DOUBLE BETA DECAY TO THE EXCITED STATES (EXPERIMENTAL REVIEW)

A.S. BARABASHITEP, MOSCOW

OUTLINE

Introduction 2-(2) -decay to the excited ststates - 100Mo - 150Nd 2-(0) –decay to the excite states ECEC to the excited states Conclusion

I. Introduction

1.1. Historical introduction

E. Fiorini (1977, NEUTRINO’77) – first time obtained limit on 0+-2+ decay in Ge-76 (as by-product for 0+-0+ transition)*):

T1/2 (0)> 3·1021 y (68% C.L.)

*) Of course, from geochemical experiments one can extract limits too.

1982 – first special experimental work to investigate 2-decay to the excited states was done: E. Bellotti et al., Lett. Nuov. Cim. 33 (1982) 273.

(58Ni, 76Ge, 92Mo, 100Mo, 148Nd, 150Nd;Transitions to 2+

1, O+1, 2+

2, … excited states)

Limits on the level (1.2-3.2)·1021 y for 76Ge and ~ 1018-1019 y for other nuclei were obtained.

1983-1988 Many new results for 76Ge (0+-2+). And

even “evidence” of the decay on 2.5 level (T1/2 1022 y) have been obtained.

3 experiments were done by E. Norman (50Cr, 58Ni, 64Zn, 92Mo, 94Zr, 96Zr, 96Ru, 106Cd, 116Cd, 124Sn; natural samples).

Limits on the level ~ 1017-1019 y were obtained.

1989-1990 It was demonstrated that 2(2;0+-

0+1)-decay can be detected in 100Mo,

96Zr and 150Nd by existing low-background HPGe detectors and new experiments were proposed (A.S.B. preprint ITEP, 188-89, 1989; JETP Lett. 51 (1990) 207).

ITEP-USC-PNL-UM experiment with 1 kg of 100Mo was started on 30 May 1990 (in Soudan mine).

Measurement was stopped in September’91

First “positive” result was reported at a few International Conferences (Moriond’91, TAUP’91, WEIN’92,…)

Final result was published in 1995 [PL B 345 (1995) 408]:

T1/2 = 6.1+1.8-1.1·1020 y

1999 – 2-nd positive result for 100Mo;

2001 – 3-d positive result for 100Mo (in ITEP-TUNL experiment);2004 – 1-st positive result for 150Nd;2007 – 4-th positive result for 100Mo (in NEMO-3 experiment).

ITEP-TUNL experiment

1.2. Present motivation Nuclear spectroscopy NME problem Checking of some “creasy” ideas ( “bosonic” neutrino, …) 0-decay: - very nice signature (2-); - high sensitivity (ECEC; resonance conditions).

II. 2-(2)-decay to the excited states

Table 1. 2 transition to 2+1 excited state.

Nuclei

E2, keV T1/2, y

Exper.

Theory, 2007[1]

Theory, 1996-1997 [2,3]

48Ca 3288.5 >1.8·1020 1.7·1024 -

150Nd 3033.6 >9.1·1019 - -

96Zr 2572.2 >7.9·1019 2.3·1025 (3.8-4.8)·1021

100Mo 2494.5 >1.6·1021 1.2·1025 3.4·1022 [4]

Table 1. (Continue)82Se 2218.5 >1.4·1021 - 2.8·1023 -

3.3·1026

130Te 1992.7 >2.8·1021 6.9·1026 (2.8-15)·1023

136Xe 1649.4 - 3.9·1026 2.0·1024

116Cd 1511.5 >2.3·1021 >3.4·1026 1.1·1024

76Ge 1480 >1.1·1021 >5.8·1028 1.0·1026

110Pd 1342 - >1.5·1025 -

Table 2. 2-decay to 0+1 excited

state

Nuclei

E2, keV T1/2, y

Exper.

