A search for double anti-kaon production in antiproton- 3 He annihilation at J-PARC

A search for double anti-kaon production in antiproton-3He 　

annihilation at J-PARC

F.Sakuma,　RIKEN

1Tum-Riken Kick-Off Meeting @ TUM, May 10-11, 2010.

2

This talk is based on the LoI submitted in June, 2009.

3

(brief) Introduction of “Kaonic Nuclear Cluster”

Possibility of “Double-Kaonic Nuclear Cluster”

by Stopped-pbar AnnihilationExperimental ApproachSummary

Contents

we will open new door to the high density matter physics, like the inside of neutron stars

Kaonic Nuclear Cluster (KNC)

4

the existence of deeply-bound kaonic nuclear cluster is predicted from strongly attractive KbarN interaction

Kaonic Nuclei

BindingEnergy[MeV]

Width[MeV]

CentralDensity

Kp 27 40 3.50

Kpp 48 61 3.10

Kppp 97 13 9.20

Kppn 118 21 8.80

T.Yamazaki, A.Dote, Y.Akiaishi, PLB587, 167 (2004).

the density of kaonic nuclei is predicted to be extreme high density

Method Binding Energy (MeV) Width (MeV)

Akaishi, YamazakiPLB533, 70 (2002). ATMS 48 61

Shevchenko, Gal, MaresPRL98, 082301 (2007). Faddeev 55-70 90-110

Ikeda, SatoPRC76, 035203 (2007). Faddeev 79 74

Dote, Hyodo, WeiseNPA804,197(2008). chiral SU(3) 19+/-3 40-70 (N-decay)

5

Theoretical Situation of KNCtheoretical predictions for kaonic nuclei, e.g., K-pp

Koike, HaradaPLB652, 262 (2007).DWIA

•whether the binding energy is deepdeep or shallowshallow•how broadbroad is the width ?

3He(K-,n)

no “narrow” structureno “narrow” structurePLB 659:107,2008

6

Experimental Situation of KNC4He （ stopped K-,p)E549@KEK-PS

12C(K-,n)

12C(K-,p)

missing mass

E548@KEK-PS

Prog.Theor.Phys.118:181-186,2007.

arXiv:0711.4943

unknown strength unknown strength between Q.F. & 2N abs.between Q.F. & 2N abs.

deep K-nucleus deep K-nucleus potential of ~200MeVpotential of ~200MeV

--

K-pnn?

K-pp/K-pnn?

K-pn/K-ppn?

4He （ stopped K-,N)E549@KEK-PS

7

Experimental Situation of KNC (Cont’d)

FINUDA@DANE OBELIX@CERN-LEAR

We need conclusive evidencewith observation of formationformation andand decaydecay !

DISTO@SATUREN

-p invariant mass

PRL, 94, 212303 (2005) NP, A789, 222 (2007)

peak structure peak structure signature of kaonic nuclei ? signature of kaonic nuclei ?

K-pp?K-pp?

PRL,104,132502 (2010)

K-pp?

8

Experimental Principle of J-PARC E15search for K-pp bound state using 3He(K-,n) reaction

K- 3He Formation

exclusive　measurement byMissing　mass　spectroscopy

andInvariant　mass　reconstruction　

Decay

K-ppcluster

neutron

p

p-

Mode to decay charged particles

Missing

mass

Spectroscop

y

via neutron

Invariant

mass

reconstructio

n

9

J-PARC E15 Setup

1GeV/cK- beam

p

p

n

NeutronToF Wall

CylindricalDetectorSystem

Beam SweepingMagnet

K1.8BR Beam Line

flight length = 15mneutron

Beam trajectory

CDS &target

SweepingMagnet

NeutronCounter

Beam LineSpectrometer

E15 will provide theE15 will provide theconclusive evidence of Kconclusive evidence of K--pppp

10

Possibility of “Double-KaonicNuclear Cluster”

by Stopped-pbar Annihilation

What will happen to put one more kaon in the kaonic nuclear cluster?

11

Double-Kaonic Nuclear ClusterThe double-kaonic nuclear clusters have been predicted theoretically.The double-kaonic clusters have much stronger binding energy and a much higher density than single ones.

B.E. [MeV] Width [MeV]

Central-Density

K-K-pp -117 35

K-K-ppn -221 37 170

K-K-ppp -103 -

K-K-pppn -230 61 140

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 with double-strangeness production:

This reaction is forbidden for stopped pbar, because of a negative Q-value of 98MeV

Double-Strangeness Production with pbar

However, if multi kaonic nuclear exists with deep bound energy, following 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

12

theoreticaltheoreticalpredictionprediction

B.E.=117MeV=35MeV

B.E.=221MeV=37MeV

Production Mechanism of K-K-pp with pbar+3He?

