ハイパー核 - kincha.kek.jpkincha.kek.jp/kincha026_takahashi.pdf · ハイパハイパ...
TRANSCRIPT
ContentsContents
• Introduction
• Λ hypernuclei– Production reactions
– Spectroscopy & ΛN Interaction• Reaction SpectroscopyReaction Spectroscopy
• γ‐ray Spectroscopy
– Baryon in Nuclei• KEK‐E419/J‐PARC E13
• S=−2 systemM ti ti– Motivation
– ΛΛ hypernuclei
– Ξ hypernuclei & J‐PARC E05Ξ hypernuclei & J PARC E05
Baryon Octet (バリオン八重項)Baryon Octet (バリオン八重項)
陽 中性 仲間陽子・中性子の仲間
• S=0– p, n I=1/2
• S=−1S 1– Λ I=0
– Σ (Σ+ Σ0 Σ−) I=1Σ (Σ ,Σ ,Σ ) I=1
• S=−2Ξ (Ξ0 Ξ−) I 1/2– Ξ (Ξ0,Ξ−) I=1/2
これらを含む原子核を
ハイパー核という
Λ ハイパー核ーもっとも軽いハイパー核-
寿命: Λの寿命(260ps)程度τ=200ps =Γ
chτ=200ps原子核の半径: r=3.5fm (A~20)光速で回転するとして、崩壊までに
* /(2* * )fmMeV 200 ⋅
=
Γτc
n=c*τ/(2*π*r) =3x108x2x10‐10/(2x3.14x3.5x10‐15)=2.8x1012
fm10102103 15108 − ××⋅×
回まわる MeV103.3 12−×=
Baryon多体系(原子核)を充分な時間形成し、状態の幅も充分狭い状態の幅も充分狭い。
3次元核図表3次元核図表
• S=0 (通常原子核)S 0 (通常原子核)
– 安定核種 ~300
– 確認 ~3000
存在 6000– 存在 ~6000
• S=−1– Λハイパー核 35
– ∑ハイパー核 1
• S=−2ダブルΛ イパ 核– ダブルΛハイパー核
3(5)
Discovery of Hypernulei in 1952Discovery of Hypernulei in 1952Marian Danysz & Jerzy Pniewski
Phil. Mag. 44 (1953) 348
Track Range G.D. Identity EnergyFragement f Charge 5
1 9 μm Black p, d, t, or α 0.7 MeV (p)
2 123 μm Black p, d, t, or α 16 MeV (α)
3 3 7±0 2 d t 82 M V ( )
gRange 90μmEnergy ~60MeVTime of Flight 3ps
3 - 3.7±0.2 p, d, t, or π 82 MeV (p)
4 2 μm Black Recoil -
Released Energy at B~140MeV
ハイパー核物理の特長ー研究の目的ー
イペ は 排他律を受けな• ハイペロンは、Pauli排他律を受けない
– 原子核深部を探るプローブ
• Impurity Physics– Grue‐like role
– 核構造の変化
– 媒質中のhadronの性質媒質中 性質
• Baryon‐Baryon Interaction– YN YY Interaction based on SU(3)fYN, YY Interaction based on SU(3)f
– 核力の統一的理解
Reactions to Produce Λ HypernucleiReactions to Produce Λ Hypernuclei
• In‐flight (K−,π−), (K−,π0) Reaction– Recoilless production PK=~0.5GeV/c
– Substitutional states
• (π+,K+) Reaction– Large mometum transfer ~400MeV/c > kFLarge mometum transfer 400MeV/c > kF– Spin‐streched states
• Stopped (K− π−) Reaction• Stopped (K ,π ) Reaction– Large production rates
No special selectivity– No special selectivity
• (γ,K+), (e,e’K+) Reaction– Large momentum transfer sim. (π,K)– Both spin‐flip and spin‐non‐flip states
Transfered momentum for elementary reactions
+ →K+Λ
γp →K+Λ
