how to produce polarized antiprotons and what to do with

P.Lenisa Polarized Antiprotons 1

dr. Paolo Lenisadr. Paolo LenisaUniversitàUniversità di Ferrara and INFN di Ferrara and INFN -- ITALYITALY

STORI 08, Lanzhou 16.09.08

How to produce polarized antiprotons How to produce polarized antiprotons and what to do with them at FAIRand what to do with them at FAIR


Introduction


The FAIR facility at Darmstadt


Intense beam of polarized antiprotons never produced:• Conventional methods (ABS) not applicable

• Polarized antiprotons from antilambda decay• I < 1.5·105 s-1 (P ≈ 0.35)

• Antiproton scattering off liquid H2 target• I < 2·103 s-1 (P ≈ 0.2)

• Little polarization from pbarC scattering exp’ts at LEAR

Polarized Antiprotons: a long storyPolarized Antiprotons: a long story

Methods not applicable to storage rings

- 1985 - Bodega Bay:“International Workshop on Polarized Antiprotons Beam”

- 2007 - Daresbury:“Polarized Antiprotons: How”

- 2008 – Bad Honnef:Heraeus Seminar: “Polarized Antiprotons”


Polarized Antiproton in Storage RingsPolarized Antiproton in Storage Rings- Two possible methods:

Spin-filtering Spin-flip


Spin-flip: a recent proposal

-> need for experimental test

•Antiproton beam polarization by interaction with a polarized positron beam

2x1013 barn!


Depolarization studies at COSY: idea

•Use proton beam and co-moving electrons•Turn experiment around: into

i.e. depolarization of a polarized proton beamepep

→→

→ pep →→


Depolarization studies at COSY: principle•Use (transversely polarized) proton beam in COSY•Switch on (detuned) electron cooler to depolarize proton bam• Analyze proton polarization with internal D2-cluster target at ANKE


Depolarization studies at COSY: cycle

250 500 750

250 s

250 s


ΔV=245 V→vrel = 1.46×10-3c

fshift(10s)= 80 Hz →vshift = 0.07×10-3cΔfbroad(10s)=25 Hz →Δvbroad = 0.02×10-3c

Negligible with respect to:




250 500 750

250 s

250 s


Depolarization studies at COSY: Polarimetry-p-d elastic scattering detection in silicon tracking telescopes


Depolarization studies at COSY: Results (Feb. 08)

-> No effect observed: cross section must bemany orders of magnitude lower than 1013 b!!


Polarized Antiproton in Storage RingsPolarized Antiproton in Storage Rings- Two possible methods:

Spin-filtering Spin-flip


Spin-filteringPolarization build-up of an originally unpolarized particle beamby repeated interaction with polarized hydrogen target:

Spin-filtering is known to work (FILTEX); not clear how


Spin-filtering at TSR:“FILTEX”


Spin-filtering at TSR: “FILTEX” proof of principle


Spin-filtering at COSY: understand and optimize “FILTEX”

Spin-filtering at CERN/AD: pbar-p and pbar-d scattering

•First ever measurement of pbar-p, pbar-d spin correlations


Spin-filtering at COSY: understand and optimize “FILTEX”

Spin-filtering at CERN/AD: pbar-p and pbar-d scattering

Model D: V. Mull, K. Holinde,

Phys. Rev. C 51, 2360 (1995)

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

1323 (1991)

50 100 150 200250 T (MeV) 50 100 150 200 T (MeV)

0.050.100.150.20

P

0.050.100.150.20

P

Theoretical estimate of Antiproton Beam Polarization (Hadronic Interaction: Longitudinal Spin Filtering)


Experimental setup for spin-filtering tests


S.C. quads for low-β section:

(COSY ring)


Openable storage cellfor operation at AD


Polarized Atomic Beam Source+Breit-Rabi polarimeter(from HERMES-DESY)


Silicon detector for beampolarimetry• Pbar-Beam polarization by using the (measured) analysing power of pbar-p elastic

(after spin-filtering)

• Modular structure• 10 cm x 10 cm silicon wafers• 300 μm thick• Open cell without moving det.• Re-use of HERMES recoil


Silicon detector for beampolarimetry

HERMES recoil


dr. Paolo Lenisadr. Paolo LenisaUniversitàUniversità di Ferrara and INFN di Ferrara and INFN -- ITALYITALY

STORI 08, Lanzhou 16.09.08

How to produce polarized antiprotonsHow to produce polarized antiprotonsand what to do with them at FAIRand what to do with them at FAIR


