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Paolo Lenisa Università di Ferrara and INFN - ITALY

Polarized Antiprotons: why and how?. Paolo Lenisa Università di Ferrara and INFN - ITALY. 5 th Georgian-German School and Workshop in Basic Science Tbilisi, 07.08.12. What is spin?. Intrinsic rotation of a body around its axis. Medical physics:

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Paolo Lenisa Università di Ferrara and INFN - ITALY

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  1. Polarized Antiprotons: why and how? Paolo Lenisa Università di Ferrara and INFN - ITALY 5th Georgian-German School and Workshop in Basic Science Tbilisi, 07.08.12 Polarized antiprotons: why and how?

  2. Whatis spin? Intrinsic rotation of a body around its axis Medical physics: MRI technique based on spin-flip of the proton Spin is everywhere: Astrophysics: spin of galaxies possible indication of dark matter Solid state physics: superconductivity consequence of electron pairs with Spair=0 Polarized antiprotons: why and how?

  3. Even they were puzzled by spin N. Bohr  W. Pauli Polarized antiprotons: why and how?

  4. Pauli principle … half integer SPIN integer SPIN Knowledge of the universe • obey Pauli principle • antisymmetric under exchange of identical particles • Fermi-Dirac statistics: Fermions MATTER • don’t care for Pauli principle • symmetric • Bose-Einstein statistics: Bosons FORCES Polarized antiprotons: why and how?

  5. S = 1/2 S = 1/2 Spin and particles Proton and electron both have S=1/2 (h/2p) … but the proton is a composite object • Naive model. Theproton has a structure: • Sproton = ∑Squarks = ½+½-½ Butthereis more thanthat… Polarized antiprotons: why and how?

  6. How to study the nucleonstructure? … deep-inelastic scattering (DIS) e’ e P Internal structure q=1/l (ph. wavel.)  resolution 1964-1969 < 1960 1972-1973 ? > 1988 - QCD lagrangian - colors, sea quarks, gluons - discovery of gluons - Elementary particle? - Quark hypothesis (Gell-Mann - Zweig) - Scaling at SLAC (‘69) - Parton Model 6

  7. gluons are important ! don’t forget the orbital angular momentum! QPM: Spin Puzzle Where is the proton spin? “… the proton is an object we thought we knew so well, but which reveals another face when it spins.” J. Ellis EMC (‘88) DS=0.123 ± ... SLAC, CERN, DESY: 0.2-0.4 Polarized antiprotons: why and how?

  8. 1 1 = + + D + ΔΣ L G L q g 2 2 inclusive dis polarised beam and/or polarised target Polarized deep inelastic scattering Polarized antiprotons: why and how?

  9. Polarized electron beam vs polarized proton target:Virtual photon asymmetries Because of helicity conservation, the virtual photon can couple only to a quark of opposite helicity by changing the orientation of target nucleon spin or the helicity of incident lepton beam we can select q+(x) or q-(x) Dq Polarisation Experiments in Storage Rings

  10. 1 1 = + + D + ΔΣ L G L q g 2 2 inclusive dis polarised beam and/or polarised target semi-inclusive DIS flavour separation Polarized deep inelastic scattering Polarized antiprotons: why and how?

  11. Polarized semi-inclusive DIS flavour tagging p+ ud K- us p- ud fragmentation function distribution function , z=Eh/n Polarized antiprotons: why and how?

  12. sea quarks (u, d, s) compatible with 0 (in measured x-range: 0.02-0.6) Quark/anti-quark helicity distributions u quarks large positive polarisation d quarks negative polarisation Polarized antiprotons: why and how?

  13. 1 1 = + + D + ΔΣ L G L q g 2 2 inclusive dis polarised beam and/or polarised target semi-inclusive DIS flavour separation inclusive hadrons exclusive dis Polarized deep inelastic scattering Polarized antiprotons: why and how?

  14. The puzzle of the proton spin… the (spin) structure of the nucleon … H1, ZEUS,++ HERMES COMPASS CERN RHIC SLAC HERMES, ++ Polarized antiprotons: why and how?

  15. Transversity (h1) HERMES JLab The puzzle of the proton spin… the (spin) structure of the nucleon … H1, ZEUS,++ HERMES COMPASS CERN RHIC SLAC HERMES, ++ Polarized antiprotons: why and how?

  16. unpolarised quarks and nucleons longitudinally polarised quarks and nucleons transversely polarised quarks and nucleons Quark structure of the nucleon Polarized antiprotons: why and how?

  17. 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 Polarized antiprotons: why and how?

  18. e+ e- 2007 milestone in hadron physics: Transversity first extraction Polarized antiprotons: why and how?

  19. 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 Polarized antiprotons: why and how?

  20. Accesso totransversitythroughDrell-Yan Polarized Antiprotons

  21. h1u from p-pDrell-Yanat PAX • u-dominance • |h1u|>|h1d| PAX : M2/s=x1x2~0.02-0.3 valence quarks (ATTlarge ~ 0.2-0.3)

  22. s=200 GeV2 Antiproton-proton collider for FAIR EXPERIMENT: Asymmetric collider: polarized protons in HESR (p=15 GeV/c) polarized antiprotons in CSR (p=3.5 GeV/c) Polarized antiprotons: why and how?