V/c]
π+n →K+Λ
tum [M
eV
K−n → π−Λ
il mom
ent
10°0°
Recoi
Beam momentum [GeV/c]
K−n→ π+Λ Cross SectionK n→ π+Λ Cross Section• PK~0.8GeV/cで最大
– q~50MeV/c < kF• 充分にRecoilless条件
– Spin non‐flip– Spin non‐flip• nと同じ向きのspinをもったΛが生成
• Spin‐flip states– PK =1.1~1.5 GeV/c
大きな散乱角– 大きな散乱角
• 10~15°
• PK>1.6GeV/cでも大きいPK>1.6GeV/cでも大きい– Recoillessではない。
• q > 100 MeV/c
– Spin non‐flip
Cross Section for (π K) ReactionsCross Section for (π,K) Reactions
• 1.05GeV/c π+ beamfor Λ productionπ+n−>K+Λ
• Spin non‐flip amplitude
π+p−>K+Σ+
π+n−>K+Σ0
π−p−>K+Σ−
各反応でのスペクトル(理論予想)12Cを標的としてー 12Cを標的としてー
(K−,π−) reaction• Substitutional state: 0+
• Large production cross section ~mb/sr
(π+ K+) reaction(π ,K ) reaction• Bound states• Spin stretched states: 2+• Small production cross section ~10μb/srSmall production cross section 10μb/sr
(e,e’K+) reaction( , )• Bound states• Unnatural parity states (2−,3+) as well as natural parity states
• Very small production cross section ~10nb/sr
反応分光測定装置ー SKS & K6 beamline @KEK ー
K+
ビームπ+, 散乱K+の運動量と散乱角(粒子の飛跡)を事象ごとに測定し、Missing Massを求める。
チェレンコフ検出器粒子の識別 K g
P ~0 7G V/
粒子の識別
+
P=~0.7GeV/c
Drift Chamber粒子の飛跡を測定
π+
P 1 05G V/P=1.05GeV/cSKS
B=2.2T (max. 3T)Gap 50 cm
Plastic Sintillator飛行時間の測定
Gap 50 cmΔΩ = 100 msr
12 C Spectrum Measured with SKS12ΛC Spectrum Measured with SKS
11C Λ ( t t )11C + Λ (s‐state)
11C + Λ (p‐state)
11C* + Λ (s‐state)
Core核の励起状態にs‐stateのΛが結合した状態
SKSで初めて観測
hi l ( )H.Hotchi et. al, PRC64(2001)044302
Λハイパー核分光データからわかることー Single Particle Orbit of Λ ー
H.Hotchi et. al, PRC64(2001)044302
ポテンシャル中のΛの1粒子状態
Pauli排他律が働かない。Pauli排他律が働かない。Λは核子とは別粒子
Single Particle Energy of Λand Λ‐Nucleus Potential
Woods‐Saxon Potential
)(12
⎟⎞
⎜⎛ rdf rh51
1)(
)(1)()( 0
=
⎟⎟⎠
⎞⎜⎜⎝
⎛+= ΛΛ
Λ
rf
sldr
rdfrcm
VrfVrU LSrrh
π
51ΛV
12ΛC
M V31)1(
,))(exp(1
)(
3/10 −=
−+=
ΛVARR
aRrrf
fm840fm 1.1MeV31
with 0
0
==−=Λ
aR
V208
ΛPb139
ΛLa89
ΛY28ΛSi fm84.0=a
陽子や中性子では、−50MeV
ΛN相互作用は NN相互作用よりも弱い
Λ
E140a, T.Hasegawa et. al, ΛN相互作用は、NN相互作用よりも弱いE140a, T.Hasegawa et. al,PRC53(1996)1210
Spin Orbit PotentialSpin‐Orbit PotentialNormal Nuclei (S=0)では、重要( ) 、 要
Shell model by Mayer & Jensen
slrvV SOrr
⋅= )(
j = l±1/2でレベルが分離する
)12()(21
+><−=Δ lrvE
ΔE~20A‐2/3 (l・s) MeV
Magic Numberの発現
ΛのSpin‐Orbit Potential は?
