ヘリウム３に対する静止K-中間子吸収反応の実験的研究の可能性
藤岡宏之（京都大学）

Introduction
 antikaon-nuclear bound state, especially K-pp
– “observation” by past experiments• FINUDA [stopped K- absorption] (2005)• DISTO [p+p→Λ+p+K+] (2010)

B~100MeV, Γ~70-100MeV– theoretical situation• “shallow and broad” v.s. “deep and broad”– forthcoming experiments• E15 @ J-PARC K1.8BR [3He(in-flight K-, n/p)]• E27 @ J-PARC K1.8 [d(π+, K+)]
• FOPI @ GSI [p+p→Λ+p+K+]• AMADEUS @ DAFNE [stopped K- absorption]
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KEK理論センター研究会『ストレンジネス核物理 2010』2010/12/3

Introduction
 antikaon-nuclear bound state, especially K-pp
– “observation” by past experiments• FINUDA [stopped K- absorption] (2005)• DISTO [p+p→Λ+p+K+] (2010)

B~100MeV, Γ~70-100MeV– theoretical situation• “shallow and broad” v.s. “deep and broad”– forthcoming experiments• E15 @ J-PARC K1.8BR [3He(in-flight K-, n/p)]• E27 @ J-PARC K1.8 [d(π+, K+)]
• FOPI @ GSI [p+p→Λ+p+K+]• AMADEUS @ DAFNE [stopped K- absorption]
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KEK理論センター研究会『ストレンジネス核物理 2010』2010/12/3

Introduction
 antikaon-nuclear bound state, especially K-pp
– “observation” by past experiments• FINUDA [stopped K- absorption] (2005)• DISTO [p+p→Λ+p+K+] (2010)

B~100MeV, Γ~70-100MeV– theoretical situation• “shallow and broad” v.s. “deep and broad”– forthcoming experiments• E15 @ J-PARC K1.8BR [3He(in-flight K-, n/p)]• E27 @ J-PARC K1.8 [d(π+, K+)]
• FOPI @ GSI [p+p→Λ+p+K+]• AMADEUS @ DAFNE [stopped K- absorption]
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KEK理論センター研究会『ストレンジネス核物理 2010』2010/12/3

FINUDA and DISTO-250-200-150-100-50-150 -100 -50

25
2counts/(10MeV/c )00arbitrary unit

30-BK-pp [MeV]2015

2.2 2.25 2.3 2.35 2.4

1050
2.1

2.15

2.2

2.25

2.3

2.35

2.4

2p-Λ invariant mass [GeV/c ]

2.45

2.5

Phys. Rev. Lett. 94, 212303 (2005)

Phys. Rev. Lett. 104, 132502 (2010)

stopped K- + Li/C → Λ + p + Xp + p → Λ + p + K+

Page 5KEK理論センター研究会『ストレンジネス核物理 2010』2010/12/3

finding of FINUDA
 very small fraction of quasi-free two-nucleon absorption
stopped K-+ “pp” → Λ+pIM(Λp) ~ 2.37GeV - S(2p) abundant back-to-back correlated, low-mass Λ-p pair– deeply-bound K-pp ? (FINUDA)– effect of final state interaction ? (Magas et al.) general feature for p-shell nuclei (6/7Li, 9Be, 12/13C, 16O)
– also for helium-4 ? (→KEK-PS E549)
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effect of final state interaction
Magas et al.,Phys. Rev. C74, 025206 (2006)

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Pandejee et al.,Phys. Rev. C82, 034608 (2010)『ストレンジネス核物理 2010』2010/12/3

PΛp (CnCp

4
analysis of He(stopped K , Λp) :counts/(10 MeV/c2)

acceptance(%/reaction)

mK- + mp + mn

MΛp (MeV/c2)mΛ + mn

mK- + mp + mp

 certain fraction of
Σ0 final state (γ missing)mΛ + mp K-pp? K-ppn?

mK- + m4He - md

 low-mass Λp (Λn) pairs

mK- + m4He - 2mn

KEK-PS E549

counts/(10 MeV/c2)Mod. Phys. Lett. A23, 2520 (2008)MΛn (MeV/c2)

