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