spin filtering at cosy and perspectives for pax
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Spin Filtering at COSY and Perspectives for PAX. September 17, 2012 | Alexander Nass. Our 1st Proposal on Spin Filtering (2005). Polarize antiprotons by „ spin-filtering “. PAX Proposal to FAIR (2005). 178 Collaborators 36 Institutions (15 EU, 21 Non-EU). - PowerPoint PPT PresentationTRANSCRIPT
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Spin Filtering at COSY and Perspectives for PAX
September 17, 2012 | Alexander Nass
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Polarize antiprotons by „spin-filtering“
September 17, 2012
Our 1st Proposal on Spin Filtering (2005)
SPIN2012, Dubna, Russia
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3September 17, 2012
PAX Proposal to FAIR (2005)
SPIN2012, Dubna, Russia
High Energy Storage Ring (HESR) for a
beam of antiprotons
178 Collaborators36 Institutions
(15 EU, 21 Non-EU)
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4September 17, 2012
Quark structure of the nucleon
SPIN2012, Dubna, Russia
transversely polarisedquarks and nucleons
q
longitudinally polarisedquarks and nucleons
q
unpolarised quarksand nucleons
q
nxqxqxqx T1
55LTw2Corr Sγγ)(γ)(S)(
21)(
Well known Known Less known
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5September 17, 2012
Physics with Polarized Antiprotons
SPIN2012, Dubna, Russia
Polarized antiprotons will pave the way to novel double (and single) spin observables: • Proton-spin structure:
Complete map of transversity Flavour separation
• Electromagnetic Form FactorsIndependent extraction of moduli of GE-GM in Time-Like regionTest of the Rosenbluth separation in Time-Like regionMeasurement of the phase
• Hard p-pbar scatteringAdditional measurement in one of the most intriguing puzzles of
Hadron Physics • Hadron spectroscopy • Low-t pbar-p scattering
Spin and isospin dependence of nucleon-antinucleon interaction at low energy
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6September 17, 2012
Access to transversity through Drell-Yan
SPIN2012, Dubna, Russia
llqq *
q q
q qqqqqTTTT xqxqxqxqe
xhxhxhxheaA
)()()()(
)()()()(ˆ
dddd
21212
211121112
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7September 17, 2012
Phase I: Fixed target experiments in CSR
SPIN2012, Dubna, Russia
direction ofantiprotons
Physics: EMFF pbar-p elastic
Independent from HESR running
pol./unpol. antiprotons in CSR 0.2 GeV/c<p<2.5 GeV/cpolarized internal proton target
(antiprotons)
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8September 17, 2012
Phase II: Asymmetric Proton-Antiproton Collider
SPIN2012, Dubna, Russia
direction ofprotons
direction ofantiprotons
polarized antiprotons in HESR (p=15 GeV/c)polarized protons in CSR (p=3.5 GeV/c)
Physics: Transversity EMFF pbar-p elastic
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9September 17, 2012
Antiproton Polarizer Ring (APR)
SPIN2012, Dubna, Russia
Ring ParameterBeam energy 250 MeV
Number of antiprotons
1012
Ring acceptance 250 mm mrad
Betatron ampl. at IP < 0.3m
Ring circumference 86,5 m
Snake strength 2.4 Tm
Target
Electron Cooler Snake
Ion-optics at IPAtomic Beam Source (ABS) parameter
ABS flow in feeding tube
1,5·1017 /s
Storage cell length 40 cmFeeding tube diameter length
1 cm 15 cm
Long. holding field 300 mTNuclear polarization 0.9Cell temperature 100 K
Injection/Extraction
Final configuration after spin-filtering studies
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10September 17, 2012
Evaluation by QCD-PAC (March 2005)
SPIN2012, Dubna, Russia
… the PAC would like to stress again the uniqueness of the program with polarized anti-protons and polarized protons that could become available at GSI.
