dr. Paolo Lenisa Università di Ferrara and INFN - ITALY

1. http://www.fz-juelich.de/ikp/pax dr. Paolo Lenisa Università di Ferrara and INFN - ITALY DIS 2005 XIII International Workshop on Deep Inelastic Scattering Madison, April 29th 2005 PAX: Polarized Antiproton Experiments

2. PAX Collaboration Spokespersons: Paolo Lenisa lenisa@mail.desy.de Frank Rathmann f.rathmann@fz-juelich.de Yerevan Physics Institute, Yerevan, Armenia Department of Subatomic and Radiation Physics, University of Gent, Belgium University of Science & Technology of China, Beijing, P.R. China Department of Physics, Beijing, P.R. China Palaiseau, Ecole Polytechnique Centre de Physique Theorique, France High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia Nuclear Physics Department, Tbilisi State University, Georgia Forschungszentrum Jülich, Institut für Kernphysik Jülich, Germany Institut für Theoretische Physik II, Ruhr Universität Bochum, Germany Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany Physikalisches Institut, Universität Erlangen-Nürnberg, Germany Langenbernsodorf, UGS, Gelinde Schulteis and Partner GbR,Germany Department of Mathematics, University of Dublin,Dublin, Ireland Università del Piemonte Orientale and INFN,Alessandria,Italy Dipartimento di Fisica dell’Università and INFN, Cagliari, Italy Università dell’Insubria and INFN,Como,Italy Instituto Nationale di Fisica Nuclelare, Ferrara, Italy PAX: Polarized Antiproton Experiments

3. PAX Collaboration Dipartimento di Fisica Teorica, Universita di Torino and INFN, Torino, Italy Instituto Nationale di Fisica Nucleare, Frascati, Italy Andrej Sultan Institute for Nuclear Studies, Dep. of Nuclear Reactions, Warsaw, Poland Petersburg Nuclear Physics Institute, Gatchina, Russia Institute for Theoretical and Experimental Physics, Moscow, Russia Lebedev Physical Institute, Moscow, Russia Physics Department, Moscow Engineering Physics Institute, Moscow, Russia Laboratory of Theoretical Physics, Joint Institute for Nueclear Research, Dubna, Russia Laboratory of Particle Physics, Joint Institute for Nuclear Research, Dubna, Russia Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, Russia Budker Institute of Nuclear Physics, Novosibirsk, Russia High Energy Physics Institute, Protvino, Russia Institute of Experimental Physics, Slovak Academy of Science, Kosice Slovakia Department of Radiation Sciences, Nuclear Physics Division, Uppsala University, Uppsala, Sweden Collider Accelerator Department, Brookhaven National Laboratory, Broohhaven USA RIKEN BNL Research Center Brookhaven National Laboratory, Brookhaven, USA University of Wisconsin, Madison, USA Department of Physics, University of Virginia, USA 178 physicists 35 institutions (15 EU, 20 NON-EU) PAX: Polarized Antiproton Experiments

4. PAX:Polarized Antiproton Experiments Outline WHY?Physics Case HOW?Polarized Antiprotons WHAT? Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D)

5. Physics Case: Central Physics Issue Transversity distribution of the nucleon: • last leading-twist missing piece of the QCD description of the partonic structure of the nucleon • directly accessible uniquely via the double transverse spin asymmetry ATT in the Drell-Yan production of lepton pairs • theoretical expectations for ATT in DY > 0.2 • transversely polarized antiprotons • transversely polarized proton target • definitive observation of h1q(x,Q2) of the proton for the valence quarks Physics Polarization Staging Signals FAIR

6. Transversity Properties: • Probes relativistic nature of quarks • No gluon analog for spin-1/2 nucleon • Different evolution than • Sensitive to valence quark polarization Chiral-odd: requires another chiral-odd partner epe’hX ppl+l-X Direct Measurement Indirect Measurement: Convolution of with unknown fragment. fct. Impossible in DIS Physics Polarization Staging Signals FAIR

