GT transitions of Astrophysics Interest

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GT transitions of Astrophysics Interest
Yoshitaka FUJITA (Osaka Univ.) Hirschegg
Workshop /2006, Jan. 15-21
GT (st) Important weak response
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Supernova Cycle
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Crucial Weak Processesduring the Collapse
(A,Z)nuclei in the Fe, Ni region
mainly by t st
K.L G.M-P Rev.Mod.Phys.75(04)819
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SM-cal GT- from Ni isotopes
(p,n) exp.
SM cal.
E. Caurier et al., NPA653 (99) 439 KB3G int.
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GT transitions of Astrophysics Interest
Yoshitaka FUJITA (Osaka Univ.) Hirschegg
Workshop /2006, January 15-21
GT (st) Important weak response

• decay absolute B(GT), limited to low-lying
  state
• CE reaction relative B(GT), highly Ex region

• decay ? isospin symmetry ? CE reaction

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Direct Reactions with Light Projectiles
Coulomb Excitation
Elastic Scattering
Inelastic Scattering
igt ? fgt
Target
interaction (operator)
Stripping
Pick-up
Projectile 3He
Charge-exchange
Similarity with b decay!
by Berta Rubio
Ejectile t
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(3He,t) high resolution and sensitivity !
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9Be(3He,t)9B spectrum (at various scales)
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9Be(3He,t)9B spectrum (II)
Isospin selection rule prohibits proton decay of
T3/2 state!
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Key Words
High Resolution In Charge Exchange Reactions
--at Intermediate Incident Energies-- (3He,t)
reaction one order better resolution than in a
(p,n) reaction Comparison with b decay
Similarity of Active Operators Gamow-Teller
operator in b decay (weak interaction)
Spin-isospin interaction in reactions (strong
interaction) Isospin Symmetry of Nuclear
Structure Isospin-Symmetry GT Transitions are
expected
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B(GT) derivation in Charge Exchange Reactions
Interaction Reaction Mechanism
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B(GT) derivation
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Nucleon-Nucleon Int. Ein dependence at q 0
central-type interactions
Simple one-step reaction mechanism at
intermediate energies!
V0
Vst
Vt
Vs
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N.-N. Int. st Tensor-t q-dependence
st
Tt
largest at q0 ! larger than others !
Love Franey PRC 24 (81) 1073
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B(GT) derivation
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Resolutions Now and Then
Y. Fujita et al., EPJ A 13 (02) 411. H. Fujita
et al., Dr. Th. PRC
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Isospin Symmetry Structure in a Mass A Isobar
System
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T1 system
Coulomb Energy important
50Fe
A50 system
50Mn
50Cr
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T1 symmetry Structures Transitions
50Mn Z25, N25
50Fe Z26, N24
50Cr Z24, N26
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High Resolution Experiment
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Grand Raiden Spectrometer
Large Angle Spectrometer
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RCNP Ring Cyclotron
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Beam line WS-course
T. Wakasa et al., NIM A482 (02) 79.
Grand-Raiden Spectrometer
High-dispersive WS-course
RCNP Ring Cyclotron
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Matching Techniques
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GT Transitions in fp--shell Nuclei -important
in supernova explosion-
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Onion Structure in a Red Giant
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Crucial Weak Processesduring the Collapse
K.L G.M-P Rev.Mod.Phys.75(04)819
(A,Z)nuclei in the Co, Fe, Ni region
mainly by t st
can be studied by (3He,t)
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(p, n) spectra for Fe and Ni Isotopes
Rapaport Sugarbaker Rev. Mod. Phys. (94)
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54Fe(p,n) 54Fe(3He,t)
B.D. Anderson et al., (p, n) at IUCF
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(3He,t) spectra T1, pf-shell nuclei (I)
T. Adachi et al. PRC, in press
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(3He,t) spectra T1, pf-shell nuclei (II)
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Connection between Charge Exchange b decay
T1 symmetry
T1/2 symmetry
0 ??1
26Si Z14, N12
26Mg Z12, N14
26Al Z13, N13
23Na Z11, N12
23Mg Z12, N11
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Derivation of absolute B(GT) values-for A50
system-
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50Cr(3He,t)50Mn
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Isospin Symmetry Transitions 50Cr(3He,t)? 50Mn
?b-decay 50Fe
QEC8.152(61) MeV T1/20.155(11) s
0.651
(Z,N)
(24,26)
(25,25)
(26,24)
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50Fe b-decay measurement

0
50
Fe

b
decay
S
4.59
p
QEC8.152(61) MeV T1/20.155(11) s No feeding
ratios!
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50Cr(3He,t)? 50Mn ?b-decay 50Fe
QEC8.152(61) MeV T1/20.155(11) s
0.651
B(GT)0.60(14)
assuming no brancing to higher excited states!
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Reconstruction of b decayfrom (3He,t)-
assuming isospin symmetry -
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Simulation of b-decay spectrum
b-decay feeding ratio is expected !
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Absolute B(GT) values-via reconstruction of
b-decay spectrum-
ti partial half-life
Y. Fujita et al. PRL 95 (2005)
b-decay experiment T1/20.155(11) s
B(F)N-Z
Relative feeding intensity from (3He,t)
Absolute intensity B(GT)
New value B(GT)0.50(13) 20 smaller than the
b-decay 0.60(16)
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Important messages
The largest uncertainty comes from the error
of T1/2 measurement in the b-decay
?Accurate T1/2 measurement is important !
Measurement of T1/2-value is easier !
(Measurement of branching ratio is more
difficult)
Other error sources Q-value of the
b-decay Uncertainties of peak yields
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Study of Mirror GT Transitions for T1 System
Leuven Valencia Surrey Osaka
54Fe Z26, N28
54Co Z27, N27
54Ni Z28, N26
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Summary Words

• High Resolution
• (3He,t) reaction one order better resolution
  than
• in a (p,n) reaction
• ?good tool to study B(GT) distribution
  (relative values)
• Isospin Symmetry
• Combined Analysis based on Isospin Symmetry
• (3He,t) IV-spin interaction in reactions (strong
  interaction)
• Gamow-Teller operator in b decay (weak
  interaction)
• ?A New Step toward the accurate determination of
• B(GT) (absolute values)

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High resolution 54Fe(3He,t) spectrum
T. Adachi et al.
Target nuclei under study T01 46Ti, 50Cr,
54Fe, 58Ni T02 48Ti, 52Cr, 56Fe,
60Ni T03 50Ti, 62Ni T04 64Ni
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Thank you for your attention !