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PAX Polarized Antiproton eXperiments

PAX Polarized Antiproton eXperiments. M. Contalbrigo INFN – Universit à di Ferarra. PAX Collaboration. TIMELINE Jan. 04 Letter of Intent May 04 QCD-PAC meeting at GSI Aug. 04 Workshop on polarized antiprotons at GSI Jan. 05 Technical Report Mar. 05 QCD-PAC meeting at GSI.

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PAX Polarized Antiproton eXperiments

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  1. PAXPolarized Antiproton eXperiments M. Contalbrigo INFN – Università di Ferarra M. Contalbrigo - INFN Ferrara

  2. PAX Collaboration TIMELINE Jan. 04 Letter of Intent May 04 QCD-PAC meeting at GSI Aug. 04 Workshop on polarized antiprotons at GSI Jan. 05 Technical Report Mar. 05QCD-PAC meeting at GSI 178 physicists (121 in August 2004) 35 institutions (15 EU, 20 NON-EU) M. Contalbrigo - INFN Ferrara

  3. Evaluation by QCD-PAC (March 2005) … the PAC would like to stress again the uniqueness of the programwith polarized anti-protons and polarized protons that could become available at GSI. …the PAC considers it is essential for the FAIR project to commit to polarized antiproton capabilityat this time and include polarized transport and acceleration capability in the HESR, space for installation of the APR and CSR and associated hardware, and the APR in the core project • We request the PAX collaboration to: • 1) Commit to the construction and testing of the APR • 2) Explore all options to increase the luminosity to the value of 1031 cm-2s-1 • 3) Prepare a more detailed physics proposal and detector design for each of the proposed stages. These stages may include: • a) 3.5 GeV/c polarized antiprotons on a polarized proton target • b) 15 GeV/c polarized antiprotons with the PANDA detector (for single spin asymmetries) • c) 15 GeV/c polarized antiprotons on a polarized proton target in a dedicated detector • d) Collisions of 15 GeV/c antiprotons with 3.5 GeV/c polarized protons. M. Contalbrigo - INFN Ferrara

  4. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  5. Time-like e.l.m. form factors form factors Physics with polarized antiprotons at GSI-PAX Transversity via Drell-Yan processes High Energy direct access to transversity Transverse Single Spin Asymmetries QCD “theorem”: (Sivers)D-Y = – (Sivers)DIS Elastic processes spin mysteries like in pp ? Low Energy M. Contalbrigo - INFN Ferrara

  6. 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) M. Contalbrigo - INFN Ferrara

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

  8. Drell-Yan process M invariant Mass of lepton pair Elementary LO interaction: M. Contalbrigo - INFN Ferrara Plenty of single and double spin effects

  9. ≠ 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 h1 from p-p Drell-Yan at RICH/U70 RHIC: τ=x1x2~10-3 → sea quarks(ATT very small ~ 0.01) Barone, Calarco, Drago Martin, Schäfer, Stratmann, Vogelsang M. Contalbrigo - INFN Ferrara

  10. h1 from pbar-p Drell-Yan at GSI Anselmino et al. PLB 594,97 (2004) Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004) PAX : M2/s=x1x2~0.1-0.3→valence quarks(ATTlarge ~ 0.2-0.4) M. Contalbrigo - INFN Ferrara

  11. 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 M. Contalbrigo - INFN Ferrara

  12. s=45 GeV2 s=45 GeV2 s=210 GeV2 s=210 GeV2 Cross-section Asymmetry M. Contalbrigo - INFN Ferrara

  13. Transversity via Drell-Yan processes direct access to transversity Time-like e.l.m. form factors form factors Physics with polarized antiprotons at GSI-PAX High Energy Transverse Single Spin Asymmetries QCD “theorem”: (Sivers)D-Y = – (Sivers)DIS Elastic processes spin mysteries like in pp ? Low Energy M. Contalbrigo - INFN Ferrara

  14. 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 M. Contalbrigo - INFN Ferrara

  15. 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 M. Contalbrigo - INFN Ferrara

