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量子過程が生む巨視的現象

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					           GT transitions
      of Astrophysics Interest
               Yoshitaka FUJITA (Osaka Univ.)
                Hirschegg Workshop /2006, Jan. 15-21
GT (st) : Important weak response
Supernova Cycle
   Crucial Weak
     Processes
during 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
     SM-cal: GT- from Ni isotopes
(p,n) exp.




 SM cal.




                E. Caurier et al., NPA653 (‘99) 439
                           KB3G int.
             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
  Direct Reactions with Light Projectiles
                                          Coulomb Excitation

                                          Elastic Scattering

                                          Inelastic Scattering
                   |i>  |f>
               Target
interaction
(operator)
                          Pick-up        Stripping
  Projectile
     3He
                                     Charge-exchange

                                      Similarity with  decay!
by Berta Rubio                      Ejectile t
**(3He,t): high resolution and sensitivity !
9Be(3He,t)9B   spectrum (at various scales)
9Be(3He,t)9B    spectrum (II)




 Isospin selection rule prohibits
  proton decay of T=3/2 state!
                 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  decay
  Similarity of Active Operators
     Gamow-Teller operator in  decay (weak interaction)
   Spin-isospin interaction in reactions (strong interaction)

Isospin Symmetry of Nuclear Structure
 Isospin-Symmetry GT Transitions are expected
      **B(GT) derivation
in Charge Exchange Reactions


 Interaction & Reaction Mechanism
B(GT) derivation
Nucleon-Nucleon Int. : Ein dependence at q =0
         central-type interactions
      Simple one-step reaction mechanism
           at intermediate energies!
                  V0

                 Vst
                 Vt
                 Vs
  N.-N. Int. : st & Tensor-t q-dependence

st largest at q=0 !              Tt
   larger than others !




               Love & Franey PRC 24 (’81) 1073
B(GT) derivation
Resolutions Now and Then




                             Y. Fujita et al.,
                           EPJ A 13 (’02) 411.
                             H. Fujita et al.,
                             Dr. Th. & PRC
**Isospin Symmetry Structure
  in a Mass A Isobar System
T=1 system
Coulomb Energy: important

                                   50Fe

  A=50 system


                            50Mn



                 50Cr
T=1 symmetry : Structures & Transitions




   50Cr         50Mn         50Fe
 Z=24, N=26   Z=25, N=25   Z=26, N=24
**High Resolution Experiment
                            Large Angle
Grand Raiden Spectrometer   Spectrometer
RCNP Ring Cyclotron
               Beam line WS-course
                           T. Wakasa et al., NIM A482 (’02) 79.
Grand-Raiden
Spectrometer




         High-dispersive                      RCNP Ring
         WS-course                            Cyclotron
                  Matching Techniques
                                             Y. Fujita et al., N.I.M. B 126 (1997) 274.
                                              H. Fujita et al., N.I.M. A 484 ( 2002) 17.
    a)                   b)                               c)


Focal plane


 Magnetic
 Spectrometer
         Target                  -Δp        0 +Δp                    -Δp          0 +Δp

   Achromatic beam         Lateral dispersion                  Angular dispersion
    transportation             matching                           matching
 E ~200 keV              E ~ 35 keV
 for 140MeV/u 3He beam    Horiz. angle resolution           sc ~ 5mrad
                            sc > 15mrad
**GT Transitions in fp--shell Nuclei
    -important in supernova explosion-
Onion Structure in a Red Giant
   Crucial Weak            K.L &G.M-P
                           Rev.Mod.Phys.75(’04)819
     Processes
during the Collapse
(A,Z)=nuclei in the
       Co, Fe, Ni region

  mainly by t & st


   can be studied
     by (3He,t)
(p, n) spectra for Fe and Ni Isotopes




                                      Rapaport
                                         &
                                     Sugarbaker
                                Rev. Mod. Phys. (’94)
54Fe(p,n)   & 54Fe(3He,t)
                       B.D. Anderson et al.,
                          (p, n) at IUCF
  (3He,t) spectra: T=1, pf-shell nuclei (I)




T. Adachi et al. PRC, in press
(3He,t) spectra: T=1, pf-shell nuclei (II)
Connection between Charge Exchange &                          decay
 T=1/2 symmetry              T=1 symmetry                    0+ 1+




  23Na         23Mg         26Mg       26Al        26Si

Z=11, N=12   Z=12, N=11   Z=12, N=14 Z=13, N=13 Z=14, N=12
**Derivation of “absolute” B(GT) values
            -for A=50 system-
50Cr(3He,t)50Mn
    Isospin Symmetry Transitions:
  50Cr(3He,t) 50Mn -decay 50Fe




                 0.651             QEC=8.152(61) MeV
                                   T1/2=0.155(11) s




(Z,N)= (24,26)           (25,25)   (26,24)
50Fe-decay
measurement

               0+
                     50
                       Fe
                     + decay



                Sp =4.59

              QEC=8.152(61) MeV
              T1/2=0.155(11) s
              No feeding ratios!
50Cr(3He,t) 50Mn   -decay 50Fe



                                QEC=8.152(61) MeV
                                T1/2=0.155(11) s

            0.651          B(GT)=0.60(14)
                                  *assuming no
                                brancing to higher
                                  excited states!
**Reconstruction of  decay
         from (3He,t)
  - assuming isospin symmetry -
Simulation of -decay spectrum




   -decay feeding ratio is expected !
            Absolute B(GT) values
  -via reconstruction of -decay spectrum-
Feedings  1 / ti ti =partial half-life           Y. Fujita et al.
                                                  PRL 95 (2005)
           1       1         1
                       
          T1/ 2 t Fermi iGT ti
        -decay B(F)=N-Z Relative feeding intensity
      experiment                from (3He,t)
    T1/2=0.155(11) s    Absolute intensity: B(GT)


                      New value B(GT)=0.50(13)
                      *20% smaller than the -decay: 0.60(16)
              Important messages

 *The largest uncertainty comes from
  the error of T1/2 measurement in the -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 -decay
       Uncertainties of peak yields
Study of Mirror GT Transitions for T=1 System


                                            Leuven
                                           Valencia
                                             Surrey
                                             Osaka




      54Fe         54Co         54Ni
    Z=26, N=28   Z=27, N=27   Z=28, N=26
               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  decay (weak interaction)

A New Step toward the accurate determination of
    B(GT) (absolute values)
             High resolution 54Fe(3He,t) spectrum
                                                  T. Adachi et al.




Target nuclei under study :   T0=1   46Ti, 50Cr, 54Fe, 58Ni

                              T0=2   48Ti, 52Cr, 56Fe, 60Ni

                              T0=3   50Ti, 62Ni

                              T0=4   64Ni
**Thank you for your attention !

				
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