Mitglied der Helmholtz-Gemeinschaft PAX Polarized Antiprotons 2nd Meeting FAIR Experiments February...

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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