Recommendation of the STI of FAIR (Sept. 2005)The STI (Scientific and Technical Issues) requests R&D work to be continued on the proposed asymmetric collider experiment with both polarized anti-protons and protons:
- to demonstrate that the required luminosity for decisive measurements can be reached ( accomplished)
- to demonstrate that a high degree of anti-proton polarisation can be reached
The STI believes that PAX should become part of the FAIR core research program based on its strong scientific merit once the open problems are convincingly solved.
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11September 17, 2012
Luminosity Considerations for Collider Mode
SPIN2012, Dubna, Russia
Particle speciesMomentum / GeV/cNumber of bunchesTotal number of particlesBeam lifetime / hPeak luminosity / cm-2 s-1
CSR HESRproton
s antiproton
3.65 1510 30
1012 3·1011
~ 45 ~ 8001.6·1030
CSR HESRantiproton
s proton
3.65 15- -
5·1011 1012
~ 1500 ~ 3001.2·1031
“old”
“new”
Antiprotons in HESR -> protonsBunched beams -> coasting
L>1031s-1cm-2
2006: I. milestone for PAX
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12September 17, 2012
Polarized Antiprotons
SPIN2012, Dubna, Russia
Intense beam of polarized antiprotons was never produced:• Conventional methods (ABS) not applicable
• Polarized antiprotons from anti-lambda decay • I < 1.5 10∙ 5 s-1 (P ≈ 0.35)
• Antiproton scattering off liquid H2 target• I < 2 10∙ 3 s-1 (P ≈ 0.2)
Small polarization from pbar-C scattering experiments at LEAR• Stern-Gerlach spin separation in a beam (never tested, theoretically
unlikely to work)
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13September 17, 2012
Production of polarization in a stored BeamTwo Methods: Loss versus spin flip
SPIN2012, Dubna, Russia
For an ensemble of spin ½ particles with projections + () and – ()
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14September 17, 2012
A new idea (2007)
SPIN2012, Dubna, Russia
Eur. Phys. J. A 34, 447 (2007)
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15September 17, 2012
ep spin flip studies at COSY (2008)
SPIN2012, Dubna, Russia
• Use proton beam and co-moving electrons • Turn experiment around: p e → p e into p e → p e i.e. observe depolarization of a polarized proton beam
COSY electron cooler
(detuned)
Velocity mismatch
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16September 17, 2012
Principle of the Depolarization Measurement
SPIN2012, Dubna, Russia
Nominal CoolerVoltage
Tnominal = 100 s
Detuned CoolerVoltage
Tdetuned= 50 s
D2 Target onEcool on
D2 Target offEcool on/detuned
2TT
uneddet
alminno
Eh = 0.001 MeVΔV = 235 V
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17September 17, 2012
ep spin flip cross section at COSY
SPIN2012, Dubna, Russia
No effect observed: measured cross sections at least 6 orders-of-magnitude smaller than predicted 1013 b
0
4107
|Relative velocity of electrons in proton rest frame| (c)
dep
ol (b
arn)
Nominal proton energy in electron rest frame (keV)0 1 2 3
0 110-3 210-3 310-3
2107
-2107
-4107
D.Oellers et al., Physics Letters B 674 (2009) 269
Meanwhile, Mainz group discovered numerical problems in the calculation → two errata.
2008: II. milestone for PAX
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18September 17, 2012 SPIN2012, Dubna, Russia
Production of polarization in a stored BeamTwo Methods: Loss versus spin flip
For an ensemble of spin ½ particles with projections + () and – ()
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19September 17, 2012
Spin Filtering
SPIN2012, Dubna, Russia
Polarization build-up of a circulating particle beam by interaction with a polarized gas target
Unpolarized anti-p beam
Polarized target
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20September 17, 2012
Spin Filtering
SPIN2012, Dubna, Russia
Polarization build-up of a circulating particle beam by interaction with a polarized gas target
Unpolarized anti-p beam
Polarized target
Polarized anti-p beam
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21September 17, 2012
Filter Test at TSR with protons (FILTEX, 1992)
SPIN2012, Dubna, Russia
Experimental Setup
F. Rathmann. et al., PRL 71, 1379 (1993)
T=23 MeV
Low energy pp scattering
1<0 tot+<tot-
Expectation
Target Beam
PAX submitted new proposal to find out how well does spin filtering work for antiprotons Measurement of the Spin-Dependence of the pp Interaction at the AD Ring
(CERN-SPSC-2009-012 / SPSC-P-337)
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22September 17, 2012
Plan for PAX at AD / CERN (2009)
SPIN2012, Dubna, Russia
PAX target section
Electron cooler
Siberian snake
Status in 2009:• Spin-filtering only viable option• Spin-dependence of pbar-p
interaction unknown• “Warm” solution for AD lattice
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23September 17, 2012
Spin dependence of the pbar-p interaction
SPIN2012, Dubna, Russia
Model A: T. Hippchen et al., Phys. Rev. C 44, 1323 (1991).