Spin‐Orbit Potential of Λー 13
ΛC* からのγ線測定 ーBNL AGS E929BNL AGS‐E929H.Kohri et. al, PRC 65(2002) 034607A.Ajimura et. al, PRL 88(2001) 4255
13C (K−,π−) 反応で 13ΛC*を生成
48D48 Spectrometer13
ΛC* からのγ線を測定NaI Detector
12C
13ΛC
Λがp1/2Λがp3/2LS partnerLS partner
K−
π−
Spin‐Orbit Potential of Λー 13
ΛC* からのγ線測定 ー厚い標的かつスペクトロメータの分解能が悪いので厚 標的か クト タの分解能が悪 のでMissing Massではピーク構造は見えない。
BΛ(G.S)=11.69±0.12MeV (Emulsion)
γ線スペクトル
薄い標的でのスペクトル
unbound region
bound regionbound region
Spin‐Orbit Potential of Λー 13
ΛC* からのγ線測定 ー2つの kは分離できないが 1/2 ( )と3/2+( )の生成の角度分布2つのpeakは分離できないが、1/2− (p1/2)と3/2+(p3/2)の生成の角度分布が違うことを使って、2つの状態のエネルギー差を求める。
E(1/2−)=10.982±0.031±0.056 MeVE(3/2−)=10.830±0.031±0.056 MeV
ΔE=152±54 keV
Λの場合、Spin‐orbit Potentialは非常に小さい非常に小さい。核子の場合は、p‐orbitで約6MeV
Hypernuclear γ‐ray Spectroscopy and ΛN Interaction
• Small spin‐dependent ΛN interaction – Spin‐orbit splitting of 13ΛC ~150keVp p g Λ
E i t l l ti• Experimental resolution– (π+,K+), (K−,π−) with Mag. Spec. 2‐3MeV
– γ‐rays with NaI 350keV@10MeV– (e e’K+) <1MeV(e,e K ) <1MeV
– γ‐rays with Ge detector a few keV
Hypernuclear Fine Structureand ΛN (Effective) Interaction
ΛN ( ff ti ) i t tiCore Nuclei (p‐shell) + Λ in s‐state ΛN (effective) interaction
Λ
⋅+=
rrN
ssrVrVrV
)()()( 0
Central
Spin‐spin
Λ
ΛΛΛ
Λ
⋅+
⋅+
⋅+ σ
rr
rr
NNN
N
N
slrV
slrV
ssrV
)(
)(
)( p p
Λ spin‐orbit
N spin‐orbit
ΛΛ
Λ
⋅−⋅⋅=++
σσσσ rrrrrrNN
T
NNN
rrSSrV
slrV
))((3)()(
12
12Tensor
Radial integral by Λ in s‐state and N in p‐state W.F.p‐shell Λ hypernuclei
TSS N ,,, , V ΛΔp shell Λ hypernuclei
pA‐5N sΛ
HyperballHyperball
• 14 Sets of Ge & BGOff– Ge: 60% rerative efficiency
– BGO: 6 seg. per each
• Solid angle coverage: 15%• Solid angle coverage: 15%
• Photo‐peak efficiency– 2 5%@ 1MeV– 2.5% @ 1MeV
• KEK E419, E509/ BNL E930
• Transistor reset & gated• Transistor reset & gated integrator amplifier
Hyperball2Hyperball2
• Hyperball +
6 sets of Clover type Ge detetors6 sets of Clover‐type Ge detetors
• 25% solid angle coverage
• Photo peak efficiency• Photo‐peak efficiency– 4% @ 1.33MeV
• KEK E518/E566• KEK E518/E566
7 Liー Spin spin Interactionー7ΛLi ー Spin‐spin Interaction ー
KEK E419 (1998) (π+,K+) spectrum measured by SKS
H.Tamura et. al, PRL84(2000)5963PRL84(2000)5963
E(3/2)−E(1/2) = 1.444Δ +0.054SΛ +0.016SN −0.271T
Thin target data by E336
7ΛLiー Spin‐spin InteractionーΛLi Spin spin Interaction
γ ray spectra
unbound region
bound region w/o Doppler Corr.
bound region w/ Doppler Corrbound region w/ Doppler Corr.
E(3/2−>1/2)=692keV Δ = 0.43 MeV
9ΛBeー Λ spin‐orbit InteractionーΛBe Λ spin orbit Interaction
BNL E930(‘98) H.Akikawa et. al, PRL88(2002)082501H.Tamura, NPA754(2005)58c
9ΛBe: α‐α‐Λ cluster
E(3/2+ −> 1/2+) = 3067 ±3 ±1keV(3/ / ) 306 3 eE(5/2+ −> 1/2+) = 3024 ±3 ±1keV
E(3/2+)−E(5/2+) = 43 ±5 keV