Fig. 1. (color online) A correlation diagram between MΛN (horizontal) and PΛN (vercorrelation diagram, Mmiss = const lines and the event classification zones, AN , B
are indicated. The AN , BN and CN components in each of the projections are show
red, and blue lines, respectively. In the projections onto MΛN , the evaluated mode
acceptance curves are drawn by brown dotted curves, and related mass thresholds arT. Suzuki, presentation at MESON2010
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How about helium-3?
 stopped K- + 3He → Λ + p + n @ K1.8BR– kinematically complete, by detecting Λp pairs(Dalitz plot analysis)– separation from Σ0pn final state– final state interaction : much easier to treat(spectator = a nucleon)– never been measured ...
“How large is the branching ratio ofnon-mesonic (multi-nucleon) absorption?”
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experimental setup (based on E15/E17)
CDH

chargedparticlespion

carbondegrador

K-CDC

protonSDD(unmounted)X-raysliq.-3He target

E0

Ti & Ni foil

LCproton

BLC050 cm
FIGURE 1.

Page 10solenoid: 0.7Tesla

A schematic of the J-PARC E17 experimental setup

KEK理論センター研究会『ストレンジネス核物理 2010』2010/12/3

Dalitz plot for Λpn final state
250

Almost all the phase space,
except for K-+“pn”200
absorption,is within acceptance.
TR-Q/3 [MeV]

150

250
200

100

Tp

100000

3000

200

2500

150

050

TR-Q/3 [MeV]

100-50-50-100-1000(Tp-Tn)/ 3 [MeV]-100100

Entries

1000003500
3000

K-+“pp”→Λ+p2500

100

2000

50

1500

1000

01000500-50500

2000
15000Tn

250

3500

50K-+“pn”→Λ+n150
TR-Q/3 [MeV]

Entries

-100

0-100

-1000TΛ
0100

0100(Tp-Tn)/ 3 [MeV](Tp-Tn)/ 3 [MeV]Page 11

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0Λpn / Σ pn separation

1600

counts (a.u.)

1400
1200
1000

Λpn

Σ0pn

kinematically complete,even without neutron detection!

800
600

Λp+πN

400
200

0800 850 900 950 1000 1050 1100 1150 1200
-missing mass 3He(K , Rp) [MeV/c2]

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origin of Λpn final statestopped K- + 3He

nuclear Auger process

two-nucleon absorption

π-absorption

three-nucleon absorption
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Λnps Σ0nps
Λpns Σ0pns
Σ-Λ conversion

Λπ(NN)s

K-pn+prescattering

one-nucleon absorption

K-pp+nΛpn
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origin of Λpn final state
stopped K- + 3He

nuclear Auger process

Entries

100000

one-nucleon absorption

Λπ(NN)s

200

3000

200

3000

150

2500

150

2500

100

2000

100

2000

50

1500

0

1000

01000

-50500-50

500-1000(Tp-Tn)/ 3 [MeV]

1000TR-Q/3 [MeV]

250

3500

π-absorption

50

1500-100-100

0100

three-nucleon absorption(Tp-Tn)/ 3 [MeV]KEK理論センター研究会『ストレンジネス核物理 2010』0Σ-Λ conversion

3500

rescattering

TR-Q/3 [MeV]Λpns Σ0pns

250-100

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100000K-pn+pΛnps Σ0nps

two-nucleon absorption
Entries

K-pp+nΛpn
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Entries

origin of Λpn final state

13831

250

40200

35150

stopped K- + 3He

TR-Q/3 [MeV]

nuclear Auger process
30

100

2550

20

10-50

two-nucleon absorption

5-100-100100000

one-nucleon absorption

Λπ(NN)s200

3000

200

3000

2500

150

Λnps / nps→np

TR-Q/3 [MeV]

2503500

Λpns / pns→pn100

2000

50

1500

01000

01000-50500-50500-100 s→ΛpΛnps / Λp-1000(Tp-Tn)/ 3 [MeV]

