(B02 Exotic nuclei for - PowerPoint PPT Presentation

エキゾチック核子多体系で紐解く物質の階 層構造 (B02 班） Exotic nuclei for investigating hierarchical structure of matter (Grp-B02) 中村隆司 Takashi Nakamura Tokyo Institute of Technology Kickoff Symposium, “Clustering as a window on the hierarchical structure of quantum systems”, O-Okayama Campus, Tokyo Institute of Technology, Nov. 19-20, 2018

Contents • Introduction • Dineutron Cluster • Semi-hierarchy at the neutron-rich limit • Spectroscopy of Oxygen isotopes • Planned Experiments – Multi-neutron cluster • Summary and perspectives

Towards the neutron-rich limit Nuclear Chart Where is the boundary of existence of nuclei? How the nuclear properties (shell, collectivity) change? New Phenomena due to weak binding, change of surface Neutron Halo/Skin Dineutron, Neutron droplet Neutron Matter 82 New Paradigm Proton Number Z Origin of matter (Nuclear Astrophysics) 126 50 82 28 20 50 8 28 Neutron-rich Nuclei: Can be a bridge to a neutron star 20 2 8 n-star 2 Neutron Nubmer N

RI Beam Factory (RIBF) at RIKEN 2007~ The New-generation RI-beam facility in the world ECR K.Morita et al. RILAC Nh (Nihonium) 113 CSM GARIS & SCRIT GARIS2 RILAC2 SAMURAI AVF ZeroDegree Rare RI Ring RIPS RRC SRC SLOWRI SHARAQ fRC KISS BigRIPS In-Flight RI Separator with large acceptance IRC Production of RI beams: Fragmentation/ Inflight Fission SRC: World Largest Cyclotron (K=2500 MeV) High-Intense Heavy Ion Beams up to 238 U at 345MeV/u eg. 48 Ca: ~700pnA (~4x10 12 pps) ~10 times compared to 2008 238 U: ~70pnA (~4x10 11 pps) ~10 3 times compared to 2007

“ Dineutron cluster” in neutron-rich nuclei Dineutron exists in Nuclei? “ dineutron ” -states can be semi-hierarchy?

Clustering and Hierarchical Structure of Matter  Threshold: Clustering near Threshold  Semi-Hierar ar T archy y  Degree of Freedom ： Neutral alizat atio ion of Char arge, Spin(S), ), Isospin(T)  Degree of Separation: : Compositeness, Spectroscopic fac actor Ex  Larger Ex  Larger A=const. N/Z  Larger Hadron Hadron Quark 0  Color Charge N/Z ≫ ∞ 0  S 0  S, T E x E x E Neutron Halo Hoyle State L(1405) N + 𝐿 a cluster n 9 Li+2n a n Hadron 3 a N a a N/Z >2 Molecule 11 Li(3p+8n) dineutron cluster E x E E x u L Nucleus Nucleus N/Z ~1 d s Hadron 11 B(5p+6n) 12 C(gs)

Multi-neutron correlation (neutron cluster) near drip line Neutron-rich Nuclei Ordinary Nuclei Beyond drip line S n <1MeV -1MeV<S n <0MeV V continuum S p ~S n ~8MeV continuum Threshold n p n p n p Weakly bound/unbound nuclei --- Threshold ( Unitary limit )  Clustering Halo Nucleus Halo Nuclei Weakly Unbound Nuclei 4 n n 9 Li 4 n : “ Tetra neutron” E 4n = 0.83 ± 0.65 (stat)± 1.25 (syst) MeV 11 Li n K.Kisamori et al., PRL116, 052501 (2016) S 2n =0.37MeV 26 O : “ Weakly Unbound 2n” 24 O+2n E 2n = 0.018 ± 0.003(stat) ± 0.004(syst) MeV Y.Kondo et al., PRL116,102503(2016).

Dineutron? A.B.Migdal Strongly correlated “ dineutron ” on the surface of a nucleus Sov.J.Nucl.Phys.238(1973). n n Dineutron: n n @ Low-dense Neutron skin/halo? Unbound /Inner crust of Neutron star? S=0, T=1 a= -18.7 fm M.Matsuo PRC73,044309(2006). s-wave scattering length A.Gezerlis, J.Carlson, PRC81,025803(2010) neutron-star Possible dineutron site 2n Halo Nuclei? 2n weakly-unbound nuclei? q 12 (deg) n n 9 Li 24 O n 26 O 11 Li n r (fm) Hagino, Sagawa, S 2n = - 0.018(5) MeV S 2n =0.37MeV PRC93,034330(2016) T.Nakamura PRL96, 252502 (2006). Kondo, TN et al., PRL116,102503(2016).

What happens if there are ‘multiple’ dineutrons? n n n 24 O 26 O+2n n 24 O+4n 28 O 28 O ?? ~18 keV Dineutron-cluster? Dineutron-condensation? 7.65MeV a + 8 Be 3a Hoyle state a 12 C(0 + 2 ) 285keV 93keV a a alpha-cluster alpha-condensation? 12 C A.Tohsaki, H.Horiuchi, P.Schuck,G.Ropke, PRL 87, 192501 (2001).

Dineutron Clustering & Hierarchy Naïve Picture Surface-region: Dineutron-cluster hierarchy (made of dineutron-cluster) n n n n n n 10 He n n n n 28 O Core-region: Normal nuclear hierarchy (made of nucleons) Dineutron-cluster hierarchy: Semi-hierarchy?

