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Paolo Lenisa – Università and INFN – Ferrara, ITALY

PAX Polarized Antiproton Experiments. http://www.fz-juelich.de/ikp/pax. Paolo Lenisa – Università and INFN – Ferrara, ITALY. Trento, July 6 th 2006. PAX Collaboration. TIMELINE Jan. 04 Letter of Intent for FAIR May 04 QCD-PAC meeting at GSI

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Paolo Lenisa – Università and INFN – Ferrara, ITALY

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  1. PAX Polarized Antiproton Experiments http://www.fz-juelich.de/ikp/pax Paolo Lenisa – Università and INFN – Ferrara, ITALY Trento, July 6th 2006 The PAX project

  2. PAX Collaboration TIMELINE Jan. 04 Letter of Intent for FAIR May 04 QCD-PAC meeting at GSI Aug. 04 Workshop on polarized antiprotons at GSI Jan. 05 Technical Proposal for FAIR Mar. 05QCD-PAC meeting at GSI Nov. 05 LoI to CERN-SPSC to perform spin-filtering experiments with antiprotons at the AD ring Apr. 06 LoI to COSY-PAC for spin filtering experiments with protons at COSY 180 physicists 35 institutions (15 EU, 20 NON-EU) The PAX project

  3. Evaluation by QCD-PAC (March 2005) … the PAC would like to stress again the uniqueness of the program with polarized anti-protons and polarized protons that could become available at GSI. Recommendation of the STI of FAIR (Sept. 2005) The STI requests R&D work to be continued on the proposed asymmetric collider experiment with both polarized anti-protons and protons: t o demonstrate that a high degree of anti-proton polarization can be reached The STI believes that PAX should become part of the FAIR core research program based on its strong scientific merit once the open problems are convincingly solved. The PAX project

  4. Physics Motivations The PAX project

  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 The PAX project

  6. 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) h1 from pbar-p Drell-Yan at GSI The PAX project

  7. Precision in h1 measurement 1 year of data taking at 15+3.5 GeV collider L = 2∙1030 cm-2s-1 (L~1031 reachable) 10 % precision on the h1u (x) in the valence region The PAX project

  8. ≠ 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 What about p-p? Barone, Calarco, Drago Martin, Schäfer, Stratmann, Vogelsang RHIC: τ=x1x2~10-3 → sea quarks(ATT ~ 0.01) JPARC/U70: τ=x1x2~10-1 → valence and sea(ATT ~ 0.1) PAX:τ=x1x2~10-1 → valence and sea(ATT ~ 0.1) The PAX project

  9. Asymmetries evoluted from the assumptions: CDM 1 1 2 2 (~CQSM) DY in p-p: ATT A. Drago • Aymmetry is large at PAX energy (> 0.1) • Sign of the asymmetry will distinguish between the two models. • It will give indications about calculation of sea distributions. The PAX project

  10. M2/s=x1x2~0.01-0.3 x1=x2->ATT~h1u2 Direct measurement of h1u for 0.15<x<0.5 DY events distribution (√s~15 GeV) p-p p-pbar Extraction of h1u for x>0.2 p-pbar +p-p -> complete map of transversity The PAX project

  11. Std. scenario: Val. scenario: Val. scenario Models: xF=x1-x2 Std. scenario DY in p-p: ALL • Large asymmetries expected • Test of the assumptions of the fits The PAX project

  12. 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 The PAX project

  13. 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 The PAX project

  14. 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 The PAX project

  15. 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 The PAX project

  16. 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) The PAX project

  17. 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 The PAX project

  18. 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) The PAX project

  19. Experimental setup The PAX project

  20. PAX Accelerator Setup • Antiproton Polarizer Ring (APR) • Asymmetric Antiproton-Proton Collider (CSR) • High Energy Synchrotron Ring (HESR) The PAX project

  21. Antiproton Polarizer Ring The PAX project

  22. Staging: Phase I (PAX@CSR) Physics: EMFF pbar-p elastic Experiment: pol./unpol. pbar on internal polarized target Independent from HESR running The PAX project

  23. Staging: Phase II (PAX@HESR) Physics: Transversity EXPERIMENT: Asymmetriccollider: polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Second IP with minor interference with PANDA The PAX project

  24. Parameters The PAX project

  25. Symmetric collider Luminosity Asymm. collider The PAX project

  26. 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) The PAX project

  27. 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 The PAX project

  28. 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 The PAX project

  29. PAX Detector Concept GEANT simulation (200 mm) Cerenkov (20 mm) Designed for Collider but compatible with fixed target The PAX project

  30. The (long) way towards a polarized antiproton collider Phase 0: 2006-2010 Pol. buildup measurements @ COSY and CERN 2011-2013 APR final design and construction Phase I: 2014-2017 APR+CSR @ GSI Physics: EMFF, p-pbar elastic with fixed target. Phase II: 2018 - … HESR+CSR asymmetric collider Physics: h1 The PAX project

  31. The PAX project

  32. Antiproton and Proton accelerators’ scheme Energy proton HESR SIS18 HESR antiproton RESR CSR CSR HESR CSR CSR time APR The PAX project

  33. Higher energy p-p machine V. Barone, T. Calarco and A. Drago Phys. Rev. D 56 (1997) 527 • s  • Asymmetry  • √s @ PAX ideal The PAX project

  34. Transverse sea CQSM CDM V. Barone, T. Calarco and A. Drago Phys. Lett. B 390 (1997) 287 M. Wakamatsu and T. Kubota Phys. Rev. D 63 (1999) 034020 • The two models predict different sign for (with comparable amplitude). The PAX project

  35. Std. scenario: Val. scenario: Models: Longitudinal sea M. Glück et al. Phys. Rev. D 63 (2001) 094005 The PAX project

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