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Structures of light halo nuclei. Creative Research Institute “Sousei”, Hokkaido Univ. M. Kimura Meme Media Laboratory, Hokkaido Univ. N. Furutachi High energy Accelerator Research organization (KEK)

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## Structures of light halo nuclei

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**Structures of light halo nuclei**Creative Research Institute “Sousei”, Hokkaido Univ. M. Kimura Meme Media Laboratory, Hokkaido Univ. N. Furutachi High energy Accelerator Research organization (KEK) A. Dote Yukawa Institute for Theoretical Physics Y. Kanada-En'yo**Introduction**Importance of core excitation in halo nuclei 8B: one-proton halo nucleus 13% of 7Be* (Jπ=1/2+ at 429 kev) componet － From the measurements of 12C(8B,7Be+γ)X and 208Pb(8B,7Be+γ)X reactions D. Cortina-Gil et al, Nucl. Phys. A 720 (2003), 3 Two-neutron halo 11Be: one-neutron halo nucleus One-neutron halo 18% of 10Be* (Jπ=2+ at 3.34 MeV) componet One-proton halo － From the measurements of 9Be(11Be,10Be+γ)X reaction T. Aumann et al, Phys. Rev. Lett. 84 35, (2000) 19C: one-neutron halo nucleus Core enlargement has been proposed from systematic analysis of interaction cross section and ligitudinal momentum distribution measurements R. Kanungo, I. Tanihata, A. Ozawa, Phys.Lett. B512 (2001), 261**Introduction**Theoretical model for investigation of halo nuclei involving core excitation is proposed Multiple-width Gaussian basis AMD (MAMD) Nucleon wave function of AMD is improved －Superposition of Gaussian wave packets that have different width parameters Two-dimensional generator coordinate method (GCM) is introduced ・ Core excitation is naturally described as same as ordinary AMD ・ Description of halo structure is improved over that of ordinary AMD**Introduction**Efficiency of MAMD in describing halo structure is demonstrated Application to He isotopes －Core excitation is not expected in He isotopes. Description of halo structure in MAMD is discussed in detail Investigation of halo structure involving core excitation Application to 8B and 9C －α+3He+p and α+3He+p+p structures are expected in these nuclei. Structures of these nuclei are investigated focusing on their halo structure and core clustering**MAMD**Framework ) ( Multiple-width Gaussian basis AMD AMD wave function Improvement of nucleon wave function Ordinary AMD MAMD α=2 for |N-Z| neutron-(proton-) wave functions in neutron (proton) rich nuclei, and α=1 for other nucleon wave functions**Variational function**Framework Hamiltonian Energy variation ；Volkov No.2+G3RS force Angular momentum projection GCM Generator coordinate; proton and neutron radius (in He isotopes, generator coordinate is matter radius)**Results**Efficiency of MAMD Density distribution of 6,8He Binding energy of He isotopes MAMD AMD EXP. 10He 6He 8He 4He**Efficiency of MAMD: 6He**Spatial extension of neutron density distribution is described Description of shell-like structure is improved Wave function of 6He Width parameter： 1.39 fm 2.13 fm (AMD: 1.54 [fm])**Efficiency of MAMD: 8He**Wave function of 8He Width parameter： 1.41 fm 2.50 fm (AMD: 1.54 [fm])**Results of 8B and 9C**Density distributions Energy, radii, electric and magnetic moments E [MeV] rm [fm] rp [fm] rn [fm] Q [e fm2] μ[μn] 8B(2+) MAMD -35.7 2.50 2.64 2.24 4.3 0.95 AMD -34.7 2.48 2.60 2.26 4.2 0.96 Exp. -37.38 2.55 6.45 1.04 9C(3/2-) MAMD -39.2 2.40 2.54 2.08 -3.2 -1.73 AMD -36.1 2.26 2.35 2.07 -2.7 -1.72 Exp. -39.72 2.42 -1.39(Sch. -1.91)**Importance of core clustering in 8B**Energy surface 8Bの計算結果 (a) (b) E [MeV] rm [fm] Q [e fm2] μ[μn] (a) -32.1 2.26 2.9 0.77 (b) -31.8 2.35 2.2 0.72 (c) -31.7 2.55 4.7 1.11 GCM -35.7 2.50 4.3 0.95 Exp. -37.38 2.55 6.45 1.04 (c) (c)**Importance of core clustering in 9C**Energy surface (d) (e) E [MeV] rm [fm] Q [e fm2] μ[μn] (d) -35.6 2.36 -2.7 -1.43 (e) -34.7 2.21 -1.9 -1.94 (f) -34.2 2.27 -2.5 -1.11 GCM -39.2 2.40 -3.2 -1.72 Exp. -39.72 2.42 -1.39 (Sch. -1.91) (f)**Summary**Efficiency of MAMD in describing halo structure was demonstrated He isotopes Simultaneous description of spatial extension and shell-like structure of valence neutrons → Binding energies and radii of 4,6,8He are systematically reproduced Investigation of halo structure involving core excitation 8B Core has α+3He structure. Described as weakly bound α+3He+p three-body system Core clustering is important to explain large experimental value of electric quadrupole moment. －Electric quadrupole moment is sensitive to relative distance between α and 3He clusters, but insensitive to development of proton halo 9C Both of α+3He cluster structure and shell-like structure in core are important for binding of 9C Development of core clustering is important to explain experimental value of magnetic dipole moment that have large deviation from Schmidt value

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