  23. Polarized Antiprotons • Intense beam of polarized antiprotons was never produced: • Conventional methods (ABS) not appliable • Polarized antiprotons from antilambda decay • I < 1.5∙105 s-1 (P ≈ 0.35) • Antiproton scattering off liquid H2 target • I < 2∙103 s-1 (P ≈ 0.2) • Little polarization from pbarC scattering exp’ts at LEAR • Stern-Gerlach spin separation in a beam (never tested) Spin filteringis the only succesfully tested technique Polarized antiprotons: why and how?

  24. Spin-filtering Polarization build-up of an initially unpolarized particle beam by repeated passage through a polarized hydrogen target in a storage ring: Polarized antiprotons: why and how?

  25. Polarization Buildup P beam polarization Q target polarization k || beam direction σtot = σ0 + σ1·P·Q + σ2·(P·k)(Q·k) For initially equally populated spin states:  (m=+½) and  (m=-½) transverse case: longitudinal case: Unpolarized anti-p beam Polarized target Polarized antiprotons: why and how?

  26. P beam polarization Q target polarization k || beam direction Polarized anti-p beam σtot = σ0 + σ1·P·Q + σ2·(P·k)(Q·k) For initially equally populated spin states:  (m=+½) and  (m=-½) transverse case: longitudinal case: Unpolarized anti-p beam Polarization Buildup Polarized target Polarized antiprotons: why and how?

  27. Spin-filteringat TSR: „FILTEX“ – proof-of-principle F. Rathmann et al., PRL 71, 1379 (1993) Spin filteringworksforprotons PAX submitted new proposal to find out how well does spin filtering work for antiprotonsMeasurement ofthe Spin-Dependenceofthe pp Interaction atthe AD Ring (CERN-SPSC-2009-012 / SPSC-P-337) Polarized antiprotons: why and how?

  28. PAX at the AD Siberian snake Electron cooler PAX target section Polarized antiprotons: why and how?

  29. Spin-dependence of the pbar-p interaction • Measurement of the polarization buildup equivalent to the determination of σ1 and σ2 • Once a polarized antiproton beam is available, spin-correlation data can be measured at AD (50-500 MeV) Model A: T. Hippchen et al., Phys. Rev. C 44, 1323 (1991). Model OBEPF:J. Haidenbauer, K. Holinde, A.W. Thomas, Phys. Rev. C 45, 952 (1992). Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995). Polarized antiprotons: why and how?

  30. Spin-filteringexperimentat COSY Main purpose: 1. Commissioning of the experimental setup for CERN/AD 2. Quantitative understanding of the machine parameters WASA e-cooler ANKE PAX Polarized antiprotons: why and how?

  31. Experimental setupforspin-filteringstudies I – Low-bsection 2009: Installation oflow-βsection • Beamhastofitthroughstoragecell target (dt=5x1013atoms/cm2) • Increase acceptance angle at target position Polarized antiprotons: why and how?

  32. Experimental setup for spin-filtering studies II – Polarized Internal Target ABS Breit-Rabi polarimeter • Spin filtering requires >1013 atoms/cm2 → • ABS + openable storage cell • Analysis of target polarization by Breit-Rabi polarimeter (BRP) and a target gas analyzer (TGA) 2010: Installation ofpolarizedtarget Polarized antiprotons: why and how?

  33. p D2 Experimental setup for spin-filtering studies III – Beam polarimeter pdelasticscattering:detection in two (L-R) symmetric Silicon Tracking Telescopes Polarized antiprotons: why and how?

  34. 2011: Spin-filteringmeasurement cluster targ. + STT (beam polarimetry) Spin-flipper COSY ring p polarized target Polarized antiprotons: why and how?

  35. Result • Milestonefor the field! • Confirms understanding of spin-filtering as a viable method to polarize a stored beam. • Confirms complete control of the systematics of the experiment • Does not cover for the lack of knowledge of the pbar-p interaction. Polarized antiprotons: why and how?

  36. Acknowledgments - 2012 P. Benati (PhD – thesis): Development of a new trigger system for spin-filtering studies S. Bertelli (PhD – thesis):Proton induced deuteron breakup reactions at COSY Z. Bagdasarian (Diploma – thesis): Beam-polarization studies at COSY - 2011: Ch. Weidemann (PhD – thesis): Preparations for the Spin-Filtering Experiments at COSY/Jülich - 2010 D. Oellers (PhD – thesis) Polarizing a Stored Proton Beam by Spin-Flip? C. Barschel (Diploma – thesis): Calibration of the Breit-Rabi Polarimeter for the PAX Spin-Filtering Experiment at COSY/Jülich and AD/CERN - 2009 L. Barion (PhD – thesis) Internal polarized gas targets: systematic studies on intensity and correlated effects G. Guidoboni (Diploma – thesis) Design of the interlock system of a test-bench for silicon detectors A. Lupato (Diploma – thesis) Sviluppo di sorgenti atomiche di idrogeno gassoso e deuterio ad alta intensita - 2008 P. Benati (Diploma – thesis) Caratterizzazione di una nuova scheda di trigger per esperimenti di liltraggio in spin S. Bertelli (Diploma – thesis) Studio della reazione di deuteron breakup in esperimenti di spin-filtering per la polarizzazione di fasci di antiprotoni - 2013 - …. – New students are welcome! Polarized antiprotons: why and how?

  37. Polarized antiprotons: why and how?

  38. Additional calculations… PLB 690 (2010) Cross sections Projected polarizations Polarized antiprotons: why and how?

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