E(3/2+)−E(5/2+) = −0.037Δ −2.464SΛ +0.003SN +0.994T +ΛΣ
SΛ = −0.01 MeV
16ΛO ー Tensor InteractionーΛO Tensor Interaction
BNL E930(‘01) 16O(K−,π−γ)M.Ukai et. al,PRL93(2004)232501
Λ
E(1−)−E(0−) = −0.382Δ +1.378SΛ −0.004SN +7.850T +ΛΣ
E(1− −>1−) = 6534.3±1.2±1.7 keVE(1 0 ) 6560 4±1 1±1 7k VE(1− −>0−) = 6560.4±1.1±1.7keV
E(1−) – E(0−) = 26.1±1.4±0.6keV
T=0 03 MeVT=0.03 MeV
7ΛLi: Completely known levels
ー N Spin‐orbit Interaction ーBNL E930(‘01) M.Ukai et. al,
10B(K−,π−)10ΛB*7
ΛLi* + 3He
Single‐γ spectrum
,PRC73(2006)012501(R)
γ γ consident spectrumγ−γ consident spectrum
E(7/2+−>5/2+) = 470.8±1.9±0.6 keV
E(7/2+,5/2+) –E(3/2+,1/2+) = E(6Li;3+)–E(6Li;1+)−0.05Δ +0.07SΛ +0.70SN −0.08T
S 0 43 M VSN = −0.43 MeV
Obtained parameters & YN Interaction Models
• Spin‐spin Δ=0.43MeV– NSC97e, NSC97fの中間(spin‐spin力を調整した)
• Spin‐orbit SΛ=−0.01MeV, SN=−0.43MeV– Nijmegen Model (meson‐exchange model)j g ( g )
• −0.18 < SΛ < −0.13 MeV
• −0.29 < SN < −0.26 MeV
– Quark model based Interaction• consistent
• Tensor T=0.03MeV– Njimegen 0.018<T<0.054 MeV
Inconsistency y
0.578 Δ + 1.41 SΛ + 0.014 SN ‐1.07 T + ΛΣ10ΛB
2−
Λ NΛB195keV −15keV
Experimentally not observed ! <100keV
9B3/2−
1−
10ΛB
<100keVreversed order
11ΛB (M1:7/2+−>5/2+) 418keV 262keV
1 M h l ΛΣ li ff
Three‐body force by ΛΣ coupling
1. Much larger ΛΣ coupling effect2. Ambiguity of the wave function of core nuclei
‐‐ Not well known
Subjects at J‐PARC
Shrinkage of 7ΛLiー Grue like role of Λ ー
E Hi t l6Li 7ΛLi
pnrn‐p
nrn‐p
E.Hiyama et. al,PRC59(1999)2351
417 )2/15/2B(E2;Li)( ⎤⎡ → ++R
α
p
Rcore‐(n‐p) αp
Rcore‐(n‐p)Λ
5ΛHe
6 )13 B(E2;)2/15/2 B(E2;
Li)(Li)(
⎥⎦
⎤⎢⎣
⎡→→
= ++−
Λ−
d
dc
RR
α
ΛHe
B(E2): transition probabilitytransition probability
~1/ττ: lifetime
Rcore‐(n‐p)
Measurement of lifetimeー Doppler Shift Attenuation Method ー
生成したハイパー核は反跳運動量を持つ。 t << τ 幅の狭いピーク生成したハイパ 核は反跳運動量を持つ。(π+,K+)では ~0.5GeV/c
標的中で静止するまでの時間 tstopγ線放出状態の寿命 τ
tstop << τ 幅の狭いピ クtstop >> τ 幅の広いピーク
(Doppler shiftで拡がった)tstop~ τ 両者にピークの比(ピーク形状)γ線放出状態の寿命 τ tstop τ 両者にピ クの比(ピ ク形状)
から、寿命を求められる。
7Li(π+,K+γ)7ΛLi (KEK E419) K Tanida et al PRL86(2001)1982Λ
B(E2)=3.6±0.5 e2fm4+0.5‐0.4
B(E2; 6Li)=10.9±0.9 e2fm4
K.Tanida et. al, PRL86(2001)1982
S=R(7ΛLi)/R(6Li)=0.81±0.04
19%のShrinkage
Eγ [keV]
J PARC E13J‐PARC E13
• Hypernuclear γ‐ray spectroscopy via (K−,π−γ)– PK=1.5GeV/c with SksMinus & Hyperball‐JK / yp
• Targets and purposes4 H CSB f 4 H– 4
ΛHe CSB c.f. 4ΛH
– 7ΛLi B(M1) & gΛ in meaduim
– 10,11ΛB ΛΣ coupling ...
– 19ΛF sd‐shell hypernucleusΛF sd shell hypernucleus
77ΛΛLi: B(M1) measurement and Li: B(M1) measurement and ΛΛ in nucleusin nucleus
1+ 3/2+J=1 J+1/2 Nuclear medium effectNuclear medium effect
6 Li
1+ 3/2
1/2+
M1692keVT=0, L=0,S=1 •No Pauli blocking →Λ in 0s orbit6
3Li 7ΛLi
/J-1/2
1
→Λ in 0s orbit•Partial restoration of chiral symmetry?
