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不安定核でさぐる中性子星の核物質 B02 班報告 B02 班：中性子過剰な中低密度核物質の物性 中村隆司 Takashi Nakamura 東京工業大学 ２０１７年２月１６－１８日、第５回ウィンタースクール研究会

B02 班：中性子過剰な中低密度核物質の物性 計画研究 中村隆司 , 栂野泰宏 , 近藤洋介 , 小林信之 * 四方瑞紀 , 尾崎友志 , 齋藤敦美 , 坪田潤一、斗米貴斗、 平山晃大 , 安田昌弘 , 山田啓貴 , 松本真由子 , 東工大 * 現：阪大核物理研究センター 下浦享 , 木佐森慶一 他 , ＣＮＳ東大 寺西高 , 九州大学 公募研究 関口公子 , 東北大 民井淳 , 阪大 RCNP 山口貴之 , 埼玉大 小澤顕 , 筑波大学 板橋健太 , 理研

EOS δ = ρ n − ρ p ≈ N − Z A ρ 0 P = ρ 2 ∂ E Equation of State of Nuclear Matter E=E( ρ , δ ) ∂ ρ Energy/nucleon Hydrostatic Equilibrium (General Relativity: T.O.V. Eq.) + EOS à Radius, Maximum Mass, Mass-Radius Relation of N Star EOS of Nuclear Matter Pressure (Nuclear/Hadronic Interactions, E( ρ , δ ) + Fermi motion) A=N Stiffer(Softer) EOS à Pressure is high(low) N=Z à Larger(Smaller) mass is sustainable J Self-Gravity(Attractive) S( ρ )?? EOS of nuclear matter using Atomic Nuclei (nucleonic D.O.F) p Direct determination of S( ρ ) and EOS p Provide Basis of EOS with non-nucleonic D.O.F

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 /surface of neutron star? S=0 a= -18 fm M.Matsuo PRC73,044309(2006). (s) 2 (s) 2 +(p) 2 +(d) 2 + … A.Gezerlis, J.Carlson, PRC81,025803(2010) θ∼ 1/ l n-star Possible dineutron site 2n Halo Nuclei? 2n weakly-unbound nuclei? n n 9 Li 24 O n 26 O 11 Li n Hagino, Sagawa, PRC93,034330(2016) S 2n =0.37MeV S 2n = - 0.018(5) MeV Mixture of d 2 ,s 2 ,p 2 T.Nakamura PRL96, 252502 (2006). Kondo, TN et al., PRL116,102503(2016).

Approaches to Neutron-Star Physics p S( ρ ) : J , L ( pressure ), K sym ( Incompressibility ) ß Collective Motion of Neutron-rich Nuclei— Neutron Skin n-skin Y.Togano, M. Shikata, Ozaki, Pygmy Dipole CATANA à PDR of 50,52 Ca, Core Resonance (E1) à Togano’s Talk PDR/M1 of Stable Nuclei Tamii et al. PDR p Superfluidity ß Dineutron correlation in low-dense matter — Halo Coulomb Breakup of 2n Halo 22 C and 19 B Deformed Driven Halos : 31 Ne, 37 Mg TN et al., PRL112,142501(2014). n n N.Kobayashi, TN et al.,PRL112, 242501(2014). p S( ρ ) ß Nuclear force (density dependence, isospin dependence, 3N/4N force) ß Tetra neutron, Exotic nucleonic system 4n 26, 28 O 4n, Kisamori, Shimoura PRL116, 052501 (2016). 26 O, Y.Kondo et al. PRL116, 102503(2016). 3N force à Sekiguchi et al. p S( ρ ) ß Bulk Property ß Masses, Radii Yamaguchi,Ozawa

RI Beam Factory at RIKEN 2007~ ECR RILAC CSM GARIS & SCRIT GARIS2 RILAC2 SAMURAI AVF ZeroDegree Rare RI Ring RIPS RRC SRC SLOWRI SHARAQ fRC KISS BigRIPS IRC In-Flight RI Separator with large acceptance SRC: World Largest Cyclotron (K=2500 MeV) Heavy Ion Beams up to 238 U at 345MeV/u (Light Ions up to 440MeV/u) eg. 48 Ca: ~700pnA (~4x10 12 pps) ~10 times compared to 2008 238 U: ~30pnA (~2x10 11 pps) ~10 3 times compared to 2007