Model OBEPF: J. Haidenbauer, K. Holinde, A.W. Thomas, Phys. Rev. C 45, 952 (1992).
Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995).
• Measurement of the polarization buildup equivalent to the determination of σ1 and σ2
• Once a polarized antiproton beam is available, spin-correlation data can be measured at AD (50-500 MeV)
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24September 17, 2012
Additional calculations
SPIN2012, Dubna, Russia
Cross sections
Projected polarizations
PLB 690 (2010)
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25September 17, 2012
Stages of installation at AD
SPIN2012, Dubna, Russia2010 2011 2012
Installation of six magnets for the low-β insertion
Spin-filtering measurements up to 70 MeV with transverse beam
polarization
Installation of the target chamber: Machine acceptance
studies. Stacking studies
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26September 17, 2012 SPIN2012, Dubna, Russia
PAX gets acknowledgement in the community:EU-Grants
• 2008-2011 – I3HP2 WP25 (PolAntiP)• Depolarization studies• Transverse spin-filtering at COSY
• 2012-2014 – I3HP3 WP25 (PolAntiP)• Longitudinal spin-filtering at COSY
• 2010-2015 – Advanced Resarch Grant POLPBAR
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Spin Filtering at COSY (2008-2011)
WASAe-cooler
ANKE
PAX
SPIN2012, Dubna, RussiaSeptember 17, 2012
Main purpose:1. Commissioning of the experimental setup for CERN/AD2. Quantitative understanding of the machine parameters
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Commissioning (2008-2011)
SPIN2012, Dubna, RussiaSeptember 17, 2012
ABS
Breit-Rabi
polarimeter
• 2008-11: Installation and commissioning of the HERMES pol. target
p D2
• 2008-11: Installation and commissioning of the ANKE beam polarimeter
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Commissioning (2008-2011)
SPIN2012, Dubna, RussiaSeptember 17, 2012
• 2009-10: Installation and commissioning of the low-β section
• 2010-11: Studies of beam-lifetime limitations
(t: 300 s 8000 s)
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30September 17, 2012 SPIN2012, Dubna, Russia
Spin Filtering at COSY (2011)
p
cluster targ. + STT (beam
polarimetry)
polarized target
COSY ring
Spin-flipper
2011: III. milestone for PAX
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31September 17, 2012 SPIN2012, Dubna, Russia
Conclusion: Spin Filtering
• Antiproton polarization:• Spin filtering only viable mechanism • Complete understanding of spin filtering
with p• Data on spin-dependence of pbar-p
interaction needed•Polarized antiprotons remain a missing and unique tool for hadron physics
(More about in the talk of G.Ciullo)
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32September 17, 2012 SPIN2012, Dubna, Russia
Conclusion: Physics case for pol. antiprotons
• ATT in Drell-Yan production remains the unique direct way to access h1• pbar-p, pbar-d, p-p, p-d collider remains a unique machine to perform
the flavour decomposition of transversity
• Interest in Transverse Momentum dependent effect has increased• PAX physics case should be updated with the novel transverse
momentum distributions (TMD)
• Interest in proton EMFF has developed:• Different Space-Like experiments addressing two-photon
contribution• Still no individual determination yet of FF in the Time-Like region• Necessity of a complete space-time description