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2 workshop on the QCD structure of the nucleon 12-16 june 2006 Monte Porzio Catone. Polarized Antiproton at FAIR. The PAX experiment P.F.Dalpiaz Ferrara. Transversity. Drell-Yan. Direct mesurament. The most direct probe. valence quarks.

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the pax experiment p f dalpiaz ferrara

2 workshop on the QCD structure of the nucleon

12-16 june 2006

Monte Porzio Catone

PolarizedAntiproton at FAIR

The PAXexperiment

P.F.Dalpiaz

Ferrara

16 june 2006

slide2

Transversity

16 june 2006

slide3

Drell-Yan

Direct mesurament

The most direct probe

valence quarks

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

Why it works

Elementary LO interaction

LO interaction has no initial gluons

16 june 2006

slide4

The measurament

in polarized proton-antiproton scattering

valence quarks

sea quarks

At GSI-FAIR very large asymmetry expected

16 june 2006

slide5

Intense beam of never produced

Polarized Antiprotons

16 june 2006

how polarize antiproton

Theorethical, never tested

How polarize antiproton?

2006

  • 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

16 june 2006

slide7

How polarize antiproton?

2006

The Spin Filter Method

Experimentally tested in 1992

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

16 june 2006

principle of spin filter method

Principle of spin filter method

Multiple passage of a stored beam in a Polarized Internal Target (PIT)

16 june 2006

slide9

An unpolarized beam has an equal population of spin 

longitudinal case

transverse case

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

Total cross section

Low energy scattering

16 june 2006

slide10

Polarized anti-p beam

Unpolarized anti-p beam

Principle of spin filter method

Polarized H target

16 june 2006

Polarization Staging Signals Timeline

slide11

The filter

16 june 2006

gas polarized hydrogen target

gas polarized hydrogen target

a short review

16 june 2006

slide13

|1>

e-

p

1

|1>

mj = +1/2

mi=+1/2

|2>

mi=-1/2

mi=-1/2

|3>

mj = -1/2

mi=+1/2

|4>

ABS

Atomic Beam Source

Pz+ = |1> + |4>

Pz- = |2> + |3>

Pe+ = |1> + |2>

Pe- = |3> + |4>

16 june 2006

hydrogen gas targets densities
Hydrogen gas targets: densities
  • 1970
  • 1985, Novosibirsk,Zurig
  • 1998,HERMES
  • 2004,RHIC
  • 1965 -
  • 1984,W.Haeberli

accumulation cell

16 june 2006

the storage cell
The storage cell
  • Material:75 mm 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)

16 june 2006

slide16

Longitudinal Field (B=335 mT)

Dz

PT = 0.845 ± 0.028

H

Fast reorientation

in a weak field (x,y,z)

Dzz

HERMES

H

PT = 0.795  0.033

HERMES

Performance of Polarized Internal Targets

HERMES: Stored Positrons

PINTEX: Stored Protons

Transverse Field (B=297 mT)

Targets work very reliably (months of stable operation)

16 june 2006

Polarization Staging Signals Timeline

Polarization Staging Signals Timeline

test experiment on the filter method

Test experiment on the filter method

The TSR experiment with protons 1992

16 june 2006

slide19

|1>

e-

p

1

|1>

mj = +1/2

mi=+1/2

|2>

mi=-1/2

mi=-1/2

|3>

mj = -1/2

mi=+1/2

|4>

The FILTEX experiment has runned with state 1 hydrogen

~80% of electronic polarization

~80% of nuclear polarization

Transverse target polarization

16 june 2006

slide20

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

Experimental Setup

Results

F. Rathmann. et al.,

PRL 71, 1379 (1993)

16 june 2006

slide22

FILTEX RESULTS

Revolution frequency

PIT areal thickness

PIT polarization

Observedcross-section

Observedpolarization build-up:

16 june 2006

slide23

Two interpretations of FILTEX result

1994. Meyer and Horowitz: three distinct effects

  • Selective removal through scattering beyond θacc=4.4 mrad (σR=83 mb)
  • Small angle scattering of target prot. into ring acceptance (σS=52 mb)
  • 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

  • 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 = 85.6mb

16 june 2006

slide24

Spin-filtering: Present situation

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)

16 june 2006

slide25

How to disentangle

hadronic and electromagnetic contributions?

16 june 2006

slide26

Polarizing cross-section for the two models

… only had

- elm. + had.

TSR

A measurement of s with 10 % precision is needed.

Polarization measurement with DP/P = 10% requested.

16 june 2006

slide27

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

Target polarimetry difficult for pure electron polarization.

How to disentangle had. and elm contributions?

1: Injection of different combination of hyperfine states

Different combinations of elm. and hadronic contributions:

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

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

16 june 2006

slide28

How to disentangle had. and elm contributions?