)1(1 3 MBEγτ∝=Γ
Doppler Shift Attenuation
reduction of constituent quark massMethod
In the weak coupling limit between Λ and the core nucleus
mass→ change of μΛ
[ ] CN
JJ
ggJJMB −∝==∝ Λμμ 222 )(2/12/3)1(
CC JgJg += ΛΛμ gΛ,gc: Effective ffective g factor of Λ and core nucleus, respectivelyJΛ, Jc: Total spin of Λ and core nucleus, respectively
B(M1) measurementDifficulties in B(M1) measurement
Doppler Shift Attenuation Method works only when τ < tstop τ is very sensitive to Eγ because B(M1) ∝ 1/τ ∝Eγ
3. But Eγ is unknown.Cross sections and background cannot be accurately estimated.
~
To avoid ambiguities, we use the best-known hypernucleus, 7ΛLi.Energies of all the bound states and B(E2) were measured
Cross sections and background cannot be accurately estimated.Previous attempts: 10
ΛB , 11ΛB (Eγ too small −> τ >> tstop ),
7ΛLi (byproduct: indirect population)
Energies of all the bound states and B(E2) were measured,γ-ray background level was measured, cross sections are reliably calculated.
τ = 0.5ps, tstop = 2-3 ps for 1.5 GeV/c (K-,π-) and Li2O target Calc. by Motobap y
(K-,π-)
PRL 84 (2000) 5963PRC 73 (2006) 012501
S=−2 SystemS= 2 System
H i l• H particle
• ΛΛ hypernucleusyp
• Ξ hypernucleus• Baryon‐Baryon Interaction in S=−2– ΛΛ
ΞN– ΞN– ΞN −> ΛΛ– H particle ?
S=−2 Systemー Dynamical System ー
ll d ff• small mass difference between ΛΛ and ΞN
~ 28 MeV
– ΞN‐ΛΛ Mixing– Three‐body force via the
ΞN‐ΛΛ interaction
Λ ΛN
L i i ff d h b d f
Ξ
Large mixing effect and three‐body forceare expected in S=−2 system.Λ Λ N
Studies of S= 2 System at J PARCStudies of S=−2 System at J‐PARC• E03: Measurement of X rays from Ξ− atomsy
– atomic level shift• Ξ‐A Potential (surface)
• E05: Spectroscopy study of Ξ‐hypernucleus, 12ΞBe, via the 12C(K−,K+) reaction– Ξ‐A Potential ( interior)– ΞN, ΞN−>ΛΛ interaction
• E07: Systematic study of double strangeness systems with an emulsion‐counter hybrid method– double‐Λ hypernuclei ‐ ΛΛ interaction– twin‐Λ ‐ Ξ Potential (interior)– X‐rays from Ξ‐atom ‐ Ξ Potential (surface)
Production & Measurement of S=−2 System
p + K− > Ξ− + K+p + K −> Ξ + K+
Quasifree Ξ Production
~1.8 GeV/cDirect productionReaction Spectroscopy
Ξ Hypernuclei
Double Λ Compound StatesΞ− Atom
X‐rays measurements
Double Λ Fragment
Decay measurementsDecay measurementsEmulsion
Nagara Event & ΛΛ InteractionNagara Event & ΛΛ Interaction
A:H.Takahashi et. al, PRL87(2001)212502KEK E373
A:12C + Ξ− −> 6ΛΛHe + 4He + 3H
H.Takahashi et. al, PRL87(2001)212502
B:6
ΛΛHe −> 5ΛHe + p + π−
BΛΛ = 7.25±0.19 MeVΔBΛΛ = 1.01±0.20 MeV
+0.18−0.11+0.18−0.11
assuming BΞ
− = 0.13 MeV (3D state)
0.
( )Weakly attractive ΛΛ Interaction
MH ≧ 2223.7 MeV
Ξ Potential & High Density Nuclear Matter
Λ Σ Ξ K i h f N S
μ B = m B +kF
2
2m B
+ U (k F )
Λ, Σ−, Ξ−, K− in the core of Neutron‐Star
m B
depends on Mass, Charge, and PotentialUΣ <0,UΞ <0
UΣ >0,UΞ <0
UΣ >0,UΞ >0
Baryon‐Baryon Interaction ModelUΞ and Partial Wave Contributions in Nuclear Matter
(MeV)
Model T 1S03S1
1P13P0
3P13P2 UΞ ΓΞ
NHC-D 0 −2.6 0.1 −2.1 −0.2 −0.7 −1.91 −3.2 −2.3 −3.0 −0.0 −3.1 −6.3 −25.2 0.9
Ehime 01
−0.91 3
−0.58 6
−1.00 8
0.30 4
−2.41 7
−0.74 2 22 3 0 51 −1.3 −8.6 −0.8 −0.4 −1.7 −4.2 −22.3 0.5
ESC04d* 01
6.37 2
−18.4−1 7
1.2−0 8
1.5−0 5
−1.3−1 2
−1.9−2 8 −12 1 12 7
• OBE (NHC‐D, Ehime)odd state attraction
1 7.2 1.7 0.8 0.5 1.2 2.8 12.1 12.7
• ESC04d*strong attraction of 3S (T=0)– odd‐state attraction
– strong A‐dependence of VΞ
– Narrow width
– strong attraction of 3S1(T=0)– Large width
Narrow width
12C(K−,K+) Missing Mass SpectroscopyC( , ) ss g ass Spect oscopy
PKh t t l
BNL AGS E885KEK E224T.Fukuda et. al,PRC58(1998)1306 P.Khaustov et. al,
PRC61(2000)054603
ΔM=10MeV(FWHM)
PRC58(1998)1306
ΔM=13MeV(FWHM)
ΔM=10MeV(FWHM)for H(K−,K+)Ξ−
VΞ = −14 MeV ?