1 CNS, The University of Tokyo 3 Kyoto University Sciences 12 National Institute of Radiological 11 IPN Orsay 10 Kyushu University 9 NSCL, Michigan State University 8 the University of Tokyo 7 University of Miyazaki 6 Tokyo Institute of Technology 5 CYRIC, Tohoku University 4 RCNP Osaka University 2 RIKEN Nishina Center Tetra Neutron State Populated by 4 He( 8 He, 8 Be) Reaction --SHARAQ06 Collaboration-- K. Kisamori 2 , S. Shimoura, S. Noji, A. Stolz, T. Kawabata, T. Baba, M. Tsumura H. Miya 2 , S. Sakaguchi 2 S. Michimasa, S. Ota, T. Fujii, S. Go, E. Ideguchi, K. Miki, A. Tamii S. Kawase, M. Kobayashi, Y. Kubota 2 , D. Beaumel, M. Assie, F. Hammache C. S. Lee 2 , Y. Sasamoto, M. Takaki, M. Itho L. Tang, H. Tokieda, K. Yako, R. Yokoyama Y. Kondo H. Matsubara H. Baba, M. Dozono, N. Fukuda, Y. Maeda N. Inabe, D. Kameda, T. Kubo, M. Kurata-Nishimura, H. Sakai, T. Nishi M. Sasano, H. Sato, Y. Shimizu, H. Suzuki, H. Takeda, S. Takeuchi, T. Uesaka, Y. Yanagisawa 7

4n Why tetra neutron? K.Kisamoro,S.Shimoura et al. Ab-initio calculation Neutron-rich Λ nucleus S. C. Piper, Phys. Rev. Lett. 90, pure neutron matter 252501 (2003) n neutron star • Bound 4 n cannot exist • Possible resonance state 2 MeV Universality of few-body Fermion 4n in breakup of 14 Be : system Marques et al. PRC 65 (2002) 044006 Clarify whether the four-neutron system, “tetra neutron”, can exist as a resonance state

Design of the Experiment K.Kisamoro,S.Shimoura et al. p Reaction : 4 He( 8 He, 8 Be)4n 4n 8 He Q= Q= ・ Reaction with unstable beam -30.9 MeV → 4n system +27.7 MeV Compensate with small momentum transfer. (almost recoil-less condition) 4 He 8 Be Target Projectile Missing-mass spectroscopy p ü SHARAQ spectrometer at RIBF → high resolution: ~ 1 MeV ü 2 α detection at 200 MeV/u → good signal-to-noise ratio 9

E １ ＋ ＋ LUPO E CRDC 2 CRDC 1 2 ＋ FADC t Disc. Disc. (FPGA) 2 １ ＋ x direction T/H (trigger) ＋ drift plane cathode pad anode wire ADC ＋ ＋ ＋ Plastic Scintillator - discri. - - - y direction Multiplexer SHARAQ Spectrometer α α - - -- V １ 2 Readout system of 2 α ( 8 Be) part of collaborators Liquid He target 8He beam (2 Mcps; 190 A MeV) CNS-RIKEN-Tokyo-TITech-Kyoto- Slide by S.Shimoura Tohoku-Osaka-Kyushu-Miyazaki-NIRS- IPNO-NSCL

Experimental Results 12 continuum + background (a) background × 10 10 wave packet just after reaction Counts/ 2 MeV 8 resonance direct decay 6 4 2 0 -20 -10 0 10 20 30 40 50 60 E 4 n (MeV) 7 K.Kisamori, S.Shimoura et al., PRL 116 , 052501 (2016).

