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dr. Paolo Lenisa Università di Ferrara and INFN - ITALY

The PAX Experiment. 178 Collaborators 36 institutions (15 EU, 21 NON-EU). Spokespersons: Paolo Lenisa lenisa@mail.desy.de Frank Rathmann f.rathmann@fz-juelich.de. dr. Paolo Lenisa Università di Ferrara and INFN - ITALY. PBAR@FAIR Workshop Darmstadt, Dec. 03 2007.

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dr. Paolo Lenisa Università di Ferrara and INFN - ITALY

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  1. The PAX Experiment 178 Collaborators 36 institutions (15 EU, 21 NON-EU) Spokespersons: Paolo Lenisa lenisa@mail.desy.de Frank Rathmann f.rathmann@fz-juelich.de dr. Paolo Lenisa Università di Ferrara and INFN - ITALY PBAR@FAIR Workshop Darmstadt, Dec. 03 2007 The PAX Experiment

  2. 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: • to demonstrate that the required luminosity for decisive measurements can be reached (->accomplished) - to demonstrate that a high degree of anti-proton polarisation 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 Experiment

  3. Physics with Polarized Antiprotons The PAX Experiment

  4. Study of the proton spin h1= Quark structure of the nucleon unpolarised quarks and nucleons longitudinally polarised quarks and nucleons transversely polarised quarks and nucleons Only glimpse Well known Known The PAX Experiment

  5. transversely polarised quarks and nucleons Transversity • Probes relativistic nature of quarks • No gluon analog for spin-1/2 nucleon • Different evolution than • Sensitive to valence quark polarization h1 is chirally odd -> it needs a chirally odd partner Inclusive DIS Semi-inclusive DIS Drell-Yan HERMES,COMPASS,JLab The PAX Experiment

  6. M invariant Mass of lepton pair Inclusive DIS Semi-inclusive DIS Drell-Yan h1 from Drell-Yan The PAX Experiment

  7. s=200 GeV2 The PAX proposal (phase II) EXPERIMENT: Asymmetric collider: polarized protons in HESR (p=15 GeV/c) polarized antiprotons in CSR (p=3.5 GeV/c) The PAX Experiment

  8. 1year run: 10 % precision on the h1u(x) in the valence region Pp=30% Pp=10% Anselmino et al. PLB 594,97 (2004) Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004) h1 from p-p Drell-Yan at PAX • u-dominance • |h1u|>|h1d| PAX : M2/s=x1x2~0.02-0.3 valence quarks (ATTlarge ~ 0.2-0.3) First direct measurement of h1 No competitive processes The PAX Experiment

  9. Study of the Proton Electromagnetic Form-Factors Rosenbluth Polarization Space-Like FFs: proton data Time-Like FFs: proton data • JLab results dramatically changed picture of the Nucleon: • GEp/GMp decreases with Q2 • data suggest GEpcrosses 0 at Q28 GeV2 The PAX Experiment

  10. Study of the Proton Electromagnetic Form-Factors Rosenbluth Polarization Space-Like FFs: proton data Time-Like FFs: proton data • JLab results dramatically changed picture of the Nucleon: • GEp/GMp decreases with Q2 • data suggest GEpcrosses 0 at Q28 GeV2 Expected Q2 behaviour reached quite early, however ... ... there is still a factor of 2 between timelike and spacelike. Additional direct measurement needed The PAX Experiment

  11. The PAX proposal - Phase I EXPERIMENT: Fixed target experiment: polarized antiprotons protons in CSR (p>200 MeV/c) fixed polarized protons target The PAX Experiment

  12. Double polarized pbar-p annihilation E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005) • Most contain mduli GE, GM • Independent GE-GM separation • Test of Rosenbluth separation in the time-like region • Access to GE-GM phase • Very sensitive to different models The PAX Experiment

  13. (Single Spin Asymmetry) A. Z. Dubnickova et al. Nuovo Cimento A109, 241 (1996) S.J. Brodsky et al. PRD 69, 054022 (2004) • Single-spin asymmetry in pp → e+e- • Measurement of relative phases of magnetic and electric FF in the time-like region - Also sensitive to different models The PAX Experiment

