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Structures of light halo nuclei
Creative Research Institute “Sousei”, Hokkaido Univ. M. Kimura Meme Media Laboratory, Hokkaido Univ.
N. FurutachiHigh energy Accelerator Research organization (KEK) A. DoteYukawa Institute for Theoretical Physics Y. Kanada-En'yo
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Introduction
Two-neutron halo
One-neutron halo
One-proton halo
Importance of core excitation in halo nuclei8B: one-proton halo nucleus
- From the measurements of 12C(8B,7Be+γ)X and 208Pb(8B,7Be+γ)X reactions
13% of 7Be* (Jπ=1/2+ at 429 kev) componet
11Be: one-neutron halo nucleus
D. Cortina-Gil et al, Nucl. Phys. A 720 (2003), 3
18% of 10Be* (Jπ=2+ at 3.34 MeV) componet
- From the measurements of 9Be(11Be,10Be+γ)X reaction
19C: one-neutron halo nucleus
Core enlargement has been proposed from systematic analysis ofinteraction cross section and ligitudinal momentum distribution measurements
R. Kanungo, I. Tanihata, A. Ozawa, Phys.Lett. B512 (2001), 261
T. Aumann et al, Phys. Rev. Lett. 84 35, (2000)
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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
・ Core excitation is naturally described as same as ordinary AMD ・ Description of halo structure is improved over that of ordinary AMD
Two-dimensional generator coordinate method (GCM) is introduced
Introduction
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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
Application to 8B and 9C
Investigation of halo structure involving core excitation
- 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
Introduction
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MAMD AMD wave function
Improvement of nucleon wave function
Ordinary AMD
MAMD
Framework
α=2 for |N-Z| neutron-(proton-) wave functions in neutron (proton)rich nuclei, and α=1 for other nucleon wave functions
Multiple-width Gaussian basis AMD( )
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Variational function
Hamiltonian
Energy variation; Volkov No.2+G3RS force
Angular momentum projection
Framework
GCM
Generator coordinate; proton and neutron radius (in He isotopes, generator coordinate is matter radius)
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MAMD AMDEXP.
4He6He 8He
10He
Efficiency of MAMD Results
Binding energy of He isotopes
Density distribution of 6,8He
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Efficiency of MAMD: 6He
Wave function of 6He
Width parameter : 1.39 fm 2.13 fm (AMD: 1.54 [fm])
Spatial extension of neutron density distribution is described
Description of shell-like structure is improved
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Efficiency of MAMD: 8He
Wave function of 8He
Width parameter : 1.41 fm 2.50 fm (AMD: 1.54 [fm])
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E [MeV] rm [fm] r
p [fm] r
n [fm] Q [e fm2] μ[μ
n]
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)
Results of 8B and 9CDensity distributions
Energy, radii, electric and magnetic moments
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8B の計算結果
Energy surface
(a)
(b)
(c)
E [MeV] rm [fm] Q [e fm2] μ[μ
n]
(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 1.11GCM -35.7 2.50 4.3 0.95Exp. -37.38 2.55 6.45 1.04
Importance of core clustering in 8B
(c)
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Energy surface
E [MeV] rm [fm] Q [e fm2] μ[μ
n]
(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 -1.11GCM -39.2 2.40 -3.2 -1.72Exp. -39.72 2.42 -1.39 (Sch. -1.91)
Importance of core clustering in 9C
(d)
(e)
(f)
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Summary
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
Investigation of halo structure involving core excitation
Efficiency of MAMD in describing halo structure was demonstrated
Simultaneous description of spatial extension and shell-like structure of valence neutrons → Binding energies and radii of 4,6,8He are systematically reproduced
9CBoth of α+3He cluster structure and shell-like structure in coreare 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
He isotopes