P.Lenisa Polarized Antiprotons 1 dr. Paolo Lenisa dr. Paolo Lenisa Università Università di Ferrara and INFN di Ferrara and INFN - - ITALY ITALY STORI 08, Lanzhou 16.09.08 How to produce polarized antiprotons How to produce polarized antiprotons and what to do with them at FAIR and what to do with them at FAIR
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P.Lenisa Polarized Antiprotons 1
dr. Paolo Lenisadr. Paolo LenisaUniversitàUniversità di Ferrara and INFN di Ferrara and INFN -- ITALYITALY
STORI 08, Lanzhou 16.09.08
How to produce polarized antiprotons How to produce polarized antiprotons and what to do with them at FAIRand what to do with them at FAIR
P.Lenisa Polarized Antiprotons 2
Introduction
P.Lenisa Polarized Antiprotons 3
The FAIR facility at Darmstadt
P.Lenisa Polarized Antiprotons 4
The FAIR facility at Darmstadt
P.Lenisa Polarized Antiprotons 5
Intense beam of polarized antiprotons never produced:• Conventional methods (ABS) not applicable
• Polarized antiprotons from antilambda decay• I < 1.5·105 s-1 (P ≈ 0.35)
• Antiproton scattering off liquid H2 target• I < 2·103 s-1 (P ≈ 0.2)
• Little polarization from pbarC scattering exp’ts at LEAR
Polarized Antiprotons: a long storyPolarized Antiprotons: a long story
Methods not applicable to storage rings
- 1985 - Bodega Bay:“International Workshop on Polarized Antiprotons Beam”
- 2007 - Daresbury:“Polarized Antiprotons: How”
- 2008 – Bad Honnef:Heraeus Seminar: “Polarized Antiprotons”
P.Lenisa Polarized Antiprotons 6
Polarized Antiproton in Storage RingsPolarized Antiproton in Storage Rings- Two possible methods:
Spin-filtering Spin-flip
P.Lenisa Polarized Antiprotons 7
Spin-flip: a recent proposal
-> need for experimental test
•Antiproton beam polarization by interaction with a polarized positron beam
2x1013 barn!
P.Lenisa Polarized Antiprotons 8
Depolarization studies at COSY: idea
•Use proton beam and co-moving electrons•Turn experiment around: into
i.e. depolarization of a polarized proton beamepep
→→
→ pep →→
P.Lenisa Polarized Antiprotons 9
Depolarization studies at COSY: principle•Use (transversely polarized) proton beam in COSY•Switch on (detuned) electron cooler to depolarize proton bam• Analyze proton polarization with internal D2-cluster target at ANKE
Silicon detector for beampolarimetry• Pbar-Beam polarization by using the (measured) analysing power of pbar-p elastic
(after spin-filtering)
• Modular structure• 10 cm x 10 cm silicon wafers• 300 μm thick• Open cell without moving det.• Re-use of HERMES recoil
P.Lenisa Polarized Antiprotons 26
Silicon detector for beampolarimetry
HERMES recoil
P.Lenisa Polarized Antiprotons 27
dr. Paolo Lenisadr. Paolo LenisaUniversitàUniversità di Ferrara and INFN di Ferrara and INFN -- ITALYITALY
STORI 08, Lanzhou 16.09.08
How to produce polarized antiprotonsHow to produce polarized antiprotonsand what to do with them at FAIRand what to do with them at FAIR
P.Lenisa Polarized Antiprotons 28
=qδ −h1=
transversely polarisedquarks and nucleons
longitudinally polarisedquarks and nucleons
=Δq −
unpolarised quarksand nucleons
=q
Quark structure of the nucleon
Well known Known Only glimpse
{ } ++Δ+=Φ nxqxqxqx T1
55LTw2Corr Sγγ)(γ)(S)(
21)( δ
Study of the proton spin
P.Lenisa Polarized Antiprotons 29
Transversity
- Probes relativistic nature of quarks- No gluon analog for spin-1/2 nucleon- Different evolution than - Sensitive to valence quark polarizationtransversely polarised