Folie 1

Many exciting old ideas with antiprotons, pre LEAR 1977 - 1984Revival for FAIR / FLAIR

Trap experiments active at AD/CERN

pp →YY with S = ±1, ±2, ±3 (possibly YY atomic effects)CP violation test: αΛ – αΛ = 0 Compare decay asymmetry of Λ and Λ

ELENA: cooled p beams down to 100keV (best stop experim.) Walter Oelert 10.6.10

S=-2 hadronic states (B=1, 2, 3,…) via p stop. Recoilless! Highest precisionp stop and coincident channeling (dynamic unit cell tomography)Annihilat. dynamics p+9Be→{αα}380keV

Breeding of cooled d beams in double ring collider. Max. rate, max. qualityProduction of polarised p with filter method in cooler ring

…and more

Ideas get lost after a scientific lifetime

Mit

glie

d d

er

Helm

holt

z-G

em

ein

sch

aft

• Production of antiprotons• Spin filter method• Antihyperon decay• Polarised production• Comparison

Ways to make polarised antiproton beamsDieter Grzonka, Kurt Kilian, Walter Oelert, IKP FZ-Jülich

MESON2010 10.–17. 6. 2010 Krakow

Monday 14.6.2010

Folie 3

Production of antiprotonsConvert collision energy into particle-antiparticle pairs

energy → p + p (in 3S1- ?)

Quasifree production

p + p → p + (3p)0<ε<max

Symmetric in cm system

At 26 GeV/c beam

0 < ε <3360 MeV

2914 MeV/c > pcm > 0

If pcm < 150 MeV/c

then S wave production

D. Dekkers CERN PS 1968

K. Kilian et al.1977 pre LEAR memo to PSCC

26 GeV/c beam

Folie 4

pp→p+(3p)

Assumption of quasifree nucleon-nucleon interaction is reasonable.

Simple kinematical situation

At maximum (3.65 GeV/c) antiprotons are collected, cooled and piled up in storage synchrotrons. From there extremely dense beams are delivered.

At CERN (26 GeV) one gets one useful antiproton from 106 beam protons

Average p flux I0 = 107 s-1

p lab. Momentum MC simulation

Folie 5

Spin filter methodSuggested for the future ISR: P.L.Csonka, Nucl. Instr. Meth. 63 (1968) 247

If singlet and triplet cross sections are different, then an internal polarised target depletes one of the stored spin components faster than the other. Polarisation rises on the expense of intensity.

σ = σH + ΔσCb

Spin filtering for polarised antiprotons works only with cooling

avoids beam blow up and losses by multiple scattering

K.Kilian 1980, Pol. Conf. Lausanne, K.Kilian & D.Moehl 1982, Erice LEAR workshop

Filtering below 1 GeV/c →Important ΔσCb

Folie 6

Spin-filtering at TSR: „FILTEX“ – proof-of-principle

→ Spin filtering works for protons

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

6Spin-filtering studies at COSY and ADFrank Rathmann

PAX submitted new proposal to find out how well spin filtering works for antiprotons: Measurement of the Spin-Dependence of the pp Interaction at the AD Ring

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

Folie 7Frank Rathmann Spin-filtering studies at COSY and AD 7 of 19

statistical error of a double polarization observable (ATT)

NQP

1TTA

Measuring time t to achieve a certain error δATT

t ~ FOM = P2·I

Polarization Buildup: Figure of Merit

(N ~ I)

Optimum time forPolarization Buildup given by maximum of FOM(t)tfilter = 2·τbeam

0 2 4 6 t/τbeam

I/I0

0.2

0.4

0.6

0.8

Bea

m P

olar

izat

ion

P2Τ

σ↑↑ : σ↓↑ P2Τ

1 : 0.5 21%

1 : 0.8 7%

ΔσCb → will

dilute effect

2T > 4 days

?Ask F.R.

Other spin dependent processes? E.g. B. Schoch: scatter polarised photons

Folie 8

Λ → p + π+

p

plab

(p)

pcm

π+

plab

(π+)

Antihyperon decay

Decay makes p with helicity h = - 0.64. Lorentz boost creates transverse vector polarisation.

First and so far only experiment with polarised 200 GeV p at Fermilab. Λ production with primary proton beam. At the end an average of 104 polarised p s-1

A. Bravar et al. Phys. Rev. Lett. 77, 2626 (1996)

Decay momentum in cm syst. is 101 MeV/c

Folie 9

FNAL experiment: A. Bravar et al. P.R.L.77,2626,(1996)

NB: decay polarisation tagging below 0.5 mrad ! Experiment ~ km long

Folie 10

Useful antihyperon source in the GeV range (FAIR)

pp → ΛΛ → pπ+ pπ-

Decay direction of the hyperon defines the polarisation direction of the baryon.

The two decay V are tags and spectrometers for each other

Most important is geometrical reconstruction of all tracks

Will not work with internal target (miserable multi track reconstruction, miserable trigger condition)

Branching ratio σΛΛ /σtot = 10-3

cτΛ = 7.89 cm

Folie 11

Active sandwich target, tracker, baryon number identifier

pp target efficiency ~ 10-2

Insert a flat target for

p secondary scattering

(done for Λ and Λ scattering)

Folie 12

CP violation test

P. D. Barnes et al., PR C54 1877 (1996)105 pair events (at 1.642 and 1.918 GeV/c)

[ A ] = 0.013 ± 0.022 (most precise so far)

100 times smaller error allows relevant CP testNeeds 109 pair events or 2x1014 beam p (200 days)

As byproduct: “beam” of 109 polarised decay p

A = (αΛ + αΛ ) / (αΛ - αΛ ) = 0

ΛΛ production >95% triplet

Folie 13

Use the antiproton factory (nearly) as usual.

