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PolarisationPolarisation Experiments Experiments in Storage Ringsin Storage Rings
Frank RathmannFrank RathmannIKP, Forschungszentrum JülichIKP, Forschungszentrum Jülich
Cologne, March 11, 2004
COSY
EDDA
ANKE
PIT ANKE
Ayp
Frank Rathmann Polarization Experiments in Storage Rings 2
OutlineOutline
•• IntroductionIntroduction•• Experiments with Hadronic ProbesExperiments with Hadronic Probes•• Methods and InstrumentationMethods and Instrumentation•• Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons•• SummarySummary
Frank Rathmann Polarization Experiments in Storage Rings 3
IntroductionIntroduction
• Hadronic Probes:–IUCF-PINTEX:
• Proton-Proton Elastic• NN → NNπ• Proton-Deuteron Elastic
–COSY-EDDA:• Proton-Proton Elastic• Time-Reversal Invariance
–COSY-ANKE:• Proton-Deuteron Dynamics• Neutron-Proton Elastic
–RHIC-SPIN• Electromagnetic Probes:
–Bates-BLAST–Novosibirsk-VEPP-3–HERA-HERMES (Plenary Talk)
Experimental and theoreticaldevelopments pave the way to
Future Hadron PhysicsFuture Hadron Physics programs
Near future exploitationat COSY
Past ~10 years, tremendousprogress in spin-physics
experiments with polarizedbeams on internal targets
Frank Rathmann Polarization Experiments in Storage Rings 4
OutlineOutline
•• IntroductionIntroduction•• Experiments with Hadronic ProbesExperiments with Hadronic Probes•• Methods and InstrumentationMethods and Instrumentation•• Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons•• SummarySummary
Frank Rathmann Polarization Experiments in Storage Rings 5
11stst Example: Elastic Scattering (low energy)Example: Elastic Scattering (low energy)
Relative statistical error of normalization
δδδδk/k (%)
0.31
1.08
0.89
1.17
1.01
1.03
0.86
1.00
Data base beginning of 90’s After IUCF measurements
197
250
280
294
310
350
399
449
T(MeV)
PINTEXPINTEX--IUCF:IUCF: Doubling the pp elastic world data base with highlyaccurate data ~ 6 weeks of data taking!
π0threshold
Frank Rathmann Polarization Experiments in Storage Rings 6
22ndnd Example: Elastic Scattering (higher energy)Example: Elastic Scattering (higher energy)
Elastic pp scattering• Characterization of NN-interaction:
– Large kinematical range:• 1.0 - 3.3 GeV/c, 30° - 90° [c.m.]
– High precision data• Unpolarized, single, double polarized• Large impact on pp PSA >500 MeV
• Further Results:– Search for dibaryons � excluded!– Polarimetry for the pp system
T=2.1 GeVCharacterization of NN scattering
EDDAEDDA--COSYCOSY
Frank Rathmann Polarization Experiments in Storage Rings 7
33rdrd Example: Pion ProductionExample: Pion Production
• simplest inelastic NN channelsystem of nontrivial complexity
- NN → NNπ• pseudoscalar meson with spin 0
- spin algebra ½ + ½ → ½ + ½• good clean experimental signature
- pp→ppπ0 , pp→pnπ+• close to threshold
- few partial waves involved- simple detection
Prediction of Observables: (Jülich theory group)• energy dependence σ(η)• differential cross sections dσ/dΩ, d3σ/dΩdp, …• analyzing power Ay(θ,p,..)• spin correlation coeff. Cxx(θ,p,..), Czz(θ,p,..), ….
