three-body model study of unbound nucleus othree-body model study of unbound nucleus 26o --- nn2015...
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Three-body model study of unbound nucleus 26O --- NN2015 ---
June 22-26, 2105 Catania, Italy
1.di-neutron correlation and three-body model approach 2. Nuclei beyond drip line and 2n-decay 3. Summary and future perspectives
Hiroyuki Sagawa (RIKEN/U. of Aizu) and Koichi Hagino(Tohoku University)
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l Halo, Giant halo/skin structure l shell evolution l di-neutron and di-proton correlations l Shape evolution, shape coexistence l Anti-halo effect
l Coulomb breakup reactions l Nuclear breakup reactions l Nucleon transfer reactions l Direct two-nucleon decays l Sequential two-nucleon decays l n-n correlation measurements l Charge exchange reactions
Exotic structure close to drip lines
Nuclear reactions
How to probe these exotic structures ?
"100 years of subatomic physics" (Edited by E.M. Henley and S. D. Ellis) pp. 231-273 (World Scientific, 2013)
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Next generation RI beam facilities : e.g., RIBF (RIKEN, Japan)
Neutron number
Prot
on
num
ber
Prot
on
num
ber
Direct 2n decay Possible candidates 10He, 13Li, 16Be, 26O,
Direct 2p decay 17Ne, 20Mg
10He
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Nuclei beyond drip lines ---- direct two neutron decays -------
Direct 2n decay Possible candidates 26O,10He, 13Li, 16Be
Coulomb breakup
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27F à26Oà24O + 2n
R3B-LAND at GSI
2-neutron decay(MoNA@MSU)
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Density-dependent delta-force
core n
n r1
r2
VWS
VWS
G.F. Bertsch and H. Esbensen, Ann. of Phys. 209(’91)327 H. Esbensen, G.F. Bertsch, K. Hencken, Phys. Rev. C56(’99)3054 K.Hagino and H. S., PRC72(’05)044321 H. S. and K. Hagino, EPJA review (2015)
Di-neutron correlations and three-body model
11Li, 6He
All parameters are determined empirically to fit the s.p. energies of neighboring nuclei and n-n scattering lengths.
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Decay energy spectrum
24O
core n
n r1
r2
VWS
VWS
Ø 24O + n potential
e2s1/2 = -4.09 (13) MeV, e1d3/2 = + 770+20
-10 keV, Γ1d3/2 = 172(30) keV
Woods-Saxon potential to reproduce
Ø nn interaction
density-dep. contact interaction E (27F) = -2.69 MeV
continuum effects G0(I ) (E) = | ( j1 j2 )
(I )〉〈( j1 j2 )(I ) |
ε1 +ε2 −E − iη1,2∑
= −1πℑ Φi
(I ) Ψ k(I )
k∑ 1
Ek −E − iηΨ k
(I ) Φi(I )
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25F
n
n V
V
3-body model analysis for 26O decay
cf. Expt. : 27F (82 MeV/u) + 9Be à 26O à 24O + n + n
g.s. of 27F (bound)
sudden removal of proton
24O
n
n V’
V’
24O
n
n
spontaneous decay
the same config. (non-eigenstate of 24O+n+n) FSI two-particle Green’s function method
K.Hagino and H. S., PRC89 (‘14) 014331
Di-neutron correlations
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i) Decay energy spectrum for 26O decay
without nn interaction
with nn interaction
η = 0.21 MeV
very narrow three-body resonance state (Γexp ~ 10-10 MeV) Epeak
= 0.14 MeV with this setup for the Hamiltonian
cf. e1d3/2(25O) = 0.770 MeV
K.Hagino and H. S., PRC89 (‘14) 014331
(full)
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ii) distribution of opening angle for two-emitted neutrons
density of the resonance state (with the box b.c.)
r-space p-space
K.Hagino and H. S., PRC89 (‘14) 014331
correlation enhancement of back-to-back emissions Heisenberg uncertainty principle between r and p
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*higher l components: largely suppressed due to the centrifugal pot. (Edecay ~ 0.14 MeV, e1 ~ e2 ~ 0.07 MeV)
main contributions: s- and p-waves in three-body wave function (no or low centrifugal barrier)
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×
× Ab initio shell model with three-body interaction
36Ar 34S
32Si 30Mg
28Ne 26O
Excited 2+ state in 26O
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[jj](I) = 0+,2+,4+,6+,…..
0+
2+ 4+ 6+
without residual interaction
with residual interaction
I=0 pair pair
Energy spectrum of contact interaction
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E(0+)=5.0 keV E(2+)=1.338MeV
25O resonance of d3/2 state e(d3/2)=0.77MeV 2+ with a simple configuration (d3/2)2 : Ex=1.54MeV (unperturbed)
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25O (3/2+) 26O (2+)
Experiment + 770+20-10 keV ~ 1.3 MeV
USDA 1301 keV 1.9 MeV
USDB 1303 keV 2.1 MeV
sdpf-m 2.15MeV 2.6 MeV
chiral NN+3N 742 keV 1.6 MeV
continuum SM (Volya-Zelevinsky)
1002 keV 1.8 MeV
3-body model (Hagino-Sagawa)
770 keV (input)
1.35 MeV
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Summary Di-neutron correlation:spatial localization of two neutrons
ü Theroy: large model space (parity mixing) ü scattering to the continuum states enhancement of pairing on the surface
how to probe it? • Direct two-neutron emission decay (26O,14Be) ü decay energy spectrum ü Final state interaction=di-neutron correlations ü opening angle of two emitted neutrons (back-to-back)
26O ground state: very small width (Γ~10-10MeV) very small resonance energy (Ex<140keV) 2+ :The three-body model with a contact pairing interaction gives Ex=1.3MeV. ab initio and USD shell model calculations give higher energy than Ex>1.6MeV.