  • 2: Use of different energy dependence of the processes
      • Measurement at different energies

Spin-transfer

Hadronic

100

10

selm (mbarn)

1

10

100

1000

T (MeV)

(Transverse case)

16 june 2006

spin filtering studies at cosy
Spin-filtering studies at COSY
  • Goal: deeper understanding spin-filtering mechanism
    • Disentangle between two interpretations of TSR result.
      • Electromagnetic + hadronic contributions

(20-120MeV 175-2880 MeV)

16 june 2006

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

16 june 2006

slide31

Low beta section

  • bx,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)

S.C. quadrupole development applicable to AD experiment

16 june 2006

slide32

Detector 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

16 june 2006

slide34

Detector concept

  • Reaction:
      • p-p elastic (COSY)
      • p-pbar elastic (AD)
  • Good azimuthal resolution (up/down asymmetries)
  • Low energy recoil (<8 MeV)
    • Teflon cell
    • Silicon tracking telescope

16 june 2006

the anke silicon tracking telescope

3 silicon detector layers

  • 69 µm silicon
  • 300/500 µm silicon

128 x 151 segments

51 x 66 mm (≈400 µm pitch)

  • >5 mmSi(Li)

96 x 96 strip

64 x 64 mm (≈666 µm Pitch)

The ANKE silicon tracking telescope

cluster beam

COSY beam

35

16 june 2006

slide36

Detector concept

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

16 june 2006

slide37

… elm + had

- only had.

Acceptance @ ANKE

Acceptance @ new-IP

ANKE vs new interaction point

Cross sections

Lifetimes

16 june 2006

slide38

New IP

ANKE

ANKE vs new interaction point

Polarization

T=40 MeV Ninj=1.5x1010

16 june 2006

antiproton polarization build up

Antiproton polarization build-up

Test at AD

16 june 2006

slide40

ANKE

16 june 2006

commissioning of anke pit
Commissioning of ANKE PIT

Propedeutical studies to spin-filtering experiments

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

Electron-cooling at injection with storage cell

Stochastic cooling at 700 MeV

Cooler stacking to increase particles in the ring

16 june 2006

storage cell setup coll ferrara fzj
Storage Cell Setup (coll. Ferrara – FZJ)

XY-table

Target chamber

Frame with storage cell and aperture

400mm

COSY

beam

Feeding tube: l = 120 mm, Ø = 10 mm

Extraction tube:l = 230 mm, Ø = 10 mm

Beam tube : l = 400 mm, 20x20 mm2

16 june 2006

storage cell and stochastically cooled beam
Storage cell and stochastically cooled beam

Cooling off

Tp=831 MeV

Cooling on

16 june 2006

target thickness from pp d
Target Thickness (from pp→dπ+)

Storage Cell

Jet

16 june 2006

cooler stacking into the storage cell
Cooler 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

16 june 2006

slide48

Target

Snake

E-cooler

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!)

Measurements at AD at CERN (2009-2010)

study of spin-filtering in pp scattering

T:5 MeV÷2.8 GeV

Np = 3·107

16 june 2006

timeline
Timeline

Fall 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

16 june 2006

very preliminary

VERY PRELIMINARY

Polarization build-up implemantation at HESR,FAIR

16 june 2006

slide51

PAX ACCELERATOR SETUP

preliminary!

Valence region x>0.5

4<Q2<100GeV2

ATT>0.3

L2x1030 1000 events by day

Physics: Transversity

EXPERIMENT:

Asymmetriccollider: s=210GeV2

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

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

Internal polarized target with 22 GeV/c polarized antiproton beam.

s=30GeV2

16 june 2006

slide53

THE END

16 june 2006

slide58

Ψacc=50 mrad

EM only

0.4

40

30

0.3

20

Beam Polarization P(2·τbeam)

10

0.2

5

0.1

0

1

10

100

T (MeV)

Electron Transfer Polarization

?

Filter Test: T = 23 MeV

Ψacc= 4.4 mrad

16 june 2006

Polarization Staging Signals Timeline

slide59

Polarization with hadronic pbar-p interaction

Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995)

P

0.20

0.20

0.15

0.15

0.10

0.10

0.05

0.05

1

1

10

10

1000

1000

100

100

Kinetic energy (MeV)

Model A: T. Hippchen et al. Phys. Rev. C 44, 1323 (1991)

P

Kinetic energy (MeV)

16 june 2006

pp elastic scattering from zgs
pp Elastic Scattering from ZGS

Spin-dependence at large-P (90°cm):

Hard scattering takes place only with spins .

D.G. Crabb et al.,

PRL 41, 1257 (1978)

T=10.85 GeV

Similar studies in pbar p elastic scattering

16 june 2006