13

it has been observed that cross section of pbar+p->KKKK with around 1GeV/c pbar-beam is very small of less than 1b, so it would be very difficult experimentally.

For example, the possible K-K-pp production mechanisms are as follows:with stopped pbar

①direct K-K-pp production with 3N annihilation②** production with 3N annihilation followed by K-K-pp formationwith in-flight pbar

in addition above 2ways,③elementally pbar+pKKKK production followed by K-K-pp formation

It’s worthwhile to explore these exotic system with pbar,although the mechanism is NOT completely investigated!

Some theorist’s comment: If the K-K-pp bound system can be exist, such system could be ** molecular system by analogy between * K-p. Then the binding energy could be small of about from 30 to 60 MeV.

A theoretical problem: The K-K- interactions have been calculated in lattice QCD as strongly repulsive interaction. However, these K-K- interactions are neglected simply in the PLB587,167 calculation which only shows the K-K-pp bound system.

14

Double-Strangeness Production Yieldby Stopped-pbar Annihilation

From several stopped-pbar experiments, the inclusive production yields are:

Naively, the double-strangeness production yield would be considered as:

: reduction factor ~ 10-2

2( ) ~ 5 10R pp KK 3 0 2

4 0 2

( ( )) ~ 0.6 10

( ( )) ~ 1.1 10

R p He

R p He

2 5

( )

( ) ~ 10

R pA KKKK

R pp KK

15

Past Experiments of Double-Strangeness Production in Stopped-pbar Annihilation

Observations of the double-strangeness production in stopped pbar annihilation have been reported by only 2 groupsonly 2 groups, 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+--ps 34+/-8 0.17+/-0.04

OBELIX K+K+-+n- 36+/-6 2.71+/-0.47

[pbar+4He] K+K+-n 16+/-4 1.21+/-0.29

K+K+K-nn 4+/-2 0.28+/-0.14

Although observed statistics are very small,their results have indicated a high yield of ~10-4

16

Past Experiments (Cont’d)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+--ps 34+/-8 0.17+/-0.04

K+K+-+n- 36+/-6 2.71+/-0.47

K+K+-n 16+/-4 1.21+/-0.29

K+K+K-nn 4+/-2 0.28+/-0.14

17

Past Experiments (Cont’d)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 /K/p

they discuss the possibility of formation and decay of K-K-nn and K-K-pnn bound system

18

Experimental Approach

The double-strangeness production yield of ~10-4 makes it possible to explore the exotic systems.

19

How to Measure?

3 0p He K K K K pp we focus the reaction:

(although K-K-pp decay modes are not known at all,)we assume the most energetic favored decay mode:

K K pp

We can measure the K-K-pp signal exclusively by detection of all particles, K+K0, using K0+- mode

final state = K+K0

We needwide-acceptance detectors.

20

Expected Kinematicsassumptions:widths of K-K-pp = 0isotropic decay

3 0Sp He K K K K pp

B.E=120MeV B.E=150MeV B.E=200MeV(th.+11MeV)

In the KIn the K--KK--pp production channel, the kaons have very pp production channel, the kaons have very small momentum of up to 300MeV/c, even if small momentum of up to 300MeV/c, even if

B.E.=200MeV.B.E.=200MeV.

We have to construct low mass material detectors.

KK++KK00X momentum spectraX momentum spectra

~70MeV/c Kaon ~150MeV/c Kaon ~200MeV/c Kaon

~200MeV/c from K0S, ~800MeV/c , ~700MeV/c p from , ~150MeV/c - from

21

Procedure of the K-K-pp Measurement

Key points of the experimentKey points of the experimenthigh intensity pbar beamwide-acceptance and low-material detector

How to measure the K-K-pp signalHow to measure the K-K-pp signal(semi-inclusive) K0

SK+ missing-mass w/ -tag(inclusive) invariant mass(exclusive) K0

SK+ detection*1 because of the low-momentum kaon, it could be hard to detect all particles*2 semi-inclusive and inclusive spectra could contain background from 2N annihilation and K-K-pp decays, respectively

22

Beam-LineWe would like to perform the proposed experimentWe would like to perform the proposed experiment

at J-PARC K1.8BR beam line (or K1.1)at J-PARC K1.8BR beam line (or K1.1)

pbar stopping-rate

30GeV-9A,6.0degreesNi-target

pbar production yield with a Sanford-Wang

1.3x101.3x1033 stopped p stopped pbarbar/spill/spill@ 0.65GeV/c, l@ 0.65GeV/c, ldegraderdegrader14cm14cm

