Spin Filtering Studies at COSY and AD

1. Alexander Nass for the collaboration University of Erlangen-Nürnberg Spin Filtering Studies at COSY and AD SPIN 2008, Charlottesville,VA,USA, October 8, 2008

2. QCD Physics at FAIR (CDR): unpolarized Antiprotons in HESR HESR Central PAX Physics Case: Transversity distribution of the nucleon in Drell-Yan: FAIR as successor of DIS physics • last leading-twist missing piece of the QCD description of the partonic structure of the nucleon • observation of h1q (x,Q2) of the proton for valence quarks(ATT in Drell-Yan >0.2) • transversely polarized proton beam or target () • transversely polarized antiproton beam () PAX Polarized Antiprotons

3. Principle of Spin Filtering 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 p/p beam Polarized H target

4. Principle of Spin Filtering 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: Polarized p/p beam Polarized H target

5. Spin Filtering Tests at TSR (MPI Heidelberg) Results Experimental Setup T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993)

6. Interpretations of the result • Observed polarization cross section:σ = 72.5 ± 5.8 mb • Current interpretation: 2001, Milstein and Strakhovenko + Nikolaev and Pavlov: selective removal through scattering off nuclei beyond the acceptance angle => σ = 85.6mb  Experimental tests to disentangle the effects of electrons and nuclei  Experiments with protons at COSY (Jülich): • Depolarization measurements done (talk of F. Rathmann) • Spin Filtering experiments with polarized target No data to predict polarization for filtering antiprotons  Spin Filtering measurements with antiprotons at AD (CERN)

7. Requirements for Spin Filtering • Highly polarized internal gaseous target with areal densities up to 1014 atoms/cm2Storage cell • Passing of the stored p/p beam through this cell and high acceptance  Low beta section • Ability to produce and measure nuclear polarization of H and D target gas with xyz-target holding fields Atomic Beam Source and polarimeter • Longitudinal spin filtering Siberian snake • Detection of recoil particles  Silicon detectors

8. Experimental Overview Low-b-Quadrupoles ABS COSY-Quadupoles Target chamber w storage cell and detectors BRP

9. The Polarized Atomic Beam Source • Former HERMES ABS rebuilt with modified vacuum system • New cabling for fast installation and removal and new interlock system • Construction of an analysis chamber with QMS and compression tube • First intensity measurements done (intensities up to 6 x 1016 atoms/s) • Tests with a new alcohol cooled microwave dissociator on the way

10. Storage Cell and Holding field Weak holding field coils at the outside of the target chamber to provide quantization axis for the spins of the target atoms • Filtering requires 1014 atoms/cm2 storage cell • Walls of Teflon foil to let recoils pass and suppress depolarization and recombination • Openable cell to allow injected uncooled AD beam to pass • First cell prototype built and to be tested soon Cell cross section 10 x 10 mm

11. Storage Cell

12. The Breit-Rabi Polarimeter Former HERMES BRP rebuilt with modifications due to new configuration Tracking calculations  modified sextupole magnet configuration for 300 K effusive H / D beam New strong field transition cavity forhydrogen and deuterium New cabling and interlock system are installed, start-up on the way

13. The low-b-section • Increase of luminosity and acceptance to reach reasonable polarization build-up times and polarization • Calculations show that 4 (6) additional quadrupoles are necessary for COSY (AD) COSY AD Cell Size

14. The low-b-section • Superconducting quadrupoles needed to reach the necessary pole-tip fields • Design of the coils and cryostats on the way, first prototype will be produced in 2009 • Inside of cryostat will be used as cryopump Magnets in cryostat for COSY

15. Beam Line Vacuum at the Target • Flow limiters to reduce gas flow into the adjacent sections • Pump with cold surfaces of the superconducting quadrupoles

16. Silicon Detectors • Measurements of beam polarization using pp (pp)-elastic scattering at COSY (AD) • Good azimuthal resolution (up/down asymmetries) • Low energy recoils (<8 MeV) detected by silicon telescopes

17. Transverse & Longitudinal Filtering target • Use of the WASA and electron cooler solenoid to form a Siberian snake at COSY for long. filtering • Implementation of a Siberian snake into AD

18. Planned measurements • 2010/11: Filtering measurements at COSY withnuclear polarized hydrogen targetin a weak magnetic holding field using a protonbeam to produce polarized protons and commission the experiment for AD. • 2011/12: Filtering measurements at AD withnuclear polarized hydrogen and deuterium targetin a weak magnetic holding field and anantiprotonbeam to show the ability of the method toproduce polarized antiprotons.