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Double antikaonic nuclear clusters in antiproton- 3 He annihilation at J-PARC

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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)

LEAP2011 @ TRIUMF, April 27 - May 1, 2011.

Outline

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

- 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

B.E. = 103MeV

G = 118MeV

B.E. = 115MeV

G = 67MeV

K-ppLp?

K-ppLp?

PRL, 94, 212303 (2005)

PRL,104,132502 (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…

- search for the K-pp using 3He(in-flight K-,n) reaction

Neutron

ToF Wall

K1.8BR

Beam Line

Sweeping

Magnet

Beam Line

Spectrometer

Beam trajectory

CDS &

target

Neutron

Counter

neutron

flight length = 15m

Cylindrical

Detector

System

Missing mass

Spectroscopyvia neutron

p

Beam

Sweeping

Magnet

n

K-pp

L

Invariant mass reconstruction

p-

will start next year

p

1GeV/c

K- beam

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

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

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+

p

p-

p

We can investigate the DKNC

with exclusive or semi-inclusive measurement

Of course we can measure K-pp production with the dedicated detector, simultaneously.

We can also search for

H-dibaryon (H-resonance) by using LL invariant mass / missing mass.

H?

K-pp?

PRC75 022201(R)

(2007).

NP, A789, 222 (2007).

EPJ, A40, 11 (2009).

Our experiment can check the OBELIX results of the K-pp with a dedicated spectrometer

The exclusive H search with stopped-pbar beam has never been done.

There are NO results of the DKNC search, but several groups reported double-strangeness production in pbar+A annihilation

hydrogen bubble-chamber experiment @ 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).]

Although observed statistics are very small,

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

The double-strangeness production yield of ~10-4

makes it possible to explore the exotic systems.

Experimental Approach

- 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

We will perform the proposed experiment

at J-PARC K1.8BR beam line

K1.8BR

Beam Line

- key points
- high intensity pbar beam
- low mass material detector
- wide acceptance detector

CDS &

target

Beam Line

Spectrometer

0.9GeV-K- + A

L + X

~2800 L

smass=3.5+/-0.1MeV/c2

preliminary

reconstructed pp- inv. mass

in commissioning run (2010, Oct.)

- 50kW, 30GeV
- 6.0degrees
- Ni-target

pbar stopping-rate evaluation

by GEANT4

- Incident Beam
- momentum bite : +/-2.5% (flat)
- incident beam distribution : ideal

6.5x103/spill/3.5s

@ 0.7GeV/c

pbarproduction yield with

a pbar CS parameterization

- 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

250 stopped pbar/spill

@ 0.7GeV/c, ldegrader~3cm

pbar stopping-rate

expected stopped-pbar yield = 250/spill @ 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).

expected

K-K-pp event

- 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

acceptances of K+K+ and LL

- evaluated using GEANT4 toolkit
- Many-body decay are considered to be isotropic decay.
- branching ratios of K0K0S/K0Sp+p-/Lpp-are included.
- acceptance is defined by CDC

CDS @ K1.8BR

30kW, 1week

sensitivity

30kW, 2weeks

30kW, 6weeks

sensitivity to 100 double-strangeness events (~10s) detection is evaluated by the MC.

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

- 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

- 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

acceptance

- evaluated using GEANT4 toolkit
- G(K-K-pp) = 100 MeV
- isotropic decay
- branching ratios of K0K0S/K0Sp+p-/Lpp-are included.

K-K-pp binding energy

(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

(inclusive) LL invariant mass

signal

- stopped-pbar + 3He K0S + K+ + K-K-pp
- L + L
- stopped-pbar + 3He K0S + K+ + K-K-pp
- S0 + S0
- stopped-pbar + 3He K0S + K+ + K-K-pp
- 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

Sensitivity to the K-K-pp observation

is estimated using the MC

- branching ratio:
- BR(K-K-ppLL) = 0.25
- BR(K-K-ppS0S0 = 0.25
- BR(K-K-pp S0S0 p0) = 0.5

assumptions

- total yield : upper limit of pbarAKKX, 5x10-4
- 3N : 20% of yield, and 3N:2N = 1:3
- K-K-pp yield : parameter

- 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

- non-mesonic : mesonic= 1 : 1

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

3s significance of

K-K-pp production yield

(/stopped-pbar)

270kW,

6weeks

30kW,

6weeks

number of proton on target

- assumption in the figures:
- K-K-pp production yield
- = 10-4/stopped-pbar
- B.E. = 200 MeV
- G = 100 MeV

K+K0 missing mass (2K2L)

LL invariant mass

# of K-K-pp = 32

# of K-K-pp

LL = 357

The signal can be discriminated from the other backgrounds

in the exclusive K+K0 missing mass spectrum.

LL invariant mass

K+K0 missing mass

# of K-K-pp

LL = 15

# of K-K-pp = 208

- 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) channel @ 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.

The proposed experiment will start in around JFY2015???