  16. HERMES Sivers Collins SSA, SIDIS M. Contalbrigo - INFN Ferrara

  17. COMPASS SSA, SIDIS M. Contalbrigo - INFN Ferrara

  18. Transversity via Drell-Yan processes direct access to transversity Time-like e.l.m. form factors form factors Physics with polarized antiprotons at GSI-PAX High Energy Transverse Single Spin Asymmetries QCD “theorem”: (Sivers)D-Y = – (Sivers)DIS Elastic processes spin mysteries like in pp ? Low Energy M. Contalbrigo - INFN Ferrara

  19. pp Elastic Scattering from ZGS Spin-dependence at large-P (90°cm): Hard scattering takes place only with spins . T=10.85 GeV Similar studies in pp elastic scattering D.G. Crabb et al., PRL 41, 1257 (1978) M. Contalbrigo - INFN Ferrara

  20. Transversity via Drell-Yan processes direct access to transversity form factors Physics with polarized antiprotons at GSI-PAX High Energy Transverse Single Spin Asymmetries QCD “theorem”: (Sivers)D-Y = – (Sivers)DIS Elastic processes spin mysteries like in pp ? Low Energy Time-like e.l.m. form factors M. Contalbrigo - INFN Ferrara

  21. 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 M. Contalbrigo - INFN Ferrara

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

  23. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  24. 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 M. Contalbrigo - INFN Ferrara

  25. The Antiproton Facility HESR (High Energy Storage Ring) p = 1.5 - 15 GeV/c(22 GeV/c) (Length 442 m Bρ = 50 Tm) PANDA: storage ring (N=5 x 1010 pbar) High luminosity mode (Δp/p ~ 10-4) Luminosity = 2 x 1032 cm-2s-1 High resolution mode (Δp/p ~ 10-5) Luminosity = 1031 cm-2s-1 PAX : synchroton (N=3 x 1011 pbar) Preserve polarization Luminosity = 2 x 1030 cm-2s-1 SIS100/300 HESR Super FRS CR NESR Antiproton Production Target Beam Cooling: e- and/or stochastic • Antiproton production similar to CERN • Production rate107/sec at 30 GeV M. Contalbrigo - INFN Ferrara

  26. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  27. PAX Accelerator Setup • In the following, focus on two issues: • Antiproton Polarizer Ring (APR) • Asymmetric Antiproton-Proton Collider M. Contalbrigo - INFN Ferrara

  28. Staging: Phase I (PAX@CSR) Physics: EMFF pbar-p elastic Experiment: pol./unpol. pbar on internal polarized target Independent from HESR running M. Contalbrigo - INFN Ferrara

  29. Staging: Phase II (PAX@HESR) Physics: Transversity EXPERIMENT: 1. Asymmetriccollider: polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) 2. Internal polarized target with 22 GeV/c polarized antiproton beam. Second IP with minor interference with PANDA M. Contalbrigo - INFN Ferrara

  30. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  31. 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 M. Contalbrigo - INFN Ferrara

  32. The HERMES target |1> e- p • Atomic Beam Source • NIM A 505, (2003) 633 1 |1> mj = +1/2 mi=+1/2 |2> mi=-1/2 mi=-1/2 |3> mj = -1/2 mi=+1/2 |4> Pz+ = |1> + |4> Pz- = |2> + |3> M. Contalbrigo - INFN Ferrara

  33. 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) M. Contalbrigo - INFN Ferrara

  34. Exploitation of Spin Transfer PAX will employ spin-filter from internal polarized hydrogen target to antiprotons FILTEX Results Hydrogen gas target: in strong field (300 mT) F. Rathmann. et al., PRL 71, 1379 (1993) Low energy pp scattering 1<0  tot+<tot- M. Contalbrigo - INFN Ferrara

