Double antikaonic nuclear clusters in antiproton-3He annihilation

at J-PARC

F.Sakuma, RIKEN

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

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)

2

(brief) Introduction of “Kaonic Nuclear Cluster”

Possibility of “Double-Kaonic Nuclear Cluster”

in pbar+A annihilation at restExperimental ApproachSummary

Outline

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

Kaonic Nuclear Cluster (KNC)

3

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

Density [1/fm

3]

the density of the KNC is predicted to be high density more than normal nuclear-density (r0)

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.

4

Experimental Situation of KNC

FINUDA@DAFNE

We need more evidences in various channels!

DISTO@SATURENPRL, 94, 212303 (2005) PRL,104,132502 (2010)

stopped-K- + A (L + p) + X 2.85GeV-p + p (L + p) + K+

B.E. = 115MeVG = 67MeV

B.E. = 103MeVG = 118MeV

Because there is a discrepancy between THEORETICAL PREDICTIONS and EXPERIMENTAL OBSERVATIONS…

K-ppLp?K-ppLp?

5

J-PARC E15 Experiment

1GeV/cK- beam

p

p-p

n

NeutronToF Wall

K1.8BR Beam Line

neutron

Beam trajectory

CDS &target

SweepingMagnet

NeutronCounter

Beam LineSpectrometer

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

flight length = 15m

Beam SweepingMagnet

CylindricalDetectorSystem

K-pp

Missing mass

Spectroscopy

via neutron Invariant

mass reconstructio

n

L

will start next year

6

Possibility of “Double-KaonicNuclear Cluster”

in pbar+A annihilation at rest

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

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.

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

We use pbarA annihilation

PL,B587,167 (2004).

The double-kaonic clusters have much stronger binding energy and a much higher density than single ones.(AMD calc.)

ppn

ppnK-

ppnK-K-

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

the DKNC in pbarA annihilation?

if multi kaonic nuclear exists with deep bound energy, following pbar annihilation reactions will be possible!

-98MeV

3 0 109MeVppKKp He K K K K pp B

8

e.g.

0K K

We can investigate the DKNC with exclusive or semi-inclusive measurement

final state:the most energetic favored decay mode

p-pp+ p- p-p

9

Related Topics

3 0

p He K K H

We can also search for H-dibaryon (H-resonance) by using LL invariant mass / missing mass.

E522@KEK-PS

PRC75 022201(R) (2007).

12 ,C K K X

The exclusive H search with stopped-pbar beam has never

been done.

3 0

+p

p He K K pp

Of course we can measure K-pp production with the dedicated

detector, simultaneously.

OBELIX@CERN-LEAR

NP, A789, 222 (2007).EPJ, A40, 11 (2009).

K-pp?4

p He K pp X

p

H?

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

They did NOT observe any double-strangeness event in pbar - C, Ti, Ta, Pb annihilation (~80,000 events, p < 400 MeV/c)

Reaction Frequency (90% C.L.)

pbarAL0L0X <4x10-4

pbarA0K-X <5x10-4

pbarAK+K+X <5x10-4

pbarAHX <9x10-5

[Phys.Lett., B144, 27 (1984).]

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

11

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

experiment Channel # of events yield (x10-4)DIANA@ITEP

[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.

13

Experimental Strategy

I. investigation of “double-strangeness production” in pbar+3He annihilation at rest, with high statistics data

II. search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

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.

3

3 0

p He K K

p He K K

3 0

+

p He K K K K pp

K1.8BR Beam LineCDS &

targetBeam Line

Spectrometer

14

SetupWe will perform the proposed experiment

at J-PARC K1.8BR beam line

~2800 L smass =3.5+/-0.1MeV/c2

preliminary

key pointshigh intensity pbar beamlow mass material detectorwide acceptance detector

reconstructed pp- inv. mass in commissioning run (2010, Oct.)

0.9GeV-K- + A L + X

15

pbar Beam @ J-PARC K1.8BR

pbar stopping-rate

50kW, 30GeV6.0degreesNi-target

pbar production yield witha pbar CS parameterization

250 stopped pbar/spill@ 0.7GeV/c, ldegrader~3cm

Incident Beammomentum bite : +/-2.5% (flat)incident beam distribution : idealDetectorsTungsten 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

6.5x103/spill/3.5s @ 0.7GeV/c

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Trigger Scheme

pbar+3He charged particle multiplicity at restCERN LEAR, streamer chamber exp. NPA518,683 (1990).

