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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

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Searchfor Double Antikaon Productionin Nuclei byStopped Antiproton AnnihilationP. 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


Possibility of “Double-Kaonic

Nuclear Cluster” Production

by Stopped-pbarAnnihilation

Preludeto „Double-Strange Nuclei“ @ LEAP

W. Weise, arXiv: 0507.058 (nucl-th) 2005

P. Kienle, J. Mod. Phys., A22 (2007) 365

P. Kienle, J. Mod. Phys., E16 (2007) 905

J. Zmeskal et al. EXA/LEAP 08, Hyper, Int

J. Zmeskal et al. „Double-Strangeness Pro-

ductionby Antiprotons, May 2009, CERN


DeeplyBound Di-Baryon Resonance

with Strangness S =-1

  • Properties
  • p+p -> K+ +X @ highmomentumtransfer
  • MX = 2.265 (2) GeV/c² -> BX = 105(2) MeV
  • ΓX = 118(8) MeV/c²
  • Assignedtodeeplybound, denseK-ppclusterwithBxabouttwicethevaluepredictedby AY
  • High observedproductionprobabilityispredictedbythe AY reaction model forthecaseof a highdensitycluster X
  • Consequencesfor Double Strange Cluster
  • Higher bindingenergyandhigherdensityexpectedcomparedwithsinglestrangecluster
  • T. Yamazaki et al.Hyp. Inter.DO: 10.1007/ s 10751-0099997-5
double kaonic nuclear cluster
Double-Kaonic Nuclear Cluster
  • 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.

PL,B587,167 (2004). & NP, A754, 391c (2005).

  • How to produce the double-kaonic nuclear cluster?
          • heavy ion collision
          • (K-,K+) reaction
          • pbarA annihilation

We use pbarA annihilation

double strangeness production with p bar
Double-Strangeness Production with pbar

The elementary pbar-p annihilation reaction:


is forbidden for stopped pbar,

because of a negative Q-value of 98MeV

However, if deeply bound multi kaonic nuclear clusters exist, production by pbarannihilation reactions will be possible!







double strangeness production
Double-Strangeness Production

Observations of the double-strangeness production in stopped pbar annihilation have been reported by 2 groups only, DIANA@ ITEP and OBELIX@ CERN/LEAR.

Although the observed statistics is very low,

their results have indicated a high yield of ~10-4


A double-strangeness production yield of ~10-4would make it

possible to explore the exotic systems with a dedicated experiment

Experimental Approach

for J-PARC

search for the most elementary k k pp system
Searchforthe Most Elementary K-K-pp System

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:

final state = K+K0LL

  • We can detect the K-K-pp signal with:
  • exclusive measurement
  • all charged particles, K+K0LL, using K0p+p- mode
  • K0LL, and K+ ID using K0LL missing mass
  • (semi-)exclusive measurement
  • K+K0 missing mass with L-tag
  • LL invariant mass

We need

wide-acceptance detectors.

expected kinematics
Expected Kinematics
  • assumptions:
  • widths of K-K-pp/H = 0
  • many-body decay = isotropic decay

K+ K0 X momentum spectra





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.

beam line

We would like to perform the proposed experiment

at K1.1 or K1.8BR beam line

pbar stopping-rate evaluation by GEANT4

  • Incident Beam
  • momentum bite : +/-2.5% (flat)
  • incident beam distribution : ideal
  • Detectors
  • Carbon Degrader : 1.99*g/cm3
  • Plastic Scintillator : l=1cm, 1.032*g/cm3
  • Liquid He3 target : f7cm, l=12cm, 0.080*g/cm3

1.3x103 stopped pbar/spill

@ 0.65GeV/c, ldegrader~14cm

  • 30GeV-9mA,
  • 6.0degrees
  • Ni-target

pbar production yield

with a Sanford-Wang

pbar stopping-rate

expected double strangeness yield
Expected Double-Strangeness Yield
  • pbar beam momentum : 0.65GeV/c
  • beam intensity : 3.4x104/spill/3.5s
  • pbar stopping rate : 3.9%
  • stopped-pbar yield : 1.3x103/spill/3.5s
  • Double-strangeness production : 1x10-4/stopped-pbar

 9.6x104 double-strangeness/month

a mere assumption!