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 : 7cm, l=12cm, 0.080*g/cm3

pbar stopping-rate evaluation by GEANT4

23

Detector DesignKey pointslow material detector systemwide acceptance with pID E15 CDS @ K1.8BRE15 CDS @ 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 : r = 0.2mmz’s depend on the tilt angles (~3mm)ZTPC resolution : z = 1mm

r is not used for present setup

24

Trigger Scheme

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 can be accumulatedAll events with a scintillator hit can be accumulated

K-K-pp event

25

Detector Acceptance

E15 CDS @ K1.8BRE15 CDS @ K1.8BR--- detection--- K0

SK+ w/ -tag detection--- K0

SK+ detection

Pbar+3He K++K0S+K-K-pp,

K-K-pp ,(K-K-pp)=100MeV

binding energy

26

Expected K-K-pp Production Yieldpbar beam momentum : 0.65GeV/cbeam intensity : 3.4x104/spill/3.5s @ 270kWpbar stopping rate : 3.9%

stopped-pbar yield : 1.3x103/spill/3.5s

we assume K-K-pp production rate = 10-4

K-K-pp production yield = 2.3x104 /week @ 270kW

DAQ & ana efficiency = 0.7 & duty factor = 0.7

expected K-K-pp yield = 1.1x104 /week @ 270kWw/o detector acceptance

27

Expected K-K-pp Detction YieldPbar+3He K++K0

S+K-K-pp,K-K-pp ,

(K-K-pp)=100MeV

E15 CDS @ K1.8BRE15 CDS @ K1.8BR--- detection--- K0


SK+ detection

binding energy

K-K-pp production rate = 10-4

Br(K-K-pp) = 100%

28

Backgrounds(semi-inclusive) K(semi-inclusive) K00

SSKK++ missing-mass w/ missing-mass w/ -tag-tag

(inclusive) (inclusive) invariant mass invariant mass

stopped-pbar + 3He K0S + K+ + K-K-pp

stopped-pbar + 3He K0S + K+ + +

stopped-pbar + 3He K0S + K+ + 0 + 0 + 0

…

stopped-pbar + 3He K0S + K+ + K0 + 0 + (n)

stopped-pbar + 3He K0S + K+ + K- + 0 + (p)

…

3N annihilation

2N annihilation


+ stopped-pbar + 3He K0

S + K+ + K-K-pp + 0


0 + 0


+ + 0

…

missing

missing 2

missing

29

Expected Spectra

expected spectrum with the assumptions:branching ratio of K-K-pp:•BR(K-K-pp) = 0.1•BR(K-K-pp0) = 0.1•BR(K-K-pp00 = 0.1•BR(K-K-pp0) = 0.7

production rate:•K-K-pp bound-state = 10-4

•(3N) K-K- phase-space = 10-4

•(3N) K+K0000 phase-space = 10-4

•(2N) K+K0K00(n) phase-space = 10-4

•(2N) K+K0K-0(p) phase-space = 10-4

2 = detection2K = K+K0 w/ -tag detection22K = K+K0 detection

Monte-Carlo simulation using GEANT4 toolkitreaction and decay are considered to be isotropic and proportional to the phase spaceenergy losses are NOT corrected in the spectraw/o Fermi-motion

30

Expected Spectra @ 270kW, 4weeks

# of K-K-pp = 406

invariant mass (2) invariant mass (2K2)

# of K-K-pp = 35

K+K0 missing mass (2K) K+K0 missing mass (2K2)

# of K-K-pp = 1293 # of K-K-pp = 203

stopped pbarB.E=200MeV,

=100MeV270kW, 4weeks

In the In the spectra, we cannot discriminate the K-K-pp going to spectra, we cannot discriminate the K-K-pp going to signals from the backgrounds, if K signals from the backgrounds, if K--KK--pp has theses decay pp has theses decay modes.modes.In contrast, the KIn contrast, the K00 K K++ missing mass spectroscopy is attractive for missing mass spectroscopy is attractive for us because we can ignore the Kus because we can ignore the K--KK--pp decay mode. pp decay mode.

31

Summary

32

SummaryWe propose to search for double strangeness production by pbar annihilation on 3He nuclei at rest.

The proposed experiment will provide significant information on double strangeness production and double strangeness cluster states, K-K-pp.

The experimental key points are high-intensity pbar beam and wide-acceptance/low-material detector system. We propose to perform the experiment at K1.8BR beam-line with the E15 spectrometer.