W.S. Potential Calc.with Γ=1MeV
E05: Spectroscopic Study of Ξ‐Hypernucleus, 12
ΞBe, via the 12C(K−,K+) Reaction
• Missing mass spectroscopy
via the (K−,K+) reaction– K1.8 Beam Analyzer 1.8GeV/c K−
• Δp/p = 3.3x10−4
– SksPlus Spectrometer ~1 3GeV/c K+– SksPlus Spectrometer 1.3GeV/c K• 30msr
• Δp/p = 0.17%20 – ΔM=3MeV(FWHM)
• The first observation of
VΞ = −20 MeVp Ξ
Ξ hypernuclear states– Ξ‐Nucleus Potential– Ξ‐N Interaction
s Ξ– Ξ‐N Interaction– Ξ‐N −> ΛΛ Conversion VΞ = −14 MeV
K1 8 Beamline at Hadron HallK1.8 Beamline at Hadron Hall
ES2
K1.8 beamline Phase‐II (750kW) Phase‐I (270kW)
ES1
Length [m] 45.853
Acceptance [msr %] 1.4
K‐ intensity (FF) @1.8GeV/c 6.6x106 1.4x106y ( ) @ /@1.5GeV/[email protected]/c [ppp]
2.7x106
3.8x1055.4x105
8.0x104
K‐/(p‐+m‐) @1.8GeV/c 4.0 3.5
SKS MagnetSKS Magnet北CHでの解体 ・コイル容器取り出し(2008.1) J‐PARCハドロンホール
への輸送 (2008 9)への輸送 (2008.9)
残りヨーク解体 (2008.9) コイル容器改造終了@東芝京浜工場(2008 10)@東芝京浜工場(2008.10)
2008/10/27 51 特定領域研究会2008
まとめ ーハイパー核の物理ーまとめ ーハイパー核の物理ー
排他律を受 な 粒 注• Pauli排他律を受けない粒子の注入
– 原子核構造の変化原子核構造 変化
– ハドロン(ハイペロン)の性質の変化 を探る
バリオン間相互作用• バリオン間相互作用
– SU(3)fに拡張して、核力を理解する。
• S=−2のハドロン多体系
J PARCで本格的に開始– J‐PARCで本格的に開始
– multi‐strangeness系(高密度、、)への第1歩
44ΛΛHe: He: Spin dependent Charge symmetry breaking Spin dependent Charge symmetry breaking
(CSB) in (CSB) in ΛΛN interactionN interaction• Lightest mirror hypernuclei → ΔBΛdirect measure of ΔEcsb,ΛN :
ΔBΛ≈ ΔEcsb,ΛN
( )( )
keVHBHeBB 70)()( 44 ±=−=Δ ΛΛΛΛ 350
• CSB effect in NN interaction calculated from 3H and 3He ΔEcsb ΝN
keVHEHeEE 160)1;()1;(
)()(44 ±=−=Δ +
Λ+
ΛΛ
ΛΛΛΛ
270
CSB effect in NN interaction calculated from H and He ΔEcsb,ΝN
≈ 80keV (Faddeeve calculations, Y.Wu et. al., PRL 64 1875 (1990))
A few times larger CSB effect in A few times larger CSB effect in ΛΛN than in NN ??N than in NN ??
(K-,π- )
Re measure withRe‐measure with 0.5% accuracy
4ΛHe and CSB
Observed CSB looks spin-independent.
??ΛN-ΣN coupling gives spin-dependent CSB.
??