Spectroscopy of Barely Unbound 2n emitter 26 O (& Other studies on unbound oxygen isotopes) Yosuke Kondo et al. 25,26 O: Y. Kondo et al., Phys. Rev. Lett. 116, 102503, (2016)

Study of unbound nuclei 25 O and 26 O at SAMURAI Spokesperson Yosuke Kondo Experimental study of unbound oxygen isotopes towards the possible double magic nucleus 28 O T. Otsuka et al., PRL105, 032501 (2010). 28 Ne 26 Ne 29 Ne 31 Ne 32 Ne 24 Ne 25 Ne 27 Ne 30 Ne Drip line Drip line 30 F 23 F 24 F 25 F 26 F 27 F 28 F 29 F 31 F 22 O 23 O 25 O 26 O 27 O 28 O 24 O Z =8 21 N 22 N 23 N N =20 Oxygen Anomaly 20 C 21 C 22 C 3N force: significant at N>16 G. Hagen et al., PRL108, 242501(2012). N =16? 19 B H. Hergert et al., PRL110, 242501(2013). 7 ５ 0keV ? S.K.Bogner et al., PRL113, 142501(2014). 25 O+n Continuum Effect: x A.Volya, V.Zelevinski, PRL94,052501(2005). ? K. Tsukyiyama, T. Otsuka, PTEP2015, 093D01 (2015). 26 O nn correlations: 24 O+2n L.V. Grigorenko et al., PRL111,042501(2013). E. Lunderberg et al.PRL108, 142503 (2012) C. Caesar et al.PRC88, 034313 (2013). K. Hagino, H. Sagawa PRC89,014331(2014).

Experimental Setup at SAMURAI at 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

26 O Results 27 F+C à 26 O à 24 O+2n 26 O 26 O Decay Energy (MeV) Ground state (0 + ) N=16 shell closure is confirmed 5 times higher statistics than previous study USDB cannot describe 2 + energy at 18±3(stat)±4(syst)keV 26 O Finite value is determined for the first time à effects of 1 st excited state (2 + ) pf shell ?, continuum ? Observed for the first time 2n Correlations ?, 3N force? 1.28 +0.11 -0.08 MeV Y. Kondo et al., Phys. Rev. Lett. 116, 102503, (2016)

Masses of Oxygen Isotopes Beyond the dripline Doubly Magic Or not? 1.28(11) MeV (2 + ) 749(10) keV ? Extremely weakly Weakly Unbound 4n UNBOUND state! Emitter or not? 25 O+n 18(5) keV 0 + 24 O+2n 25 O+ n 26 O 27 O+n 28 O 24 O+4n 25 O+3n 26 O+2n Centrifugal Barrier E n E n n S 2n = - 0.018(5) MeV 24 O n 24 O n Kondo et al., PRL2016 n Strong 4n correlation? Or 2x 2n correlation? Strong 2n correlation?

27,28 O measurements in 2015 (SAMURAI21) Slides: Y.Kondo MINOS Superconducting MWDC NeuLAND NEBULA Dipole Magnet 2Plastics (B=2.9T) n DALI2 2 MWDCs n NeuLAND MINOS n MWDC n 29 F (from BigRIPS) Hodoscope 24 O

Day-one Collaboration Tokyo Institute of Technology: Y.Kondo , T.Nakamura , N.Kobayashi, R.Tanaka, R.Minakata, S.Ogoshi , S.Nishi, D.Kanno, T.Nakashima, J. Tsubota, A. Saito LPC CAEN: N.A.Orr , J.Gibelin , F.Delaunay, F.M.Marques, N.L.Achouri, S.Leblond, Q. Deshayes Tohoku University : T.Koabayshi, K.Takahashi, K.Muto RIKEN: K.Yoneda, T.Motobayashi ,H.Otsu, T.Isobe, H.Baba,H.Sato, Y.Shimizu, J.Lee, P.Doornenbal, S.Takeuchi, N.Inabe, N.Fukuda, D.Kameda, H.Suzuki, H.Takeda, T.Kubo Seoul National University: Y.Satou, S.Kim, J.W.Hwang Kyoto University : T.Murakami, N.Nakatsuka GSI : Y.Togano Univ. of York: A.G.Tuff GANIL: A.Navin Technische Universit¨at Darmstadt: T.Aumann Rikkyo Univeristy: D.Murai Universit´e Paris-Sud, IN2P3-CNRS: M.Vandebrouck