We are now preparing the proposal for J-PARC based on the LoI.

33

34

Back-Up

35

K-pp Production with pbar at rest

3 0p He K K pp Of course, we can measure K-pp production!

From several stopped-pbar experiments, the inclusive production yields are:

2( ) ~ 5 10R pp KK

Very simply, expected K-pp yield is 100 times larger than the K-K-pp production!

OBELIX@CERN-LEAR

-p invariant mass

NP, A789, 222 (2007)

K-pp?

4

p He K pp X

p

36




K+K0 missing-mass2 (2K2)

37


37

# of K-K-pp = 75


# of K-K-pp = 6


# of K-K-pp = 239 # of K-K-pp = 38


=100MeV50kW, 4weeks

38



=100MeV50kW, 4weeks


in-flight experiment

40

Detector Acceptance

E15 CDS @ K1.8BRE15 CDS @ K1.8BR



binding energy

--- detection--- K0


SK+ detection

stopped1GeV/c

41

Expected K-K-pp Production Yieldpbar beam momentum : 1GeV/cbeam intensity : 6.4x105/spill/3.5s @ 270kW

we assume K-K-pp production rate = 10-4 for 1GeV/c pbar+p (analogy from the DIANA result of double-strangeness production although the result are from pbar+131Xe reaction)

inelastic cross-section of 1GeV/c pbar+p is (117-45) = 72mb

K-K-pp production CS = 7.2b for 1GeV/c pbar+p

42

Expected K-K-pp Production Yield (Cont’d)

DAQ & ana efficiency = 0.7 & duty factor = 0.7

expected K-K-pp yield = 7.5x104 /week @ 270kWw/o detector acceptance

K-K-pp production yield = 1.5x105 /week @ 270kW

L3He parameters: * = 0.08g/cm3

* l = 12cmN = * NB * NT•N : yield• : cross section•NB : the number of beam•NT : the number of density per unit area of the target

BG rate:total CS = 117mbpbar = 6.4x105/spill BG = 1.4x104/spill

43

Expected K-K-pp Detection Yield

E15 CDS @ K1.8BRE15 CDS @ K1.8BR



binding energy

--- detection--- K0


SK+ detection

stopped1GeV/c

44


44

# of K-K-pp = 1397


# of K-K-pp = 94


# of K-K-pp = 8095 # of K-K-pp = 392

1GeV/c pbarB.E=200MeV,


45





with Dipole-setup @ K1.1

47

Detector Design (Cont’d)new dipole setup @ K1.1new 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 -nuclei experiment with in-flight pbar-beamB = 0.5TDouble Cylindrical-Drift-Chamber setuppID is performed with dE/dx measurement by the INC

INC resolution : r = 0.2mm , z = 2mm (UV)CDC resolution : r = 0.2mm, z = 2mm (UV)CDC is NOT used for the stopped-pbar experiment

48

Detector Acceptance

dipole @ K1.1dipole @ K1.1--- detection--- K0


SK+ detection



binding energy

stopped1GeV/c

49

Expected K-K-pp Detection Yield

dipole @ K1.1dipole @ K1.1--- detection--- K0


SK+ detection



binding energy

stopped1GeV/c

50


50

# of K-K-pp = 282


# of K-K-pp = 27


# of K-K-pp = 1719 # of K-K-pp = 238



51





52


52

# of K-K-pp = 1112


# of K-K-pp = 76


# of K-K-pp = 7915 # of K-K-pp = 435



53





54

55

Interpretation of the Experimental ResultsAlthough 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=0B=0 B>0B>0B>0B>0

the mechanism is NOT known well

because of low statistics

of the experimental results!

56

K+K0 Final State & Background3 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 mass angle

K-K-pp very small ~ at rest M > 2M back to back

H-dibaryon large boosted M ~ 2M ~ 0

Possible background channelsdirect K+K0 production channels, like:

0 contaminations, like:

3 0

3 0 0 ...

p He K K

p He K K

3 0 0

0

p He K K

K K

be eliminated by the kinematical constraint,

ideally

be distinguished by inv.-mass only major background source

57

Expected Kinematics (Cont’d)3 0p He K K

MH = 2M

3 0p He K K H

momentum inv. mass spectraspectra

opening-angle

strong correlation of strong correlation of opening-angle opening-angle in Kin K--KK--pp/H productionspp/H productions

58

Schedule

Year (JFY) K1.8BR K1.1 (N)2009 beam-tune proposal2010 E17 R&D, design2011 E17 R&D, design2012 E15/E31 construction2013 E15/E31 commissioning2014 … data taking

The proposed experiment will be scheduled in around JFY2014, whether we conduct the experiment at K1.8BR or K1.1 beam-line.K1.8BR : after E17/E15/E31?K1.1 : joint project with the N experiment?