PINTEXPINTEX--IUCF:IUCF: Double polarized pion production
N
N
PNN, LNN
q, lπ
π
π=ηm
)(qmax Near Threshold: η
Frank Rathmann Polarization Experiments in Storage Rings 8
33rdrd Example: Pion ProductionExample: Pion Production
)2(2)()(
)(2)()(
Pp*
PpPsSsL
Pp*
SsPsT
PpPsSstot
σ−σ−σ−σ=→σ−→σ=σ∆
σ+σ−σ=↑↑σ−↑↓σ=σ∆
σ+σ+σ=σ
Experiment• polarized beam on polarized target ±Py, ±Qx, ±Qy, ±Qz• identification of three-body reaction channel• integration over full phase space
Interpretation (Partial Wave Analysis): pp→ppπ0
Labels:(LNN, lπ)=0,1
σσ∆+
σσ∆+=
σσ
tot
L
tot
T
tot
Ps
211
41
Direct measurement of the Ps cross section
Total SpinTotal Spin--dependent Cross Sectionsdependent Cross Sections
Frank Rathmann Polarization Experiments in Storage Rings 9
33rdrd Example: Pion ProductionExample: Pion Production
pp→ppπ00m
)(q 0maxπ
π=η
Phase Space
Jülich Model
Measured Partial Wave Contributions
Phenomenological Models unsatisfactory (finished)New approach to pion production using χPT underway (Jülich group)
Frank Rathmann Polarization Experiments in Storage Rings 10
Ongoing Experiments: Deuteron BreakupOngoing Experiments: Deuteron Breakup
Tp (GeV)
pd dp
pd (pp)+n
ONESS
∆
0.3 0.4 0.5 0.6 0.65
qNN (GeV/c)
0.5 1 1.5 2 2.5 3
10-2
10-1
1
10
102
103
dσ/
dΩ
cm pp (µ
b/s
r)
Reid Soft Core
Paris
– Investigate pd dynamics at high momentum transfer:
– pd � (pp)s n– Kinematics like pd backward
elastic→ S-wave pp-pairs→ Suppression of ∆
– Progress1. cross sections (�)2. Analyzing Power Ayp (�)3. Future: Polarized target
– Analyzing Power T20 – Spin-Correlation Parameters
(double polarized)
Differential cross sectionANKEANKE--COSYCOSY:
Epp < 3 MeV
V. Komarov et al., PLB 562, 227 (2003)
Frank Rathmann Polarization Experiments in Storage Rings 11
Ongoing Experiments: Deuteron BreakupOngoing Experiments: Deuteron Breakup
ANKEANKE--COSYCOSYSurprisingly large Aypin pd � (pp)s n
• Explanation?
Effect shows strong energy dependence
Epp < 3 MeV
Epp < 3 MeV
p d
pp
n
θcm~166o?
Frank Rathmann Polarization Experiments in Storage Rings 12
npddσσσσσσσσ/d/dΩΩΩΩΩΩΩΩ
Future Experiments: NN Interaction (I=0)Future Experiments: NN Interaction (I=0)
• pn elastic data base scarcely populated• Phase Shift Analysis needed• Both Isospin channels required
0-101I3
0npnnnp 1pp
I
Methods:– Charge-Exchange breakup
•• dpdp→→((pp)pp)ssnn– Polarized deuteron target with
spectator tagging•• pdpd→→ppsspnpn..
Future:–– Similar data set for pn as produced Similar data set for pn as produced
by EDDA for pp systemby EDDA for pp system
COSYCOSY--ANKEANKE
ppddσσσσσσσσ/d/dΩΩΩΩΩΩΩΩ
symmetric
Frank Rathmann Polarization Experiments in Storage Rings 13
Future Experiments: NN Interaction (I=0)Future Experiments: NN Interaction (I=0)
COSYCOSY--ANKE:ANKE:Method: Charge-Exchange breakup
sensitive to spin-dependent amplitudes
Deuteron acts as a spin filter
Direct reconstruction of spin-flip amplitudes in collinear kinematics (q=0)
( )( ) )cos(Re2IC
,2IT
2I
*y,y
2220
22
βε ϕ−ϕ⇒εβ−=
εβ⇒
ε−β=
ε+β=
double polarized
( ) npppd0
1S→�
�
Method works
Frank Rathmann Polarization Experiments in Storage Rings 14
Future Experiments: Time Reversal Invariance TestFuture Experiments: Time Reversal Invariance Test
COSYCOSY--TRIC: PTRIC: P--even, Teven, T--oddodd
Total polarization correlation coefficient Ay,xz leads to relative difference of current slopes
