search for double antikaon production in nuclei by stopped antiproton annihilation p. kienle,...
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Search for Double Antikaon Production in Nuclei by Stopped Antiproton Annihilation
P. Kienle, Excellence Cluster Universe, TU München
• Introduction into the search for double kaonic
nuclear cluster production by stopped
antiproton annihilation• Experimental approach @ J-PARC
• Experimental approach @ AD and FAIR
A Proposal for the CERN AD
Letter of Intent for J-PARC
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Possibility of “Double-KaonicNuclear Cluster” Productionby Stopped-pbar Annihilation
Prelude to „Double-Strange Nuclei“ @ LEAP
W. Weise, arXiv: 0507.058 (nucl-th) 2005P. Kienle, J. Mod. Phys., A22 (2007) 365P. Kienle, J. Mod. Phys., E16 (2007) 905J. Zmeskal et al. EXA/LEAP 08, Hyper, IntJ. Zmeskal et al. „Double-Strangeness Pro- duction by Antiprotons, May 2009, CERN
Deeply Bound Di-Baryon Resonancewith Strangness S =-1
Properties• p+p -> K+ +X @ high momentum transfer• MX = 2.265 (2) GeV/c² -> BX = 105(2) MeV• ΓX = 118(8) MeV/c² • Assigned to deeply bound, dense K-pp cluster with Bx about twice the value predicted by AY• High observed production probability is predicted by the AY reaction model for the case of a high density cluster X
Consequences for Double Strange Cluster Higher binding energy and higher density expected compared with single strange cluster
T. Yamazaki et al.Hyp. Inter.DO: 10.1007/ s 10751-0099997-5
Double-Kaonic Nuclear Cluster
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Double-kaonic nuclear clusters have been predicted theoretically. Double-kaonic clusters are expected to have a stronger binding energy and a higher density than single ones.
B.E. [MeV] Width [MeV]
Central-Density
K-K-pp -117 35
K-K-ppn -221 37 17r0
K-K-ppp -103 -
K-K-pppn -230 61 14r0
K-K-pppp -109 -
How to produce the double-kaonic nuclear cluster?heavy ion collision(K-,K+) reactionpbarA annihilation
We use pbarA annihilation
PL,B587,167 (2004). & NP, A754, 391c (2005).
p p K K K K
The elementary pbar-p annihilation reaction:
is forbidden for stopped pbar, because of a negative Q-value of 98MeV
Double-Strangeness Production with pbar
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However, if deeply bound multi kaonic nuclear clusters exist, production by pbar annihilation reactions will be possible!
-98MeV
3
3 0
4
4 0
106MeV
109MeV
126MeV
129MeV
pnKK
ppKK
pnnKK
ppnKK
p He K K K K pn B
p He K K K K pp B
p He K K K K pnn B
p He K K K K ppn B
theoreticalprediction
B.E.=117MeVG=35MeV
B.E.=221MeVG=37MeV
Double-Strangeness Production
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Observations of the double-strangeness production in stopped pbar annihilation have been reported by 2 groups only, DIANA@ ITEP and OBELIX@ CERN/LEAR.
experiment channel events yield (10-4)
DIANA K+K+X 4 0.31+/-0.16
[pbar+Xe] K+K0X 3 2.1+/-1.2
K+K+S-S-ps 34+/-8 0.17+/-0.04
OBELIX K+K+S-S+np- 36+/-6 2.71+/-0.47
[pbar+4He] K+K+S-Ln 16+/-4 1.21+/-0.29
K+K+K-Lnn 4+/-2 0.28+/-0.14
Although the observed statistics is very low,their results have indicated a high yield of ~10-4
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Experimental Approachfor J-PARC
A double-strangeness production yield of ~10-4 would make itpossible to explore the exotic systems with a dedicated
experiment
Search for the Most Elementary K-K-pp System
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3 0p He K K K K pp In the following discussion, we focus on the reaction:
(although K-K-pp decay modes are not known,)we assume the most energetic favored decay mode:
K K pp
We can detect the K-K-pp signal with:exclusive measurementall charged particles, K+K0, using K0p +p - modeK0, and K+ ID using K0 missing mass(semi-)exclusive measurementK+K0 missing mass with -tag invariant mass
final state = K+K0LL
We needwide-acceptance
detectors.