Very large CSB !?
stop K- on 6Li by NaI (1979)
Liq. 4He 25cm (1.25 g/cm2)10 hours
Very large CSB !?Not theoretically understood.
stop K- on 6Li by NaI (1979)4
ΛHe: Only one dataBad quality
4ΛH* : (e,e’K+) at Jlab
(K-,π0γ) at J-PARC
1010ΛΛB: the puzzleB: the puzzle
Shell model prediction10B (K‐,π‐ γ) 10ΛB 0.8~0.93GeV/c(BNL E930)
Experimentally not observedExperimentally not observed3/2-
2-0.578 Δ + 1.41 SΛ + 0.014 SN ‐1.07 T + ΛΣ
195keV ‐15keV
(BNL‐E930)
EEγγ Experimentally not observed:Experimentally not observed:(1)Eγ below experimental sensitivity
→ E <~100keV
9B/
1-
10ΛB
γγ
→ Eγ< 100keV• Δ < 0.3• ΛΣ >> ‐15keVThree‐body force by
ΛΣ coupling• better wave function for 9B
(2) 2‐ (non spin‐flip) and 1‐ (spin‐flip) reversed in energy
p g‐‐ Not well known
reversed in energy• pk= 0.8~0.93GeV/c (BNL E930)
→ non spin‐flip population→ non spin flip population• pk = 1.8GeV/c (E13 J‐PARC)
→ spin flip/non spin flip
Expected yield and sensitivityExpected yield and sensitivityYield estimate
NK = 0.5 x 106 /spillTarget (7Li in Li2O) = 20cm x 2.0g/cm3 x 14/30 x 0.934 / 7 x 6.02x1023
∫dσ/dΩ(1/2;1) ΔΩ x BR(1/2+;1->3/2+) = 0.84 μb x 0.5ε(Ge) x ε (tracking) = 0.7 x 0.6 => Yield (3/2+->1/2+) = 7.3 /hr(1000 spill)
= 3600 / 500 hrsBackground estimated from E419 7ΛLi spectrum
Stat. error Δτ/τ = 5.4%Δ|g -g |
Fitting result: 0.478±0.027 psSyst error < 5%
Δ|gΛ-gc||gΛ-gc|
~ 3%=>
Syst. error < 5%mainly from stopping time
H ParticleH Particle
• predicted by R.L.Jaffe in 1977– uuddss
Phys. Rev. Lett. 38 (1977) 195
– JPC = 0++
– M = 2150 MeV/c2 by MIT bag model
• Color‐magnetic interaction/⋅⋅−=Δ ∑ mm jijiji λλσσα
rrrr N: # of constituent quarks
Δ 24 for H
)1(34
218/ 6 ++−=⋅⋅∑
<
<
JJCNmmji
jijiji
ji
λλσσrrrr C6: SU(6)flavor‐spin Casimir operator
– Δ=−24α for H
• ΣΣ−Ξ+ΛΛ=83
84
81 NH
888
Mass of H and ΛΛ hypernucleusMass of H and ΛΛ hypernucleus
If MH > 2MΛ, H decays to ΛΛ viastrong interaction.MH < 2MΛ.H Λ
If double‐Λ hypernucleus whichdecays via weak interaction exists, mass of H is limitted,exists, mass of H is limitted,MH > 2 MΛ – BΛΛ.
Z)(2BZ)(B Z)(B)ZM()M(2)ZM(Z)(B
1AAΛΛ
A
A2AAΛΛΛΛ
−ΛΛΛΛΛΛΛΛ
ΛΛ−
−=Δ−Λ+=
ΛΛ Interaction Energy
ΛΛ Nucleus Events (1)ー Emulsionー
D.J.Prowse, PRL17(1966)782M.Danysz et. al, NP49(1963)121
10ΛΛBeor
ΔBΛΛ=4.5±0.4 MeV
6ΛΛHe ? ΔBΛΛ=4.7±1.0 MeV
11ΛΛBe ΔBΛΛ=3.2±0.6 MeV
ΛΛ Nucleus Events (2)ー Couter‐Emulsion Hybrid Method ー
S.Aoki, et. al, KEK PS E373Prog. Theor. Phys. 85 (1991)1287
KEK PS‐E176
KEK PS‐E373
Demachiyanagi‐Event
Ξ 12C 10 B (*) tΞ− + 12C −> 10ΛΛBe(*) + t
BΛΛ = 12.3±0.2 MeVΔBΛΛ = −1.1±0.2 MeV(g.s.)
