Polarization Experiments in Storage Rings

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Polarization Experimentsin Storage Rings
XV GIORNATE DI STUDIO sui RIVELATORI
Part II future Spin-physics with polarized
antiprotons?
dr. Paolo Lenisa Università di Ferrara and INFN -
sez. Ferrara
Torino, 1-4 Febbraio 2005
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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location andTime Schedule
• APPENDIX

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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location andTime Schedule
• APPENDIX

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Basics twist 2 distribution functions
Probabilistic interpretation in helicity base
f1(X)
q(x) spin averaged (well known)
Dq(x) helicity diff (known)

• No probabilstic interpretation in the helicity
  base (off diagonal)

NEW BASE
u? 1/?2(uR uL) u? 1/?2(uR - uL)
Transversity base
dq(x) helicity flip (unknown)
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Transversity
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Transversity and DIS

• f1 and g1 preserve quark helicity
• h1 a chiral-odd object (involves helicity flip)
• Quark chirality conserved in QCD and electroweak
  processes

• Tranversity decouples from inclusive DIS
• Transversity is difficult to measure

• Another chiral odd object flipping chirality
  needed
• Collins fragmentation function (H?1)

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Transverse asymmetries in pion production
hep-ex/0408013, submitted to PRL
Indirect Measurement Convolution of transversity
with unknown fragmentation function
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Transversity in Drell-Yan processes
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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location andTime Schedule
• APPENDIX

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Polarized internal target
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Principle of spin filter method
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Principle of spin filter method
Polarized p target
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Principle of spin filter method
For low energy pp scattering ?1lt0 ? ?totlt?tot-
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Experimental Setup at TSR (1992)
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1992 Filter Test at TSR with protons
Results
Experimental Setup
T23 MeV
F. Rathmann. et al., PRL 71, 1379 (1993)
Low energy pp scattering ?1lt0 ? ?totlt?tot-
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Puzzle from FILTEX Test
Observed polarization build-up dP/dt (1.24
0.06) x 10-2 h-1
Expected build-up P(t)tanh(t/tpol),
1/tpols1Qdtf2.4x10-2 h-1 ? about factor 2
larger!
s1 122 mb (pp phase shifts) Q 0.83 0.03 dt
(5.6 0.3) x 1013cm-2 f 1.177 MHz

• Three distinct effects
• Selective removal through scattering beyond
  ?acc4.4 mrad sR?83 mb
• Small angle scattering of target protons into
  ring acceptance sS?52 mb
• Spin transfer from polarized electrons of the
  target atoms to the stored protons
• sEM?70 mb (-)

Horowitz Meyer, PRL 72, 3981 (1994) H.O. Meyer,
PRE 50, 1485 (1994)
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Spin transfer from electrons to protons
Horowitz Meyer, PRL 72, 3981 (1994) H.O. Meyer,
PRE 50, 1485 (1994)
a fine structure constant ?p(g-2)/21.793 ano
malous magnetic moment me, mp rest
masses p cm momentum a0 Bohr
radius C022p?/exp(2p?)-1 Coulomb wave
function ?za/? Coulomb parameter (negative for
antiprotons) v relative lab. velocity between p
and e z beam charge number
PAX will exploit spin-transfer from polarized
electrons of the target to antiprotons
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Spin Transfer Cross Section
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Beam lifetimes in the APR
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Polarization Buildup optimal polarization time
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Optimum Beam Energies for Buildup in APR
F. Rathmann et al., physics/0410067 (2004)
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Beam Polarization
Filter Test T 23 MeV ?acc 4.4 mrad
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Transfer from APR to HESR and Accumulation
Injection
Siberian Snake
HESR
APR
440 m
e-cooler
e-cooler
150 m
Extraction
ABS
Polarizer Target
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Accumulation of polarized beam in HESR
PIT dt7.21014 atoms/cm2 tHESR11.5 h
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Accelerators layout for the experiment
2 possible options
1. Fixed polarized with 22 GeV polarized
antiproton beam.
2. Asymmetric collider polarized antiprotons in
HESR (15 GeV) polarized protons in CSR (3.5 GeV)
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Estimated Luminosity for Double Polarization
R L sint
Polarized Internal Target in HESR
Collider luminosity estimated around 5 1030
cm-2s-1
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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location andTime Schedule
• APPENDIX

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Transversity in Drell-Yan processes
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ATT for PAX kinematic conditions
RHIC tx1x2M2/s10-3 ? Exploration of the sea
quark content (polarizations small!) ATT very
small ( 1 )
PAX M210-100 GeV2, s45-200 GeV2,
tx1x2M2/s0.2-0.3 ? Exploration of valence
quarks (h1q(x,Q2) large)
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ATT for PAX kinematic conditions
RHIC tx1x2M2/s10-3 ? Exploration of the sea
quark content (polarizations small!) ATT very
small ( 1 )
PAX M210 GeV2, s45-200 GeV2,
tx1x2M2/s0.2-0.3 ? Exploration of valence
quarks (h1q(x,Q2) large)
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Signal Estimate
Polarized Antiproton Beam ? Polarized Proton
Target (both transversely polarized)
2) Angular distribution of the asymmetry.
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Drell-Yan cross section and event rate

• M2 s x1x2
• xF2QL/vs x1-x2

Collider with L5 x 1030 cm-2s-1 gets comparable
rates
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ATT asymmetry angular distribution

• Asymmetry is largest for angles 90
• Asymmetry varies like cos(2f).

