Nuclear Structure, Weak-induced Reactions and Nucleosynthesis

Toshio Suzuki Nihon University NAOJ-RIKEN Oct. 17, 2012

・ New shell-model Hamiltonians and successful description of Gamow-Teller (GT) and spin-dipole (SD) strengths SFO (p-shell): GT in 12 C, 14 C Suzuki, Fujimoto, Otsuka, PR C69, (2003) CK+MK+ monopole corrections in spin-isospin-flip 2BME SFO-tls (p-sd shell): SD in 16 O Suzuki, Otsuka, PR C78, (2008) SFO + (π+ρ)-tensor in p-sd cross shell interaction GXPF1J (fp-shell): GT in Ni isotopes Honma, Otsuka, Mizusaki, Brown, PR C65 (2002); C69 (2004) Suzuki, Honma et al., PR C79, (2009) VMU (monopole-based universal interaction) ＊

important roles of tensor force

G-matrix vs phenom. interactions tensor force Three-body force more repulsion than G in T=1 more attraction than G in T=0

○ Electron capture reactions in stellar environments ・ e-capture rates on 56 Ni, 58 Ni and 60 Ni ・ synthesis of 56 Ni, 58 Ni in type-Ia supernovae ○ ν-nucleus reactions ・ ν 12 C and synthesis of 11 B in supernova explosions ・ ν 13 C by solar neutrinos ・ ν 16 O reactions ・ ν 56 Ni and synthesis of Mn in supernova explosions ○ β-decays of waiting-point nuclei at N=126 and r-process nucleosynthesis

● Important roles of tensor force ・ SFO: p-shell p-sd space up to 2-3 hw excitations CK-MK (p: Cohen-Kurath, p-sd: MK, sd: G-matrix) → Enhancement of spin-isospin channel of monopole terms Monopole terms p1/2-p3/2 (T=0) is enhanced T V ( j j ) M 1 2   J (2J  1)  j j ; JT | V | j j ; JT 1 2 1 2   J (2J  1)

B(GT) values for 12 C -> 12 N Magnetic moments of p-shell nuclei

SFO

B(GT) values for 14 N -> 14 C

SFO present = SFO Suzuki, Fujimoto, Otsuka, PR C67 (2003)

Negret et al., PRL 97 (2006)

Space: up to 2-3 hw

KVI RCNP

SFO*: g A eff /g A =0.95

B(GT: 12 C)_cal =experiment

Shell evolution in N=8 isotones N=20 isotones N=8 16 N=6 20 πp3/2

Change of magic number N=8 → N=6 N=20 → N=16

SFO p-sd shell Suzuki, Fujimoto, Otsuka, PR C67, 044032 (2003)

GT stengths in 12 C: reproduced with

g A eff /g A =0.95

Nearly vanishing GT strength in 14 C

Nucleosynthesis processes of light elements

12 12 PR C55, 2078 (1997) Enhancement of 11 B and 7 Li abundances in supernova explosions 4 4   3   3

Effects of contamination of 13 C on inclusive ν 12 C reaction cross sections 12 C 98.9% 13 C 1.1%

12 C (ν, e ) 12 Ng.s. ΔM =16.83 MeV 13 C (ν, e ) 13 Ng.s. ΔM = 1.71 MeV → σ( 13 C) > σ( 12 C) Below E ν = 15 MeV: pure ν 13 C reactions No contamination from ν 12 C reactions

13 C: attractive target for very low energy ν ν-induced reactions on 13 C

13 C (  e , e  ) 13 N 13 C (  e ,  e ') 13 C GT transitions

GT GT GT+IAS

Fukugita et al., PR C41 (1990) p-shell: Cohen-Kurath g A eff /g A =0.69

Detector for solar ν

p-sd shell: SFO

Solar ν cross sections folded over 8 B ν spectrum (  e , e  ) CK : [ 1 2  ( g .

s .)  3 2  ( 3 .

50 1 .

07  10  42 cm 2 MeV )] SFO : 1 .

34  10  42 cm 2 (  ,  ' ) CK : 3  ( 3 .

69 MeV ) 2 1 .

16  10  43 cm 2 SFO : 2 .

23  10  43 cm 2 Suzuki, Balantekin, Kajino, PR C

86

, 015502 (2012).

○

New shell-model Hamiltonians in fp-shell: GXPF1:

Honma et al., PR C65 (2002); C69 (2004) ・

KB3:

○ Caurier et al., Rev. Mod. Phys. 77, 427 (2005) KB3G A = 47-52 KB + monopole corrections ○ GXPF1 A = 47 -66

Spin properties of fp-shell nuclei are well described

B(GT ) for 58 Ni g A eff /g A free =0.74

M1 strength (GXPF1J) Fujita et al.

g S eff /g S =0.75

± 0.2

8-13MeV

●

Electron-capture rate in steller environment

e



T

  0

Z A :

    

Z

 1

A

 

M( Z

 1

Z

 1

A)

10 7 10 10 g / cm 3  

ln

2 6146

( s )



j Q j

 2 

T

10 9

K ,



Y e

 1  2

N A (

  

e



p( Q j

  

e

2 

e

2

e



) ( S e

0  

exp[( E e p

 1 

e ) / kT ]

 1 

p

  

e

 

f7/2 -> f5/2 e-capture rates in stellar environments Sasano et al.