7. PAX:Polarizedantiproton beam → polarizedproton target (both transverse) l+ q2=M2 l- q qT p p qL M invariant Mass of lepton pair Transversity in Drell-Yan processes Physics Polarization Staging Signals FAIR

8. Other Topics • Electromagnetic Form Factors • Hard Scattering Effects • SSA in DY, origin of Sivers function • Soft Scattering • Low-t Physics • Total Cross Section • pbar-p interaction Physics Polarization Staging Signals FAIR

9. PAX:Polarized Antiproton Experiments Outline WHY? Physics Case HOW?Polarized Antiprotons WHAT? Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D)

10. Polarized internal target Physics PolarizationStaging Signals FAIR

11. 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) Physics Polarization Staging Signals FAIR

12. 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 Physics Polarization Staging Signals FAIR

13. Principle of spin filter method P beam polarization Q target polarization k || beam direction Polarized anti-p beam 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 Physics Polarization Staging Signals FAIR

14. 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: For low energy pp scattering: 1<0  tot+<tot- Physics Polarization Staging Signals FAIR

15. Experimental Setup at TSR (1992) Physics Polarization Staging Signals FAIR

16. 1992 Filter Test at TSR with protons Results Experimental Setup T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993) Physics Polarization Staging Signals FAIR

17. Spin transfer from electrons to protons Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) α fine structure constant λp=(g-2)/2=1.793 anomalous magnetic moment me, mp rest masses p cm momentum a0 Bohr radius C02=2πη/[exp(2πη)-1] Coulomb wave function η=zα/ν Coulomb parameter (negative for antiprotons) v relative lab. velocity between p and e z beam charge number PAX will exploit spin-transfer from polarized electrons of the target to antiprotons Physics Polarization Staging Signals FAIR

18. 100 10 EM (mbarn) 1 10 100 1000 T (MeV) Spin Transfer Cross Section Physics Polarization Staging Signals FAIR

19. Beam lifetimes in the APR Beam Lifetime Coulomb Loss Total Hadronic ψacc(mrad) 40 10 8 beam lilfetime τbeam (h) 6 30 25 4 20 2 10 10 100 1000 T (MeV) Physics Polarization Staging Signals FAIR

20. Polarization Buildup: optimal polarization time statistical error of a double polarization observable (ATT) Measuring time t to achieve a certain error δATT ~ FOM = P2·I (N ~ I) I/I0 Optimimum time for Polarization Buildup given by maximum of FOM(t) tfilter = 2·τbeam 0.8 Beam Polarization 0.6 0.4 0.2 0 2 6 4 t/τbeam Physics Polarization Staging Signals FAIR

21. Optimum Beam Energies for Buildup in APR ψacc= 50 mrad FOM AP Space charge limit 15 40 mrad 10 5 30 mrad 20 mrad 10 mrad T (MeV) 10 100 1 F. Rathmann et al., Phys. Rev. Lett. 94, 014801 (2005) Physics Polarization Staging Signals FAIR

22. Ψacc=50 mrad EM only 0.4 40 30 0.3 20 Beam Polarization P(2·τbeam) 10 0.2 5 0.1 0 1 10 100 T (MeV) Beam Polarization Filter Test: T = 23 MeV Ψacc= 4.4 mrad Physics Polarization Staging Signals FAIR

23. Antiproton Polarizer Ring (APR) B Mechansim: spin transfer from electrons to protons RING PARAMETERS: Energy: 50 MeV (p~300 MeV/c) ex,y: 500 p mm mrad Circumeference: 100 m No. Particles: 1012 EQUIPMENT: Polarized target Snake e-cool Stochastic cooling? Injection Siberian Snake APR e-cooler e-cooler 100 m ABS Polarizer Target PROJECTION: P > 30% after 18-20 hrs (1011 pbar) PhysicsPolarizationStaging Signals FAIR

