The PAX experiment P.F.Dalpiaz Ferrara

P.F.Dalpiaz 16 june 2006 1

PolarizedPolarized Antiproton Antiproton at at FAIRFAIR

The PAXThe PAX experimentexperiment

P.F.DalpiazP.F.Dalpiaz

FerraraFerrara

2 workshop on the QCD 2 workshop on the QCD structure of the nucleonstructure of the nucleon

12-16 june 200612-16 june 2006

Monte Porzio CatoneMonte Porzio Catone


TransversityTransversity


The most direct probe elXllpp , ,

Drell-Yan

q

1xq

2xq

Why it works

Elementary LO interaction

J. Ralston and D.Soper, 1979 J. Cortes, B. Pire, J. Ralston, 1992

Direct mesurament

* eeqq

LO interaction has no initial gluons

valence quarksvalence quarks


The measurament

At GSI-FAIR very large asymmetry expected

in polarized proton-antiproton scattering

TTA

TTA

Xeepp

valence valence quarksquarks


Polarized Antiprotons

Intense beam of never producedp


How polarize antiproton?

Polarized pbar from antilambda decay (1987-90) Pbar scattering off liquid H2 target (1995)

(Niinikoscki and Rossmanith 1985) Stern-Gerlach separation of a stored beam Very recently :(Th. Walcher et al) polarized electron beam

350 ;1051 15 . P s. I -

20 ;102 13 . P s I -

2006

Theorethical, never tested


How polarize antiproton?

The Spin Filter MethodThe Spin Filter Method

Experimentally tested in 1992

2006

P.L.Csonka,1968, NIM 63 (1968) 247


Multiple passage of a stored beam in a Polarized Internal

Target (PIT)

Principle of spin filter Principle of spin filter methodmethod


“parallel spin” scatter more often then ” antiparallel spin,” resulting in a polarized (less intense )beam,after passages in a polarized target kQkPQPtot

210

Total cross section targetbeam pp

Low energy scattering tottot

Qtot 10 Qtot 210

An unpolarized beam has an equal population of spin

longitudinal case

transverse case


Principle of spin filter Principle of spin filter methodmethod

Unpolarized anti-p beam

Polarized H target

Polarized anti-p beam

Polarization Staging Signals Timeline


The filter


gas polarized hydrogen target

a short review


Atomic Beam Source ABS

2H

ep

ep

H ep

mmjj = = ++1/21/2

mmjj = = --1/21/2

mmii=-1/2=-1/2

mmii=-1/2=-1/2

mmii=+1/=+1/22

mmii=+1/=+1/22

1|1>|2>

|3>|4>

ep

ee-

pp|1>

Pz+ = |1> + |4>

Pz- = |2> + |3>Pe+ = |1> + |2>

Pe- = |3> + |4>


Hydrogen gas targets: densities

1970

1985, Novosibirsk,Zurig

1998,HERMES

2004,RHIC

1965 -

1984,W.Haeberli

210 /10 cmatomsI

211 /102 cmatomsI 211 /104 cmatomsI

211 /108.7 cmatomsI

accumulation cellaccumulation cell

214 /10 cmatomsI


The storage cellThe storage cell

•Material:75 m Al with Drifilm coating•Size: length: 400mm, elliptical cross section (21 mm x 8.9 mm)•Working temperature: 100 K ( variable 35 K – 300 K)


Performance of Polarized Internal Performance of Polarized Internal TargetsTargets

PT = 0.795 0.033

HERMES

HTransverse Field (B=297 mT)

HERMES

Dz

Dzz

PT = 0.845 ± 0.028

Longitudinal Field (B=335 mT)

HERMES: Stored Positrons PINTEX: Stored Protons

H

Fast reorientation in a weak field (x,y,z)

Targets work very reliably (months of stable operation)

Polarization Staging Signals TimelinePolarization Staging Signals Timeline


Test experiment on the Test experiment on the filter methodfilter method

The TSR experiment with protons The TSR experiment with protons 19921992


Experimental Setup at TSR (1992)Experimental Setup at TSR (1992)


mmjj = = ++1/21/2

mmjj = = --1/21/2

mmii=-1/2=-1/2

mmii=-1/2=-1/2

mmii=+1/=+1/22

mmii=+1/=+1/22

1|1>|2>

|3>|4>

ee-

pp|1>The FILTEX

experiment has runned with state 1

hydrogen

~80% of electronic

polarization

~80% of nuclear

polarization

Transverse target Transverse target polarizationpolarization


Experimental SetupExperimental Setup ResultsResults

F. Rathmann. et al., PRL 71, 1379 (1993)

1992 Filter Test at TSR 1992 Filter Test at TSR with protons, with protons, T=23 MeV

213 /106 cmatomsI


SPIN filtering works! but how?


