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