GT () : Important weak process

decay : absolute B(GT), limited to low-lying stateCE reactions : relative B(GT), highly Ex region

decay isospin symmetry CE reaction

High-resolution (3He,t) CE reaction

and analogous -decay for the study of GT strengths

Yoshitaka FUJITA (Osaka Univ.) 　　　　　　 @ Spin 2006 / Oct. 02, 2006

Supernova Cycle

mainly by

K.L &G.M-PRev.Mod.Phys.75(’04)819

(A,Z)=nuclei in theCr, Mn, Fe, Co, Ni region pf -shell Nuclei !

Crucial Weak Processesduring the

Core Collapse

58Ni(p, n)58Cu Ep = 160 MeV

58Ni(3He, t)58Cu E = 140 MeV/u

Cou

nts

Excitation Energy (MeV)0 2 4 6 8 10 12 14

Comparison of (p, n) and (3He,t) spectra

Y. Fujita et al.,EPJ A 13 (’02) 411.

H. Fujita et al.,Dr. Th. & PRC

Grand Raiden Spectrometer

Large AngleSpectrometer

3He beam

(3He, t) reaction

RCNP Ring Cyclotron

Good quality 3He beam (140 MeV/nucleon)

Matching Techniques

Lateral dispersion matching

E ～ 35 keV Horiz. angle resolution sc > 15mrad

Achromatic beamtransportation

E ～200 keV for 140MeV/u 3He beam

Angular dispersionmatching

sc ～ 5mrad

Focal plane

Magnetic Spectrometer

Target

Y. Fujita et al., N.I.M. B 126 (1997) 274.

a) b) c)

-Δ p +Δ p0

H. Fujita et al., N.I.M. A 484 (2002) 17.

-Δ p 0 +Δ p

B(GT) derivation

**Isospin Symmetry Structurein Mass A Nuclei (Isobars)

T=1 system

2612Mg14

A=26 systemCoulomb Energy: important

2613Al13

2614Si12

26MgZ=12, N=14

26AlZ=13, N=13

26SiZ=14, N=12

T=1 symmetry : Structures & Transitions

B(GT) values from Symmetry Transitions (A=26)

Y. Fujita et al., PRC 67 (‘03) 064312

Supernova and Neutron Star

High resolution 54Fe(3He,t) spectrumT. Adachi et al.

Target nuclei under study : T0=1 46Ti, 50Cr, 54Fe, 58NiT0=2 48Ti, 52Cr, 56Fe, 60NiT0=3 50Ti, 62NiT0=4 64Ni

**Derivation of “absolute” B(GT) values

26MgZ=12, N=14

26AlZ=13, N=13

26SiZ=14, N=12

Tz=+1/2(Z,N+1) (Z+1,N)

-decay

Tz=-1/2

VV

(p,n)-typeV

M1(e,e')

-decayM1

-decayM1

23NaZ=11, N=12

23MgZ=12, N=11

T=1 symmetry

Connection between Charge Exchange & decay

T=1/2 symmetry 0+ 1+

26MgZ=12, N=14

26AlZ=13, N=13

26SiZ=14, N=12

Tz=+1/2(Z,N+1) (Z+1,N)

-decay

Tz=-1/2

VV

(p,n)-typeV

M1(e,e')

-decayM1

-decayM1

23NaZ=11, N=12

23MgZ=12, N=11

T=1 symmetry

Connection between Charge Exchange & decay

T=1/2 symmetry 0+ 1+

not enough-decay

data

not forTi, Cr, Fe

region

Mirror nuclei

46Ti

50Cr

54Fe50Fe

54Ni

46Cr

ß+

(3He,t)

N=Z

T=1 Isospin Symmetry in pf-shell Nuclei

5428Ni26

5426Fe28

T z=0

T z=1

T z=-1

LeuvenValencia

SurreyOsaka

by B. Rubio

Isospin Symmetry Transitions: 50Cr(3He,t) 50Mn -decay 50Fe

QEC=8.152(61) MeVT1/2=0.155(11) s

0.651

(Z,N)= (24,26) (25,25) (26,24)

50Cr(3He,t)50Mn

50Fe -decay measurement

50Fe

+ decay

0+

QEC=8.152(61) MeVT1/2=0.155(11) s

**Reconstruction of decay from (3He,t)

---assuming isospin symmetry ---

Simulation of -decay spectrum

-decay feeding ratios are deduced !

Absolute B(GT) values-via reconstruction of -decay spectrum-

GTi

iFermi ttT111

2/1

-decay experiment

T1/2=0.155(11) s

itFeedings /1

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 (3He,t)

ti =partial half-life

Mirror nuclei

46Ti

50Cr

54Fe50Fe

54Ni

46Cr

ß+

(3He,t)

N=Z

T=1 Isospin Symmetry in pf-shell Nuclei

5428Ni26

5426Fe28

T z=0

T z=1

T z=-1

LeuvenValencia

SurreyOsaka

by B. Rubio

Mirror nuclei

48V

52Mn

56Co50Co

56Cu

48Mn+

(3He,t)

N=Z

T = 2 Isospin Symmetry in pf-shell Nuclei

5228Ni24

5224Cr28

T z=0

T z=1

T z=-1

52Ni

T z=2

T z=-2

52Cr48Cr

52Fe

56Ni

56Fe

56Zn

48Ti

48Fe

B. Rubio, Y. Fujita

Mirror nuclei

48V

52Mn

56Co50Co

56Cu

48Mn+

(3He,t)

N=Z

T = 2 Isospin Symmetry in pf-shell Nuclei

5228Ni24

5224Cr28

T z=0

T z=1

T z=-1

52Ni

T z=2

T z=-2

52Cr48Cr

52Fe

56Ni

56Fe

56Zn

48Ti

48Fe

B. Rubio, Y. Fujita

Even T1/2’s are uncertain!

Comparison: (p, n) and (3He,t)IAS

g.s.

52Cr(p, n)52MnEp =120 MeV

-decay Half-life T1/2

-via reconstruction of -decay spectrum-

GTi

iFermi ttT111

2/1

itFeedings /1

abs. B(GT) distributionfrom (3He,t)

B(F)=N-Z

52Ni -decay Half-life T1/2

GTi

iFermi ttT111

2/1

-decay exp. (PRC 49, 2440, ‘94)

T1/2= 38 (5) ms(total proton counts: ~160)

itFeedings /1

abs. B(GT) distributionfrom 52Cr(3He,t)

QEC=11.262 MeV

B(F)=N-ZIsospin symmetry estimation

T1/2= 56 (10) ms

SM cal. (PRC 57, 2316, ’98)

T1/2= 50 msMass formula (T. Tachibana et al.)

T1/2= 35 ms

Summary

* Isospin Symmetry was introduced

* High resolution of the (3He,t) reaction

allowed the comparison of analogous transitions

* Properties of proton-rich “far-stability nuclei” is deduced

by the combined analysis of -decay and (3He,t) reaction

--- B(GT), Half-life T1/2 ---