1. Double antikaonic nuclear clusters in antiproton-3He annihilation at J-PARC
F.Sakuma, RIKEN
C. CURCEANU (INFN Frascati, Italy), M. IWASAKI (RIKEN, Japan),
P. KIENLE (TUM, Germany), H. OHNISHI (RIKEN, Japan),
M. TOKUDA (TITECH, Japan), K. TSUKADA (Tohoku-U, Japan),
E. WIDMANN (SMI, Austria), T. YAMAZAKI (RIKEN/U-Tokyo, Japan),
J. ZMESKAL (SMI, Austria)
TRIUMF, April 27 - May 1, 2011.

2. Outline (brief) Introduction of “Kaonic Nuclear Cluster”
Possibility of
“Double-Kaonic Nuclear Cluster”
in pbar+A annihilation at rest
Experimental Approach
Summary

3. Kaonic Nuclear Cluster (KNC)
KbarN interaction is clarified to be strongly attractive by Kaonic-atom experiments in 20th.
This leads the prediction of deeply-bound kaonic nuclear cluster (KNC), as many theorists pointed out.
the density of the KNC is predicted to be high density more than normal nuclear-density (r0)
Density [1/fm3]
T.Yamazaki, A.Dote, Y.Akiaishi, PLB587, 167 (2004).
we will open new door to the high density matter physics, like the inside of neutron stars

4. Experimental Situation of KNC
B.E. = 103MeV
G = 118MeV
B.E. = 115MeV
G = 67MeV
K-ppLp?
K-ppLp?
PRL, 94, (2005)
PRL,104, (2010)
stopped-K- + A  (L + p) + X
2.85GeV-p + p  (L + p) + K+
We need more evidences in various channels!
Because there is a discrepancy
between THEORETICAL PREDICTIONS and EXPERIMENTAL OBSERVATIONS…

5. search for the K-pp using 3He(in-flight K-,n) reaction
J-PARC E15 Experiment
search for the K-pp using 3He(in-flight K-,n) reaction
K1.8BR
Beam Line
neutron
Beam trajectory
CDS &
target
Sweeping
Magnet
Neutron
Counter
Spectrometer
Neutron
ToF Wall
flight length = 15m
Cylindrical
Detector
System
Missing mass
Spectroscopy via neutron p
Beam
Sweeping
Magnet n
K-pp L
Invariant mass reconstruction p-
will start next year p
1GeV/c
K- beam

6. Possibility of “Double-Kaonic Nuclear Cluster”
What will happen to put one more kaon
in the kaonic nuclear cluster?
Possibility of “Double-Kaonic
Nuclear Cluster”
in pbar+A annihilation at rest
Why at rest?
probability of multi-nucleon annihilation
(exotic B>0 annihilation) should be
larger than in-flight reactions

7. Double-Kaonic Nuclear Cluster (DKNC)
The double-kaonic nuclear clusters have been predicted theoretically.
ppn
The double-kaonic clusters have much stronger binding energy and a much higher density than single ones.
(AMD calc.)
ppnK-
PL,B587,167 (2004).
How to produce the double-kaonic nuclear cluster?
heavy ion collision
(K-,K+) reaction
pbarA annihilation
ppnK-K-
We use pbarA annihilation

8. the DKNC in pbarA annihilation?
The elementary pbar-p annihilation reaction with double-strangeness production:
-98MeV
This reaction is forbidden for stopped pbar, because of a negative Q-value of 98MeV
if multi kaonic nuclear exists with deep bound energy,
following pbar annihilation reactions will be possible!
e.g.
the most energetic favored decay mode
final state: p- p p+
We can investigate the DKNC
with exclusive or semi-inclusive measurement

9. Related Topics We can also search for
H-dibaryon (H-resonance) by using LL invariant mass / missing mass.
Of course we can measure K-pp production with the dedicated detector, simultaneously. H?
K-pp?
PRC (R)
(2007).
NP, A789, 222 (2007).
EPJ, A40, 11 (2009).
The exclusive H search with stopped-pbar beam has never been done.
Our experiment can check the OBELIX results of the K-pp with a dedicated spectrometer