121006.024.1 hdt

dP

fQd

ttP

t1

1

1

1 ;tanh

mb8.55.721

ObservedObserved polarization build-up:polarization build-up:

beampp 1ObservedObserved cross-sectioncross-section beampp 1

PIT areal thickness

PIT polarization

Revolution frequency

FILTEX RESULTSFILTEX RESULTS


Two interpretations of FILTEX Two interpretations of FILTEX resultresult

1994. Meyer and Horowitz: three distinct effects1. Selective removal through scattering beyond θacc=4.4 mrad (σR=83 mb)

2. Small angle scattering of target prot. into ring acceptance (σS=52 mb)

3. Spin-transfer from pol. el. of target atoms to stored prot. (σE=-70 mb)

σ1= σR+ σS + σE = 65 mb

2005. Milstein & Strakhovenko + Nikolaev & Pavlov: only one effect

1. Selective removal through scattering beyond θacc=4.4 mrad (σR=85.6 mb)

No contribution from other two effects

(cancellation between scattering and transmission)

σ1 = 85.6 mb


Spin-filtering: Present Spin-filtering: Present situationsituation

Spin filtering works, but:

• controversial interpretations of TSR result

• no experimental basis for antiprotons

Experimental tests:- Protons (40-800 MeV) (COSY)- Antiprotons (5MeV-3GeV)(AD)


How to disentangleHow to disentangle

hadronic and hadronic and electromagnetic electromagnetic contributions?contributions?


… only had

- elm. + had.

TSR

A measurement of with 10 % precision is needed.

Polarization measurement with P/P = 10% requested.

Polarizing cross-section for the two Polarizing cross-section for the two modelsmodels


How to disentangle had. and elm How to disentangle had. and elm contributions?contributions?1: Injection of different combination of hyperfine

states

Inj. states Pe Pz Interaction Holding field

|1> +1 +1 Elm. + had. Transv. + Long.

Weak (20 G)

|1>+|4> 0 +1 Only had. Long. Strong. (3kG)

|1>+|2> +1 0 Only elm

Experiment at AD will require both transverse and longitudinal (weak)field.

Different combinations of elm. and hadronic contributions:

Strong field can be applied only longitudinally (minimal beam interference)

Target polarimetry difficult for pure electron polarization.

Null experiment (elm. component = 0) possible in strong holding field


Spin-transfer

1 10 100 1 103

1 104

1 105

0.01

0.1

1

10

100

1 103

181.621

0.022

etr T

1.5 1045 T

10 100 1000 T (MeV)

elm

(mba

rn)100

10

1

Hadronic

2: Use of different energy dependence of the processesMeasurement at different energies

How to disentangle had. and elm How to disentangle had. and elm contributions?contributions?

(Transverse case)


Spin-filtering studies at COSY Spin-filtering studies at COSY

Goal: deeper understanding spin-filtering mechanismDisentangle between two interpretations of TSR result.

•Electromagnetic + hadronic contributions

(20-120MeV 175-2880 MeV)(20-120MeV 175-2880 MeV)


Experimental setupExperimental setup

• Low-beta section • Polarized target (HERMES)• Detector• Snake• Commissioning of AD setu-up


• x,ynew=0.3 -> increase a factor 30 in density respect ANKE

•Lower buildup time, higher rates•Higher polarization buildup-rate due to higher acceptance

•Use of HERMES target (in Jülich since March 2006)

Low beta sectionLow beta section

S.C. quadrupole development applicable to AD experiment


Detector conceptDetector concept•Reaction:

•p-p elastic (COSY)•p-pbar elastic (AD)

•Good azimuthal resolution (up/down + left/right asymmetries)•Low energy recoil (<8 MeV)

•Teflon cell requested


Teflon cell (IUCF – 2002)Teflon cell (IUCF – 2002)




•Good azimuthal resolution (up/down asymmetries)•Low energy recoil (<8 MeV)

•Teflon cell•Silicon tracking telescope


The ANKE silicon tracking telescope

3 silicon detector layers➔ 69 µm silicon➔ 300/500 µm silicon

128 x 151 segments51 x 66 mm (≈400 µm pitch)

➔ >5 mm Si(Li)96 x 96 strip64 x 64 mm (≈666 µm Pitch)

COSY beam

cluster beam




•Good azimuthal resolution (up/down asymmetries)•Low energy recoil (<8 MeV)

•Teflon cell•Silicon tracking telescope

•Angular resolution on the forward particle for p-pbar•AD experiment will require an opening-cell


ANKE vs new interaction pointANKE vs new interaction point

Acceptance @ ANKE

Cross sections

Acceptance @ new-IP

… elm + had

- only had.

