Transcript Folie 1 - Jagiellonian University

Many exciting old ideas with antiprotons, pre LEAR 1977 - 1984
Revival 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 precision
p 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. quality
Production of polarised p with filter method in cooler ring
…and more
Ideas get lost after a scientific lifetime
Folie 1
Mitglied der Helmholtz-Gemeinschaft
Ways to make polarised antiproton beams
Dieter Grzonka, Kurt Kilian, Walter Oelert, IKP FZ-Jülich
• Production of antiprotons
• Spin filter method
• Antihyperon decay
• Polarised production
• Comparison
MESON2010 10.–17. 6. 2010 Krakow
Monday 14.6.2010
Production of antiprotons
26 GeV/c beam
D. Dekkers
CERN PS
1968
Convert collision energy into particleantiparticle 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
K. Kilian et al.1977
pre LEAR memo to
PSCC
2914 MeV/c > pcm > 0
If pcm < 150 MeV/c
then S wave production
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pp→p+(3p)
p lab. Momentum
MC simulation
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
Folie 4
Spin filter method
Suggested 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.
Filtering below
1 GeV/c →
Important ΔσCb
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
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Spin-filtering at TSR: „FILTEX“ – proof-of-principle
F. Rathmann et al.,
PRL 71, 1379 (1993)
→ Spin filtering works for protons
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)
Frank Rathmann
Spin-filtering studies at COSY and AD
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6
Polarization Buildup: Figure of Merit
statistical error of a double
polarization observable (ATT)
 ATT
Measuring time t to achieve a
certain error δATT
(N ~ I)
1

PQ N
t ~ FOM = P2·I
?
Ask
F.R.
I/I0
Optimum time for
Polarization Buildup
given by maximum of FOM(t)
tfilter = 2·τbeam
0.8
0.6
σ↑↑ : σ↓↑
P2Τ
1
:
0.5
21%
1
:
0.8
7%
ΔσCb → will
dilute effect
Frank Rathmann
Beam Polarization
Other spin dependent processes? E.g. B. Schoch: scatter polarised photons
0.4
P2Τ
0.2
2T > 4 days
0
2
4
Spin-filtering studies at COSY and AD
6
t/τbeam
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7 of
Antihyperon decay
Λ → p + π+
plab(p)
p
π+
plab(π+)
pcm
Decay momentum in cm syst. is 101 MeV/c
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)
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FNAL experiment: A. Bravar et al. P.R.L.77,2626,(1996)
NB: decay polarisation tagging below 0.5 mrad ! Experiment ~ km long
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Useful antihyperon source in the GeV range (FAIR)
pp → ΛΛ → pπ+ pπDecay 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
cτΛ = 7.89 cm
Will not work with internal target
(miserable multi track reconstruction,
miserable trigger condition)
Branching ratio σΛΛ /σtot = 10-3
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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)
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CP violation test
A = (αΛ + αΛ ) / (αΛ - αΛ ) = 0
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 test
Needs 109 pair events or 2x1014 beam p (200 days)
As byproduct: “beam” of 109 polarised decay p
ΛΛ production >95% triplet
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Polarised production
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
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y
x
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S wave region
Red lines: angular and momentum acceptance of AD
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y
x
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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
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p production and transport to AD
Necessary cuts in p distribution easily made in the existing beam line
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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
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AD tune diagram
and
Limit of spin stability
(red lines)
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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
A
corresponds to 38 mrad
for p+p scattering at 3.5 GeV/c
Polarisation test at CERN PS
2mb polarim. react.
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)
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Measurement of antiproton polarisation
detector components in vacuum
straw tubes
( track resolution
~ 100 μm )
antiproton
production
target
1 cm W
Cerenkov
detector
n=1.03
scintillator
hodoscope
PT < 700 MeV/c
AD acceptance
P = 3.4 – 3.6 GeV/c
1m
24 GeV/c
proton
beam
beam
dump
dipole magnet
1.6 T
PT < 150 MeV/c
( s-wave )
liquid hydrogen
analyser target
2% precision in p polarisation with 4 10^16 primary protons on 8mm W target
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Comparison
Λ decay
Filter methode
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 ?
External target for Λ
production
Decay spectrometer
and –polarimeter
Is there p polarisation?
Polarisation
dependence of filter
reactions ?
(not spin transfer)
Sibirian snake needed
Proof with protons ok
Test experiment on
external PS beam
Pol. p scattering
parasitic with CP test?
Has been used (FNAL)
Numbers are known
Would be by far
simplest solution
Folie 23
Comparison
Λ decay
Filter methode
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 ?
External target for Λ
production
Decay spectrometer
and –polarimeter
Is there p polarisation?
Pol. p scattering
parasitic with CP test?
If p not polarised, use polarised
26 GeV proton beam
Polarisation
dependence of filter
reactions ?
(not spin transfer)
Sibirian snake needed
Proof with protons ok
Has been used (FNAL)
Numbers are known
Test experiment on
external PS beam
Would be by far
simplest solution
Folie 24
Thank you for your attention
Folie 25
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 26
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
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Geometry spectrometer (PS185 at LEAR)
A stack of 23 wire
chambers
Decay spectrometer
and polarimeter with
full acceptance and
very high precision
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