YN/YY 相互作用とハイパー核ΞN interaction をめぐって

Y. YamamotoTsuru University

2007/3/2 伊勢志摩

核力から核構造・反応へ

核物理の原点・ Shell model の成立・ BBG theory G-matrix

lowest order

G-matrix theory は核物理における確立した基礎理論　　　　　　　　　　　有用なツール

Nuclear Saturation Problem は基本的には解決済み

Nuclear saturation curve for ESC04

Fujita-Miyazawa

including MIR

MIR is quite similar to Illinois-TBR

中性子星

Nucleon optical potential

Hyperon-nucleus potential

derived in the same frameworkfrom underlying BB interactions

背景に同じ物理がある

核力　　　 G-matrix interaction folding

核力から核構造YN/YY hypernuclei

本当の意味は？

bare interaction を使って計算すれば良いということではない！

π

玉垣さんのテキストより

π

核力の特性とメソンの役割

● OPEP tail π● 領域Ⅱの強い引力　“ σ”● テンソル力　 π-ρ● LS 力　“ σ”+ω+ρ ● repulsive core

原子核の性質領域Ⅲの性質は顕著には現れない（ひっそりと支える）テンソル力は２次項が支配的役割

QM core ?

原子核における π もしくはテンソル力

dominant rolesdominant roles “σ” の実体、３体力　　　　 saturation のコントロール

minor rolesminor roles OPEP tail effective tensor による weak mixing

by 玉垣さん2000/7Before NAGARA

σ-meson の実体

Fujita-Miyazawa TBF

核力における引力の主要項

2π-exchange via Δ-excitation

ΛΛΛΛ 引力は弱い引力は弱い

ESC では pair terms

PS, S, V, AV nonets

PS-PS exchange

(ππ),(πρ),(πω),(πη),(σσ)

not taken

ESC modeling

Repulsive core の成因

ESC ポメロン +ω 　　　チャネル・状態依存性はあまりない

FSS/fss2 QM に特有のチャネル依存性がある

ハイパー核で領域Ⅲを見れるか？

領域Ⅲ

実は ESC04 の顕著な特質は r<1 fm に依拠しているheavy mesons

Region Ⅲ = repulsive core ではない !? 　豊かな物理 ?

ハイパー核物理の目標Λ 核の諸特性、 Σ 核、 ΛΛ 核、 Ξ 核 ・・・多様な存在形態を相互作用の特質(mesons & core) と関連付けて統一的に理解すること

S=0 系には登場しない多彩なメソンの役割は？領域Ⅲの特質はいかに発現するか？

YN/YY 相互作用の研究はストレンジネス多体系の新たな質の発見と連動する現在進行形である

ESC-modeling における新たな実体（多様な pair terms 、 AV mesons)の導入は、その方向に沿った試みである

attractive UΞ 、 repulsive UΣ 、 small s.o. splitting

BNL-E885

U0 ～ -14 MeV

Motoba’s calculation

P-state nuclearbound state

UΞ ～ -16 MeV

KEK-E176

Our methodology

① Study of Ξ hypernuclei/ΞN interaction is in a phenomenological stage ( 現象論的段階）

② Our starting point is to consider the experimental suggestions of attractive UΞ( ～ -14MeV) as a working assumption ( 作業仮説）

③ ΞN interaction models giving rise to attractive UΞ

are investigated through structure calculations for Ξ hypernuclei

Special modeling in NDrelated to attractive ΞN interaction

not taken

まずは古い話から・・・

ΞΞNN NNNN

No space-exchange component in VΞN(OBE)because S=-2 cannot be carried by a boson

Another possibility ESC04dESC04d 　　　　　　　　　

A longstanding model giving attractive UΞ

NHC-DNHC-D

Special modeling to include only singlet scalar meson (σ)

NHC-FNSC89NSC97

repulsive!

What difference from NHC-D ?

Extended Soft-Core Model ESC0 ４

●Two-meson exchange processes are treated explicitly no effective bosons are used

●PS, S, V, AV meson-nonets are taken into account

● Meson-Baryon coupling constants are consistent with Quark-model predictions

Parameter fitting G-matrix Hypernuclear data

not only YN scattering data

Phys. Rev. C73, 044008 (2006)

Different predictions for Ξ hypernuclear states

most interesting for Ξstates

From the particle-physics point of viewFrom the particle-physics point of viewESC04d is favoredESC04d is favored 1. pv-coupling for the pseudo-scalar mesons1. pv-coupling for the pseudo-scalar mesons 2. SU3-symmetry for the couplings2. SU3-symmetry for the couplings

ESC06

ESC04

Too complicated ???

ΛΛ phase shifts

Old data

NagaraPair

Pair

Strong ΛΛ-ΞN coupling from Pair terms

Total

Total （ repulsion ）

OBE

diagonal coupling

Pair

Exp 　 ~ 1.0

ESC04 models are consistent with NAGARA data

Strong Ξ Ｎ -ΛΛ coupling

strong P-state attractionStrong 13S1 attraction !

Adjustable parts: ESC04 Medium-induced repulsion NHC-D Hard-core radius

Specific bound states in 2-,3-,4-body systems

OBE

Pair

Total

ΛN: Pair attractive OBE repulsive

On the other hand

Λ Ｎ 　 caseCanceling of Scalar and VectorCanceling of Scalar and Vector

S

V

S

V

OBEOBErepulsiverepulsive

PairPairattractiveattractive

PS V

S AV

OBE attraction in Ξ Ｎ 13S1 state

Canceling ofV and AV

Attraction of S appears

cancel

attractive

ω

a1

ε

A folding model for Ξ-hypernuclei

Density-dependent G-matrix interaction

Lane term

includingimaginarypart

(standard in derivations of optical potential)

Ξ-+closed-core systems

Mass-dependenceConversion widthNote!Note!

adjusted

Ξ hypernuclei produced by (K-,K+) reactions on available targets

Lane term ~ (N-Z+1)/4

(K-,K0)

N=Zcores

N>Zcores

available

with ESC04d

(K-,K+)

Features of ESC04d and NHC-D

ESC04d NHC-D

Mass-dep of BΞ weak strong

Lane term strong weak

light Ξ-states ○ 　　　　　 × 　　

Conversion width 　　　　　　 　 large small 　

In the case of FSS/fss2

Conclusion （ ESC04 and Ξhypernuclei ）

A ”solution” of ESC04 modeling leads to attractive UΞ

U0≒-14 MeV(if true) is realized by strong strong 1313SS11 attraction attraction in ESC04 model

There exist some s-shell some s-shell ΞΞ-bound states-bound statesdominated by 13S1 components

Conversion width ΓΞ is large due to strong ΞN-ΛΛ coupling in 11S0 state

These features are completely different from FSS/fss2 models!!!