– Milestone: Operation of Precision BCT
IBeam
time
COSY used as acceleratorand detector:
Frank Rathmann Polarization Experiments in Storage Rings 15
Future Experiments: Future Experiments: Parity of Parity of θθ+ + PentaquarkPentaquark
Double polarization fixes parity of θ+ free of any model!Spin-correlation coefficient Axx in pp ����θ+ΣΣΣΣ+
+1
-1
50 Q [MeV]0
neg. Parity
pos. Parity
Axx
appears s
oon in PL
B
WASAWASA--COSYCOSYwith a polarized
jet target
Frank Rathmann Polarization Experiments in Storage Rings 16
OutlineOutline
•• IntroductionIntroduction•• Experiments with Hadronic ProbesExperiments with Hadronic Probes•• Methods and InstrumentationMethods and Instrumentation•• Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons•• SummarySummary
Frank Rathmann Polarization Experiments in Storage Rings 17
Methods and InstrumentationMethods and Instrumentation
• Polarized Beams– Conservation of hadron beam polarization in a ring routinely done– Export of a calibrated beam polarization to other energies– Spin manipulation of stored beams
• flipping the beam spin• transverse and/or longitudinal polarizations possible
• Polarized Targets– Polarized gas targets are routinely used at many storage rings
• New Instrumentation– Polarized Target for ANKE– Spectator Detector (pn physics at ANKE)
Frank Rathmann Polarization Experiments in Storage Rings 18
11stst Example: Polarization ExportExample: Polarization Export
Possible only with a stored beam
Export polarization from a beam energy, where it is calibrated
COSYCOSY--ANKEANKEMethod employed for pd-breakup
calibrated
unknown
time
Frank Rathmann Polarization Experiments in Storage Rings 19
22ndnd Example: Polarized Internal Gas TargetExample: Polarized Internal Gas Target
Spectrometer magnet
Lamb-Shift Polarimeter
Atomic Beam Source
COSYCOSY--ANKE goes double polarized ANKE goes double polarized
TalkR. Engels
Features of polarized internal targets1. rapid reversal of target spin (x,y,z): 2. isotopically purity3. low background (absence of container walls)4. no radiation damage (gas replenished every few ms)
Frank Rathmann Polarization Experiments in Storage Rings 20
33rdrd Example: SpectatorExample: Spectator--Proton DetectionProton Detection
Features:– Three layers (double sided)
– 1st: 60 µm– 2nd:300 µm– 3rd: 5000 µm
– Ekin~2-40 MeV– 800 Channels– Self-triggering– On-board electronics– UHV compatible– Large Acceptance
- 10% per telescope- 30 mm from the beam
Frank Rathmann Polarization Experiments in Storage Rings 21
OutlineOutline
•• IntroductionIntroduction•• Experiments with Hadronic ProbesExperiments with Hadronic Probes•• Methods and InstrumentationMethods and Instrumentation•• Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons•• SummarySummary
Frank Rathmann Polarization Experiments in Storage Rings 22
HESR
HESR: High Energy Storage Ring• Energy: 0.8- 15 GeV• Length 442 m• N = 5 x 1010 antiprotons• High luminosity
- 2 x 1032 cm-2s-1
• High resolution- ∆p/p ~ 10-5 (8 MV HE e-cooling)
• Development of Cooling methods– electron and/or stochastic– 2MV prototype e-cooler at COSY
PANDA: Internal Detector
Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons
Production Target Production rate 107/sec at
30 GeV
Future Facility at GSIFacility at GSI
Letter of Intent: PAXPolarized Antiproton EXperiments(www.fz-juelich.de/ikp/pax)
NESR
CR
