Search for + EC and ECEC processes in 112 Sn A.S. Barabash 1) , Ph. Hubert 2) , A. Nachab 2) and V. Umatov 1) 1) ITEP, Moscow, Russia 2) CNBG, Gradignan, France
Search for +EC and ECEC processes in 112Sn
A.S. Barabash1), Ph. Hubert2), A. Nachab2)
and V. Umatov1)
1) ITEP, Moscow, Russia2) CNBG, Gradignan, France
Outline
Introduction Experiment Results Conclusion
I. Introduction
2+, +EC and ECEC processes:
0-transitions: (A,Z) (A,Z-2) + 2e+
eb + (A,Z) (A,Z-2) + e+ + X
2eb + (A,Z) (A,Z-2) + (2,e+e-,e-,…) + 2X 2-transitions: (A,Z) (A,Z-2) + 2e+ + 2 eb + (A,Z) (A,Z-2) + e+ + 2 + X
2eb + (A,Z) (A,Z-2) + 2 + 2X
Q value
2+: Q' = M – 4me – 2b (Q'max 0.8 MeV) (6 nuclei) +EC: Q' = M – 2me – b (Q'max 1.8 MeV)
(22 nuclei) ECEC: Q' = M – 2b (Q'max 2.8 MeV) (34 nuclei)
[ Q(2-) 3 MeV ]
ECEC(0) to the ground state 2eb + (A,Z) (A,Z-2) + 2X + brem
+ 2 + e+e-
+ e-int
E,.. = M - e1 -e2
Suppression factor is ~ 104 (in comparisonwith EC+(0)) – M. Doi and T. Kotani, Prog. Theor. Phys. 89 (1993)139.
ECEC(0)
Transition to the ground state. For the best
candidates (<m> = 1 eV):
++ (0) ~ 1028-1030 y+EC(0) ~ 1026-1027 yECEC(0) ~ 1028-1031 y
(One can compare these values with ~ 1024-1025 y for 2--decay)
Resonance conditions In 1955 (R.Winter, Phys. Rev. 100 (1955) 142) it was mentioned
that if there is excited level with “right” energy then decay rate can be very high.
(Q’-E* has to be close to zero. Q’-energy of decay to g.s., E*-energy of excited state)
In 1982 the same idea for transition to excited and ground states was discussed (M. Voloshin, G. Mizelmacher, R. Eramzhan, JETP Lett. 35 (1982)).
In 1983 (J. Bernabeu, A. De Rujula, C. Jarlskog, Nucl. Phys. B 223 (1983) 15) this idea was discussed for 112Sn (transition to 0+ excited state). It was shown that enhancement factor can be on the level ~ 106!
J. Bernabeu, A. De Rujula, C. Jarlskog, Nucl. Phys. B 223 (1983) 15
112Sn 112Cd [0+(1871)] M = 1919.5±4.8 keV (old value)Q’(KK;0+) = M – E*(0+) – 2EK = = (-4.9 ± 4.8) keV
T1/2 (0) 3·1024 y (for <m> = 1 eV)(if Q’ ~ 10 eV) [ECEC(2) transition is strongly suppressed!!!]
Nice signature: in addition to two X-rays we have here two gamma-rays with strictly fixed energy (617.4 and 1253.6 keV)
J. Bernabeu, A. De Rujula, C. Jarlskog, Nucl. Phys. B 223 (1983) 15
112Sn112Cd(0+;1870 keV)
The ECEC(0) mode is shownas a function of the degeneracyparameter Q-E
Resonance conditions In 2004 the same conclusion was done by
Z. Sujkowski and S. Wycech (Phys. Rev. C 70 (2004) 052501).
Resonance condition (using single EC(,)argument):Ebrems = Q’res = E(1S,Z-2)-E(2P,Z-2)
(i.e. when the photon energy becomes comparable to the 2P-1S level difference in the final atom)
Q’-Q’res < 1 keV
Z. Sujkowski and S. Wycech
Decay-scheme of 112Sn
Here M = 1919.82±0.16 keV
(PRL 103 (2009) 042501)
Q’ = M - 2Eb = 1866.42 keV
Q’(E*) = Q’–1871.137(72)
- 4.71±0.23 keV
Isotope-candidates (transition to the excited state)
Nuclei A, % M, keV E*, keV , keV EK*) EL2
*)
74Se 0.89 1209.7±2.3
1209.240±0.007 (new!)