Theory[2]

Theory[4]

150Nd 2627.1 =1.4·1020 -

96Zr 2202.5 >6.8·1019 2.7·1021 3.8·1021

100Mo 1903.7 =6.2·1020 1.6·1021 [5] 2.1·1021

82Se 1507.5 >3.0·1021 (1.6-3.3)·1021 -

48Ca 1274.8 >1.5·1020 - -

Table 2. (Continue)124Sn 1131 - - -

116Cd 1048.2 >2.0·1021 1.1·1022 1.1·1021

76Ge 916.7 >6.2·1021 7.5·1021 -3.1·1023

4.5·1021

136Xe 889 - 2.5·1021 6.3·1021

130Te 735.7 >2.3·1021 5.1·1022 –1.4·1023

-

References[1] A.A. Raduta and C.M. Raduta, Phys. Lett. B 647 (2007) 265.

[2] M. Aunola and J. Suhonen, Nucl. Phys. A 602 (1996) 133.

[3] J. Toivanen and J. Suhonen, Phys. Rev. C 55 (1997) 2314.

[4] S. Stoica and I. Mihut, Nucl. Phys. A 602 (1996) 197.

[5] J.G. Hirsch et al., Phys. Rev. C 51 (1995) 2252.

Table 3. Present “positive” results on 2(2) decay of 100Mo to the first 0+ excited state of 100Ru

T1/2, y;

x1020

N S/B Year, method

6.1+1.8-1.1

9.3+2.8-1.7 ± 1.4

6.0+1.9-1.1 ± 0.6

5.7+1.3-0.9 ± 0.8

133

153

19.5

37.5

~ 1/3

~ 1/3

8/1

3/1

1995, HPGe [6]

1999, HPGe (many samples) [7]

2001, 2xHPGe (coincidence) [8,9]

2007, NEMO-3, (2e+2) [10]

Average value: 6.2+0.9-0.7·1020 y

References

[6] A.S. Barabash et al., Phys. Lett. B 345 (1995) 408.

[7] A. S. Barabash et al., Phys. At. Nucl. 62 (1999) 2039.

[8] L. De Braeckeleer et al., Phys. Rev. Lett. 86 (2001) 3510.

[9] M.J. Hornish et al., Phys. Rev. C 74 (2006) 044314.

[10] R. Arnold et al., Nucl. Phys. A 781 (2007) 209.

NEMO-3

100Mo: bb decay to exc. states

2 decay to the 01+ state: S/B = 3.0

T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y

0 decay to the 01+ state:

T1/2 > 8.9 1022 y @ 90 % C.L.

2 decay to the 21+ state:

T1/2 > 1.1 1021 y @ 90 % C.L.

0 decay to the 21+ state:

T1/2 > 1.6 1023 y @ 90 % C.L.

Nucl. Phys. A 781 (2007) 209

2 decay to the 01+ state: S/B = 3.0

T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y

0 decay to the 01+ state:

T1/2 > 8.9 1022 y @ 90 % C.L.

2 decay to the 21+ state:

T1/2 > 1.1 1021 y @ 90 % C.L.

0 decay to the 21+ state:

T1/2 > 1.6 1023 y @ 90 % C.L.

Nucl. Phys. A 781 (2007) 209

Clear topology:

01+: 2e- + 2 in time & energy and TOF cuts

21+: 2e- + 1 in time & energy and TOF cuts

100Mo

0+

21+ (540 keV)

01+ (1130 keV)

41+ (1227 keV)

0+ (g.s.)100Ru

22+ (1362 keV)

303

4 k

eV

1

2

NEMO-3; 334.3 days of data (Phase I)

TOP VIEW SIDE VIEW

1

2

1

2

e1

e2

e1

e2

100Mo (NEMO-3)

Reconstructed event-candidate

100Mo (NEMO-3)

The main characteristics of selected events

150Nd

Decay scheme

150Nd

0+

21+ (333.9keV)

01+ (740.4 keV)

41+ (773.3 keV)

0+ (g.s.)150Sm

22+ (1046.1 keV)

336

7 k

eV

1

2

E1 = 333.9 keV

E2 = 406.5 keV

SCHEME OF EXPERIMENT

E = 1.9 keV

(for 1332 keV)

T = 11320.5 h

Experiment is done in Modane Underground Laboratory, 4800 m w.e.