PRL 107, 202501 (2011 ) f7/2 -> f7/2 f7/2 -> f5/2 ρY e =10 9 10 8 10 7 10 7 10 10 g / cm 3

● preliminary Sasano et al.

58 Ni → 58 Co 60 Ni → 60 Co

Exp: Hagemann et al., PL B579 (2004) Exp: Anantaraman et al., PR C78 (2008)

Type-Ia supernova explosion

Accretion of matter to white-dwarf from binary star → supernova explosion when white-dwarf mass is over Chandrasekhar limit → 56 Ni (N=Z) → 56 Ni (e , ν) 56 Co Y e =0.5 → Y e < 0.5 (neutron-rich) → production of neutron-rich isotopes; more 58 Ni Decrease of e-capture rate on 56 Ni → less production of 58 Ni.

e-capture rates: GXPF1J < KB3G ←→ Y e (GXPF1J) > Y e (KB3G) Famiano

Problem of over-production of 58 Ni

Famiano

● Neutral current reaction on 56 Ni B(GT)=6.2 (GXPF1J) B(GT)=5.4 (KB3G) cf: HW02 gamma p n

56 Synthesis of Mn in Population III Star 55 ' p) Co, 55   55   55 Mn 54 55 Co 59 Co : 58 59   59   59 Co Yoshida, Umeda, Nomoto Suzuki et al., PR C79 (2009) OBS: Cayrel et al., Astron. Astrophys.

416 (2004)

R-Process Nucleosynthesis and Beta Decays of N=126 Isotones

Focus on the 3 rd peak region Waiting point nuclei

GT strengths ∑B(GT)=14.4

Q=g A eff /g A =0.

7

∑B(GT)=14.6

E x =0 ←→ g.s. of the parent nuclei

∑B(GT)=11.7

∑B(GT)=8.5

∑B(GT)=5.6

SD+E1 (1 ) strengths g A eff /g A =0.7

spin part only Q=g A eff /g A =0.7

E=0: g.s. of the parent nuclei

Shell Model calculations

cf.

Moller, Pfeiffer, Kratz, PR C 67, 055802 (2003) Q=g A eff /g A =0.7, ε =2.0 (0 ) Neumann-Cosel et al, PRL 82 (1999) Q=g s eff /g s =0.64: 2- in 90 Zr (e-scatt.)

r-process nucleosynthesis Constant Entropy Wind Model L ν =0.5x10

51 erg/s S=133 k B (γ, e , e + ) dm/dt=2.34x10

-6 M sun τ= 5.60 ms for T 9 =5 ->T 9 =2 T 9f =0.8

Neutrino processes on n, p and 4 He are included Half-lives: Standard (Moller et al.) Modified

Large quenchings are favored in A =206 (g A eff /g A ,g V eff /g V )=(0.34,0.67), (0.51, 0.30), (0.47, 0.64) Warburton, PR C 44, 233 (1991) PR C42, 2479 (1990) Rydstrom, NP A512, 217 (1990) g A eff /g A =0.34, g V eff /g V =0.67

+ ΔQ =1.0 MeV

Dependence on (g A eff /g A , g V eff /g V ） Exp: Benlliure et al.

Summary

• •

A new shell model Hamiltonian SFO well describes the spin responses in p-shell and p-sd shell nuclei → new GT (SD) strengths in C isotopes ( 16 O) and new ν 12 C, 13 C and ν 16 O cross sections A new shell model Hamiltonian GXPF1J well describes the spin responses in fp-shell niclei → new GT strengths in Ni isotopes which reproduce recent experimental data

•

Electron capture rates in 56 Ni, 58 Ni and 60 Ni are well described by GXPF1J. Suzuki, Honma, Mao, Otsuka, Kajino, PR C83, 044619 (2011)

→ Abundance ratio of 58 Ni/ 56 Ni in type Ia supernova explosions is improved

・

New ν-nucleus reaction cross sections in 56 Ni → enhancement of production rates of Mn and Co in supernova explosions Suzuki, Honma et al., PR C79, 061603(R) (2009)

・

Short half-lives for beta decays of N=126 isotones compared to a standard model (FRDM) → The 3 rd peak of the r-process element abundances is shifted toward larger mass number region. Suzuki, Yoshida, Kajino, Otsuka, PR C85, 015802 (2012)

Collaborators M. Honma a , T. Yoshida b , S. Chiba c , H. Mao d , K. Higashiyama e , T. Kajino b,f , T. Otsuka g B. Balantekin h , T. Umeda b , K. Nomoto b,i , Famiano f,j a University of Aizu b Department of Astronomy, University of Tokyo c Tokyo Institute of Technology d ENSPS, Strasbourg e Chiba Institute of Technology f National Astronomical Observatory of Japan g Department of Physics and CNS, University of Tokyo h University of Wisconsin i IPMU, j RIKEN