Needs a large acceptance detector (LAD)
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Detector concept

• Drell-Yan process requires a large acceptance
  detector

Good hadron rejection needed (stot 50 mb, sDY
1nb) 102 at trigger level, 104 after data
analysis for single track.
QUESTION electron or muons?
Magnetic field envisaged Increased invariant
mass resolution compared to calorimeter Improved
PID through Energy/momentum ratio Separation of
wrong charge combinatorial background
QUESTION solenoid or toroid field?
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The PAX detector (collider option)
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Double Polarization Experiments ? Azimuthal
Symmetry
Possible solution Toroid (8 superconducting
coils)

• 800 x 600 mm coils
• 3 x 50 mm section (1450 A/mm2)
• average integrated field 0.6 Tm
• free acceptance gt 80

Superconducting target field coils do not affect
azimuthal acceptance.
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Estimated signal
L5x1030 cm-2s-1 180 days of data taking at 50
efficiency
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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location and Time Schedule
• APPENDIX

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Faciltiy for Antiproton and Ion Research (GSI,
Darmstadt, Germany)

• Proton linac (injector)
• 2 synchrotons (30 GeV p)
• A number of storage rings
• ? Parallel beams operation

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The FAIR project at GSI
SIS100/300
50 MeV Proton Linac
HESR High Energy Storage Ring PANDA (and PAX)
CR-Complex
FLAIR (Facility for very Low energy Anti-protons
and fully stripped Ions)
NESR
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Time schedule

• Jan. 04 LOI submitted
• 15.06.04 QCD PAC meeting at GSI
• 18-19.08.04 Workshop on polarized antiprotons at
  GSI
• 15.09.04 Additional PAX document on polarization
  at GSI
• F. Rathmann et al., physics/0410067 (2004)
• 15.01.05 Technical Report (with Milestones)
• Evaluations Green Light for Construction
• 2005-2008 Technical Design Reports (for
  Milestones)
• gt2012 Commissioning of HESR

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More informations
http//www.fz-juelich.de/ikp/pax
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Outline
Spin-physics with polarized antiprotons

• WHY? Physics Case transversity
• HOW? Polarized Antiprotons
• WHAT? Transversity Measurement
• WHERE ANDWHEN? Location and Time Schedule
• APPENDIX Medical applications of polarized
  targets

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Polarized 3He for NMRs of the human lung (Werner
Heil)
Spin-Off of Polarized Gas Target Technology
Human Lung with 0.7 bar?liter of polarized 3He

PH mB/kT 510-6
PHe 1
?H/?He 2500
signal Pµ?
S/SH gt 10
amount of gas
Helium - MRI (3He)
Proton - MRI (1 H)
1 bar liter
DKFZ, HD Nov. 1995
Lancet
1996
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Polarized 3He for NMRs of the human lung

• Production of Polarized 3He at Mainz-University
• Storage in cells inserted in permanent magnetic
  field

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Polarized 3He for NMRs of the human lung
Transport time Mainz-Sheffield 10
h Mainz-Copenhagen lt 7 h Mainz-Orsay ( Paris )
8 h T1160 h

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Magnetic Resonance Imaging with 3He
Human Lung with 0.7 bar?liter of polarized 3He
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Final Remark
Polarization data has often been the graveyard of
fashionable theories. If theorists had their way,
they might just ban such measurements altogether
out of self-protection.
J.D. Bjorken St. Croix, 1987
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The world (of hadron physics)needs PAX
Lets go after it!
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The Antiproton Facility

• HESR (High Energy Storage Ring)
• Length 442 m
• B? 50 Tm
• N 5 x 1010 antiprotons
• High luminosity mode
• Luminosity 2 x 1032 cm-2s-1
• ?p/p 10-4 (stochastic-cooling)
• High resolution mode
• ?p/p 10-5 (8 MV HE e-cooling)
• Luminosity 1031 cm-2s-1

SIS100/300
HESR
Super FRS
CR
Gas Target and Pellet Target cooling power
determines thickness
NESR
Antiproton Production Target
Beam Cooling e- and/or stochastic 2MV prototype
e-cooling at COSY

• Antiproton production similar to CERN
• Production rate 107/sec at 30 GeV
• T 1.5 - 15 GeV/c (22 GeV)

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The new polarization facility
HESR
APR
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Background
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Final Remark

• In 1981 Rudolf Fleischmann (1903-2002)
• Professor of Physics in Erlangen
• originator of the first polarized atomic beam
  source (1956)
• asked himself at a conference, why progress in
  physics sometimes was so slow and took so many
  roundabouts.
• It seems to me that the main reason is that too
  much confidence is put in theoretical, and
  therefore quite hypothetical concepts and models,
  which are popular during the corresponding period
  and that it is very difficult to free oneself
  from them.

from D. Fick, Talk held on 5.5 2003 in the
Physics Colloquium at University of Erlangen
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The PAX detector
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Conclusion

• Challenging opportunities and new physics
  accessible at HESR
• Unique access to a wealth of new fundamental
  physics observables
• Central physics issue h1q (x,Q2) of the proton
  in DY processes
• Other issues
• Electromagnetic Formfactors
• Polarization effects in Hard and Soft Scattering
  processes
• differential cross sections, analyzing powers,
  spin correlation parameters
• Projections for HESR fed by a dedicated APR
• Pbeam gt 0.30
• 5.61010 antiprotons
• L ? 2.7 1031 cm-2s-1 for fixed target double
  polarized experiment
• Exact luminosity for the collider under
  evaluation 5 1030
• Detector concept
• Large acceptance detector with a toroidal magnet

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Comparison to standard MRI
?H/?He 2500
Proton - MRI (1 H)