Cut out kinematical regions in the antiproton production spectrum which would dilute vector polarisation

• Avoid pure s wave antiprotons• Cut one side in the horizontal angular distribution• Cut up and down angles• In addition avoid depolarisation in the cooler synchrotron

Polarised production

Folie 14

y

x

Folie 15

Red lines: angular and momentum acceptance of AD

S wave region

Folie 16

y

x

Folie 17

Clean cuts may need a “pointlike” source, means a shorter production target

Reduction 1/5

Cuts in kinematics

Reduction 1/5

I/I0 ~ 1/25

Folie 18

p production and transport to AD-

Necessary cuts in p distribution easily made in the existing beam line

Folie 19

Existing AD for p stop experiments

Acceptance H, V (π mm mrad) 200/180

Acceptance Δp/p (%) ±3.2%

Number of p injected 5 107 per cycle

Folie 20

AD tune diagram and

Limit of spin stability

(red lines)

Folie 21

CNI polarimeter reaction (coulomb-nuclear interference) allows to check if polarised p come out

A = 4.5% maximum

at t = - 0.0037 (GeV/c)2

corresponds to 38 mrad

for p+p scattering at 3.5 GeV/c

Polarisation test at CERN PS

Cu (lH2 ) target on external beam

1.5 Tm dipole, 10 cm gap

Straw tracker stacks before and after an lH2 analyser target on the p exit side. Adapted to 3.3 to 3.7 GeV/c p

Trigger szintillators

All in vacuum

(Target and detectors exist at COSY TOF)

A

2mb polarim. react.

Folie 22

Measurement of antiproton polarisationdetector components in vacuum

1 m

PT < 150 MeV/c( s-wave )

PT < 700 MeV/c

AD acceptance

straw tubes( track resolution ~ 100 μm )

Cerenkovdetectorn=1.03

liquid hydrogenanalyser target

24 GeV/cprotonbeam

antiprotonproductiontarget1 cm W

dipole magnet1.6 T

38 mrad

scintillatorhodoscope

P = 3.4 – 3.6 GeV/c

beam dump

2% precision in p polarisation with 4 10^16 primary protons on 8mm W target

Folie 23

Comparison

Filter methode Λ decay Polarised production

P 0 – 40% ?? >45% ! 0 - 40% ??

I/I0 10-1 – 10-2 ? 10-3 x 10-2 x .2 ~ 2 10-

6 0.2 x 0.2 ~ 4 10-2

P2 I < 1.6 10-2 4 10-7 < 6.4 10-3

T0 ~ 2 days (hadronic)

Reduced duty factor ?

Polarisation dependence of filter reactions ?

(not spin transfer)

Sibirian snake needed

Proof with protons ok

External target for Λ productionDecay spectrometer and –polarimeter

Pol. p scattering parasitic with CP test?

Has been used (FNAL)

Numbers are known

Is there p polarisation?

Test experiment on external PS beam

Would be by far simplest solution

Folie 24

Comparison

Filter methode Λ decay Polarised production

P 0 – 40% ?? >45% ! 0 - 40% ??

I/I0 10-1 – 10-2 ? 10-3 x 10-2 x .2 ~ 2 10-

6 0.2 x 0.2 ~ 4 10-2

P2 I < 1.6 10-2 4 10-7 < 6.4 10-3

T0 ~ 2 days (hadronic)

Reduced duty factor ?

Polarisation dependence of filter reactions ?

(not spin transfer)

Sibirian snake needed

Proof with protons ok

External target for Λ productionDecay spectrometer and –polarimeter

Pol. p scattering parasitic with CP test?

Has been used (FNAL)

Numbers are known

Is there p polarisation?

Test experiment on external PS beam

If p not polarised, use polarised 26 GeV proton beam

Would be by far simplest solution

Folie 25

Thank you for your attention

Folie 26

polarisation dependent interactions

Spin filter idea with cooling (K. Kilian & D. Moehl 1980 Lausanne Pol. Conf., 1982 Erice LEAR workshop) Stimulated activities.

Most successful: E. Steffens and the FILTEX collaboration at the TSR in MPI Heidelberg. Proof that it works with protons. F. Rathmann PRL 71 1379 (1993)

Idea of spin transfer at very low energy e↑ + p → e + p↑ in beam – beam interaction. PAX collaboration at COSY showed that there is no effect

D. Oellers et al. Phys. Lett. B674 (2009) 269

Certainly polarisation dependent is interaction of circularly polarised photons with p

γ + p → n + π B. Schoch, EPJ 2010

Folie 27

Intensity loss - polarisation gain - FOM

With a storage cell target (3 1013 pol. prot. cm-2 )

T0 ~ 2 days (hadronic)

K.K. & D.M. Erice 1982

Folie 28

Geometry spectrometer (PS185 at LEAR)

A stack of 23 wire chambers

Decay spectrometer and polarimeter with full acceptance and very high precision