  • branching ratio to K+K0LL final state : 0.1

 9.6x103 K+K0LL/month

detector design i
Detector Design I
  • design concept
  • low material detector system
  • wide acceptance with PID
  • useful for other experiments

We are considering

2-types of detector

E15 setup @ K1.8BR

  • B = 0.5T
  • CDC resolution : srf = 0.2mm
  • sz’s depend on the tilt angles (~3mm)
  • ZTPC resolution : sz = 1mm
    • srf is not used for present setup
detector design ii
Detector Design II

New dipole setup @ K1.1

  • The design goal is to become the common setup for the f-nuclei experiment with in-flight pbar-beam
  • B = 0.5T
  • Double Cylindrical-Drift-Chamber setup
  • pID 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
Expected Signals

LL inv-mass with NEW setup

LL inv-mass with E15 setup

53 K-K-pp events/month

42 K-K-pp events/month

sK-K-pp = 27MeV

sH = 0.7MeV

sK-K-pp = 34MeV

sH = 14MeV

Backgrounds from S0gL have to be taken into account

K+K0 miss-mass with NEW setup

K+K0 miss-mass with E15 setup

sK-K-pp = 8MeV

sH = 25MeV

sK-K-pp = 12MeV

sH = 45MeV

17 K-K-pp events/month

24 K-K-pp events/month

  • 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.


  • We 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.
interpretation of the experimental results
Interpretation of the Experimental Results
  • 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

the mechanism is NOT known well

because of low statistics

of the experimental results!










diana results
  • DIANA[Phys.Lett., B464, 323 (1999).]
  • pbarXe annihilation
  • p=<1GeV/c pbar-beam @ ITEP 10GeV-PS
  • 700-liter Xenon bubble chamber, w/o B-field
  • 106 pictures7.8x105pbarXe inelastic  2.8x105pbarXe @ 0-0.4GeV/c
obelix results
  • OBELIX(’86~’96) [Nucl. Phys., A797, 109 (2007).]
  • pbar4He annihilation
  • stopped pbar @ CERN/LEAR
  • gas target (4He@NTP, H2@3atm)
  • cylindrical spectrometer w/ B-field
  • spiral projection chamber,
  • scintillator barrels, jet-drift chambers
  • 2.4x105/4.7x104 events of 4/5-prong in 4He
  • pmin = 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
Expected Kinematics II


LL spectra

L-L opening-angle

L momentum

LL inv. mass

strong correlation of LL opening-angle

in K-K-pp/H productions

trigger scheme
Trigger Scheme

pbar3He charged particle multiplicity at rest

CERN LEAR, streamer chamber exp. NPA518,683 91990).


expected stopped-pbar yield = 1.3x103/spill

All events with a scintillator hit will be accumulated

expected signals i
Expected Signals I
  • pbar+3HeK+K0S+ X (X=KKpp/H/LL) events are generated isotropically at the center of the detector system
  • # of generated events is 200k for each case
  • obtained yields are scaled by the estimated K+K0LL yield
  • chamber resolution, multiple scattering and energy losses are fully took into account using GEANT4 toolkit
  • charged particles are traced with spiral fit
  • assumptions:
  • widths of K-K0pp/H = 0
  • B.E. of K-K-pp = 200MeV
  • MH = 2xML
  • branching ratio to K+K0LL final state = 0.1
  • DAQ & analysis efficiency = 0.7  6.7x103 K+K0LL/month
  • Generated ratio  K-K-pp:H:LL = 0.1:0.1:0.8
  • KKppLL and HLL decay branches are assumed to be 100%
  • S0gL contribution is NOT considered for the inclusive measurements

LL invariant mass : inclusive events

K+K0 missing mass : semi-inclusive events (w/ one more L)

k k 0 final state background
K+K0ΛΛFinal State & Background

This exclusive channel study is equivalent to

the unbound (excited) H-dibaryon search!

Possible background channels

  • direct K+K0LL production channels, like:

be distinguished by inv.-mass only

 major background source

  • S0gL contaminations, like:

be eliminated by

the kinematical constraint