The PAX Project and HEPI TSU Contribution

06 August, GGSWBS’12, Tbilisi.

Mirian Tabidze

High Energy Physic Institute of TSU

Hadron Physics

• Understanding of all matter comprised of quarks and gluons

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Introduction: Quark distributions

Very well known q(x) = q+(x) + q-(x)

Well known Δq(x) = q+(x) - q-(x)

Largely unknown Chirality Odd nature

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Soffer inequality: q(x) + Δq(x) ≥ 2|δq(x)|

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Proton Spin

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Introduction: Drell Yan

Double transverse spin asymmetry

ATT d d

d d ˆ a TT

eq2h1

q (x1,M2)

q h1

q (x2,M2)

eq2q(x1,M

2)q q (x2,M

2)

• Interaction between quark and antiquark

• Direct access to “transversity“ in Drell Yan

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PAX DETECTOR: Artists view

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Drell-Yan signal and background

*

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PolarisationFor an ensemble of spin ½ particles with projections + () and – ()

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σ(↑↑) ≠ σ(↑↓)

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Spin Flip

Polarised positron

beam

Un-polarised anti-proton

beam

Polarised anti-proton beam

Spin transfer

Velocity mismatch Dv/c ~ 0.002

Idea:

How to check this idea with the existing experimental facilities?

Do polarised electrons (positrons) polarise a proton (anti-proton) beam ?

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Spin Flip: Depolarisation study at COSY

p

Tp = 49 MeV COSY

e-coolerANKE cluster target & STT

• Use (transversely) polarised proton beam circulating in COSY• Switch on electron cooler to depolarise proton beam

• Analyze proton polarisation with internal D2-cluster target of ANKE

circumference 184 mMirian Tabidze HEPI TSU

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Spin Flip: Depolarisation study at COSY

pd elastic scattering:detection in two (L-R) symmetric Silicon Tracking Telescopes

Deuteron identification

d

p

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Spin Flip: Depolarisation study at COSY

Ratio of beam polarisations withand without 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 !

D.Oellers et al., Physics Letters B 674 (2009) 269

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Spin Filtering

Unpolarised anti-p beam

Polarised target

P beam polarizationQ target polarizationk || beam direction

σtot = σ0 + σ1·P·Q + σ2·(P·k)(Q·k)

Qtot 10 Transversecase: Qtot )( 210 Longitudinal

case:

For initially equally populated spin states: (m=+½) and (m=-½)

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Spin Filtering

Unpolarised anti-p beam

Polarised target

P beam polarizationQ target polarizationk || beam direction

σtot = σ0 + σ1·P·Q + σ2·(P·k)(Q·k)

Qtot 10 Transversecase: Qtot )( 210 Longitudinal

case:

For initially equally populated spin states: (m=+½) and (m=-½)

Mirian Tabidze HEPI TSU

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Spin Filtering

Polarised anti-p beam

Polarised target

P beam polarizationQ target polarizationk || beam direction

σtot = σ0 + σ1·P·Q + σ2·(P·k)(Q·k)

Qtot 10 Transversecase: Qtot )( 210 Longitudinal

case:

For initially equally populated spin states: (m=+½) and (m=-½)

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ANKE

TOF

WASA

PAX

COSYe-cooler

Spin Filtering: PAX at COSY

Low-ß section:- Quadrupoles- ABS (SC, BRP)

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Skeleton view of new detector setup for SF

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PAX Georgian Participants

HEPI TSU Bagdasarian Zara (PhD), Lomidze Nodar, Mchedlishvili David (PhD), Nioradze Mikheil, Tabidze Mirian.IKP Jülich Kacharava Andro, Chiladze David (PosDoc).JINR Dubna Macharashvili Gogi.

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Summary• Outstanding physics potential of polarized antiprotons

• Very small cross-section for Spin Flip

• Spin Filtering seems to be the only way

• Investigations on Spin Filtering at COSY with transversely polarized target was done successfully (August 2011).

• Next step spin filtering at COSY with longitudinally polarized target (2014/2015).

• Next: Design of Antiproton Polariser Ring (APR?).

• Finally: asymmetric p-pbar collider (3.5-15 GeV/c) at FAIR.

Simulation results of SF

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