Energy spectrum in the range 333.9 keV

Energy spectrum in the range 406.5 keV

Analysis of events in the range of peaks under study

Peak, keV 333.9 ± 1.12 406.5 ± 1.12

Number of events

779 603

Continuous background

656.6 484.5

Isotopes

E, keV

214Bi 227Th 228Ac

333.1, 334.78; 334.37; 332.37

214Bi 211Pb

405.74 404.85

Contribution from background

8.8 22.6 5.4 9.7 8.7

Excess of events

86 ± 28 100 ± 25

150Nd. Transition to the 0+ excited state

T1/2 = [1.4+0.4-0.2(stat) ± 0.3(syst)]·1020 y

[JETP. Lett. 79 (2004) 10]

Comparison of NME for transition to the 0+ ground and 0+

1excited states (for 100Mo and 150Nd)

Conclusion is

NME(g.s.) NME(0+1)

But, in fact, it looks like: NME(g.s.) (1.2-1.3)xNME(0+

1)

III. 2(0)-decay to excited states

Very nice signature:2e- and two (one) gamma with fixed energy Possibility to have “zero” background Possibility to have high sensitivity(if registration efficiency and energy resolution are high enough)

3.1. 2(0)-decay to 2+1 excited

state

Many years people thought that this decay is sensitive only to right-handed currents.T. Tomoda demonstrated that this is not through:“…relative sensitivity of 0+-2+ decays to the neutrino mass

and the right-handed currents are comparable to those of 0+-0+ decays.”

[T. Tomoda, Phys. Lett. B 474 (2000) 245]

The decay is suppressed in ~ two order of magnitude in comparison to transition to 0+

g.s.

Table 4. Best present limits on 2(0)-decay to 2+

1 excited state

Nuclei E2, keV T1/2, y (90%CL)76Ge 1480 > 8.2·1023 (G-M)100Mo 2494.5 > 1.6·1023 (NEMO-3)130Te 1992.7 > 1.4·1023 (MiBeta)116Cd 1511.5 > 2.9·1022 (Solotvino)

136Xe 1649.4 > 6.5·1021 (Milan)82Se 2218.5 > 2.8·1021 (HPGe)

Table 5. Best present limits on 2(0)-decay to the 0+

1 excited state

Nuclei E2, keV T1/2, y (90%CL)

Theory [11-14]

Theory [15]

150Nd 2627.1 >1.0·1020 - -

96Zr 2202.5 >6.8·1019 2.6·1024 *) -

100Mo 1903.7 >8.9·1022 2.6·1026 *) 1.5·1025 *)

82Se 1507.5 >3.0·1021 9.5·1026 *) 4.5·1025 *)

48Ca 1274.8 >1.5·1020 - -

Table 5. (Continue)

116Cd 1048.2 >1.4·1022 1.25·1027 *) -

76Ge 916.7 >1.3·1022 5.6·1026 *) 2.4·1026 *)

130Te 735.3 >3.1·1022 7.5·1025 -

*) For <m> = 1 eV

[11] J. Suhonen, Phys. Lett. B 477 (2000) 99.

[12] J. Suhonen, Phys. Rev. C 62 (2001) 042501.

[13] J. Suhonen, Nucl. Phys. A 700 (2002) 649.

[14] J. Suhonen and M. Aunola, Nucl. Phys. A 723 (2003) 271.

[15] F. Simkovic et al., Phys. Rev. C 64 (2001) 035501.

2(0)-decay to 0+1 excited

state

Future possibilities: - MAJORANA and GERDA with 76Ge ~ 1027 y; - CUORE with 130Te ~ 1026 y; - SuperNEMO with 82Se (or 150Nd) ~ 1024-1025 y;

IV. ECEC to the excited states

1994 (A.S.B. JETP Lett. 59 (1994) 677).

Main assumption: NME(2; 0+g.s. ) NME(2; 0+

1):

then T1/2(0+1) ~ 1021-1022 y for 96Ru, 106Cd, 124Xe, 136Ce;

~ 1023 y for 78Kr and 130Ba

Very nice signature: in addition to two X-rays we have here

two gamma with strictly fixed energy (E ~ 300-1300 keV)

New experiments were proposed

Table 6. Best present limits on ECEC(2) to the 0+

1 excited state

Nuclei EECEC, keV T1/2, y (90%CL) Theory

130Ba 1236 >1.5·1021 *) ~ 1022-1024

106Cd 1580 >7.3·1019 ~ 1021-1023

78Kr 1343 >1.2·1021 **) ~ 1023-1027

92Mo 230 >8.1·1020 ~ 1029

96Ru 1519 >4.5·1016 ~ 1023-1027

*) Extracted from geochemical experiment

**) Extracted from result for 0+-0+g.s. transition

IV.2. ECEC(0); resonance conditions

Transition to the ground state. For the bestcandidates (<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)

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.