0 3
+0.3−0.1+0.3−0.1
side‐view
ΔBΛΛ = 1.9±0.2 MeV(e.s.)+0.3−0.1
3‐body case3‐body caseΔBΛΛ > 1.5 MeV+2.4
−0.7
10ΛΛBeor
ΔBΛΛ = ‐4.9±0.7 MeVor
13ΛΛB ΔBΛΛ = 4.9±0.7 MeV
Counter‐Emulsion Hybrid Methodー KEK PS E373 ー
• Identify Ξ− production via the (K−,K+) by spectrometer• Measure the track of Ξ− by SciFi‐Bundle detector • Search for Ξ− absorption point (and its decay) in the emulsion• Search for Ξ absorption point (and its decay) in the emulsion
Twin Λ Hypernuclei EventsTwin Λ Hypernuclei EventsSecond Event in E373
Ξの吸収点から2つのΛハイパー核が生成
Ξの束縛エネルギーを求める
Twin Λ Hypernuclei EventsTwin Λ Hypernuclei Events• E176 Yokohama Event • E373 First Event PLB500(2001)37
– Ξ−+12C−>4ΛH+9ΛBe BΞ=0.54±0.20 MeV
– Ξ−+14N−>4ΛH+11ΛB BΞ=0.35±0.20 MeV
– Ξ−+16O−>4 H+13 C B =6 62 MeV
– Ξ−+14N−>5ΛHe+5ΛHe+4He+n
BΞ=−2.6±1.2 MeVconsistent with the capture +0.23
Prog. Ther. Phys. 89(1993)493
– Ξ + O−> ΛH+ ΛC BΞ=6.62 MeV
• E176 Korea Event– Ξ−+12C−>4
ΛH+9ΛBe BΞ=3.70 MeV12 4 9
from the atomic oribit
• E373 Second Event– Ξ−+12C−>7
ΛLi(*)+6ΛH+0.18
‐0.22
‐0.190 18
PLB355(1995)45
– Ξ−+12C−>4ΛH+9ΛBe* BΞ=0.62 MeV
– Ξ−+12C−>4ΛH*+9ΛBe BΞ=2.66 MeV
• E176 Kariya Event
Ξ + C > ΛLi( )+ ΛH
BΞ=1.6±0.3 MeV (g.s.)
BΞ=0.9±0.3 MeV (e.s.)– Ξ−+12C−>7 Li(*)+5 He+n
+0.18
+0.18‐0.19
‐0.19
Ξ + C > ΛLi( )+ ΛHe+n
BΞ=1.1±0.4 MeV (g.s.)
BΞ=0.4±0.4 MeV (e.s.)Ξ−+14N >9 Be(*)+5 He+n– Ξ +14N−>9
ΛBe( )+5ΛHe+n
BΞ=10.0±1.0 MeV (g.s.)
BΞ= 6.9±1.0 MeV (g.s.)
E373 Thi d E t
Attractive Potential for Ξ‐A and Ξ‐N ?
• E373 Third Event
中性子過剰ハイパー核を探る中性子過剰ハイパー核を探る ((E10 E10 実験)実験)
ハイパー核に関する研究
(K π)や (π K)反応を用いるのが主流
ハイパー核の構造ハイペロン・核子間力バリオン間力の統合的理解
通常の原子核 従来のハイパー核研究 J‐PARCで可能になる
(K,π) や (π,K) 反応を用いるのが主流 バリオン間力の統合的理解
通常の原子核 従来のハイパ 核研究ハイパー核研究
(K-,π-) 反応
(π+,K+) 反応
などを利用
荷電交換なし
中性子過剰ハイパー核
2重荷電交換反応(DCX)
(K-,π+)および (π-,K+) 反応を利用ハイパ 核の生成・研究
中性子過剰ハイパー核の特徴中性子多数環境のハイペロン・核子間力
ラムダ・シグマ混合中性子星の構造
ラムダ・シグマ混合の効果 中性子数とハイパー核構造の変化
中性子多数環境のハイペロン 核子間力
過剰中性子による構造変化
中性子星の構造より多様な核構造
ラムダ・シグマ混合の効果 中性子数とハイパー核構造の変化
コアが結合の強い通常の通常の原子核原子核
ラムダラムダハイパー核ハイパー核
原子核の場合ΔΔNN
ΣΣNN
原子核原子核 ハイパー核ハイパー核原子核原子核 Λ
コア核+ラムダ
nary
ΛΛNN290MeV
77MeV励起励起
Λ
コアが結合の弱い原子核の場合
Ordi
ΛΛNN290MeV
通常原子核の通常原子核の場合の場合の1/4 1/4 の差の差
励起励起原子核原子核
Λ
n
コア核変形(励起)
ラムダ 核子間力が強くなる
NNNN →→ 大きな混合大きな混合
ハイパー核ハイパー核
n中性子過剰
ハイパー核の場合
ハイパ 核
Exotic
ラムダ・核子間力が強くなる
中性子星の内部構造・進化
ハイパー核+中性子ハロー