1 isospin symmetry. beta-decay studies of tz=-1 nuclei at rising. b. rubio for the...

Brighton 12-13 Jan 2011 1

Isospin symmetry. Beta-decay studies of Tz=-1 nuclei at Rising.

B. Rubio for the

Valencia-Osaka-Surrey-Leuven-Santiago-GSIIstambul-Lund-Legnaro

Collaboration

Ph. D Thesis of F. Molina(spokespersons, Y. Fujita, B. Rubio, W. Gelletly)

B. Rubio


B(GT) kI (E)

f (Q E,Z)T1/ 2

I (E)

B(GT) f k k

k i

2

T1/ 2

In this paper we are interested in extracting information about the B(GT) strength in f-shell nuclei from beta decay studies

Theoretically

Experimentally

From the present experiment

Parent half life

Beta feeding to states in the daughter nucleus

B. Rubio


N=Z

Z=28

Z=20

N=28

N=20

In this work I will present the studyOf the beta-decay of the Tz=-1 nuclei54Ni, 50Fe,46Cr and 42Ti

Fragmentation of 58Ni

B. Rubio


We choose Tz=-1 nuclei with Z=22 to 28 because these cases are specially “clean” since they involve only

f7/2 to f7/2and

f7/2 to f5/2

281 f 7/2

282 p 3/21 f 5/22 p 1/2

1 f 7/2

2 p 3/21 f 5/2

and

2 p 1/2

First reason

B. Rubio


CE reactions

Tz=+1 Tz=-1Tz=0

0+ 0+0+

1+1+

1+

1+

(p,n)-typeFor instance(3He,t)

V

+-decay

V

“in isospin symmetry space”

, IAS

This is the pattern we expect

(f7/2)2 f7/2 f5/2

(f7/2)2 f7/2 f7/2

(f7/2)2 f7/2 f7/2B. Rubio


CE reactions

Tz=+1 Tz=-1Tz=0

0+ 0+0+

1+1+

1+

1+

(p,n)-typeFor instance(3He,t)

V

+-decay

V

, IAS

Second Reason

We choose the Tz=-1 Tz=0 casesbecause the mirror Tz=+1 Tz=0 cases exists

CE reactions: No restriction in excitation energy of Gamow-Teller states

Beta Decay: Absolute Normalization of B(GT)

If isospin symmetry exists, mirror nuclei should populate the same states with the same probability, in the daughter nuclei, in the two mirror processes: CE reactions and Beta DecayAdvantages :

B. Rubio


46Ti

50Cr

50Fe

54Ni

46Cr

ß+(3He,t)

N=Z

T z=0

T z= +1

T z= -1

54Fe

42Ti

4220Ca22

We have the stable targetsTz=+1

We have large Q-valuesTz=-1

Adventages of studying f Shell Nuclei with T=1

Tz=(N-Z)/2B. Rubio


(3He,t) CE Reactions @ RCNP(Osaka)

46Ti

50Cr

50Fe

54Ni

46Cr

(3He,t)

N=Z

5830Zn28

58Ni

54Fe

42Ti

4220Ca22

θlab = 0° (3He,t) CE reaction

3He

3He

Stable Target

triton

B. Rubio

Brighton 12-13 Jan 2011 9B. Rubio


III. Beta Decay Experiments @ RISINGProduction of 54Ni,50Fe, 46Cr and 42TiBeam 58Ni@680 MeV/u 109 ppsTarget Be 4g/cm2

Separation in flight with theFragment Separator (FRS)

50Fe

~2 millions countsTypically 300 counts/secOf the nucelus of interest

B. Rubio


15 Euroball Cluster Ge Detectors (7 crystals each)RISING (Ge Array)

Francisco Molina IFIC(Valencia)

Beta(keV) and H.I.(GeV) detector

Santiago, December 2009B. Rubio


3395

1+

3895

1+

4550

1+

4828

1+

3395

1+

3895

1+

4550

1+

4828

1+

1+

1+

1+

1+

B. Rubio


1+ 1+

1+

1+

B. Rubio

14Z.Hu et al. : Nucl. Instr. and Meth. In Phys. Res. A 419 (1998) 121-131

y = p0+p1*x + p2*x2 + p3*x3 +p4*x4+p5*x5 , y=log(eff) and x=log(E)

RISING Efficiency Simulation

Rising Ge simulation Including + Si + Box

15

Combined Analysis (CE – β Decay)

j

A precise value of the parent half-life is very important!!!

In β decay

In charge exchange

Fujita et al PRL 95 (2005) 212501

16

T1/2 analysis of 54Ni g.s nuclei was done using heavy ion implantation-beta correlationsfor identified 54Ni ions produced and implantaion beta-gamma correlations .

Each decay was correlated with all implants happening before and after the decayTo assure no-systematic errors and well defined background

17



HI-beta correlations same pixel

HI-beta correlations opposite pixel

Background normalised

18

Least square fit

19

Experimental value of the ground state to ground state feeding estimation

T1/2 =114.71.7T1/2 =114.20.3

Systematic errors such as beta efficiency error or survival probability errorscancels!, only gamma efficiency counts!!!

Experimental Result g.s. feed 54Ni =0.792

Parent

?

20

Tz=-1

Tz=0

0+

0+

1+1+

1+

1+

, IAS

This is a super-allowed 0+0+ Fermi transition with B(F)=N-ZAnd hence

TF 6144.0(16)2(1 c) f

Parent Fermi estim Exp. G.s feed54Ni 0.82(3) 0.79(2)

50Fe 0.74(4) 0.74(2)

50Cr 0.78(1) 0.77(2)

42Ti 0.49(1) 0.44(4)

Comparison of “g.s to g.s feeding”estimated from Fermi transition probabilityand our experimental result

21

Many 1+ 0+ , few 1+ 2+, but never 1+ 1+ M1 transitions were observed!!!!