10. Past Experiments of Double-Strangeness Production in Stopped-pbar Annihilation
There are NO results of the DKNC search, but several groups reported double-strangeness production in pbar+A annihilation
hydrogen bubble-chamber BNL
in association with the H-dibaryon search
They did NOT observe any double-strangeness event in
pbar - C, Ti, Ta, Pb annihilation (~80,000 events, p < 400 MeV/c)
[Phys.Lett., B144, 27 (1984).]
Reaction
Frequency (90% C.L.)
pbarAL0L0X
<4x10-4
pbarAL0K-X
<5x10-4
pbarAK+K+X
pbarAHX
<9x10-5

11. Past Experiments of Double-Strangeness Production in Stopped-pbar Annihilation
Channel
# of events
yield (x10-4)
[pbar+Xe]
PLB464, 323 (1999).
K+K+X 4
0.31+/-0.16
K+K0X 3
2.1+/-1.2
OBELIX
@CERN/LEAR
[pbar+4He]
NPA797, 109 (2007).
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
Although observed statistics are very small,
their results have indicated a high yield of ~10-4

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

13. Experimental Strategy
Current situation of the double-strangeness production in pbar+A (A>2) annihilation at rest:
NO results using a dedicated spectrometer except for bubble chamber experiments.
NO results with high-statistics measurement.
investigation of “double-strangeness production” in pbar+3He annihilation at rest, with high statistics data
search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

14. Setup K1.8BR key points Beam Line preliminary
We will perform the proposed experiment
at J-PARC K1.8BR beam line
K1.8BR
Beam Line
CDS &
target
Spectrometer
key points
high intensity pbar beam
low mass material detector
wide acceptance detector
~2800 L
smass =3.5+/-0.1MeV/c2
preliminary
0.9GeV-K- + A
 L + X
reconstructed pp- inv. mass
in commissioning run (2010, Oct.)

15. pbar stopping-rate evaluation
pbar J-PARC K1.8BR
Incident Beam
momentum bite : +/-2.5% (flat)
incident beam distribution : ideal
Detectors
Tungsten Degrader : r=19.25g/cm3
Plastic Scintillator : l=1cm, r=1.032g/cm3
Liquid He3 target : f=7cm, l=12cm, r=0.080g/cm3
pbar stopping-rate evaluation
by GEANT4
50kW, 30GeV
6.0degrees
Ni-target
6.5x103/spill/3.5s
@ 0.7GeV/c
pbar production yield with
a pbar CS parameterization
250 stopped pbar/spill
@ 0.7GeV/c, ldegrader~3cm
pbar stopping-rate

16. Trigger Scheme All events with a scintillator hit can be accumulated
expected stopped-pbar yield = 50kW
All events with a scintillator hit can be accumulated
pbar+3He charged particle multiplicity at rest
CERN LEAR, streamer chamber exp. NPA518,683 (1990). Nc
Branch (%) 1
5.14 +/- 0.04 3
/- 0.88 5
/- 0.91 7
7.06 +/- 0.46 9
0.19 +/- 0.08
<Nc>
4.16 +/- 0.06
expected
K-K-pp event

17. Experimental Strategy
present situation of the double-strangeness production in pbar+A (A>2) annihilation at rest:
NO results with a dedicated spectrometer and high intensity beam except for bubble chamber experiments.
high-statistics measurement is NOT performed!
investigation of “double-strangeness production” in pbar+3He annihilation at rest
search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

18. Double-Strangeness Measurement
acceptances of K+K+ and LL
evaluated using GEANT4 toolkit
Many-body decay are considered to be isotropic decay.
branching ratios of K0K0S/K0Sp+p-/Lpp- are included.
acceptance is defined by CDC
K+K+LS- channel
K+K0LL channel
K+K+
detection
2.4 x 10-1 LL
4.1 x 10-2
K+K+L
4.4 x 10-2
LLK+
2.1 x 10-2
K+K+Lp-
2.8 x 10-2
LLK+K0
2.9 x 10-3
K1.8BR

19. Double-Strangeness Measurement (Cont’d)
30kW, 1week
sensitivity
30kW, 2weeks
sensitivity to 100 double-strangeness events (~10s) detection is evaluated by the MC.
30kW, 6weeks
OBELIX/
DIANA
50kW, 6weeks
1.E-04
production-yield
(/stopped-pbar)
* The following are included
duty factor of the accelerator and apparatus : 21h/24h
DAQ and analysis eff. : 0.7
100kW, 6weeks
number of proton on target
if we assume
the double-strangeness production-yield to be
10-4 / stopped-pbar
as reported by the OBELIX and DIANA groups:
expected yield
30kW, for 2weeks
K+K+ event
750
LL event
130

