Di-neutron correlation and BCS-BEC crossover in the structure and - - PowerPoint PPT Presentation

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Di-neutron correlation and BCS-BEC crossover in the structure and - - PowerPoint PPT Presentation

Aug 27, 2023 351 likes •490 views

Di-neutron correlation and BCS-BEC crossover in the structure and decay of light neutron-rich nuclei Kouichi Hagino Tohoku University, Sendai, Japan Hiroyuki Sagawa RIKEN/ University of Aizu 1. Neutron-rich nuclei 2. Di-neutron correlation

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SLIDE 1

Di-neutron correlation and BCS-BEC crossover in the structure and decay of light neutron-rich nuclei

  • 1. Neutron-rich nuclei
  • 2. Di-neutron correlation and BCS-BEC crossover
  • 3. Two-neutron decay of 26O
  • 4. Summary

Kouichi Hagino Tohoku University, Sendai, Japan

Hiroyuki Sagawa RIKEN/ University of Aizu

International Symposium on Neutron Star Matter (NSMAT2016), Nov. 21-23, 2016, Sendai, Japan

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SLIDE 2

Introduction: neutron-rich nuclei

light neutron-rich nuclei → three-body structure

9Li

n n

11Li = 9Li + n + n

→ large radius nn attraction Borromean nuclei unbound bound

11Li, 6He

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SLIDE 3

nn attraction Borromean nuclei unbound bound

11Li, 6He

nn attraction three-body resonance unbound unbound, but nearly bound

10He, 13Li, 16Be, 26O

26O

  • Y. Kondo et al.,

PRL116(‘16)

Role of nn correlation in Borromean nuclei and in the decay dynamics of unbound nuclei?

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SLIDE 4

Di-neutron correlation and BCS-BEC crossover

Three-body model calculations: vnn without nn interaction [(p1/2)2] with nn interaction large asymmetry in density distribution = di-neutron correlation

11Li = 9Li + n + n

  • cf. Coulomb hole in He atom

(He nucleus + e- + e-) e- e-

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SLIDE 5

pairing gap in infinite nuclear matter

  • M. Matsuo, PRC73(’06)044309

R Density distribution

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SLIDE 6

BCS-type BEC-type

K.H. et al., PRL99 (’07) 022506

11Li

spatially compact

  • cf. inifinite neutron matter
  • M. Matsuo, PRC73(’06)044309
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SLIDE 7

Two-neutron decay of 26O

  • Expt. : 27F (201 MeV/u) + 9Be → 26O → 24O + n + n

22O 23O 24O 25O 26O

24O 25O 26O

749 keV 18 keV 2n decay (neutron drip line) → Edecay = 18 +/- 3 +/- 4 keV

  • Y. Kondo et al., PRL116(’16)102503
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SLIDE 8

3-body model analysis for 26O decay

  • Expt. : 27F (201 MeV/u) + 9Be → 26O → 24O + n + n

continuum dynamics, FSI

K.H. and H. Sagawa,

  • PRC89 (‘14) 014331
  • PRC93(‘16)034330

without nn interaction with nn interaction

  • cf. e1d3/2(25O)

= 0.749 MeV

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SLIDE 9

a prominent second peak at E = 1.28 +0.11

  • 0.08 MeV
  • Y. Kondo et al.,

PRL116(’16)102503

2+ state in 26O

K.H. and H. Sagawa, PRC90(‘14)027303; PRC93(‘16)034330.

(d3/2)2 1.498 0+ 0.018 2+ 1.282 (MeV) Γ = 0.12 MeV three-body model calculation: I=0 pair pair

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SLIDE 10

correlation enhancement of back-to-back emissions

K.H. and H. Sagawa, PRC89 (‘14) 014331; PRC93 (‘16) 034330

Angular correlations of two emitted neutrons

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SLIDE 11

Two-particle density in the bound state approximation (d3/2)2 : 66.1% (f7/2)2 : 18.3% (p3/2)2 : 10.5% (s1/2)2 : 0.59% rms radius = 3.39 +/- 0.11 fm r-space p-space Fourier transform enhancement of large

  • pening angles

dineutron correlation

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SLIDE 12

Summary

  • 2n emission decay of 26O

 Decay energy spectrum: strong low-energy peak  2+ energy  Angular distributions: enhanced back-to-back emission dineutron correlation Three-body model for light neutron-rich nuclei

  • Borromean nuclei

 di-neutron correlation  similarity to BCS-BEC crossover phenomenon

  • A challenge: extension to five-body model cf. 28O → NSMAT