Past Experiments of Stopped-pbar Annihilation

pbar+3He　charged　particle　multiplicity　at　restCERN LEAR, streamer chamber exp.NP A518, 683 (1990).

nc1 5.14 +- 0.403 39.38 +- 0.885 48.22 +- 0.917 7.06 +- 0.469 0.19 +- 0.08

<nc> 4.155 +- 0.06

branch(%)

charged particle multiplicity at restform Rivista Del Nuovo Cimento 17, 1 (1994).

pbar+4He　charged　particle　multiplicity　at　restCERN LEAR, streamer chamber exp.NP A465, 714 (1987).[data in nuovo- ciment is listed below, which is a higher statistics than NPA465]

nc1 3.36 +- 0.352 5.03 +- 0.423 33.48 +- 0.924 12.26 +- 0.635 35.68 +- 0.936 3.51 +- 0.367 6.24 +- 0.478 0.19 +- 0.089 0.24 +- 0.10

<nc> 4.097 +- 0.07

branch(%)

CERN LEAR streamer chamber exp.NIM A234, 30 (1985).

70.4 2.5%

29.6 2.5%

0.42 0.05

a

a

a a

pp

pn

pn pp

They obtained

KKbar production-rate for pbar+p at restform Rivista Del Nuovo Cimento 17, 1 (1994).

the KKbar production-rate R for pbar+p annihilation at rest(obtained from hydrogen bubble chamber data)

0 0

0 0

0 0 0 0 0

0 0 0 0

1.733 0.067%

1.912 0.141%

1.701 0.082%

3 1 2.149 0.065%4 25.35 0.18%

S

R K K

R K K

R K K R K K

R K R K K R K K R K K

R KK R K K R K K R K K R K K

There is a great deal of data on the production of strange particles on 1H and 2H but only few ones on heavier nuclei.

/K0s production-rate and multiplicity for pbar+A at rest

form Rivista Del Nuovo Cimento 17, 1 (1994).

charge multiplicities decrease by ~1 when /K0S is produced

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/cpbarXeK+K+X : 4 events (0.31+/-0.16)x10-4

pbarXeK+K0X : 3 events (2.1+/-1.2)x10-4

4 events 3 events

interpretation of the DIANA result (pbarXe)from J.Cugnon et al., NP, A587, 596 (1995).

The observed double strangeness yield is explained by conventional processes described by the intranuclear cascade model, as listed in the following tables.

They also show the B=2 annihilations, described with the help of the statistical model, are largely able to account for the observed yield: i.e., the branching ratio of the KK state in pbar-NNN annihilation is equal to ~10-4 at rest (B=1 annihilations are not so helpful).

However they claim the frequency of even B=1 annihilation is of the order of 3-5% at the most [J.Cugnon et al., NP, A517, 533 (1990).] (is it common knowledge ?), so they conclude it would be doubtful to attempt a fit of the data with a mixture of B=0 and 2 annihilations.

On the other hand, the Crystal Barrel collaboration @ CERN/LEAR concludes their pbardK0/0K0 measurements disagree strongly with conventional two-step model predictions and support the statistical (fireball) model.

experimental values are not final values of the DIANA data

Crystal Barrel (’86~’96) [Phys. Lett., B469, 276 (1999).]pbar4He annihilationstopped pbar @ CERN/LEARliquid deuteron targetcylindrical spectrometer w/ B-fieldSVX, CDC, CsI crystals~106 events of 2/4-prong with topological triggers

0 6

0 0 6

5

( ) (2.35 0.45) 10

( ) (2.15 0.45) 10

( ) (1.3 1.0) 10

Br pd K

Br pd K

Br pd p

support the statistical model

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 chambers238,746/47,299 events of 4/5-prong in 4Hepmin = 100/150/300MeV/c for /K/p

4

( )

( )

( )

( )

s s

p He

K K p K K nnp

K K n K K nnn

K K n K K p nn

K K K nn K K K p nn

34+/-8 events (0.17+/-0.04)x10-4

4-prong

5-prong

5-prong

5-prong

* (xx) is not observed

4+/-2 events (0.28+/-0.14)x10-4

36+/-6 events (2.71+/-0.47)x10-4

16+/-4 events (1.21+/-0.29)x10-4

they discuss the possibility of formation and decay of K-K-nn and K-K-pnn bound system

Documents

A search for double anti-kaon production in antiproton- 3 He annihilation at J-PARC