1 dr. Paolo Lenisa Università di Ferrara and INFN – ITALY on behalf of the PAX-Collaboration Perspectives for Polarized Antiprotons Polarized Antiprotons P.Lenisa XIV International Workshop on Polarized Sources, Targets and Polarimetry St. Petersburg, 13.09.2011
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dr. Paolo Lenisa Università di Ferrara and INFN – ITALY on behalf of the PAX-Collaboration
Perspectives for Polarized Antiprotons. dr. Paolo Lenisa Università di Ferrara and INFN – ITALY on behalf of the PAX-Collaboration. XIV International Workshop on Polarized Sources, Targets and Polarimetry St. Petersburg, 13.09.2011. Polarized Antiprotons. Motivation: - PowerPoint PPT Presentation
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dr. Paolo LenisaUniversità di Ferrara and INFN – ITALY
on behalf of the PAX-Collaboration
Perspectives for Polarized Antiprotons
Polarized AntiprotonsP.Lenisa
XIV International Workshop on Polarized Sources, Targets and PolarimetrySt. Petersburg, 13.09.2011
For an ensemble of spin ½ particles with projections + () and – ()
13Polarized AntiprotonsP.Lenisa
Spin-filtering
14P.Lenisa
Polarization build-up of a circulating particle beam by interaction with a polarized gas target
Polarized Antiprotons
Unpolarized anti-p beam
Polarized target
Polarization Buildup
P.Lenisa 15
S beam-particle spinQ target polarizationk || beam direction
)ˆ)(ˆ()( 210 kQkSQStot
)/tanh()(
tNN
NNtP
fdQ t
1
~1
fQdt)~~(
1
1
||
Polarized Antiprotons
Unpolarized anti-p beam
Polarized target
Polarized anti-p beam
P.Lenisa 16
Polarization BuildupS beam-particle spinQ target polarizationk || beam direction
)ˆ)(ˆ()( 210 kQkSQStot
)/tanh()(
tNN
NNtP
fdQ t
1
~1
fQdt)~~(
1
1
||
Polarized Antiprotons
Optimum (black curve) after 2 lifetimes filtering
Spin-filtering at TSR: „FILTEX“ – proof-of-principle
Spin filtering works for protons
F. Rathmann et al., PRL 71, 1379 (1993)
17Polarized AntiprotonsP.Lenisa
PAX@AD/CERN:Antiproton polarization
PAX@COSY :Proton polarization
PAX@FAIR:Eexperiments with
pol. pbar
P.Lenisa 18Polarized Antiprotons
Polarized AntiprotonsExperimental program:
Measurements with pbar at AD-Ring
P.Lenisa 19
PAX target section
Measurements at AD (CERN)•Aim: 1st measurement of the spin-dependence of the pbar-p cross section•Method: measurement of polarization build-up by spin-filtering
Polarized Antiprotons
Spin-dependence of the pbar-p interaction
P.Lenisa 20
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).
Polarized Antiprotons
Expected polarizations after filtering for two lifetimes
transverse
A
D
21
longitudinal
Polarized AntiprotonsP.Lenisa
• Measurement of the polarization buildup allows determination of σ1 and σ2
• Once pbar polarization available, spin-correlation coefficients accessible
Polarized Antiprotons 22
More recent calculations…
PLB 690 (2010)
P.Lenisa
Cross sections
Projected polarizations
PAX@AD/CERN:Antiproton polarization
PAX@COSY :Proton polarization
PAX@FAIR:Experiments with pol. pbar
P.Lenisa 23Polarized Antiprotons
Polarized AntiprotonsExperimental program
Measurements with p at COSY-Ring (Germany)
WASA
e-cooler
ANKE
PAX
Spin-filtering at COSY
Main purpose:1. Commissioning of the experimental setup for CERN/AD2. Quantitative understanding of the machine parameters
P.Lenisa 24Polarized Antiprotons
Installation of low-β section (2009)
•Beam has to fit through storage cell target (dt=5x1013 atoms/cm2)•Increase acceptance angle at target position
P.Lenisa 25Polarized Antiprotons
• Model in good agreement with measurement: β ~ 0.3m -> beam fits through the cell!
• No negative impact on the COSY operation
Commissioning of the experimental setup (2010)I. Machine studies: Low- section
P.Lenisa 26Polarized Antiprotons
In case intra-beam scattering poses a limitation, increase of beam emittance should increase lifetime! (Touschek)
• Increase of beam emittance by tilting of electron cooler beam• Beam emittance measured with ionisation profle monitor
P.Lenisa 27Polarized Antiprotons
Commissioning of the experimental setup (2010)I. Machine studies: Studies of beam-lifetime