Evolution Towards the Stability Limit Where is the neutron drip line? What are characteristic features of drip-line nuclei? How does nuclear structure evolve towards the drip line? Shell? Ca K Deformation? Ar Cl Halo? S Drip Line? P Si N=28 Continuum? Al Deformation Mg N=20 Driven Halo Na N.Kobayashi et al., Ne 37 Mg N=16 PRL 112 , 242501 (2014). F 31 Ne TN et al., PRL 112 , 142501 (2014). O N C B Oxygen Anomaly 26 O 28 O Be 21 B Li 1n halo known Multi-neutron cluster He 13 Li 2n halo known H candidates 10 He 6 He 4n halo/skin

Previous Experiments 我々の先行研究 Spectroscopy of Super-heavy oxygen isotopes --Barely Unbound 2n emitter 26 O & 4n emitter 28 O Yosuke Kondo, TN et al.

Knockout Reaction/Quasi-Free Reaction    20 27 F( 12 C,pX) 26 O  24 O+2n ( ), ( ), ( C ) P n P n P 24 O 24 O   27 F n 20 P ( n ), P ( C   n 26 O 20 ( ), ( C ) P n P ~210MeV/u 12 C p Invariant Mass Method  p   24 O+4n   29 F(p,pp) 28 O 20 20 P ( n ), P ( C ) ( ), ( C ) P n P n    24 O 20 29 F ( ), ( ), ( C ) P n P n P 24 O   n 20 P ( n ), P ( C ) p 28 O   n 20 P ( n ), P ( C )  p    n 20 P ( n ), P ( C ) 20 ( ), ( C ) P n P Invariant Mass Method: + High Yield, + Good Resolution ~ a few 100 keV - Require Measurement of All the Decay Particles Missing Mass Method: - Low Yield, - Worse Resolution ~ a few MeV + Measurement of projectile and recoil protons only Review: T.Nakamura, H.Sakurai, H.Watanabe, Prog. Part. Nucl. Phys. 97, 53 (2017).

Experimental Setup at SAMURAIat RIBF C target MWDC Ionization (1.8g/cm 2 ) Superconducting NEBULA Chamber n Dipole Magnet (B=3.0T) 2 MWDCs 2Plastics n 27 F ~210MeV/u DALI2 (from BigRIPS) MWDC 24 O Hodoscope

Result of 26 O 27 F+C  26 O  24 O+2n 1.28(11) MeV (2 + ) 749(10) keV 0 + 25 O+n 18(5) keV 24 O+2n 25 O+ n 26 O 24 O+4n 25 O+3n 26 O+2n Decay Energy (MeV) Centrifugal Ground state (0 + ) Barrier 5 times higher statistics than previous study 18 ± 3(stat) ± 4(syst)keV E Finite value is determined for the first time n 1 st excited state (2 + ) 24 O Observed for the first time n 1.28 +0.11 -0.08 MeV Y. Kondo et al., Phys. Rev. Lett. 116, 102503, (2016) dineutron correlation?

Towards 28 O (doubly magic nucleus?) 28 O measurement @ RIBF-SAMURAI MINOS Superconducting MWDC NeuLAND NEBULA Dipole Magnet 2Plastics (B=2.9T) n DALI2 2 MWDCs n NeuLAND MINOS n MWDC 29 F n (from BigRIPS) Hodoscope 24 O NeuLAND+NEBULA 15cm thick LH2  ~ 50% efficiency for 1n

Planned Experiments in this project Multi-neutron 4n and 6n states in extremely neutron-rich nuclei beyond the neutron drip line RI-beam  10 He, 21 Be, 28 O  4 n, 6 n n n n n n n 10 He n n n n 28 O 6 n 2 n Strong Inside, Weak outside? 中は強く、外は弱く ? nn interaction >> 2 n- 2 n interaction  (Semi)-Hierarchy (Strong Inside) (Weak Outside)

First exp. Focusing on 10 He: 6n states 11 Li(p,pp) 10 He* 10 He*  8 He+2n, 6 He+4n, 4 He+2n   20 ( ), ( C ) P n P  p    20 n 20 P ( n ), P ( C ) ( ), ( C ) P n P    n 11 Li 20 4 He ( ), ( ), ( C ) P n P n P 4 He   20 P ( n ), P ( C ) n   n 20 ( ), ( C ) P n P p 10 He   ~200 MeV/u n 20 ( ), ( C ) P n P  p    n 20 ( ), ( C ) P n P 20 ( ), ( C ) P n P Invariant Mass Method: + High Yield, + Good Resolution ~ a few 100 keV - Require Measurement of All the Decay Particles Missing Mass Method: - Low Yield, - Worse Resolution ~ a few MeV + Measurement of projectile and recoil protons only “6n” mass can be also extracted Submitted to RIBF NP-PAC in Oct. Doctor Thesis of T. Tomai

“Large - acceptance missing mass setup at SAMURAI” CATANA PLUS and STRAßE CsI(Na) Scintillators (E detector) CATANA PLUS Si Trackers Construction Proposal: Submitted to RIBF NP-PAC in Oct. TN, A. Obertelli (TU Darmstadt) et al.

Bridge between nuclear/hadron hierarchies & T. Wakasa 若狭智嗣 Deeper understanding of nuclear system/hierarchy K. Sekiguchi 関口仁子 π ω , ρ 2π, σ 2N system 0.5 1.0 1.5 2.0 [fm] r 1 r 1,2 r 1 r 1 r 1 3N system r 2 r 2 r 2 r 2 r 2 Short range Many-body force in vacuum Long range K.Sekiguchi Few-nucleon system Unified compare exp. data with understanding rigorous calc. (Faddeev) with s-quark Intermediate: N*, ∆∆,… Intermediate: ∆ nuclear nuclear multi-n matter structure (2n,3n,4n,…) Many-body NN scatt. in medium system experimentally deduce (in medium) 2NF in nuclear medium SR repulsion Vertex corr. to SR-2NF Vertex corr. to OPE T.Wakasa High density Low density In-medium 2-body force