  35. Puzzle from FILTEX Test Observed polarization build-up: dP/dt = ± (1.24 ± 0.06) x 10-2 h-1 • Expectedbuild-up: P(t)=tanh(t/τpol), • 1/τpol=σ1Qdtf=2.4x10-2 h-1 •  about factor 2 larger! σ1 = 122 mb (pp phase shifts) Q = 0.83 ± 0.03 dt = (5.6 ± 0.3) x 1013cm-2 f = 1.177 MHz Three distinct effects (measured s1=69 mb): • Selective removal through scattering beyond Ψacc=4.4 mradσR=83 mb • Small angle scattering of target protons into ring acceptanceσS=52 mb • Spin transfer from polarized electrons of the target atoms to the stored protons σEM=70 mb (-) Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) M. Contalbrigo - INFN Ferrara

  36. Ψacc=50 mrad EM only 0.4 40 30 0.3 20 Beam Polarization P(2·τbeam) 0.2 10 0.1 5 0 1 10 100 T (MeV) Filter Test: T = 23 MeV Ψacc= 4.4 mrad Beam Polarization(Electromagnetic Interaction) M. Contalbrigo - INFN Ferrara

  37. 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 Beam Polarization (Hadronic Interaction: Longitudinal Case) 3 beam lifetimes Ψacc=20 mrad 2 beam lifetimes Ψacc=10-50 mrad • Experimental Tests required: • EM effect needs protons only (COSY) • Final Design of APR: Filter test with p at AD (CERN) M. Contalbrigo - INFN Ferrara

  38. From COSY to FAIR… SMILE:Spin Measurements in Interactions at Low Energy • Study of spin-filtering process. • Electromagnetic interaction: unpolarized protons on polarized internal target at COSY • Hadronic interaction: unpolarized antiprotons on polarized internal target at AD (CERN). M. Contalbrigo - INFN Ferrara

  39. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  40. RINGS SETUP asymmetric collider L = 2∙1030 cm-2s-1 M. Contalbrigo - INFN Ferrara

  41. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  42. PAX Detector Concept Physics: h1 distribution sin2q EMFF sin2q pbar-p elastic high |t| Azimuthally Symmetric: BARREL GEOMETRY LARGE ANGLES Experiment:Flexible Facility e+e- Detector: Extremely rare DY signal (10-7 p-pbar) Maximum Bjorken-x coverage (M interval) Excellent PID (hadron/e rejection ~ 104) High mass resolution (≤2 %) Moderate lepton energies (0.5-5 GeV) Magnet: Keeps beam polarization vertical Compatible with Cerenkov Compatible with polarized target TOROID NO FRINGE FIELD M. Contalbrigo - INFN Ferrara

  43. PAX Detector Concept GEANT simulation (200 mm) Cerenkov (20 mm) Designed for Collider but compatible with fixed target M. Contalbrigo - INFN Ferrara

  44. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  45. q-p Phase Space acceptance Background peaks at * low energy * forward direction M. Contalbrigo - INFN Ferrara

  46. Background to Drell-Yan e+e- ½ hour experiment: 2∙108 p-pbar interactions several DY events +- ++ & -- combinatorial +charm bckg Background 1:1 to signalafterPID, E>300 MeV, conversion veto, mass cut * the combinatorial component can be subtracted (wrong-sign control sample) * the charm can be reduced (vertex decay) M. Contalbrigo - INFN Ferrara

  47. q-p Phase Space Better than 2% mass resol * x dependence of h1 * resonance vs continuum Mandatory to study M below J/ψ mass Vertex resolution high enough to study charm background M. Contalbrigo - INFN Ferrara

  48. Outline • Introduction • Physics Case • The FAIR project • PAX Accelerator Setup • Staging • Antiproton Polarizer Ring • Asymmetric Antiproton-Proton Collider • Experiment • Conceptual Detector Design • Preliminary Results for Drell-Yan Studies • Rate estimates M. Contalbrigo - INFN Ferrara

  49. Precision in h1 measurement 1 year of data taking at 15+3.5 GeV collider L = 2∙1030 cm-2s-1 10 % precision on the h1u (x) in the valence region M. Contalbrigo - INFN Ferrara

  50. Summary • PAX project has an innovative spin physics program * transversity * SSA * EMFF * hard p-pbar scatterings • A method to obtain an antiproton beam with high degree of polarization has to be optimized (APR) • PAX viable accelerator setup 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) M. Contalbrigo - INFN Ferrara

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