  14. Estimated signal: PAX-Phase I EXPERIMENT: Fixed target experiment (+ asymmetric collider): Npbar = 1x1011 f=LCSR/bc dt=1x1014cm-2 Q=0.8 (p pol) P=0.3 (pbar pol) e=0.5 ppbar>200 MeV/c s>3.76 GeV2 Running days to get DO = 0.05 The PAX Experiment

  15. P Beam Target Hard p-p polarized scattering T=10.85 GeV “The greatest asymmetries in hadron physics ever seen by a human being” (Brodsky) D.G. Crabb et al., PRL 41, 1257 (1978) “One of the unsolved mysteries of hadron physics”(Brodsky, 2005) It would be very interesting to perform these measurements with polarized antiprotons. The PAX Experiment

  16. Cross section estimation for p=3.6 GeV/c, q=120° BNL E838 2 hours to get Estimated signal: PAX-Phase I EXPERIMENT: Fixed target experiment (+ asymmetric collider): Npbar = 1x1011 f=LCSR/bc dt=1x1014cm-2 Q=0.8 (p pol) P=0.3 (pbar pol) e=0.5 ppbar>200 MeV/c s>3.76 GeV2 The PAX Experiment

  17. Physics with Polarized Antiprotons Polarized antiprotons will open the way to a new spin-physics era: * Proton-spin structure: Complete map of transversity Flavour separation * Electromagnetic Form Factors Independent extraction of moduli of GE-GM in Time-Like region Test of the Rosenbluth separation in TL Measurement of the phase * Hard p-pbar scattering Additional measurement in one of the most intriguing puzzles of HF * Hadron spectroscopy * Low-t pbar-p scattering Spin and isospin dependence of nucleon-antinucleon interaction at low energy (Wealth of single-spin asymmetries) The PAX Experiment

  18. Accelerator setup The PAX Experiment

  19. Antiproton Polarizer Ring (APR) Final configuration after spin-filtering studies -> F. Rathmann’s talk Target Injection/Extraction Electron Cooler Snake Ion-optics at IP The PAX Experiment

  20. Phase I: Fixed target experiments in CSR Physics: EMFF pbar-p elastic pol./unpol. Antiprotons in CSR 0.2 Gev/c<p<2.5 GeV/c polarized internal proton target direction of antiprotons (antiprotons) Independent from HESR running The PAX Experiment

  21. Phase II: Asymmetric Proton-Antiproton Collider(Old setup as in Technical Proposal) Physics:Transversity EMFF pbar-p elastic polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) direction of antiprotons direction of protons The PAX Experiment

  22. Luminosity Considerations for Collider Mode “old” “new” Antiprotons in HESR -> protons L>1031s-1cm-2 Bunched beams -> coasting The PAX Experiment

  23. Phase II: Asymmetric Proton-Antiproton Collider(New setup) Physics:Transversity EMFF pbar-p elastic E-cool modification necessary polarized protons in HESR (p=15 GeV/c) polarized antiprotons in CSR (p=3.5 GeV/c) direction of protons direction of anti-protons (anti-protons) (protons) The PAX Experiment

  24. Requests The PAX Experiment

  25. Accelerator setup for polarized beams • Polarized protons •  polarized proton source •  jump quads and correction dipoles for SIS18 •  E-cool for HESR (opposite direction of rotation) •  Siberian snake in HESR for polarization preservation • Polarized antiproton •  antiproton polarizer ring APR with Siberian snake •  beam-line from RESR to APR •  jump quads and correction dipoles for CSR • Additional equipment •  several polarimeters and spin flipper The PAX Experiment

  26. Antiproton production rate = 2 ·107 s-1 Integrated Luminosities Antiproton Beam Polarization Ppbar=0.2, Proton Polarization Pp=0.8 Phase-I: L=1.5·1031 cm-2s-1 Phase-II: L=2·1031 cm-2s-1 Absolute Error ΔDSA=0.05 fb-1 Integrated Luminosity (1 y) (4 y) h1, DSA, M>4 GeV, Δ=20% EMFF, DSA, s=9 GeV2 (1 y) h1, DSA, M>2 GeV, Δ=10% EMFF, DSA, s=3.76 GeV2 pb-1 ppbar elastic, DSA, t=4 GeV2 The PAX Experiment

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