Expected Kinematics
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assumptions:widths of K-K-pp/H = 0many-body decay = isotropic decay
3 0Sp He K K K K pp
B.E=109MeV B.E=150MeV B.E=200MeV(threshold)
In the K-K-pp production channel, the kaons have very small momentum of up to
300MeV/c, even if B.E.=200MeV.
We have to construct low mass material detectors.
K+ K0 X momentum spectra
Beam-Line
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We would like to perform the proposed experiment at K1.1 or K1.8BR beam line
Incident Beammomentum bite : +/-2.5% (flat)incident beam distribution : ideal
DetectorsCarbon Degrader : 1.99*g/cm3
Plastic Scintillator : l=1cm, 1.032*g/cm3
Liquid He3 target : f7cm, l=12cm, 0.080*g/cm3
pbar stopping-rate evaluation by GEANT4
pbar stopping-rate
30GeV-9mA,6.0degreesNi-target
pbar production yield with a Sanford-Wang
1.3x103 stopped pbar/spill@ 0.65GeV/c, ldegrader~14cm
Expected Double-Strangeness Yield
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pbar beam momentum : 0.65GeV/cbeam intensity : 3.4x104/spill/3.5spbar stopping rate : 3.9%
9.6x104 double-strangeness/month
9.6x103 K+K0LL/monthbranching ratio to K+K0LL final state : 0.1
stopped-pbar yield : 1.3x103/spill/3.5s
Double-strangeness production : 1x10-4/stopped-pbar
a mere assumption!
Detector Design I
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design conceptlow material detector systemwide acceptance with PIDuseful for other experiments
E15 setup @ K1.8BR
CDCType A A’ A U U’ V V’ A A’ U U’ V V’ A A’
Layer 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
radius 190.5 204.0 217.5 248.5 262.0 293.0 306.5 337.5 351.0 382.0 395.5 426.5 440.0 471.0 484.5
ZTPCLayer 1 2 3 4
radius 92.5 97.5 102.5 107.5
B = 0.5TCDC resolution : srf = 0.2mm
sz’s depend on the tilt angles (~3mm)ZTPC resolution : sz = 1mm
srf is not used for present setup
We are considering2-types of detector
Detector Design II
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New dipole setup @ K1.1
CDCType A A’ A U U’ V V’ A A’ U U’ V V’ A A’
Layer 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
radius 500 525 550 575 600 625 650 675 700 725 750 775 800 825 850
INC (wire chamber)Type A A’ A U U’ V V’ A A’ A U U’ V V’ A A’ A
Layer 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
radius 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420
The design goal is to become the common setup for the f-nuclei experiment with in-flight pbar-beamB = 0.5TDouble Cylindrical-Drift-Chamber setuppID is performed with dE/dx measurement by the INC
INC resolution : srf = 0.2mm , sz = 2mm (UV)CDC resolution : srf = 0.2mm, sz = 2mm (UV)CDC is NOT used for the stopped-pbar experiment
Expected Signals
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LL inv-mass with E15 setup
K+K0 miss-mass with E15 setup
LL inv-mass with NEW setup
K+K0 miss-mass with NEW setup
sK-K-pp = 34MeVsH = 14MeV
sK-K-pp = 27MeVsH = 0.7MeV
sK-K-pp = 12MeVsH = 45MeV
sK-K-pp = 8MeVsH = 25MeV
53 K-K-pp events/month 42 K-K-pp events/month
17 K-K-pp events/month 24 K-K-pp events/month
Backgrounds from S0gL have to be taken into account
Summary
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OutlookWe are investigating further realistic estimation of the K+K0LL yield and the backgrounds for (semi-)inclusive measurements.
We are now preparing the proposal for J-PARC based on the LoI.
We propose to search for double strangeness production by pbar annihilation on helium nuclei at rest.
The proposed experiment will provide significant information on double strangeness production and double strangeness cluster states, like K-K-pp.