SuperFRS
Frank Rathmann Polarization Experiments in Storage Rings 23
PPolarized olarized AAntiproton ntiproton EEXXperimentsperiments at HESRat HESR
Central physics issue
Transversity distribution of the nucleon– last leading-twist missing piece of the QCD
description of the partonic nucleon structure– directly accessible uniquely via the double
transverse spin asymmetry ATT in Drell-Yan– h1q (x,Q2) of the proton for valence quarks
Frank Rathmann Polarization Experiments in Storage Rings 24
Antiproton Polarizer: Antiproton Polarizer: SpinfilterSpinfilter
Expected Buildup
1 10 100 1 .103 1 .104 1 .1050.01
0.1
1
10
100
1 .103181.621
0.022
σ etr T( )
1.5 104×5 T10 100 1000 T (MeV)
σ e⊥
(mba
rn) 100
10
1
0 5 10 15 20 25 300
0.01
0.02
0.03
0.04
0.05
0.06
0.07
beam lifetime [h]
Pola
rizat
ion
0.08
4.72 10 8−×
P2 t 800,( )
P2 t 500,( )
I t 10 3600⋅,( )
302.778 10 5−× t3600 t (h)5 10 15 20
antip
roto
nP
olar
izat
ion
(%) 8
6
4
2
T=500 MeV
T=800 MeV
Target thickness 5·1014 atoms/cm2Electron Polarization 0.9
Goal
Spin-Transfer Cross Section(Electrons to Antiprotons)
unpolarizedbeam
polarized target
polarized beam
Frank Rathmann Polarization Experiments in Storage Rings 25
Method: Method: TransversityTransversity in in DrellDrell--YanYan processesprocesses
)M,x(q)M,x(qe
)M,x(h)M,x(heâ
ddddA 2
2q
21
2q
22
q1
q
21
q1
2q
TTTT∑
∑=
σ+σσ−σ≡
↑↓↑↑
↑↓↑↑
p pqL
q
l+
l-q2=M2
qT
PAX: Polarized antiproton beam → polarized proton target (both transverse)
,...d,d,u,uq =
M invariant Massof lepton pair
φθ+
θ= 2coscos1
sinâ 22
TT
Elementary QED process−+→ llqq
θ: polar angle of leptonin l+l- rest frame
ϕ: azimuthal angle with respectto proton polarization
Frank Rathmann Polarization Experiments in Storage Rings 26
Measurement of ATT also planned at RHIC, but τ=x1x2=M2/s~10-3→ Exploration of the sea quark
content ATT very small (< 1%)
Main contribution to Drell-Yan events at PAX from x1~x2~√τ→ deduce x-dependence of h1u(x,M2)
xF=x1-x20 0.2 0.4 0.6
0.15
0.20
0.25TT
TT
âA
Anselmino, Drago, Nikolaev
T=22 GeV
T=15 GeV
0.3
PAX typical kinematics M2~10 GeV2, s~30-50 GeV2 → τ=x1x2=M2/s~0.2-0.3
only valence quarks quarks withlarge x contribute → h1q(x,Q2) large
Predictions: Predictions: TransversityTransversity
Models predict |h1u|>>|h1d|
)M,x(u)M,x(u)M,x(h)M,x(hâA 2
22
1
22
u1
21
u1
TTTT =
)qqqwhere( pp ==
Frank Rathmann Polarization Experiments in Storage Rings 27
Detector ConceptDetector Concept
Large Acceptance Detector for PAXLarge Acceptance Detector for PAX
Frank Rathmann Polarization Experiments in Storage Rings 28
OutlineOutline
•• IntroductionIntroduction•• Experiments with Hadronic ProbesExperiments with Hadronic Probes•• Methods and InstrumentationMethods and Instrumentation•• Far Future: Polarized AntiprotonsFar Future: Polarized Antiprotons•• SummarySummary
Frank Rathmann Polarization Experiments in Storage Rings 29
SummarySummary
New methods and instrumentation allow for a broad strong spin-physics program at COSY1. NN studies
– pn system– Time Reversal Invariance Test
2. Deuteron breakup3. Double polarized Heavy Meson Production
– Parity of Pentaquark with WASA-COSY– η and η‘ studies
Future GSI offers unique oportunities for spin physics– Polarized Antiprotons– Measure Transversity distribution of the nucleon
Frank Rathmann Polarization Experiments in Storage Rings 30
