1. Mitglied der Helmholtz-Gemeinschaft PAX Polarized Antiprotons 2nd Meeting FAIR Experiments February 25, 2009 | Hans Ströher (FZ-Jülich)

2. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 2 Goal: Provide an effective method for in-situ polarization of (anti-)protons: PAX: Polarized Antiprotons

3. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 3 Direct access to „transversity“ in Drell Yan A main motivation Goal: Goal: Provide an effective method for in-situ polarization of (anti-)protons: Double transverse spin asymmetry: Transversity: unknown piece of partonic structure of nucleon p p PAX: Physics Case

4. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 4 Direct access to „transversity“ in Drell Yan A main motivation Discussed methods Goal: Goal: Provide an effective method for in-situ polarization of (anti-)protons: Double transverse spin asymmetry: p e  p e PAX: Polarization of Antiprotons p p

5. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 5 Do polarized electrons (positrons) polarize a proton (anti-proton) beam ? Polarized positron beam Un-polarized anti-proton beam Polarized anti-proton beam Spin transfer Velocity mismatch  v/c ~ 0.002 Idea: VERY different predictions for cross section: R ~ 10 16 !! PAX: Polarization of Antiprotons – 1

6. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 6 Do polarized electrons (positrons) polarize a proton (anti-proton) beam ? Unpolarized electron beam Polarized proton beam De-polarized proton beam Spin transfer Velocity mismatch  v/c ~ 0.002 Polarized positron beam Un-polarized anti-proton beam Polarized anti-proton beam Spin transfer Velocity mismatch  v/c ~ 0.002 Idea: Test at COSY: PAX: Polarization of Antiprotons – 1

7. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 7 p e-cooler T p = 49 MeV COSY e-cooler Polarization analysis by pd elastic scattering pe interaction in electron cooler PAX: Polarization of Antiprotons – 1 Expt.: Expt.: Proton depolarization at COSY – Setup

8. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 8 Expt.: Expt.: Proton depolarization at COSY – Results (submitted PL B, Febr. 09) Ratio of beam polarizations with and w/o electron beam during interaction cycles: Upper limit for longitudinal and transverse spin-flip cross section:  Cross section much too small to be a useful method ! PAX: Polarization of Antiprotons – 1

9. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 9 Direct access to „transversity“ in Drell Yan A main motivation Discussed methods Goal: Goal: Provide an effective method for in-situ polarization of (anti-)protons: Double transverse spin asymmetry: p e  p e PAX: Polarization of Antiprotons

10. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 10 Spin-filtering: spin-dependent (strong) interaction – works !! (FILTEX) Repeated interaction of the beam with a polarized target in a storage ring: a)Spin-filtering experiment (w/ protons) at COSY b)Spin-filtering experiment (w/ antiprotons) at CERN/AD PAX: Polarization of Antiprotons – 2

11. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 11 ANKE TOF WASA PAX PAX: Polarization of Antiprotons – 2 a) „Low-ß section“: - Quadrupoles - ABS (SC, BRP) Commissioning of low-ß section, optimization of spin-filtering (w/ p) ! COSY

12. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 12 PAX: Polarization of Antiprotons – 2 b) Spin-filtering of antiprotons ! (First ever double polarized pp, pd) e-cooler Target Snake CERN AD „Low-ß section“: - Quadrupoles - ABS (SC, BRP)

13. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 13 PAX: Polarization of Antiprotons – 2 b) Spin-filtering of antiprotons ! (First ever double polarized pp, pd) e-cooler Target Snake CERN AD „Low-ß section“: - Quadrupoles - ABS (SC, BRP) Next: Antiproton Polarizer Ring (APR) – large emittance ! Finally: Asymmetric pp Collider (3.5 & 15 GeV/c) at FAIR

14. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 14 PAX is proposing to produce and exploit polarized antiprotons at FAIR Commitment to find method to effectively polarize antiprotons Stepwise approach: (i) Electromagnetic (selective flip)- NO !! (ii) Strong interaction (selective loss)- works ! - COSY (in 2010) - CERN AD (> 2011) (iii) APR (~ 2013) and asymmetric collider (?) Now and here or never ! PAX: Summary

15. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 15 End PAX: Polarized Antiprotons

16. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 16 Next step: Antiproton polarizer ring (APR) We need a large acceptance cooler ring to polarize antiprotons by „spin-filtering“ APR PAX: Once we know how to spin-filter …

17. 10. Januar 2015 Institut für Kernphysik (IKP) Folie 17 Final step: Asymmetric (double polarized) proton (15 GeV/c) – antiproton (3.5 GeV/c) collider using HESR, CSR and APR PAX: HESR Upgrade