A search for deeply-bound kaonic nucA search for deeply-bound kaonic nuclear states lear states

by in-flight by in-flight 33He(KHe(K--,n) reaction ,n) reaction at J-PARC at J-PARC

Hiroaki OhnishiHiroaki OhnishiRIKEN Nishina CenterRIKEN Nishina Center

J-PARC E15 experimentS. Ajimura, G. Beer, H. Bhang, P. Buehler, L. Busso, M. Cargnelli, J. Chiba,

S. Choi, C. Curceanu, D. Faso, H. Fujioka, T. Fukuda, Y. Fukuda, C. Guaraldo, T. Hanaki, R. S. Hayano, A. Hirtl, M. Iio, M. Iliescu, T. Ishikawa, S. Ishimoto,

T. Ishiwatari, K. Itahashi, M. Iwasaki, P. Kienle, J. Marton, Y. Matsuda, Y. Mizoi, O. Morra, T. Nagae, H. Ohnishi, S. Okada, H. Outa, A. Sakaguchi, M. Sato, M. Sekimoto, D. Sirghi, F. Sirghi, S. Suzuki, T. Suzuki, H. Tatsuno, D. Tomono, A. Toyoda, E. Widmann, T. Yamazaki, H. Yim, and J. Zmeskal

Search for Kaonic nuclear bound stateSearch for Kaonic nuclear bound stateExperiment Reaction Target Experimental method

KEK E471/ E549 stopped K- 4He missing mass

FINUDA stopped K- 6Li,7Li,12C invariant mass

BNL E930, KEK E548 in- flight K- 16O,12C missing mass

GSI FOPI invariant massOBELIX anti- p 4He invariant mass

Heavy ion collision

Phys. R

ev. Lett. 94

212303 (2005)

Taken from

OH

P at T

rento WS

2006

KEK E549 FINUDA

KEK E548

Taken from

OH

P at T

rento WS

2006

GSI FOPI

What we need to answer the basic question, What we need to answer the basic question, whether the deeply bound state really exists?whether the deeply bound state really exists?

The situation is still controversial!

OBELIX

Experiment Reaction Target Experimental methodKEK E471/ E549 stopped K- 4He missing & invariant mass

FINUDA stopped K- 6Li,7Li,12C invariant mass

BNL E930, KEK E548 in- flight K- 16O,12C missing mass

GSI FOPI invariant massOBELIX anti- p 4He invariant mass

Heavy ion collision

Results of in

variant m

ass analysis

from E549 will

be presented

in INPC2007 conference

by Dr. T. S

uzuki

What we want to What we want to do ?do ? Back to the original questionBack to the original question

Structure inside Structure inside (1405)(1405) multiquarks state?multiquarks state? Double pole resonance ? Double pole resonance ? bound state of Kbound state of K--p ?p ?

Existence of K-pp bund stateWill open new door to

the physics of K-cluster

If we assume If we assume (1405) to be a K(1405) to be a K--p bound statep bound state Second simplest bound state, KSecond simplest bound state, K--pp, will also existpp, will also exist

( natural extension) ( natural extension)

A search for deeply bound A search for deeply bound kaonic nuclear stateskaonic nuclear states

Direct production of K-pp clusters Direct production of K-pp clusters via via 33He(in-flight KHe(in-flight K--,n) reaction,n) reaction

Goal for the experiment J-PARC E15Goal for the experiment J-PARC E15 To answering the basic question : To answering the basic question :

whether the deeply bound state really exists?whether the deeply bound state really exists?

K-3He K-pp

clusterneutron

Missing

mass

Spectroscop

y

via neutron

Reaction

Decay???

Possible KPossible K--pp decay modespp decay modesFINUDA

fit region

K -pp?? Phy

s. R

ev. L

ett.

94, 2

1230

3 (2

005)

Invariant massInvariant massreconstructionreconstruction

+-p-+p

K-pp2370 MeV

2275 MeV

2267 MeV

0p

p

2131 MeV

2054 MeV

p

p

-

p decay mode

Dominant Decay mode

= YN

B.E. = 115 MeV

K-ppcluster

p

p

-

p decay mode

Experimental Principle Experimental Principle 33He(KHe(K--,n) reaction,n) reaction

K-3He K-pp

cluster

neutron

Missing

mass

Spectroscop

y

via neutron

Reaction

This mode allows us to investigateK-pp bound state in both

Missing mass spectroscopyand

Invariant mass reconstruction

p

p

-

Mode to decay charged particlesDecay

Invariant

mass

reconstructio

n

Signals from KSignals from K--pp and “Two nucleon absorption”pp and “Two nucleon absorption”forward neutronforward neutron

K-3He

reaction

　　 33He(K-,n) KHe(K-,n) K--pp formationpp formationneutron

K-ppcluster

@ 1GeV/c K- andB.E. = 100 MeV

~ 1.3 GeV/c

　　 Two nucleon absorptionTwo nucleon absorption 　　

reactionK-3He

neutron

p (spectator)

@ 1GeV/c K-

~ 1.5GeV/c

How was decay side?How was decay side?