24. PAX:Polarized Antiproton Experiments Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT? Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D)

25. Staging: Phase I (PAX@CSR) Physics: EMFF pbar-p elastic Experiment: pol./unpol. Pbar (3.5 GeV/c) on int. pol. target Independent from HESR running Physics Polarization Staging Signals FAIR

26. Staging: Phase II (PAX@HESR) Physics: Transversity EXPERIMENT: 1. Asymmetric collider: 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 Physics Polarization Staging Signals FAIR

27. PAX:Polarized Antiproton Experiments Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT? Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D)

28. PAX:Polarizedantiproton beam → polarizedproton target (both transverse) l+ q2=M2 l- q qT p p qL M invariant Mass of lepton pair Transversity in Drell-Yan processes Physics Polarization Staging Signals FAIR

29. ATT for PAX kinematic conditions ATT/aTT > 0.2 Models predict |h1u|>>|h1d| RHIC: τ=x1x2=M2/s~10-3 → Exploration of the sea quark content(polarizations small!) ATT very small (~ 1 %) PAX: M2~10-100 GeV2, s~45-200 GeV2, τ=x1x2=M2/s~0.05-0.6 →Exploration ofvalence quarks(h1q(x,Q2) large) Physics Polarization Staging Signals FAIR

30. 2 k events/day collider 22 GeV M (GeV/c2) • M2 = s x1x2 • xF=2QL/√s = x1-x2 Kinematics and cross section • Estimated luminosities: • Fixed target: 2.7x1031 cm-2s-1 • Collider: 1-2 x 1030 cm-2s-1 Physics Polarization Staging Signals FAIR

31. ATT asymmetry: angular distribution • Asymmetry is largest for angles =90° • Asymmetry varies like cos(2f). Needs a large acceptance detector (LAD) Physics Polarization Staging Signals FAIR

32. PAX detector concept GEANT simulation (200 mm) Cerenkov (20 mm) Designed for Collider but compatible with fixed target Physics Polarization Staging Signals FAIR

33. Estimated signal for h1 (phase II) 1 year of data taking Collider: L=2x1030 cm-2s-1 Fixed target: L=2.7x1031 cm-2s-1 Physics Polarization Staging Signals FAIR

34. PAX:Polarized Antiproton Experiments Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT? Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D)

35. Faciltiy for Antiproton and Ion Research (GSI, Darmstadt, Germany) • Proton linac (injector) • 2 synchrotons (30 GeV p) • A number of storage rings •  Parallel beams operation Physics Polarization Staging Signals FAIR

36. The FAIR project at GSI SIS100/300 50 MeV Proton Linac HESR: High Energy Storage Ring: PANDA and PAX CR-Complex FLAIR: (Facility for very Low energy Anti-protons and fully stripped Ions) NESR Physics Polarization Staging Signals FAIR

37. Timeline Phase 0: 2005-2012 APR design and construction @ Juelich Phase I: 2013-2017 APR+CSR @ GSI Physics: EMFF with fixed target Phase II: 2018 - … HESR+CSR asymmetric collider Physics: h1 Physics Polarization Staging Signals FAIR

38. Conclusions • Challenging opportunities accessible with polarized pbar. • Unique access to a wealth of new fundamental physics observables • Central physics issue: h1q(x,Q2) of the proton in DY processes • Other issues: • Electromagnetic Formfactors • Polarization effects in Hard and Soft Scattering processes • differential cross sections, analyzing powers, spin correlation parameters • Staging approach • Projections for double polarization experiments: • Pbeam > 0.30 • L> 1.6 ·1030 cm-2s-1(Collider),L 2.7 ·1031 cm-2s-1(fixed target) • Detector concept: • Large acceptance detector with a toroidal magnet

39. Georg Christoph Lichtenberg (1742-1799) “Man muß etwas Neues machen, um etwas Neues zu sehen.” “You have to make something new, if you want to see something new”