1204.2 (2+) 2.5±0.1 (LL) 11.1 1.23
78Kr 0.35 2846.4±2.0 2838.9 (2+?) 4.5±2.1 (LL) 12.6 1.47
96Ru 5.52 2718.5±8.2 2700.2 (2+) -4.5±8.2 (KL)
2712.68 (?) 0±8.2 (LL)
20 2.86
106Cd 1.25 2770±7.2 2741.0 (4+) 1.1±7.2 (KL)
2748.2 (2,3) -5.6±7.2 (KL)
24.3 3.33
112Sn 0.97 1919.5±4.8
1919.82±0.16 (new!)
1871.137 (0+) -4.7±0.23 (KK)
1870.74(4+) -4.3±0.21 (KK)
26.7 3.73
130Ba 0.11 2617.1±2.0 2608.42 (?) -1.2±2.0 (LL)
2544.43 (?) 3.7±2 (KK)
34.5 5.10
136Ce 0.20 2418.9±13 2399.87 (1+,2+?) 7.5±13 (LL)
2392.1 (1+,2+?) - ??? -16±13 (KL)
2390.79(3) -14.6±13 (KL)
37.4 5.62
162Er 0.14 1843.8±5.6 1745.7(1+) -9.5±5.6 (KK)
1782.68(2+) -1±5.6 (KL)
53.8 8.58
*)EK and EL2 are given for daughter nuclei 2+: suppression factor is ~ 104
g.s.-g.s. transitions
152Gd (0.2%), 164Er (1.56%),180W(0.13%)
(There are only X-rays in this case)
0+G.S.-0+
G.S.
152Gd-152Sm M = 54.6±3.5 keV =0±3.5 keV K – 46.8 keV (KL case) L1 = 7.73; L2 = 7.31; L3 = 6.71 keV
164Er-164Dy M = 23.3±5.5 keV =5.7±3.9 keV
K – 53.78 keV (LL case) L1 = 9.05; L2 = 8.58; L3 = 7.79 keV
180W-180Hf M = 144.4±6.1 keV =13.7±4.5 keV K – 65.34 keV KK -? L1 = 11.27; L2 = 10.74; L3 = 9.56 keV 180W-180Hf(2+;93.32 keV) M = 51.08±6.1 keV
Problems There is no good theoretical description of the ECEC
processes and “resonance” conditions Accuracy of M (and Q as a result) is not very good (~ 2-
10 keV) and has to be improved Quantum numbers are not known in some cases
[It is possible to improve the accuracy of M to ~ 10-100 eV: 112Sn: M = 1919.82±0.16 keV, PRL 103 (2009) 042501;74Se: M = 1209.240±0.007 keV, PRC 81 (2010) 032501R
M = 1209.169±0.049 keV, PLB 684 (2010) 17]
List of needed M measurements
Priority #1: 152Gd-152Sm, 130Ba-130Xe, 96Ru-96Mo,
Priority #2: 164Er-164Dy, 162Er-162Dy, 136Ce-136Ba,
106Cd-106Pd
II. EXPERIMENT
M = 1919.82 ± 0.16 keV
= 0.97%
SCHEME OF EXPERIMENT
E = 2.0 keV
(for 1332 keV)
T = 3175.23 h
Experiment is done in Modane Underground Laboratory, 4800 m w.e.
100 g of 112Sn;Enrichment is 94.3% 5.05·1023 nuclei
380 cm3 low-background HPGe detector
112Sn (spectra)
Efficiency: 4.61% (617.5 keV) and 2.83% (1253.4 keV)
112Sn (spectra)
112Sn (results) Transition
T1/2, 1020 y
This work Previous work [1] T1/2th(2), y [2]
+ЕС(0+2); g.s. > 0.97 > 0.56 3.81024
+ЕС(0+2); 2+1 > 7.02 > 2.79 2.31032
ECEC(0) L1L2; g.s. > 6.43 > 4.10
ECEC(0) K1L2;g.s. > 8.15 > 3.55
ECEC(0) K1K2;g.s. > 10.63 > 3.97
ECEC(0); 2+1 > 9.72 > 3.93
ECEC(0); 0+1 > 12.86 > 6.87
ECEC(0); 2+2 > 8.89 > 3.45
[1] A.S.B. et al., PRC 80 (2009) 035501; [2] P. Domin et al., NPA 753 (2005) 337.
