Yoshitaka FUJITA (Osaka Univ.) Hirschegg Workshop /2006, Jan. 15-21

GT () : Important weak response

GT transitions of Astrophysics Interest

Supernova Cycle

mainly by &

K.L &G.M-PRev.Mod.Phys.75(’04)819

(A,Z)=nuclei in theFe, Ni region

Crucial Weak Processes

during the Collapse

SM-cal: GT- from Ni isotopes

E. Caurier et al., NPA653 (‘99) 439KB3G int.

(p,n) exp.

SM cal.

Yoshitaka FUJITA (Osaka Univ.) Hirschegg Workshop /2006, January 15-21

GT () : Important weak response decay : absolute B(GT), limited to low-lying stateCE reaction : relative B(GT), highly Ex region

decay isospin symmetry CE reaction

GT transitions of Astrophysics Interest

Direct Reactions with Light Projectiles

Projectile3He

Target

Coulomb Excitation

Elastic Scattering

Inelastic Scattering

Pick-up Stripping

Charge-exchange

Similarity with decay!by Berta Rubio

|i> |f>

interaction(operator)

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 WordsHigh 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

V

V

V

V

central-type interactionsSimple one-step reaction mechanism

at intermediate energies!

N.-N. Int. : & Tensor- q-dependence

Tlargest at q=0 !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

50Cr

A=50 system

Coulomb Energy: important

50Mn

50Fe

T=1 symmetry : Structures & Transitions

50MnZ=25, N=25

50FeZ=26, N=24

50CrZ=24, N=26

**High Resolution Experiment

Grand Raiden SpectrometerLarge AngleSpectrometer

RCNP Ring Cyclotron

Beam line WS-course

T. Wakasa et al., NIM A482 (’02) 79.

Grand-Raiden Spectrometer

RCNP Ring Cyclotron

High-dispersive WS-course

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

**GT Transitions in fp--shell Nuclei -important in supernova explosion-

Onion Structure in a Red Giant

mainly by &

can be studiedby (3He,t)

K.L &G.M-PRev.Mod.Phys.75(’04)819

(A,Z)=nuclei in theCo, Fe, Ni region

Crucial Weak Processes

during the Collapse

(p, n) spectra for Fe and Ni Isotopes

Rapaport&

SugarbakerRev. 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)

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+

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

-for A=50 system-

50Cr(3He,t)50Mn

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)

50Fe -decay measurement

50Fe

Sp =4.59

+ decay

0+

QEC=8.152(61) MeVT1/2=0.155(11) sNo feeding ratios!

50Cr(3He,t) 50Mn -decay 50Fe

B(GT)=0.60(14)

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

0.651

*assuming no brancing to higher

excited states!

**Reconstruction of decayfrom (3He,t)

- assuming isospin symmetry -

Simulation of -decay spectrum

-decay feeding ratio is expected !

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

Important messages

*The largest uncertainty comes from the error of T1/2 measurement in the -decay

*Other error sourcesQ-value of the -decayUncertainties of peak yields

Accurate T1/2 measurement is important !

**Measurement of T1/2-value is easier ! (Measurement of branching ratio is more difficult)

Study of Mirror GT Transitions for T=1 System

54FeZ=26, N=28

54CoZ=27, N=27

54NiZ=28, N=26

LeuvenValencia

SurreyOsaka

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) spectrumT. Adachi et al.

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

**Thank you for your attention !