20. Experimental Strategy
present situation of the double-strangeness production in pbar+A (A>2) annihilation at rest:
NO results with a dedicated spectrometer and high intensity beam except for bubble chamber experiments.
high-statistics measurement is NOT performed!
investigation of “double-strangeness production” in pbar+3He annihilation at rest
search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

21. Procedure of the K-K-pp Search
methods of the measuremt
(semi-inclusive) K0K+ missing-mass w/ L-tag
(inclusive) LL invariant mass
(exclusive) K0K+LL measurement
--- K0K+ w/ L-tag
--- LL
--- K0K+LL
K-K-pp binding energy
acceptance
evaluated using GEANT4 toolkit
G(K-K-pp) = 100 MeV
isotropic decay
branching ratios of K0K0S/K0Sp+p-/Lpp- are included.

22. Backgrounds (semi-inclusive) K0K+ missing-mass w/ L-tag
signal
stopped-pbar + 3He  K0 + K+ + K-K-pp
stopped-pbar + 3He  K0 + K+ + L + L
stopped-pbar + 3He  K0 + K+ + L + L + p0 …
stopped-pbar + 3He  K0 + K+ + K0 + S0 + (n)
stopped-pbar + 3He  K0 + K+ + X0 + (n) …
3N annihilation
2N annihilation
K0K+ missing-mass
*each spectrum is obtained with the same production yield

23. Backgrounds (Cont’d) (inclusive) LL invariant mass
signal
stopped-pbar + 3He  K0S + K+ + K-K-pp
L + L
 S0 + S0
 S0 + S0 + p0 …
missing 2g
missing 2g+p0
LL invariant mass
B.E = 200 MeV
G = 100 MeV
*each spectrum is obtained with the same production yield

24. Sensitivity to the K-K-pp observation is estimated using the MC
Expected Yield
Sensitivity to the K-K-pp observation
is estimated using the MC
assumptions
production yield:
K-K-pp bound-state = ?
(3N) K-K-LL phase-space = 5x10-5
(3N) K+K0S0S0p0 phase-space = 5x10-5
(2N) K+K0K0S0(n) phase-space = 3x10-4
total yield : upper limit of pbarAKKX, 5x10-4
3N : 20% of yield, and 3N:2N = 1:3
K-K-pp yield : parameter
branching ratio:
BR(K-K-ppLL) = 0.25
BR(K-K-ppS0S = 0.25
BR(K-K-pp S0S0 p0) = 0.5
non-mesonic : mesonic = 1 : 1

25. Sensitivity to the K-K-pp signal (Exclusive)
significance [s=S/sqrt(S+B)] is obtained
in exclusive missing-mass spectra
50kW,
6weeks
--- BKK = 120 MeV
--- BKK = 150 MeV
--- BKK = 200 MeV
100kW,
6weeks
K-K-pp production yield
3s significance of
(/stopped-pbar)
270kW,
6weeks
30kW,
6weeks
number of proton on target

26. Expected Spectra @ 50kW, 6weeks
# of K-K-pp = 32
K+K0 missing mass (2K2L)
assumption in the figures:
K-K-pp production yield
= 10-4/stopped-pbar
B.E. = 200 MeV
G = 100 MeV
The signal can be discriminated from the other backgrounds
in the exclusive K+K0 missing mass spectrum.
# of K-K-pp
LL = 357
LL invariant mass
K+K0 missing mass
# of K-K-pp = 208
LL invariant mass
# of K-K-pp
LL = 15

27. Summary
We will search for Double-Kaonic Nuclear Cluster (DKNC) by pbar + 3He annihilation at rest, using the pbar + 3He  K+ + K0 + X (X = K-K-pp) J-PARC K1.8BR beam line.
In preparation for the DKNC search, double-strangeness production measurement will be conducted as a first step.
We are now improving this experimental idea toward the proposal submission to J-PARC.

28. The proposed experiment will start in around JFY2015???
Schedule
Year (JFY)
K1.8BR
2009
beam-tune
2010
2011
recovery
2012
E17/E15
2013
E15/E31
2014
2015
here?
The proposed experiment will start in around JFY2015???