Lifetimes


PIT Filter. time Polar. Total rate Meas. Time (P/P=10%)

ANKE 2= 16 h 1.2 % 7.5x102 s-1 44 min

5 = 42 h 3.5 % 5x10 s-1 26 min

New IP 2= 5 h 16 % 2.2x104 s-1 1 s

5= 13 h 42 % 1.5x103 s-1 < 1 s

ANKE vs new interaction pointANKE vs new interaction point

Polarization

T=40 MeV Ninj=1.5x1010

New IP

ANKE


Antiproton polarization build-up

Test at AD


ANKE


Commissioning of ANKE PITCommissioning of ANKE PIT

Goal: installation of a storage cell with a polarized target in COSY

Electron-cooling at injection with storage cellStochastic cooling at 700 MeVCooler stacking to increase particles in the ring

Propedeutical studies to spin-filtering experiments


Storage Cell Setup (coll. Ferrara – Storage Cell Setup (coll. Ferrara – FZJ)FZJ)

COSYbeam

XY-table Frame with storage cell and aperture

Target chamber

Feeding tube: l = 120 mm, Ø = 10 mmExtraction tube: l = 230 mm, Ø = 10 mmBeam tube : l = 400 mm, 20x20 mm2

400mm

400mm


Storage cell and stochastically cooled Storage cell and stochastically cooled beambeam

Cooling off

Cooling on

Tp=831 MeV


Target Thickness (from Target Thickness (from pp→dpp→dππ+)+)

Jet Storage Cell

Method Jet [atoms/cm2] Storage Cell [atoms/cm2]

ABS flux (+ cell geometry) (1.6±0.1)·1011 (1.9±0.1)·1013

Rates (pp→dπ+) (1.5±0.1)·1011 (2.1±0.1)·1013


Cooler Stacking into the Storage CellCooler Stacking into the Storage Cell

28 stacks followed by • 2s electron cooling • after 58s acceleration toTp=600 MeV

Cooler Stacking allows for higher polarized beam intensities with cell.

2.5·1010 protons have been injected in the ring


Ferrara is building an ion-deflector

Next step: Installation of the Lamb-shift Next step: Installation of the Lamb-shift polarimeterpolarimeter

October 2006


Antiproton polarization build-up

AD


Measurements at AD at CERN (2009-2010)Measurements at AD at CERN (2009-2010)

Target Snake

E-cooler

T:5 MeV÷2.8 GeV

Np = 3·107

study of spin-filtering in pp scattering

Measurement of effective polarization cross-section.Both transverse and longitudinal.Variable ring acceptance.

First measurement at all for spin correlations in pp (not pure text experiment!)


TimelineFall 2006 Submission of Technical Proposal for COSY

Spring 2007 Submission of Technical Proposal for AD

2006-08 Design and construction phase COSY

2008 Spin-filtering studies at COSY Commissioning of AD experiment

2009 Installation at AD

2009-2010 Spin-filtering studies at AD


VERY PRELIMINARY

Polarization build-up implemantation at HESR,FAIR


PAX ACCELERATOR SETUPPAX ACCELERATOR SETUP

EXPERIMENT: Asymmetric collider: s=210GeV2

polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c)

Physics: Transversity

preliminary!

Internal polarized target with 22 GeV/c polarized antiproton Internal polarized target with 22 GeV/c polarized antiproton beam. beam. s=30GeV2s=30GeV2

Valence region x>0.5

4<Q2<100GeV2

ATT>0.3

L2x1030 1000 events by day


http://www.fz-juelich.de/ikp/pax


THE ENDTHE END


0.1

0.2

0.3

0.4B

eam

Pola

riza

tion P

(2·τ

beam)

10 T (MeV)100

EM only

5

10

30

20

40

Ψacc=50 mrad

0

1

Filter Test: T = 23 MeV Ψacc= 4.4 mrad

Electron Transfer Electron Transfer PolarizationPolarization

Polarization Staging Signals Timeline

??


Polarization with hadronic Polarization with hadronic pbar-p interactionpbar-p interaction

Model A: T. Hippchen et al. Phys. Rev. C 44, 1323

(1991)

P

Kinetic energy (MeV)10 100 100

01

0.05

0.10

0.15

0.20

Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360

(1995)

P

Kinetic energy (MeV)

10 100 1000

1

0.05

0.10

0.15

0.20


pp Elastic Scattering from ZGSpp Elastic Scattering from ZGSSpin-Spin-dependence at dependence at large-Plarge-P (90°90°cmcm):):

Hard Hard scattering scattering takes takes place only place only with spins with spins ..

D.G. Crabb et al., PRL 41, 1257 (1978)

T=10.85 GeV

Similar Similar studies in studies in pbar p pbar p elastic elastic scatteringscattering

dtddtd

The PAX experiment P.F.Dalpiaz Ferrara

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