=qδ −h1=

transversely polarisedquarks and nucleons

longitudinally polarisedquarks and nucleons

=Δq −

unpolarised quarksand nucleons

=q

Quark structure of the nucleon

Well known Known Only glimpse

{ } ++Δ+=Φ nxqxqxqx T1

55LTw2Corr Sγγ)(γ)(S)(

21)( δ

Study of the proton spin


Transversity

- Probes relativistic nature of quarks- No gluon analog for spin-1/2 nucleon- Different evolution than - Sensitive to valence quark polarizationtransversely polarised

quarks and nucleons

=q1h −

2Q qΔ

Inclusive DIS Semi-inclusive DIS Drell-YanHERMES,COMPASS,JLab

h1 is chirally odd -> it needs a chirally odd partner


,...d,d,u,uq =

M invariant Massof lepton pair /2 / 2

2121 sQxsMxxxxx LFF =≡=−= τ

[ ])( )()( )(1 94

21212

212

2

2

2

xqxqxqxqexxsMdxdM

dq

qF

++

= ∑πασsM 2

−+→→ llqq *γ

S Drell-Yan

[ ][ ]∑

∑+

+=

+−

=↑↓↑↑

↑↓↑↑

q q

q qqqqqTTTT xqxqxqxqe

xhxhxhxheaA

)()()()(

)()()()(ˆ

dddd

21212

211121112

σσσσ

h1 from Drell-Yan


EXPERIMENT:Asymmetric collider:

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

s=200 GeV2

PAX phase-II: Asymmetric collider


h1 from p-p Drell-Yan at PAX

PAX : Μ2/s=x1x2~0.02-0.3valence quarks

(ATT large ~ 0.2-0.3 )

)()()()(ˆ

21

2111

xuxuxhxhaA uu

TTTT ≈

[ ][ ]∑

∑+

+=

+−

=↑↓↑↑

↑↓↑↑

q q

q qqqqqTTTT xqxqxqxqe

xhxhxhxheaA

)()()()(

)()()()(ˆ

dddd

21212

211121112

σσσσ

• u-dominance• |h1u|>|h1d|

Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004)

Anselmino et al.PLB 594,97 (2004)

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

Pp=10%Pp=30%


Polarization

Rosenbluth

Space-Like FFs: proton data

Study of the Proton Electromagnetic Form-Factors

JLab results dramatically changed picture of the Nucleon:

- GEp/GM

p decreases with Q2

- data suggest GEp crosses 0 at Q2 ≈8 GeV2

Time-Like FFs: proton data

Expected Q2 behaviour reachedquite early, however ...... there is still a factor of 2between timelike and spacelike.

Additional direct measurement needed


PAX-Phase I: fixed target experiments

EXPERIMENT:Fixed target experiment:

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


• Most contain mduli 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 (next transparencies)

Double polarized pbar-p annihilation

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


Hard p-p polarized scattering

“One of the unsolved mysteries of hadron physics”(Brodsky, 2005)

It would be very interesting to performthese measurements with polarized antiprotons.

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

T=10.85 GeV

“The greatest asymmetries in hadron physicsever seen by a human being” (Brodsky)

Beam

Target

P⊥


Summary•Outstanding physics case for polarized antiprotons

•PAX Collaboration took over the challenge of polarizing antiprotons

COSY

ADFAIR

-2008-09 beam lifetime-2009-10 SC quadrupoles

+ int.region-2010-11 spin-filtering

-2012-13 spin-filtering

-2013 APR design


Theoretical modelsSpacelike Timelike

)2

(GeV2Q0 1 2 3 4 5 6 7 8 9

p*G

Ep

/GM

pμ

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

a

)2

(GeV2Q0 5 10 15 20 25 30

pμG

Mp

/GD

/0.6

0.7

0.8

0.9

1

1.1

1.2

b

)2

(GeV2Q0.2 0.4 0.6 0.8 1 1.2 1.4

GE

n

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

c

)2

(GeV2Q0 2 4 6 8 10

n/G

Dμ

GM

n/

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

d

VDM : IJLF. Iachello..PLB 43, 191 (1973)

Extended VDM E.L.Lomon PRC 66, 045501 2002)

HohlerNPB 114, 505 (1976)

QCD inspiredBosted PRC 51, 409 (1995)

Electric Magnetic

neut

ron

prot

on

Electric Magnetic



Polarization and Models in T.L. Region

VDM : IJL

Ext. VDM ‘QCD inspired’

R

AyAxx Ayy

Axz

Azz


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