j-parc e27 実験の概要

J-PARC E27 実験の概要

　岡村敦史 (Kyoto.　Univ.)　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

2010/12/3ストレンジネス核物理 20101

　for　E27　Collaborations

Index

Introduction K-pp bound state

E27 experiment Setup Preparation status

Summary

2010/12/3 ストレンジネス核物理 2010 2

3

K-pp bound state Kbar N Isospin = 0 is strong attrective!

scattering experiment Xrays from Kaonic atom

Lambda(1405) = Kbar N system? K-pp is the simplest Kaonic Nuclei.

Binding energy, Width

theoritical prediction : 20-100,40-100

experimental result : exist? unconsistent B.E., Width More measurements via various reaction are necessary!!

J-PARC E15, E27 experiment 2010/12/3 ストレンジネス核物理 2010

Λ(1405) from　PDG Mass : 1406.5 ± 4.0 MeV Width: 50 ± 2 MeV JP : ½-Unable to explain with 3 quark model Lighter than N*(1530)Meson baryon molecule state? (Chiral Unitary model)

4

E15 and E27E15 E27

Beam Line K1.8 BR K1.8

beam 1.4M Kaon /spill (1.0 GeV/c)

5 Mpion /spill (1.6 GeV/c)

reaction in-flight (K-,N) (π+, K+)

Target Liq He3 Liq Deuteron

beam time request (in proposal)

38.5 days 40 days

method missing mass,invariant mass( K-pp-> Λp->pππ)

missing mass

Detectors CDS, NC SKS system. RC

expected yield(in proposal)

1000 ev 300 ev

2010/12/3 ストレンジネス核物理 2010

previous talk by Mr. T.Hiraiwa

J-PARC E27 Collaboration

2010/12/3 ストレンジネス核物理 2010 5

,Y.Ichikawa

6

D(π+ K+)X reaction Λ Hypernuclei via (π+,K+) reaction at 1.06 GeV/c Λ* production (th ~1.4 GeV/c ) The possibility the production of K-pp　bound state

with deuteron target. (Λ* doorway)


Yamazaki & Akaishi, Phys. Rev. C76 (2007) 045201.

π+ + 　“ n” → 　“ Λ*”+ K+

“Λ*” + “p” → 　 bound K-pp minor （ ~ 1.0% ） → 　 quasi free Λ* dominant 　Dr. Harada’s calculation

preriminaly

sticking　prabability　Λ　with　C12　target　~3%(mom　transfer　500MeV/c)

D(π+ K+)X reaction

ストレンジネス核物理 2010 7

Missing mass spectroscopyΔM = 2.5MeV

SKS: Superconducting Kaon SpectrometerΔp=2MeV/c

Δp/p=10^-4

n

pK-

ppd

Λ*

π+ K+

Missing mass

8

Scattered K+ momentum with π [email protected]/c


ΛΣ

Σ*+

Σ*0Λ*Σπ

Λπ

D ( π+, K+ ) X

Λ,　 Σ 　＋ Ns

Λ*,　 Σ* 　＋ Ns

Λπ,　 Σπ 　＋ Ns

X

SKS Acceptance Bound Region

QF process is a large background.

exclusive Measurement

K-pp → Λ + p1, K-pp → Σ0 + p1,

→ p2 + π- （ 64% ） → Λ + γ, （ 100% ）

→ p2 + π-

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π+ +d → Λ* + K+ + p1s, Λ* → Σ + π, Σ+ → p2 + π0

Quasifree process

P1s< 250MeV/c

Confirm K-pp by tagging the two high-momentum protons

Back ground suppression


Range Counter (Y.Ichikawa’s talk)

2010/12/3 ストレンジネス核物理 2010 10

Range counter = particle ID by beta vs range Effective selection of fast (300 ~ 700 MeV/c) proton

Proton Pion

Red : protonBlack : π-

10mm

20mm

20mm

50mm

10mm

K-pp → Λ + p,

→ p + π-

proton2 theta_Lab

pro

ton

1 th

eta

_La

bangular distribution of 2proton （ >300MeV/c) from K-

pp

11

K-pp → Σ0 + p

→ Λ + γ,

→ p + π-

pro

ton

1 th

eta

_La

b

proton2 theta_Lab2010/12/3 ストレンジネス核物理 2010

2 proton tagging at Forward (33 ~ 93 degree)

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Range counter for E27 ~ detect the fast 2 proton ~

K+

33°

93°

p

Target

500

p

π+

ＳＫＳ

BH2

Detection coverage is 33°~93° 14% acceptance

Yeild Estimation π+ intensity = 5M/spil dσ/dΩ = 60μb/sr, ΔΩ = 100 msr Deuteron = 1.4 g/cm2 ηdecay, ηtrack = 0.5, 0.5

Λ(1405) production rate = 6.0x104/day

Λ* trapping probability = 1% K-pp non-mesonic decay branch = 20% Λ+ Σ0decay modes = 2/3 Λ to emit proton = 2/3 Two-proton tagging efficiency = 14%

K-pp event rate =~8.0/day ~300events/40days


132010/12/3 ストレンジネス核物理 2010

The differential cross section for π-p →Λ(1405)K0

• Λ（ 1405） production cross section in the very forward direction is 5μb/sr （ CM） .

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→ 　60μb/sr （ Lab ）

D.W. Thomas et al., Nucl. Phys. B56 (1973) 15.

Range Counters Status (Y.Ichikawa’s talk)

2010/12/3 ストレンジネス核物理 2010 14

Range counter Test experiment performed (Dec 2009)

@K1.8 scattered particle Configuration determined

test experiment (Oct 2010) Analysis method optimization

construction

1/3 of all Range Counters were finished

including Support structure. The construction will be finished

at Feb. 2011.

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inclusive measurement with 1M Pion1M pi /spill

*(86400sec/6sec)

*1.4g/cm2 /2

*NA

*334.3e-30 cm2

*0.5(K decay)

*0.5 (eff.)

　　~　0.5M　events!!

　uppper　limit　

　　　　　of　Yield　　of　K-pp feasibility　

　　　　　of　2　proton　Tag


FINUDA, DISTO

K-pp 50 ev/ day

MC spectrum

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Future Plan

deuteron He3

K-pp K-ppp

satellite state

2proton　tagging?


Summary

2010/12/3 ストレンジネス核物理 2010 17

J-PARC E27 experiment search for a K-pp bound state using D(π,K) reaction measure the missing mass K-pp states 2 proton tagging

The preparation is well under way. RC construction by Feb. 2011

Inclusive measurement Upper limit

Thank you for your Attention!

j-parc e27 実験の概要

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