1000100

2500

50

2000

π-absorption1500

Λpn-100s / Λns→Λn-100
0100

three-nucleon absorption(Tp-Tn)/ 3 [MeV]KEK理論センター研究会『ストレンジネス核物理 2010』0Σ-Λ conversion

3500

rescattering

TR-Q/3 [MeV]

EntriesΛnps Σ0nps
Λpns Σ0pns

0100

250

150

Page 150(Tp-Tn)/ 3 [MeV]

100000K-pn+p150

Entries

K-pp+nΛpn
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origin of Λpn final state
stopped K- + 3He

nuclear Auger process

Entries

9354

25025050Σ0nps / Σ ps→Λp100

403050200150

TR-Q/3 [MeV]

TR-Q/3 [MeV]200

10-50-100-1000100

040

Λπ(NN)s35

Σ0pns / Σ0ns→Λn2050π-absorption
15
10-50

5-100(Tp-Tn)/ 3 [MeV]-100

0100(Tp-Tn)/ 3 [MeV]three-nucleon
absorption+(他にもΣ+nns / Σ ns→Λp や Σ-pps / Σ-ps→Λn)
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Λpns Σ0pns『ストレンジネス核物理 2010』0Σ-Λ conversion

150one-nucleon
absorption
013003

rescattering200

K-pn+pΛnps Σ0nps

two-nucleon absorption
Entries

K-pp+nΛpn
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origin of Λpn final state
stopped K- + 3He

nuclear Auger process
250

200
two-nucleon
absorption100

Λπ(NN)s0-50π-absorption

-100
-100

0100

Λnps Σ0nps
Λpns Σ0pns(Tp-Tn)/ 3 [MeV]three-nucleon absorption
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Σ-Λ conversion

one-nucleon50 absorption

K-pn+prescattering

TR-Q/3 [MeV]150

K-pp+nΛpn
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Entries

origin of Λpn final state

250

25200
150

20K pp+n10015

nuclear Auger process
TR-Q/3 [MeV]

stopped K- + 3He

K-pn+p50

100

two-nucleon absorption5041

Λnps Σ0nps
5-50-10000Λpns Σ pns

-100

0100

(Tp-Tn)/ 3 [MeV]

π-absorption

three-nucleon absorption
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Σ-Λ conversion

Λπ(NN)srescattering

one-nucleon absorption

Λpn2010/12/3

origin of Λpn final state
stopped K- + 3He

nuclear Auger process
Entries

1833

K-pp+n (B=100MeV, Γ=0MeV)
250

K-pn+p12

Λnps Σ0nps

10Λpns Σ0pns

two-nucleon absorption

200

K-pp+n8

one-nucleon absorption

Λπ(NN)s

650
04-502-100-1000100

π-absorption

0

three-nucleon absorption(Tp-Tn)/ 3 [MeV]Page 19

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Σ-Λ conversion

100rescattering

TR-Q/3 [MeV]

150

Λpn
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invariant-mass resolution
400

counts (a.u.)

350
300
250

~12MeV FWHM
after kinematic fitting

200
150
100
50
02150

2200

2250

2300

2350

2400

Rp invariant mass [MeV/c2]

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3cf. stopped π absorption in He @ PSI
D.Gotta et al., Phys. Rev. C 51, 469 (1995)
two-nucleon absorption
rescattering?
two-nucleon emission

inr
tteg?

rescattering?

asc
re

FSI

three-nucleon absorption(<5.5%)

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summary K- multi-nucleon absorption in 3He (first measurement)– 3He(K-, Λp)n w/ E15/E17 setup @K1.8BR
low-mass Λp pair?? (FINUDA, E549)– separation in Dalitz plot among:• two-nucleon absorption + rescattering / Σ-Λ conversion• three-nucleon absorption• (one-nucleon absorption + π-absorption)• nuclear Auger process = production of K-pp, K-pn

 (K-, π±) ΣNN? cf. LoI by Tamura et al.: (in-flight K-, π±)Page 22

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