Perspectives for Polarized Antiprotons
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Perspectives for Polarized Antiprotons. dr. Paolo Lenisa Università di Ferrara and INFN – ITALY on behalf of the PAX-Collaboration. XIV International Workshop on Polarized Sources, Targets and Polarimetry St. Petersburg, 13.09.2011. Polarized Antiprotons. Motivation:

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Perspectives for Polarized Antiprotons

dr. Paolo Lenisa

Università di Ferrara and INFN – ITALY

on behalf of the PAX-Collaboration

XIV International Workshop on Polarized Sources, Targets and Polarimetry

St. Petersburg, 13.09.2011

Polarized Antiprotons


Polarized Antiprotons

Motivation:

Missing tool for Hadron Physics

Polarized Antiprotons


Quark structure of the nucleon

longitudinally polarised

quarks and nucleons

transversely polarised

quarks and nucleons

unpolarised quarks

and nucleons

Known

Well known

Less known

Polarized Antiprotons


Quark structure of the nucleon

longitudinally polarised

quarks and nucleons

transversely polarised

quarks and nucleons

unpolarised quarks

and nucleons

Inclusive DIS Semi-inclusive DIS Drell-Yan

HERMES,COMPASS,JLab

Polarized Antiprotons


Accesso totransversitythroughDrell-Yan

Polarized Antiprotons


A double polarized pbar-p collider for FAIR

Asymmetric (double-polarized)

proton (15 GeV/c) – antiproton (3.5 GeV/c) collider

p

p

Polarized Antiprotons


h1u from p-p Drell-Yan at PAX

Pp=30%

  • u-dominance

  • |h1u|>|h1d|

Pp=10%

1 year run -> 10 % precision on the h1u (x) in the valence region

Polarized Antiprotons


Rosenbluth

Polarization

Study of the Proton Electromagnetic Form-Factors

Space-Like FFs: proton data

Time-Like FFs: proton data

  • JLab results dramatically changed picture of the Nucleon:

    • GEp/GMp decreases with Q2

    • data suggest GEpcrosses 0 at Q28 GeV2

Expected Q2 behaviour reached quite early, however ...

... there is still a factor of 2

between timelike and spacelike.

Additional and more precise measurements needed

Polarized Antiprotons


Double polarized pbar-p annihilation:

E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005)

  • Most contain moduli GE, GM

    • Independent GE-GM separation

    • Test of Rosenbluth separation in the time-like region

  • Access to GE-GM phase

  • Very sensitive to different models

Polarized Antiprotons


Axx

Ayy

Ay

VDM : IJL

Ext. VDM

‘QCD inspired’

Axz

Azz

R

Polarization and Models in T.L. Region

E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005)

Polarized Antiprotons


Polarized Antiprotons

Method:

The mechanism of spin-filtering

Polarized Antiprotons


Polarized antiprotons

  • Intense beam of polarized pbarnever produced:

  • Synchr. radiation ~ m(g4/R) -> tpol~107 y in 20 TeV pbar ring

  • Conventional methods (ABS) not applicable

  • Polarized pbar from antilambda decay

    • I< 1.5∙105 s-1 (P ≈ 0.35)

  • Pbar scattering off liquid H2 target

    • I< 2∙103 s-1 (P ≈ 0.2)

PAX Status Report


Productionofpolarization in a stored beamTwoMethods: Loss versus spinflip

For an ensembleofspin ½ particleswithprojections+() and– ()

Polarized Antiprotons


Spin-filtering

Polarization build-up of a circulating particle beam

by interaction with a polarized gas target

Polarized Antiprotons


Polarization Buildup

Unpolarized anti-p beam

Polarized target

S beam-particlespin

Q targetpolarization

k || beam direction

Polarized Antiprotons


Polarized anti-p beam

Unpolarized anti-p beam

Polarization Buildup

S beam-particlespin

Q targetpolarization

k || beam direction

Optimum (blackcurve)

after 2 lifetimesfiltering

Polarized target

Polarized Antiprotons


Spin-filteringat TSR: „FILTEX“ – proof-of-principle

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

Spin filteringworksforprotons

PAX submitted new proposal to find out how well does spin filtering work for antiprotonsMeasurement ofthe Spin-Dependenceofthe pp Interaction atthe AD Ring

(CERN-SPSC-2009-012 / SPSC-P-337)

Polarized Antiprotons


[email protected] :Proton polarization

Polarized Antiprotons

Experimental program:

Measurements with pbar at AD-Ring

[email protected]/CERN:Antiproton polarization

[email protected]:Eexperimentswith pol. pbar

Polarized Antiprotons


Measurements at AD (CERN)

  • Aim: 1st measurement of the spin-dependence of the pbar-p cross section

  • Method: measurement of polarization build-up by spin-filtering

PAX target section

Polarized Antiprotons


Spin-dependence of the pbar-p interaction

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

Model OBEPF:J. Haidenbauer, K. Holinde, A.W. Thomas, Phys. Rev. C 45, 952 (1992).

