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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
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Brighton 12-13 Jan 2011 2
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
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Brighton 12-13 Jan 2011 3
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
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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
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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
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Brighton 12-13 Jan 2011 6
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
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Brighton 12-13 Jan 2011 7
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
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Brighton 12-13 Jan 2011 8
(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
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Brighton 12-13 Jan 2011 9B. Rubio
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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
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Brighton 12-13 Jan 2011 11
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
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3395
1+
3895
1+
4550
1+
4828
1+
3395
1+
3895
1+
4550
1+
4828
1+
1+
1+
1+
1+
B. Rubio
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1+ 1+
1+
1+
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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
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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
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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
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17
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
HI-beta correlations same pixel
HI-beta correlations opposite pixel
Background normalised
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18
Least square fit
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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
?
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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
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21
Many 1+ 0+ , few 1+ 2+, but never 1+ 1+ M1 transitions were observed!!!!
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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
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Brighton 12-13 Jan 2011 23
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
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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
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FIN
B. Rubio
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Brighton 12-13 Jan 2011 26
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
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Esta es la última tabla que me entregó Pancho sin errors en los valores de CE
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Brighton 12-13 Jan 2011 28B. Rubio
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N=Z
Z=28
Z=20
N=28
N=20
Luckly enough we have all Stable targets in the f shell
β+ or β-
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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
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31
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
HI-beta correlations same pixel
HI-beta correlations opposite pixel
Possible systematic errorsa) Deadtimeb) contaminants
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32
Maximum likelihood fit
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T1/2 from gammas
46Cr missing
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Gamma spectrum after background subtraction from opposite pixel
46Cr missing
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Brighton 12-13 Jan 2011 37
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
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
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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
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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
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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
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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
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42
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2411
1+
2694
1+ 33
92 1
+
3654
1+
4332
1+
5728
1+
1+
1+
B. Rubio
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1+1+
1+
1+
1+
1+
1+1+
1+
1+
1+
1+
B. Rubio