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, E-energy of excited state)

In 1982 the same idea for transition to ground and excited 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 keVQ’(KK;0+) = M – E*(0+) – 2EK = = (-4.9 ± 4.8) keV

T1/2 3·1024 y (for m = 1 eV)

(if Q’ ~ 10 eV)

Resonance conditions In 2004 the same conclusion was done by

Z. Sujkowski and S. Wycech (Phys. Rev. C 70 (2004) 052501).

Resonance condition (using EC(2)arguments):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

Decay-scheme of 74Se

Here Q = M = 1209.7 keV

Q’ = M - 2Eb

Q’(E*) = Q’ – 1204.2

74Se. (Nucl. Phys. A 785 (2007) 371)

400 cm3 HPGe detector (Modane Underground Laboratory; 4800 m w.e.)

563 g of natural Se (4.69 g of 74Se) Measurement time is 436.56 h

74Se

74Se (Nucl. Phys. 785 (2007) 371.)

74Se. (Nucl. Phys. A 785 (2007) 371)

Transition to 2+2(1204.2 keV) state

(595.8 keV and 608.4 keV lines wereinvestigated):

T1/2(0;L1L2) > 0.55·1019 y

74Se. Possible improvements

1 kg of 74Se ~ 3·1021 y

200 kg of 74Se (using an installation such as GERDA or MAJORANA)

~ 1026 y

Other isotope-candidates

Nuclei A,% M,keV E*,keV EK EL2

74Se 0.89 1209.7±2.3 1204.2(2+) 11.1 1.2378Kr 0.35 2846.4±2.0 2838.9(2+) 12.6 1.4796Ru 5.52 2718.5±8.2 2700(?) 20 2.86106Cd 1.25 2770±7.2 2741.0(1,2+) 24.3 3.33112Sn 0.97 1919.5±4.8 1871.0(0+) 26.7 3.73130Ba 0.11 2617.1±2.0 2608.4(?) 34.5 5.10136Ce 0.20 2418.9±13 2399.9(1+,2+

2392.1(1+,2+

37.4 5.62

162Er 0.14 1843.8±5.6 1745.7(1+) 53.8 8.58

Table 7. Best present limits on ECEC(0) to the excited state (for isotope-candidates

with possible resonance conditions)

Nuclei E*(Jf) T1/2, y

106Cd 2741 (1,2+) > 3·1019 [16]> 5·1019 *) [17]

74Se 1204.2(2+) > 0.55·1019 [18]

130Ba 2608.4(?) > 1.5·1021 [19,20](geochemical)

78Kr 2838.9(2+) > 1.2·1021 *) [21]

*) Extracted from result for 2(0+-0+g.s.) transition

References[16] P. Belli et al., Astr. Phys. 10 (1999) 115.[17] N.I. Rukhadze et al., Phys. At. Nucl. 69 (2006) 2117.[18] A.S. Barabash et al., Nucl. Phys. A 785 (2007) 371.[19] A. P. Meshik et al., Phys. Rev. 64 (2001) 035205.[20] A.S. Barabash and R.R. Saakyan, Phys. At. Nucl. 59

(1996) 179.

[21] Ju.M. Gavriljuk et al., Phys. At. Nucl. 69 (2006) 2124.

g.s.-g.s. transitions

152Gd (0.2%), 164Er (1.56%),180W(0.13%)

(There are only X-rays in this case)

Problems

There is no good theoretical description

Accuracy of M (and Q as a result) is not very good (~ 2-10 keV)

[It is possible to improve the accuracy of M to ~ 200 eV]

CONCLUSION 2(2)-decay to 0+ excited state was detected for 100Mo and 150Nd There are good prospects to search for

2(2) and 2(0)-decay to 0+ excited states in future (large) experiments

ECEC(0) is a “new-old” possibility to search for neutrino mass (in case of resonance conditions)