2007/3/2 伊勢志摩 YN/YY 相互作用とハイパー核 ΞN interactionをめぐって Y. Yamamoto Tsuru University 核力から核構造・反応へ 核物理の原点 ・Shell model の成立 ・BBG theory lowest order G-matrix 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 中性子星 including MIR Fujita-Miyazawa MIR is quite similar to Illinois-TBR Nucleon optical potential Hyperon-nucleus potential derived in the same framework from 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！ 玉垣さんのテキストより π 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 QM core ? 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 原子核におけるπ もしくはテンソル力 dominant roles “σ” の実体、３体力 saturation のコントロール minor roles OPEP tail effective tensor による weak mixing 2π-exchange via Δ-excitation σ-meson の実体 核力における 引力の主要項 ESCではpair terms by 玉垣さん 2000/7 Before NAGARA Fujita-Miyazawa TBF ΛΛ引力は弱い ESC modeling PS, S, V, AV nonets not taken (ππ),(πρ),(πω),(πη),(σσ) PS-PS exchange 領域Ⅲ Repulsive core の成因 ESC ポメロン+ω FSS/fss2 チャネル・状態依存性はあまりない 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？ 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 Motoba’s calculation U0～ -14 MeV KEK-E176 P-state nuclear bound state UΞ～ -16 MeV 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 まずは古い話から・・・ Special modeling in ND related to attractive ΞN interaction not taken ΞN NN No space-exchange component in VΞN(OBE) because S=-2 cannot be carried by a boson A longstanding model giving attractive UΞ NHC-D Special modeling to include only singlet scalar meson (σ) Another possibility ESC04d What difference from NHC-D ? NHC-F NSC89 NSC97 repulsive! Phys. Rev. C73, 044008 (2006) Extended Soft-Core Model ESC0４ ●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 not only YN scattering data Hypernuclear data Different predictions for Ξ hypernuclear states most interesting for Ξstates From the particle-physics point of view ESC04d is favored 1. pv-coupling for the pseudo-scalar mesons 2. SU3-symmetry for the couplings ESC04 ESC06 Too complicated ??? ΛΛ phase shifts Old data Pair Nagara diagonal coupling Total OBE Total （repulsion） Pair Pair Strong ΛΛ-ΞN coupling from Pair terms Strong ΞＮ-ΛΛ coupling Exp ~ 1.0 ESC04 models are consistent with NAGARA data Strong 13S1 attraction ! strong P-state attraction Adjustable parts: ESC04 Medium-induced repulsion NHC-D Hard-core radius Specific bound states in 2-,3-,4-body systems Pair OBE Total On the other hand ΛN: Pair attractive OBE repulsive OBE repulsive Pair attractive ΛＮ case Canceling of Scalar and Vector V V S S OBE attraction in ΞＮ 13S1 state PS Canceling of V and AV Attraction of S appears V ω cancel S ε attractive AV a1 A folding model for Ξ-hypernuclei Density-dependent G-matrix interaction including imaginary part Lane term (standard in derivations of optical potential) Ξ-+closed-core systems adjusted Note! Mass-dependence Conversion width with ESC04d Lane term ~ (N-Z+1)/4 available (K-,K+) N=Z cores N>Z cores (K-,K0) Ξ hypernuclei produced by (K-,K+) reactions on available targets Features of ESC04d and NHC-D Mass-dep of BΞ Lane term light Ξ-states Conversion width ESC04d NHC-D weak strong strong ○ large weak × 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 13S1 attraction in ESC04 model There exist some s-shell Ξ-bound states dominated 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!!!
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