J-PARC E27実験の概要
岡村 敦史(Kyoto. Univ.)
for E27 Collaborations
1

ストレンジネス核物理 20102010/12/3

Index Introduction
 K-pp bound state E27 experiment Setup Preparation status Summary

2010/12/3

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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.

Λ(1405) from PDG
Mass : 1406.5 ± 4.0 MeV
Width: 50 ± 2 MeV
JP : ½-

Unable to explain with 3 quarkmodel Binding energy, Width

Lighter than N*(1530)

Meson baryon molecule state?

theoritical prediction : 20-100,40-100 (Chiral Unitary model)
experimental result : exist? unconsistent B.E., Width More measurements via various reaction are necessary!!

J-PARC E15, E27 experiment
2010/12/3

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E15 and E27
E15

E27

Beam Line

K1.8 BR

K1.8beam

1.4M Kaon /spill (1.0 GeV/c)

5 Mpion /spill (1.6 GeV/c)reaction

in-flight (K-,N)(π+, K+)

TargetLiq He3

Liq Deuteronbeam time request 38.5 days(in proposal)

40 daysmethod

missing mass,
missing massinvariant mass( K-pp-> Λp->pππ)

Detectors

CDS, NC

SKS system. RC

expected yield(in proposal)

1000 ev

300 evprevious talk by Mr. T.Hiraiwa
2010/12/3

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J-PARC E27 Collaboration,Y.Ichikawa

2010/12/3

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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 statepreriminalywith deuterontarget. (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
sticking prabability Λ with C12 target ~3%(mom transfer 500MeV/c)
2010/12/3

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D(π+ K+)X reaction

π+dnp

MissingmassΛ*

SKS: Superconducting
KaonSpectrometer

K+Kpp

Missing mass spectroscopy
ΔM = 2.5MeV
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Scattered K+ momentum with π beam@1.69GeV/c
SKS Acceptance

Bound Region

D ( π+, K+ ) XΣΛXΛ, Σ ＋ NsΛ*, Σ* ＋ Ns

Σ*+Σπ

Λ*Λπ

Λπ, Σπ ＋ Ns
QF process is alarge background.

Σ*0exclusive
Measurement
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Back ground suppression
K-pp → Λ + p1,→ p2 + π- （64%）

K-pp → Σ0 + p1,→ Λ + γ, （100%）→ p2 + πQuasifree process
π+ +d → Λ* + K+ + p1s,
Λ* → Σ + π,
Σ+ → p2 + π0P1s< 250MeV/c

Confirm K-pp by tagging
the two high-momentum
protons
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Range Counter (Y.Ichikawa’s talk) Range counter = particle ID by beta vs range Effective selection of fast (300 ~ 700 MeV/c) proton

10mm

50mm

20mm
20mm

Red : proton
Black : π-10mm

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proton1
proton1theta_Lab
theta_Labangular distribution of 2proton （>300MeV/c) from K-pp
2 proton tagging at Forward (33 ~ 93degree)
K-pp → Σ-0 + p
K pp → Λ + p,
→ Λ + γ,
→ p +- π→p+π

proton2
proton2theta_Lab
theta_Lab
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Range counter for E27 ~ detect the fast 2 proton ~Detection coverage is 33°~93°ＳＫＳ

14% acceptanceYeild Estimationπ+ intensity

dσ/dΩ = 60μb/sr, ΔΩ = 100 msr

Deuteron = 1.4 g/cm2

ηdecay, ηtrack = 0.5, 0.5

K+= 5M/spil33°

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%

93°

500

ppTargetK-pp event rate =~8.0/day
π+~300events/40days
2010/12/3

BH2

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The differential cross section for π-p →Λ(1405)K0• Λ（1405）production cross section in the very
forward direction is 5μb/sr （CM）.

→ 60µb/sr（Lab）

D.W. Thomas et al., Nucl.
Phys. B56 (1973) 15.
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Range Counters Status (Y.Ichikawa’s talk) 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 finishedincluding Support structure.
 The construction will be finishedat Feb. 2011.
2010/12/3

ストレンジネス核物理 201014inclusive measurement with 1M Pion
1M pi /spill*(86400sec/6sec)

MC spectrum*1.4g/cm2 /2*NA*334.3e-30 cm2*0.5(K decay)*0.5 (eff.)~ 0.5M events!!

 uppper limitof Yield of K-pp
 feasibilityof 2 proton Tag
2010/12/3

FINUDA, DISTO
K-pp 50 ev/ day

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Future Plan deuteron

 He3

 K-pp

 K-ppp satellite state 2proton tagging?

2010/12/3

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Summary 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!
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