K-3He

reaction

　　 33He(K-,n) KHe(K-,n) K--pp formationpp formation

　　 Two nucleon absorptionTwo nucleon absorption 　　

reactionK-3He

Major background, i.e. event from “two nucleon absorption process”can be identified!

neutron

K-ppcluster

p

p

-

neutron

p (spectator)

p

-

p (spectator)

Binding energy assumed as １００ＭｅＶ

=> emitted proton momentum ～ 500 MeV/c

Design for the Design for the experimentexperiment

Beam Line at J-PARCBeam Line at J-PARC

K1.8BR Beam LineK1.8BR Beam Line Design for low momentum Kaon Design for low momentum Kaon

(<1.2 GeV/c ) (<1.2 GeV/c ) Single ES stageSingle ES stage Beam line length = 27.6mBeam line length = 27.6m

PrimaryProton beam

ES

Q7

D4

Q8

FFBeamSpectrometer

QDQ to focus at Final Focus (FF)QDQ to focus at Final Focus (FF) Momentum resolution ~ 2x10Momentum resolution ~ 2x10-4 -4

(position resolution of the beam (position resolution of the beam tracker assumed to be 200 tracker assumed to be 200 m (m () ) ) )

E15 DetectorE15 Detectorconceptconcept

Experiment will be performed atK1.8BR beam line.

Neutron counter

Cylindrical detector systemCDH

CDC

Solenoid Magnet

K-Proton

Proton

GEANT4 detector simulation

B.E. = 100 MeV

Expected decay mode for K-pp Expected decay mode for K-pp K-pp Λp pπ-p ➾ ➾K-pp Λp pπ-p ➾ ➾ K-pp ➾K-pp ➾ 00p ➾p ➾ Λp ➾Λp ➾ pπ-p pπ-p

Assume Assume K-ppK-pp= 60 MeV= 60 MeV 　　　　

Invariant mass of Λp (MeV)

∑0 channel Λ channel

Expected detector performanceExpected detector performance

p

p

-

p decay mode

p

p

-

p decay mode

Status of the Status of the preparationpreparation

Neutron counterNeutron counter We will use same neutron counter used for We will use same neutron counter used for

KEK E549 experiment ( exist! ) KEK E549 experiment ( exist! )

20x5x150 cm3 　（ W Ｘ T Ｘ L ） Plastic scintillator 　Configuration 16 (wide) 　 x 　 7 (depth)Surface area 3.2m X 1.5m 　

3.2 m

1.5 m

E549 neutron counter

Solenoid Solenoid magnetmagnet

Z常伝導ソレノイド電磁石 方向磁場分布

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

-750 -500 -250 0 250 500 750 Z(mm)測定位置

(T)

磁場

強度

X=- 100,Y=0X=+100,Y=0X=- 50,Y=0X=+50,Y=0X=0,Y=0

(4361- 1)X=0,± 50,± 100,Y=0

Solenoid magnet for E15 experiment has been constructed.

Field strength; upto 0.7TSpace inside; Φ=1.2m, L=1.2m weight ; 23 t

Cylindrical Drift Cylindrical Drift ChamberChamber Design work for CDC is in progressDesign work for CDC is in progress

• He based chamber gas will be used(to reduce material budget)

Basic concept ;• Cell structure has been chosen as Hexagonal

• 1800 readout channels in total

• 15 readout layers AA’A UU’ VV’ AA’ UU’ VV’ AA

Garfi

eld

sim

ula

tion

don

e b

y D

r. F

. S

aku

ma

3He target cell

3He heat exchanger

1 K tank(1.25 K)

4 K pot(4 K)

LN2 tank

Prototype 3He target cell　

Target system

R&D work for Liquid 3He target is in progress ( Dr. S. Ishimoto (KEK) and Dr. M. Iio (RIKEN) )

Event rate estimationEvent rate estimation ParametersParameters

Assume production cross section asAssume production cross section as 3He(K-,n)K-pp3He(K-,n)K-pp= 10 = 10 b/srb/sr Acceptance of Neutron counter = 30 msrAcceptance of Neutron counter = 30 msr Target thickness = 20cm, density = 0.080 g/cmTarget thickness = 20cm, density = 0.080 g/cm33

Neutron detection efficiency = 30%Neutron detection efficiency = 30% Assume 1/3 of K-pp decay in to (Assume 1/3 of K-pp decay in to (+p or +p or +p) +p) +p reconstruction efficiency in CDC = 47%+p reconstruction efficiency in CDC = 47%

Expected event rateExpected event rate 1.86x101.86x10-9-9 per an incident K per an incident K--

Event rate per dayEvent rate per day 0.8x100.8x1066 K- per 3.53s (0.7s flat top) K- per 3.53s (0.7s flat top) 24475 spill per day = 1.96x1024475 spill per day = 1.96x101010 K- per day K- per day ~ 50 events per day ~ 50 events per day

We will expect about ~1500 events in a month !!!

SummarySummary J-PARC E15 experimentJ-PARC E15 experiment

Search for simplest deeply bound kaonic nucleSearch for simplest deeply bound kaonic nuclear state, the Kar state, the K--pp bound state, pp bound state, via the via the 33He(K-,n) reaction He(K-,n) reaction

Detector construction is in progress Detector construction is in progress Solenoid magnet Solenoid magnet ;; constructedconstructed CDCCDC ; ; under real designunder real design 33He targetHe target ; ; R&D R&D Other detectorsOther detectors ;; conceptual design completed conceptual design completed

Experiment will be ready before Dec. 2008 Experiment will be ready before Dec. 2008

Thank you very muchThank you very much