112Sn (results-2)ECEC(0); 0+
2 > 6.86·1020 > 2.68·1020
ECEC(0); 2+3 > 6.46 > 2.64
ECEC(0); 0+3 > 13.43 > 4.66
ECEC(2); 2+1 > 11.94 > 4.84 4.91028
ECEC(2); 0+1 > 16.25 > 8.67 7.41024
ECEC(2); 2+2 > 11.24 > 4.39 1.91032
ECEC(2); 0+2 > 8.64 > 3.43
ECEC(2); 2+3 > 8.19 > 3.40 6.21031
ECEC(2); 0+3 > 13.43 > 4.66 5.41034
How to increase the sensitivity:
1 kg of 112Sn, 1 y ~ 1022 y 200 kg of 112Sn (using GERDA or
MAJORANA), 10 y ~ 1026 y .
Comparison of existing experimental results for 112Sn-112Cd(1871 Kev) transition
> 1.61018 y (J. Dawson et al., 2008; 1.2 kg of natural Sn) > 0.921020 y (A.S.B. et al., 2008; 4 kg of natural Sn) > 0.81019 y (J. Dawson et al., 2008; 1.2 kg of natural Sn)
> 1.31019 y (M. Kidd et al., 2008; 3.9 g of 112Sn) > 4.71020 y (A.S.B. et al., 2009; 50 g of 112Sn) > 1.31021 y (A.S.B. et al., 2010; 100 g of 112Sn)
Table. Best present limits on ECEC(0) to the excited state (for isotope-candidates with possible resonance conditions)
Nuclear (natural abundance)
E*(Jf) T1/2, y Experiment, year
74Se (0.89%) 1204.20 (2+) > 5.5·1018 Modane (ITEP-Bordeaux), 2007
78Kr (0.35%) 2838.49 (2+) > 1.2·1021 *) Baksan (INR), 2010
96Ru (5.54%) 2700.21 (2+)2712.68 (?)
> 4.9·1018
> 1.3·1019
Gran Sasso(DAMA-Kiev), 2009
106Cd (1.25%) 2741.0 (4+)2748.2 (2,3-)
> 1.7·1020 TGV-II, 2010
112Sn (0.97%) 1871.13 (0+)1870.74 (4+)
> 1.3·1021
> 1.1·1021
Modane (ITEP-Bordeaux), 2010
130Ba (0.106%) 2608.4 (?)2544.43 (?)
> 1.5·1021 *) Geochemical, 2001
136Ce (0.185%) 2399.87 (1,2+)2392.1 (1,2+)
> 4.1·1015
> 2.4·1015
Gran Sasso(DAMA-Kiev), 2009
162Er (0.14%) 1745.7 (1+) - -
*) Estimation from existing experimental data
CONCLUSION New limits on the +EC and ECEC processes for 112Sn
on the level 1020-1021 y have been obtained (limits are in ~ 1.5-3 times better than previous results)
Possible resonance ECEC(0) transition 112Sn-112Cd (1801.13 keV) has been investigated and limit 1.3·1021 y was obtained
New M measurements are needed for other isotope-candidates
Quantum numbers have to be established for 2608.42 and 2544.43 keV levels in 130Xe and 2712.68 kev in 96Mo
BACKUP SLIDES
Last best achievements for such processes ECEC(2):
- T1/2(130Ba) = (2.2 ± 0.5)·1021 y (geochemical) - > 2.4·1021 y (78Kr, Baksan) - > 4.2·1020 y (106Cd, TGV-II) - > 5.9·1021 y (40Ca, DAMA-Solotvino)
2+(0+2), EC+ (0+2), ECEC(0): > 1020-1021 y (78Kr, 106Cd, 40Ca; Baksan-Spain, DAMA-Solotvino) > 1015-1019 y (120Te, 108Cd, 136Ce, 138Ce, 64Zn, 180W; COBRA, DAMA, Solotvino)