Hiroaki OhnishiRIKEN

For the J-PARC E15 collaboration

A search for deeply bound kaonic nuclear states

by in-flight 3He(K-,n) reaction

ストレンジネスとエキゾティクス・理論の課題 March 1-3 2007 Toba

A search for deeply bound kaonic nuclear states

Direct production of K-pp cluster via Direct production of K-pp cluster via 33He(K-,n) reactionHe(K-,n) reaction

K-3He K-pp

clusterneutron

reaction

Missing mass

spectroscopy

???

Decay?

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

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

Possible K-pp decay mode

K-ppcluster

FINUDA

fit region

K -pp??

Phy

s. R

ev. L

ett.

94, 2

1230

3 (2

005)

Invariant mass reconstruction

+-p-+p

K-pp2370 MeV

2275 MeV

2267 MeV

0p

p

2131 MeV

2054 MeV

p

p

-

p decay mode

Dominant Decay mode

= YN

p

p

-

p decay modeB.E. = 115 MeV

Formation of K-pp via 33He(K-,n) reactionHe(K-,n) reaction

K-3He K-pp

clusterneutron

Missing mass

reaction

decay

This mode allows us to investigate K-pp cluster with both missing mass and invariant mass spectroscopy

p

p

-

Only charged particles in final state

Invariant

mass

Detector concept• Missing mass spectroscopy with forward going neutron

• Bound state tagging with the measurement of decay product – Good charged particle detection efficiency– Good charged particle momentum resolution

K- beam momentum used for the experiment 1 GeV/c

In the case, if B.E. = 100 MeV ( FINUDA case)

Momentum of outgoing neutron will be 1.3 GeV

reconstruction will be crucial for this measurement

E15 DetectorExperiment 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 – K-pp Λp pπ-p ➾ ➾– K-pp ➾ 0p ➾ Λp ➾ pπ-p

• Assume K-pp= 60 MeV 　　

Invariant mass of Λp (MeV)

∑ channel Λ channel

Expected detector performance

p

p

-

p decay mode

p

p

-

p decay mode

Possible K-pp decay mode(2)

+-p-+p

K-pp2370 MeV

2275 MeV

2267 MeV

0p

p

2131 MeV

2054 MeV

Back to the beginning

Akaishi-Yamazaki predictionbased on (1405) as KN bound state

Y.Akaishi & T.Yamazaki, PLB 535(2002) 70.

Question

BR( K-pp → p)BR( K-pp → YN) 　

1) Can we identify K-pp bound state only from missing mass?

= ???

In this case,K-pp can be decay to

mode

p

np

p

p

YN mode

0p

p

+

2) How to tag formation of K-pp bound state via decay product?

Hyperon production

Concerning on the decay mode of K-pp →p

• Can we use +- from target region as a tag of decay ?

mode

p

np

p

p

K-pp decay mode pn p

n

n from decayp

+

--

+

n from decay

n

proton cannotescape from target

Still need to investigate

Summary

• J-PARC E15 experiment– Search for simplest deeply bound kaonic nucl

ear state, K-pp bound state via 33He(K-,n) reactionHe(K-,n) reaction

• Detector construction is in progress

• Experiment will be ready before Dec. 2008

Λ

Λ 　 momentum (MeV/c) momentum (MeV/c)

K-pp state

σ（

MeV

）

σ（

MeV

）

• Expected decay mode for K-pp – K-pp Λp pπ-p ➾ ➾– K-pp ➾ 0p ➾ Λp ➾ pπ-p

• Assume K-pp= 60 MeV 　　

Invariant mass of Λp (MeV)

∑ channel Λ channel

Expected detector performance

p

p

-

p decay mode

p

p

-

p decay mode