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

Polarized Antiprotons


Expected polarizations after filtering for two lifetimes

  • Measurement of the polarization buildup allows determination of σ1andσ2

  • Oncepbarpolarizationavailable, spin-correlationcoefficientsaccessible

transverse

longitudinal

A

D

Polarized Antiprotons


More recentcalculations…

PLB 690 (2010)

Cross sections

Projected polarizations

Polarized Antiprotons


Polarized Antiprotons

Experimental program

Measurements with p at COSY-Ring (Germany)

[email protected]/CERN:Antiproton polarization

[email protected] :Proton polarization

[email protected]:Experiments withpol. pbar

Polarized Antiprotons


Spin-filtering at COSY

Main purpose:

1. Commissioning of the experimental setup for CERN/AD

2. Quantitative understanding of the machine parameters

WASA

e-cooler

ANKE

PAX

Polarized Antiprotons


Installation of low-β section (2009)

  • Beamhastofitthroughstoragecell target (dt=5x1013atoms/cm2)

  • Increase acceptance angle at target position

Polarized Antiprotons


Commissioningofthe experimental setup (2010)

I. Machinestudies: Low-bsection

  • Nonegative impact on the COSY operation

  • Model in goodagreement

  • withmeasurement: β~ 0.3m

  • -> beam fitsthroughthecell!

Polarized Antiprotons


Commissioningofthe experimental setup (2010)

I. Machinestudies: Studies of beam-lifetimelimitations

In case intra-beam scattering poses a limitation, increase of beam emittance should increase lifetime! (Touschek)

  • Increaseofbeam emittancebytiltingofelectron cooler beam

  • Beam emittancemeasuredwithionisationproflemonitor

Polarized Antiprotons


Commissioningofthe experimental setup (2010)

II. Polarized Target

ABS

Breit-Rabi

polarimeter

  • Spin filtering requires >1013 atoms/cm2 →

  • ABS + openable storage cell

  • Analysis of target polarization by Breit-Rabi polarimeter(BRP) and a target gas analyzer (TGA)

Polarized Antiprotons


BRP: Continousmonitoringofthetargetpolarization

Polarized Antiprotons


Commissioningofthe experimental setup (2010)

III. Beam Polarimeter

p

D2

pdelasticscattering:detection in two (L-R) symmetricSilicon Tracking Telescopes

Deuteron identification

d

p

Polarized Antiprotons


Commissioningofthe experimental setup (Aug. 2011)

IV. Installation of NEG pump (12000 l/s)

Polarized Antiprotons


September 2011 ongoingbeamtime:

I Measurement of ring acceptance

In an ideal machine Single-Coulomb scattering at the target dominates beam loss

cooled

beam

ring acceptance

target

lost

movableframesystem

COSY beam

Polarized Antiprotons


September 2011 ongoingbeamtime:

II Ring polarizationstudies

  • Measurement of polarization lifetime: tP>105s

  • Measurement of spin-flip efficiency: e=0.987

Polarized Antiprotons


Spin-filtering cycle

Polarization

dP/dt0.18%/h

Cycle

COSY measurement

Polarized Antiprotons


To be continued ….

Ferrara - Castello Estense

Sebastiano Filippi: “The spinning top game" – XVI cent.

Polarized Antiprotons


Additional slides

Polarized Antiprotons


pp interaction models

Polarized Antiprotons


0penable storagecell

  • Atomic beam source provides polarized hydrogen target

  • Storage cell target to reach dt=5x1013atoms/cm2

open

closed

Nuclear polarization of the hydrogen target determined with the Breit-Rabi polarimeter after opening and closing of the storage cell a few times

Polarized Antiprotons


Polarisation buildup cross sections

Folie 34


Polarizedantiprotons on fixed target

(PAX-PhaseI)

EXPERIMENT:

Fixed target experiment:

polarized antiprotons protons in CSR (p>200 MeV/c)

fixed polarized protons target

Polarized Antiprotons


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