22

Tz=-1

Tz=0

0+

0+

1+1+

1+

1+

IAS

2+T=0

T=0

T=0

T=0

T=1

T=1

M1 transitions from T=0 to T=0 in self-conjugate nuclei are strongly suppressed!!!!al

lpw

ed

Strongly supressed


Results: BGT values from beta decayIsospin symmetry works in general (full strength) but some differences appear at high excitation energy, which should be understood

This is the first experimental testof BGT symmetry in the f shell. These cases are specially “clean” since they

involve only

f7/2 to f7/2and

f7/2 to f5/2

kind of transitionsand we compare only the two gs states

B. Rubio


summaryWe have studied the beta decay of four Tz=-1 nuclei in the f7/2 shell

They were all produce in fragmentation of 58Ni beams

In spite of the complex set-up we could get extremely clean results

Very accurate T1/2 and g.s beta decay feeding values were obtained

The four decay schemes were obtained and the corresponding B(GT)values for all observed levels could be determined where only Q-beta

A very selective isospin Quasi selection rule of was clearly observed

The results were compared with the mirror CE reaction process thanks to theEfficiency and high quality of the RISING array. The isospin symmetry works well for the strong transitions but small transitions show difference up to 50% which still have to be understood.

ONE CAN PERFORME DELICATE SPECTROSCOPY STUDIES IN FRAGMENTATION REACTIONS IF ONE ACHIEVES CLEAN IMPLANTATION

B. Rubio


FIN

B. Rubio


Results: BGT values from beta decayIsospin symmetry works in general (full strength) but some differences appear at high excitation energy, which should be understood


involve only

f7/2 to f7/2and

f7/2 to f5/2


B. Rubio


Esta es la última tabla que me entregó Pancho sin errors en los valores de CE

B. Rubio

Brighton 12-13 Jan 2011 28B. Rubio


N=Z

Z=28

Z=20

N=28

N=20

Luckly enough we have all Stable targets in the f shell

β+ or β-

B. Rubio


Absolute BGT normalisation is always needed:It can be obtained using the combined analysis

Y. Fujita… et al.PRL 95 (2005)

+GTi

iFermi ttT111

2/1

From-decay B(F)=N-Z From (3He,t)

We set up a series of experiments to test this idea

B. Rubio

31



HI-beta correlations same pixel

HI-beta correlations opposite pixel

Possible systematic errorsa) Deadtimeb) contaminants

32

Maximum likelihood fit

33

T1/2 from gammas

46Cr missing

34

Gamma spectrum after background subtraction from opposite pixel

46Cr missing


Results: preliminary BGT values from beta decay

Francisco MolinaAnalysis in progress IFIC(Valencia)

A=54 B(GT) decay B(GT) CE

937 keV 0.471(55) 0.493(62)

3378 keV 0.074(14) 0.079(11)

3889 keV 0.064(17) 0.103(14)

4544 keV 0.075(27) 0.147(20)

A=50

652 keV 0.547(90) 0.510(14)

2404 keV 0.126(23) 0.151(40)

2685 keV 0.090(19) 0.106(28)

3380 keV 0.281(55) 0.350(93)

A=46

994 keV 0.330(329) 0.368(44)

1433 keV 0.107(107) 0.122(15)

2462 keV 0.146(146) 0.201(24)

2698 keV 0.111(111) 0.205(25)

2978 keV 0.479(478) 0.625(75)

3870 keV 0.105(119) 0.117(14)

Large B(GT) uncertainties are due to the errors in the beta decay half-life. A better value should come from the present experiment.

Isospin symmetry works in general (full strength) but some differences appear at high excitation energy, which should be understood


involve only

f7/2 to f7/2and

f7/2 to f5/2


B. Rubio


Beta Decay Results and comparison with CEA=54, T=1

First 4th GT States till 4.5MeV were seen by beta decay

937

(1+)

937

(1+)

3377

(1+)

3377

(1+)

3895

(1+)

3895

(1+)

4550

(1+)

4828

(1+)

5921

(1+)

4550

(1+)0+

1

+0+

1

+9402 counts

94448 counts

0+

1+

0+

1+

0+

1+0+

1

+

347 counts

150 counts

1816 counts

2598 counts

B. Rubio


A=50, T=1

First 4th GT States till 3.3 MeV were seen by beta decay

652

(1+)

2411

(1+)

2694

(1+)

3392

(1+)

3392

(1+)

2694

(1+)

2411

(1+)

652

(1+)

3654

(1+)

4332

(1+)

5728

(1+)

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

B. Rubio


A=46, T=1

All the GT States were seen by beta decay

994

(1+)

1433

(1+)

2461

(1+)

2699

(1+)

2978

(1+)

3870

(1+)

994

(1+)

1432

(1+)

2460

(1+)

2697

(1+)

2978

(1+)

3870

(1+)

T. Adachi et al., PRC 73, 024311 (2006).

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

0+

1+

B. Rubio

41Z.Hu et al. : Nucl. Instr. and Meth. In Phys. Res. A 419 (1998) 121-131

y = p0+p1*x + p2*x2 + p3*x3 +p4*x4+p5*x5 , y=log(eff) and x=log(E)

Rising Ge simulation Including + Si + Box

2.26%

RISING Efficiency Simulation


2411

1+

2694

1+ 33

92 1

+

3654

1+

4332

1+

5728

1+

1+

1+

B. Rubio


1+1+

1+

1+

1+

1+

1+1+

1+

1+

1+

1+

B. Rubio

1 isospin symmetry. beta-decay studies of tz=-1 nuclei at rising. b. rubio for the...

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