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PAXPolarized Antiprotons
2nd Meeting FAIR Experiments
February 25, 2009 | Hans Ströher (FZ-Jülich)
11. April 2023 Institut für Kernphysik (IKP) Folie 2
Goal: Provide an effective method for in-situ polarization of (anti-)protons:
PAX: Polarized Antiprotons
11. April 2023 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
11. April 2023 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
11. April 2023 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
beamSpin
transfer
Velocity mismatch v/c ~ 0.002
Idea:
VERY different predictions for cross section: R ~ 1016 !!
PAX: Polarization of Antiprotons – 1
11. April 2023 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
beamSpin
transfer
Velocity mismatch v/c ~ 0.002
Idea:
Test at COSY:
PAX: Polarization of Antiprotons – 1
11. April 2023 Institut für Kernphysik (IKP) Folie 7
p
e-cooler
Tp = 49 MeVCOSYe-cooler
Polarization analysis by pd elastic scatteringpe interaction in electron cooler
PAX: Polarization of Antiprotons – 1
Expt.:Expt.: Proton depolarization at COSY – Setup
11. April 2023 Institut für Kernphysik (IKP) Folie 8
Expt.:Expt.: Proton depolarization at COSY – Results (submitted PL B, Febr. 09)
Ratio of beam polarizations withand 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
11. April 2023 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
11. April 2023 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. April 2023 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
11. April 2023 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)
11. April 2023 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
11. April 2023 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 !Now and here or never !
PAX: Summary
11. April 2023 Institut für Kernphysik (IKP) Folie 15
End
PAX: Polarized Antiprotons
11. April 2023 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“APRAPR
PAX: Once we know how to spin-filter …
11. April 2023 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