Experimental Approach for AD of CERN and FAIR
Thanks for Your Attention
Interpretation of the Experimental Results
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Although observed statistics are very small, the results have indicated a high yield of ~10-4, which is naively estimated to be ~10-5.
Possible candidates of the double-strangeness production mechanism are:rescattering cascades, exotic B>0 annihilation (multi-nucleon annihilation)
formation of a cold QGP, deeply-bound kaonic nuclei,H-particle, and so on
single-nucleonannihilation
rescatteringcascades
multi-nucleonannihilation
B=0 B>0B>0
the mechanism is NOT known well
because of low statistics
of the experimental results!
DIANA RESULTS
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DIANA [Phys.Lett., B464, 323 (1999).]pbarXe annihilationp=<1GeV/c pbar-beam @ ITEP 10GeV-PS700-liter Xenon bubble chamber, w/o B-field106 pictures 7.8x105 pbarXe inelastic 2.8x105 pbarXe @ 0-0.4GeV/c
Channel events yield (10-4)
K+K+X 4 0.31+/-0.16
K+K0X 3 2.1+/-1.2
channel events yield (10-4)
K+K+S-S-ps 34+/-8 0.17+/-0.04
K+K+S-S+np- 36+/-6 2.71+/-0.47
K+K+S-Ln 16+/-4 1.21+/-0.29
K+K+K-Lnn 4+/-2 0.28+/-0.14
OBELIX RESULTS
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OBELIX (’86~’96) [Nucl. Phys., A797, 109 (2007).]pbar4He annihilationstopped pbar @ CERN/LEARgas target (4He@NTP, H2@3atm)cylindrical spectrometer w/ B-fieldspiral projection chamber, scintillator barrels, jet-drift chambers2.4x105/4.7x104 events of 4/5-prong in 4Hepmin = 100/150/300MeV/c for p/K/p
they discuss the possibility of formation and decay of K-K-nn and K-K-pnn bound system
Expected Kinematics II
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3 0p He K K MH = 2ML
3 0p He K K H
L momentum LL inv. mass
LL spectra-L L opening-angle
strong correlation of LL opening-angle in K-K-pp/H productions
Trigger Scheme
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pbar3He charged particle multiplicity at restCERN LEAR, streamer chamber exp. NPA518,683 91990).
Nc Branch (%)
1 5.14 +/- 0.04
3 39.38 +/- 0.88
5 48.22 +/- 0.91
7 7.06 +/- 0.46
9 0.19 +/- 0.08
<Nc> 4.16 +/- 0.06
expected stopped-pbar yield = 1.3x103/spill&
All events with a scintillator hit will be accumulated
Expected Signals I
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assumptions:widths of K-K0pp/H = 0B.E. of K-K-pp = 200MeVMH = 2xML
branching ratio to K+K0LL final state = 0.1DAQ & analysis efficiency = 0.7 6.7x103 K+K0LL/monthGenerated ratio K-K-pp:H:LL = 0.1:0.1:0.8KKppLL and HLL decay branches are assumed to be 100%S0gL contribution is NOT considered for the inclusive measurements
pbar+3HeK+K0S+ X (X=KKpp/H/LL) events are generated isotropically at the
center of the detector system# of generated events is 200k for each caseobtained yields are scaled by the estimated K+K0LL yieldchamber resolution, multiple scattering and energy losses are fully took into account using GEANT4 toolkitcharged particles are traced with spiral fit
LL invariant mass : inclusive eventsK+K0 missing mass : semi-inclusive events (w/ one more L)
K+K0ΛΛ Final State & Background
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3 0
0
p He K K X
K K
This exclusive channel study is equivalent tothe unbound (excited) H-dibaryon search!
Q-value X momentum LL mass -L L angle
K-K-pp very small ~ at rest MLL > 2xML back to back
Possible background channelsdirect K+K0 production channels, like:
S0gL contaminations, like:
3 0
3 0 0 ...
p He K K
p He K K p
3 0 0
0
p He K K
K K
S
be eliminated by the kinematical constraint
be distinguished by inv.-mass only major background source