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GT ( ) : Important weak process decay : absolute B(GT), limited to low-lying state CE reactions : relative B(GT), highly Ex region decay isospin symmetry CE reaction High-resolution ( 3 He,t) CE reaction and analogous -decay for the study of GT strengths Yoshitaka FUJITA (Osaka Univ.) @ Spin 2006 / Oct. 02, 2006
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Supernova Cycle
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mainly by K.L &G.M-P Rev.Mod.Phys.75(’04)819 (A,Z)=nuclei in the Cr, Mn, Fe, Co, Ni region pf -shell Nuclei ! Crucial Weak Processes during the Core Collapse
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58 Ni(p, n) 58 Cu E p = 160 MeV 58 Ni( 3 He, t) 58 Cu E = 140 MeV/u Counts Excitation Energy (MeV) 0 2 4 6 8 10 12 14 Comparison of (p, n) and ( 3 He,t) spectra Y. Fujita et al., EPJ A 13 (’02) 411. H. Fujita et al., Dr. Th. & PRC
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Grand Raiden Spectrometer Large Angle Spectrometer 3 He beam ( 3 He, t) reaction
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RCNP Ring Cyclotron Good quality 3 He beam (140 MeV/nucleon)
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Matching Techniques
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B(GT) derivation
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**Isospin Symmetry Structure in Mass A Nuclei (Isobars)
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T=1 system 26 12 Mg 14 A=26 system Coulomb Energy: important 26 13 Al 13 26 14 Si 12
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26 Mg Z=12, N=14 26 Al Z=13, N=13 26 Si Z=14, N=12 T=1 symmetry : Structures & Transitions
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B(GT) values from Symmetry Transitions (A=26) Y. Fujita et al., PRC 67 (‘03) 064312
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Supernova and Neutron Star
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High resolution 54 Fe( 3 He,t) spectrum T. Adachi et al. Target nuclei under study : T 0 =1 46 Ti, 50 Cr, 54 Fe, 58 Ni T 0 =2 48 Ti, 52 Cr, 56 Fe, 60 Ni T 0 =3 50 Ti, 62 Ni T 0 =4 64 Ni
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**Derivation of “absolute” B(GT) values
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26 Mg Z=12, N=14 26 Al Z=13, N=13 26 Si Z=14, N=12 23 Na Z=11, N=12 23 Mg Z=12, N=11 T=1 symmetry Connection between Charge Exchange & decay T=1/2 symmetry 0 + 1 +
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26 Mg Z=12, N=14 26 Al Z=13, N=13 26 Si Z=14, N=12 23 Na Z=11, N=12 23 Mg Z=12, N=11 T=1 symmetry Connection between Charge Exchange & decay T=1/2 symmetry 0 + 1 + not enough -decay data not for Ti, Cr, Fe region
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Mirror nuclei 46 Ti 50 Cr 54 Fe 50 Fe 54 Ni 46 Cr ß+ ( 3 He,t) N=Z T=1 Isospin Symmetry in pf-shell Nuclei 54 28 Ni 26 54 26 Fe 28 T z =0 T z =1 T z =-1 Leuven Valencia Surrey Osaka by B. Rubio
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Isospin Symmetry Transitions: 50 Cr( 3 He,t) 50 Mn -decay 50 Fe Q EC =8.152(61) MeV T 1/2 =0.155(11) s 0.651 (Z,N)=(24,26)(25,25)(26,24)
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50 Cr( 3 He,t) 50 Mn
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50 Fe -decay measurement 50 Fe + decay 0 + Q EC =8.152(61) MeV T 1/2 =0.155(11) s
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**Reconstruction of decay from ( 3 He,t) ---assuming isospin symmetry ---
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Simulation of -decay spectrum -decay feeding ratios are deduced !
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Absolute B(GT) values -via reconstruction of -decay spectrum- -decay experiment T 1/2 =0.155(11) s New value B(GT)=0.50(13) *20% smaller than the -decay: 0.60(16) Absolute intensity: B(GT) Y. Fujita et al. PRL 95 (2005) B(F)=N-Z Relative feeding intensity from ( 3 He,t) t i =partial half-life
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Mirror nuclei 46 Ti 50 Cr 54 Fe 50 Fe 54 Ni 46 Cr ß+ ( 3 He,t) N=Z T=1 Isospin Symmetry in pf-shell Nuclei 54 28 Ni 26 54 26 Fe 28 T z =0 T z =1 T z =-1 Leuven Valencia Surrey Osaka by B. Rubio
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Mirror nuclei 48V48V 52 Mn 56 Co 50 Co 56 Cu 48 Mn ++ ( 3 He,t) N=Z T = 2 Isospin Symmetry in pf-shell Nuclei 52 28 Ni 24 52 24 Cr 28 T z =0 T z =1 T z =-1 52 Ni T z =2 T z =-2 52 Cr 48 Cr 52 Fe 56 Ni 56 Fe 56 Zn 48 Ti 48 Fe B. Rubio, Y. Fujita
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Mirror nuclei 48V48V 52 Mn 56 Co 50 Co 56 Cu 48 Mn ++ ( 3 He,t) N=Z T = 2 Isospin Symmetry in pf-shell Nuclei 52 28 Ni 24 52 24 Cr 28 T z =0 T z =1 T z =-1 52 Ni T z =2 T z =-2 52 Cr 48 Cr 52 Fe 56 Ni 56 Fe 56 Zn 48 Ti 48 Fe B. Rubio, Y. Fujita Even T 1/2 ’s are uncertain!
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Comparison: (p, n) and ( 3 He,t) IAS g.s. 52 Cr(p, n) 52 Mn Ep =120 MeV
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-decay Half-life T 1/2 -via reconstruction of -decay spectrum- abs. B(GT) distribution from ( 3 He,t) B(F)=N-Z
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52 Ni -decay Half-life T1/2 -decay exp. (PRC 49, 2440, ‘94) T 1/2 = 38 (5) ms (total proton counts: ~160) abs. B(GT) distribution from 52 Cr( 3 He,t) Q EC =11.262 MeV B(F)=N-Z Isospin symmetry estimation T 1/2 = 56 (10) ms SM cal. (PRC 57, 2316, ’98) T 1/2 = 50 ms Mass formula (T. Tachibana et al.) T 1/2 = 35 ms
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Summary * Isospin Symmetry was introduced * High resolution of the ( 3 He,t) reaction allowed the comparison of analogous transitions * Properties of proton-rich “far-stability nuclei” is deduced by the combined analysis of -decay and ( 3 He,t) reaction --- B(GT), Half-life T 1/2 ---
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