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DOUBLE BETA DECAY TO THE EXCITED STATES (EXPERIMENTAL REVIEW)

DOUBLE BETA DECAY TO THE EXCITED STATES (EXPERIMENTAL REVIEW). A.S. BARABASH ITEP, MOSCOW. OUTLINE. Introduction 2  - (2) -decay to the excited ststates - 100 Mo - 150 Nd 2  - (0) –decay to the excite states ECEC to the excited states Conclusion. I. Introduction.

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DOUBLE BETA DECAY TO THE EXCITED STATES (EXPERIMENTAL REVIEW)

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  1. DOUBLE BETA DECAY TO THE EXCITED STATES (EXPERIMENTAL REVIEW) A.S. BARABASH ITEP, MOSCOW

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

  3. I. Introduction

  4. 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.

  5. 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.

  6. 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.

  7. 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 kgof 100Mo was started on 30 May 1990 (in Soudan mine).

  8. 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

  9. 1999 – 2-nd positive result for100Mo; 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).

  10. ITEP-TUNL experiment

  11. 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).

  12. II. 2-(2)-decay to the excited states Table 1. 2 transition to 2+1 excited state.

  13. Table 1. (Continue)

  14. Table 2. 2-decay to 0+1excited state

  15. Table 2. (Continue)

  16. 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.

  17. Table 3.Present “positive” results on 2(2) decay of 100Mo to the first 0+ excited state of 100Ru Average value: 6.2+0.9-0.7·1020 y

  18. 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.

  19. 0+ 100Mo 3034 keV 41+ (1227 keV) g2 01+ (1130 keV) 21+ (540 keV) 22+ (1362 keV) g1 0+ (g.s.) 100Ru NEMO-3100Mo: bb decay to exc. states NEMO-3; 334.3 days of data (Phase I) 2nbb decay to the 01+ state: S/B = 3.0 T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y 0nbb decay to the 01+ state: T1/2 > 8.9  1022 y@ 90 % C.L. 2nbb decay to the 21+ state: T1/2 > 1.1  1021 y @ 90 % C.L. 0nbb decay to the 21+ state: T1/2 > 1.6  1023 y@ 90 % C.L. Nucl. Phys. A 781 (2007) 209 Clear topology: 01+: 2e- + 2g in time & energy and TOF cuts 21+: 2e- + 1g in time & energy and TOF cuts

  20. TOP VIEW SIDE VIEW e1 2 e1 e2 1 2 1 e2 100Mo (NEMO-3) Reconstructed event-candidate

  21. 100Mo (NEMO-3) The main characteristics of selected events

  22. 0+ 150Nd 3367 keV 41+ (773.3 keV) g2 01+ (740.4 keV) 21+ (333.9keV) 22+ (1046.1 keV) g1 0+ (g.s.) 150Sm 150Nd Decay scheme E1 = 333.9 keV E2 = 406.5 keV

  23. 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.

  24. Energy spectrum in the range 333.9 keV

  25. Energy spectrum in the range 406.5 keV

  26. Analysis of events in the range of peaks under study

  27. 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]

  28. 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)

  29. 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)

  30. 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.

  31. Table 4. Best present limits on 2(0)-decay to 2+1 excited state

  32. Table 5. Best present limits on 2(0)-decay to the 0+1excited state

  33. Table 5. (Continue) *) 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.

  34. 2(0)-decay to 0+1excited state • Future possibilities: - MAJORANA and GERDA with 76Ge  ~ 1027 y; - CUORE with 130Te  ~ 1026 y; - SuperNEMO with 82Se (or 150Nd)  ~ 1024-1025 y;

  35. 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

  36. Table 6. Best present limits on ECEC(2) to the 0+1 excited state *) Extracted from geochemical experiment **) Extracted from result for 0+-0+g.s. transition

  37. IV.2. ECEC(0); resonance conditions Transition to the ground state. For the best candidates (<m> = 1 eV): ++ (0) ~ 1028-1030 y +EC(0) ~ 1026-1027 y ECEC(0) ~ 1028-1031 y (One can compare these values with ~ 1024-1025 y for 2--decay)

  38. 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 comparison with EC+(0)) – M. Doi and T. Kotani, Prog. Theor. Phys. 89 (1993)139.

  39. 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!

  40. J. Bernabeu, A. De Rujula, C. Jarlskog, Nucl. Phys. B 223 (1983) 15 112Sn  112Cd [0+(1871)] M= 1919.5±4.8 keV Q’(KK;0+) = M – E*(0+) – 2EK = = (-4.9 ± 4.8) keV T1/2 3·1024 y (for m = 1 eV) (if Q’ ~ 10 eV)

  41. 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

  42. Decay-scheme of 74Se Here Q = M = 1209.7 keV Q’ = M - 2Eb Q’(E*) = Q’ – 1204.2

  43. 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

  44. 74Se

  45. 74Se (Nucl. Phys. 785 (2007) 371.)

  46. 74Se.(Nucl. Phys. A 785 (2007) 371) Transition to 2+2(1204.2 keV) state (595.8 keV and 608.4 keV lines were investigated): T1/2(0;L1L2) > 0.55·1019 y

  47. 74Se. Possible improvements • 1 kg of 74Se  ~ 3·1021 y • 200 kg of 74Se (using an installation such as GERDA or MAJORANA)  ~ 1026 y

  48. Other isotope-candidates

  49. Table 7. Best present limits on ECEC(0) to the excited state (for isotope-candidates with possible resonance conditions) *) Extracted from result for 2(0+-0+g.s.) transition

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