Final RemarkFinal 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
Frank Rathmann Polarization Experiments in Storage Rings 31
PINTEXPINTEX--IUCF: NN ScatteringIUCF: NN Scattering
Atomstrahl: 2 HFS 6.7⋅1016 H/s1 HFS 3.6 ⋅1016 H/s
Polarization: Pmax= 0.87Dissoziator
SextupolmagneteMFT
ProjektilStrahl
Speicherzelle und Rückstoßdetektoren schwaches Führungsfeld (∼∼∼∼ 3 G)
Frank Rathmann Polarization Experiments in Storage Rings 32
Methods: Conservation of Beam PolarizationMethods: Conservation of Beam Polarization
Indiana Cooler
H.O. Meyer et al., PRE 56, 3578 (1997)T=200-450 MeV
Frank Rathmann Polarization Experiments in Storage Rings 33
Instrumentation: Polarized Beam Sources Instrumentation: Polarized Beam Sources
I=7.5⋅1016 H/s
Tremendous progress since 1956 ~ 106 more atoms/s
Luminosity (double polarized)Electron machines: ~1031 cm-2s-1Proton machines: ~1030 cm-2s-1
Frank Rathmann Polarization Experiments in Storage Rings 34
MethodMethod: Spin Manipulation: Spin Manipulation
SPIN@COSY (A. Krisch et al.)– Frequent spin-flips reduce
systematic errors– Spin-Flipping of protons and
deuterons by artifical resonance • RF-Dipole
– Applicable at High Energy Storage Rings (RHIC, HESR)
Stored protons:P(n)=Pi(η)n
⇒ η=(99.3±0.1)%
New Ferrite Rf-dipole– higher ∫Bdl=0.58 T mm– stored deuterons flipped
also• efficiency η>0.9
Frank Rathmann Polarization Experiments in Storage Rings 35
WASAWASA--COSY: Parity of COSY: Parity of θθ++ PentaquarkPentaquark
Rate Estimate:• Polarized proton beam on polarized atomic jet in WASA
– L = Np·frev·dt =5·1010·1.6·106·1012 = 8·1028 cm-2s-1 ~ 1028 cm-2s-1
– N = L·400 nb = 4/day with 10% detection efficiency– δAxx = 1/(P·Q) ·1/sqrt(N) = 0.1
[achievable after 100 days (400 evts)]
pp → Σ+θ+ → pπ0
pK0
Ks0→π0 π0 (0.5·0.31=0.15)pπ0 (0.52) BR=0.08
Frank Rathmann Polarization Experiments in Storage Rings 36
Instrumentation: HighInstrumentation: High--Energy Electron CoolingEnergy Electron Cooling
• Luminosity (“1032”): intense beams and dense targets• Internal beam heating � need High Energy Electron Cooler (2 MV) • “Toroidal Racetrack”
Cooling Section (3m)
HV Terminal
COSYBeam
�First step to HESR Cooler: (2 MV � 8 MV)
Frank Rathmann Polarization Experiments in Storage Rings 37
Instrumentation: Photon DetectorInstrumentation: Photon Detector
• Detection of multi-photon final states: new physics window• “Photon-blind” � necessitates an electromagnetic calorimeter
– Unique opportunity: WASA COSY in 2005
1.5 m
Pellet Target
Forward DetectorElectromagnetic Calorimeter
Large acceptanceneutral and charged
particle detector
WASA at TSL / CELSIUS
(Uppsala)
Frank Rathmann Polarization Experiments in Storage Rings 38
ANKEANKE--COSYCOSY: Deuteron Breakup– new theoretical calculation
using CD Bonn Potential
Deuteron BreakupDeuteron Breakup
J. Haidenbauer and Yu.N. UzikovPLB 562 (2003) 227
Improvement:• relative softness of the CD Bonn
wave functions compared to RSC Paris potentials:
• 3S1–3D1 and 1S0
Frank Rathmann Polarization Experiments in Storage Rings 39
Deuteron BreakupDeuteron Breakup
Paris
CD-Bonn
Frank Rathmann Polarization Experiments in Storage Rings 40
HERA e+/- ring: •45 mA•27.5 GeV•P ≈ 55 %
HERMES spectrometer
HERMES experiment at DESYHERMES experiment at DESY--HERAHERA
Electromagnetic Probes: HERMESElectromagnetic Probes: HERMES
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