproton Experiments

  45. Two interpretations of FILTEX result Observedpolarization build-up: dP/dt = ± (1.24 ± 0.06) x 10-2 h-1 P(t)=tanh(t/τ1), 1/τ1=σ1Qdtf σ1 = 72.5 ± 5.8 mb Spin-filtering works! But how? 1994. Meyer and Horowitz: three distinct effects • Selective removal through scattering beyond θacc=4.4 mrad (σR=83 mb) • Small angle scattering off 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 PAX Polarized Antiproton Experiments

  46. How to disentangle had. and elm contributions? 1: Injection of different combination of hyperfine states Different combinations of elm. and hadronic contributions: Pure polarization possible in strong holding field 2: Longitudinal and transverse target polarization 3: Beam energy variation 4: Beam acceptance variation Different behaviour of elm. and hadronic contribution PAX Polarized Antiproton Experiments

  47. … only had - elm. + had. Polarizing cross-section for the two models TSR A measurement of s with 10 % precision is sufficient. Polarization measurement with DP/P = 10% requested. PAX Polarized Antiproton Experiments

  48. Measurements at COSY at FZJ (2008-2009) Existing ANKE setup Only weak transverse field possible. Goals: Propedeutical studies (beam lifetime) Depolarization studies (e effect) Reproduce TSR set-up PAX Polarized Antiproton Experiments

  49. Measurements at COSY at FZJ (2008-2009) New low-beta IP Strong and weak field polarized target Goals: Disentangle h and e effects Commissioning of AD setup PAX Polarized Antiproton Experiments

  50. 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 PAX Polarized Antiproton Experiments

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