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 = 250/spill @ 50kW

All events with a scintillator hit can be accumulated

expectedK-K-pp event

17

Experimental Strategy

I. investigation of “double-strangeness production” in pbar+3He annihilation at rest

II. search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

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!

3 0

+

p He K K K K pp

3

3 0

p He K K

p He K K

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Double-Strangeness Measurement3

3 0

p He K K

p He K K

K+K+LS- channel K+K0 LL channelK+K+

detection 2.4 x 10-1 LLdetection 4.1 x 10-2

K+K+Ldetection 4.4 x 10-2 LLK+

detection 2.1 x 10-2

K+K+Lp-

detection 2.8 x 10-2 LLK+K0

detection 2.9 x 10-3

CDS @ K1.8BR

evaluated using GEANT4 toolkitMany-body decay are considered to be isotropic decay.branching ratios of K0K0

S/K0Sp+p-/Lpp- are included.

acceptance is defined by CDC

acceptances of K+K+ and LL

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Double-Strangeness Measurement (Cont’d)

30kW, for 2weeksK+K+ event 750LL event 130

if we assumethe double-strangeness production-yield to be 10-4 / stopped-pbar

as reported by the OBELIX and DIANA groups:

expected yield

* The following are includedduty factor of the accelerator and apparatus : 21h/24hDAQ and analysis eff. : 0.7

sensitivity

1.0E+18 1.0E+19 1.0E+20

1E-06

1E-05

1E-04

1E-03

double K+double Λ

30kW, 2weeks30kW, 6weeks

30kW, 1week

50kW, 6weeks

100kW, 6weeks

OBELIX/

DIANA

number of proton on targetpr

oduc

tion-

yiel

d (/

stop

ped-

pbar )

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

the MC.

1.E-04

20

Experimental Strategy

I. investigation of “double-strangeness production” in pbar+3He annihilation at rest

II. search for “double-kaonic nuclear cluster” in pbar+3He annihilation at rest

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!

3 0

+

p He K K K K pp

3

3 0

p He K K

p He K K

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

3 0

+

p He K K K K pp

B.E.=120MeV B.E.=150MeV B.E.=200MeV0.00

0.05

0.10

0.15ac

cept

ance

--- K0K+ w/ L-tag --- LL--- K0K+LL

K-K-pp binding energy

evaluated using GEANT4 toolkit G(K-K-pp) = 100 MeVisotropic decaybranching ratios of K0K0

S/K0Sp+p-/Lpp- are

included.

acceptance

22

Backgrounds(semi-inclusive) K0K+ missing-mass w/ L-tag

stopped-pbar + 3He K0 + K+ + K-K-pp

stopped-pbar + 3He K0 + K+ + L + Lstopped-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

signal

*each spectrum is obtained with the same production yield

K0K+ missing-mass

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Backgrounds (Cont’d)(inclusive) LL invariant mass

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

L + Lstopped-pbar + 3He K0

S + K+ + K-K-pp S0 + S0

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

S0 + S0 + p0 …

missing 2g

missing 2g+p0

B.E = 200 MeVG = 100 MeV

signal

*each spectrum is obtained with the same production yield

LL invariant mass

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

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Expected Yield

total yield : upper limit of pbarAKKX, 5x10-4

3N : 20% of yield, and 3N:2N = 1:3

K-K-pp yield : parameter

Sensitivity to the K-K-pp observation is estimated using the MC

non-mesonic : mesonic = 1 : 1

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

assumptions

1.0E+19 1.0E+201E-05

1E-04

1E-03

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Sensitivity to the K-K-pp signal (Exclusive)

significance [s=S/sqrt(S+B)] is obtained in exclusive missing-mass spectra

--- BKK = 120 MeV--- BKK = 150 MeV--- BKK = 200 MeV

30kW, 6weeks

100kW, 6weeks

270kW, 6weeks

50kW,6weeks

number of proton on target

3s s

igni

fican

ce o

fK- K

- pp

prod

uctio

n yi

eld

(/st

oppe

d-pba

r )

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Expected Spectra @ 50kW, 6weeks3 0 ( )p He K K X

# of K-K-pp = 32

K+K0 missing mass (2K2L)

0 K K X

# of K-K-ppLL = 357

LL invariant mass

0 ( )K K X

LL invariant mass

# of K-K-ppLL = 15

0 K K X

K+K0 missing mass

# of K-K-pp = 208

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.

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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) 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.

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Schedule

Year (JFY) K1.8BR2009 beam-tune2010 beam-tune2011 recovery2012 E17/E152013 E15/E312014 E15/E312015 here?

The proposed experiment will start in around JFY2015???