Current status and future of double β decay experiments. Fedor Danevich Institute for Nuclear Research, Kyiv, Ukraine

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1 Current status and future of double β decay experiments Fedor Danevich Institute for Nuclear Research, Kyiv, Ukraine 1

2 content 2β-experiments current status projects normal hierarchy? conclusions 2

3 2β decay decay modes and channels Decay channels: modes: Two neutrino ββ decay (A,Z) (A,Z+2) + e - + e - + ν e + Double (electron) decay ν e 2β - conserving lepton number In contrast, the neutrinoless decay (A,Z) (A,Z+2) + e - + e - violates lepton number by two units and is forbidden in the standard electroweak theory Another Double decay electron mode capture, involves the emission electron of capture a light neutral with boson (s), positron a Majoron, emission, double as postulated positron in decay some extensions of the standard electroweak theory (A,Z) (A,Z+2) + e - + e - + χ 2ε, εβ +, 2β + 3

4 Half-life life of 0ν2β0 (T 1/2 0ν ) -1 G 0ν2 β (Q 2β,Z) M 0ν2 β 2 m 2β 2 G 0ν2 β (Q 2β,Z) phase space integral M 0ν2 β nuclear matrix element m 2β = Σm j U ej2 effective neutrino Majorana mass T 1/2 0ν yr m 2β = 0.05 ev F. Simkovic et al., PRC 77 (2008)

5 2β decay and neutrino oscillations m 3 atmospheric ν e ν µ ν τ m 2 m 1 m 3 m 2 m 1 solar m 2 m 1 m 3 normal inverted degenerated 5

6 double β decay can clarify very important problems of Particle Physics and Cosmology: Nature of neutrino (Majorana or Dirac particle) Absolute scale of the neutrino mass Neutrino mass hierarchy Lepton number conservation Establishing a possible Majorana nature of neutrino would be a fundamental discovery Status and Perspectives of Astroparticle Physics in Europe, ASPERA Roadmap Phase I,

7 experimental methods Geochemical 82 Se Radiochemical 238 U Direct registration of ββ events 96 Zr 100 Mo 128,130 Te 130,132 Ba (?) detector source (tracing) detector = source (calorimetric) 7

8 Heidelberg-Moscow [1] T 1/2 T 1/2 1/ yr m ν 0.35 ev IGEX [2] 1/ yr m ν 0.38 ev 76 Ge? 55 kg year 71 kg year T 1/ yr m ν ev [3] [1] H.V. Klapdor-Kleingrothaus et al., EPJA 12 (2001) 147 [3] Mod. Phys. Lett. A. 21 (2006) 1547 [2] C.E. Aalseth et al., PRC 59 (1999)

9 136 Xe T 1/2 > yr m ν <2.2 ev R. Luescher et al., PLB 434 (1998) 407 9

10 The NEMO-3 2β decay experiment 2β tracking detector energy of electrons angular distributions event vertex 7.1 kg of 97% 100 Mo yr m ν ev 0.96 kg of 97% 82 Se yr m ν ev kg of 91% 150 Nd yr m ν ev A. Barabash (for NEMO-3) JPSC 173 (2009)

11 130 Te Energy absorber single TeO 2 crystal 790 g, 5 x 5 x 5 cm Thermometer (doped Ge chip) MT = 18 kg ( 130 Te) yr BG = 0.18±0.01 c/kev/kg/y FWHM = 7 kev (average for 790 g detectors) m ββ ββ < ev M. Sisi, presentation on TAUP Co sum peak 2505 kev 130 Te 0νββ Τ 1/2 0ν2 β > yr (90% c.l.) 11

12 2β experiments with crystal scintillators PHYSICAL REVIEW 146 (1966) CaF 2 (Eu), 19 g T 1/2 0ν > yr CdWO Cd, 114 Cd, 116 Cd, 180 W, 186 W CaF 2 40 Ca, 48 Ca GSO 160 Gd ZnWO 4 64 Zn, 70 Zn, 180 W, 186 W CeF 3, CeCl Ce, 138 Ce BaF Ba, 132 Ba T 1/2 0ν > yr T 1/2 2ν = yr (2ν2β in 116 Cd) 12

13 CaF 2 (Eu) crystal scintillators 48 Ca 1553 kg day kg day of exposure Energy resolution (FWHM): 4.27 MeV Background: 0 events was observed T 0ν2β 1/2 ν2β > yr yr m ν ev PRC 78 (2008)

14 160 Gd Search for 2β2 decay of 160 Gd Gd 2 SiO 5 (Ce), 635 g, h 2β 160 Gd Q 2β = 1730 kev T 1/2 0ν 1/ yr T 1/2 2ν 1/ yr at 90 % C.L. 160 Gd is interesting candidate for high sensitive 2β experiment due to the large natural abundance (21.86%) and promising theoretical estimations of the matrix elements Yad. Fiz. 58 (1995) 195; NPA 694 (2001)

15 116 Cd 2β decay of 116 Cd Plastic active shield CdWO CdWO 4 crystal ~0.5 kg Plastic light guide The main results: T 2ν 1/2 = yr T 0ν 1/ yr m ν 1.7 ev PRC 68 (2003)

16 Nuclide 48 Ca 76 Ge 82 Se 100 Mo 116 Cd 130 Te 136 Xe Nd 150 Nd best 0ν2β0 - experiments Experimental limits T 1/2 (yr) > > , > = > > > > > > Limits m ν (ev) < (3.5 22) < ( ) = < ( ) < ( ) 0.9) < 1.7 < ( ) 0.7) < 2.2 < ( ) [1] S. Umehara et al., PRC 78 (2008) [2] H.V. Klapdor-Kleingrothaus et al., EPJA 12 (2001) 147 [3] C.E. Aalseth et al., PRC 59 (1999) 2108 [4] H.V. Klapdor-Kleingrothaus, I. Krivosheina, Mod. Phys. Lett. A. 21 (2006) 1547 [5] A. Barabash, JPSC 173 (2009) [6] F.A. Danevich et al., PRC 68 (2003) [7] M. Sisi, presentation on TAUP-2009 [8] R. Luescher et al., PLB 434 (1998) 407 Ref. [1] [2,3] [4] [5] [5] [6] [7] [8] [5] 16

17 2ε, εβ +, 2β 2 + processes mν mν m 0 1 0ν 2 0ν 0ν ν 0ν 2 0ν 2 ( T1 / 2 ) = Cmn ( ) + Cm λ λ ( ) + Cm η η ( ) + Cλλ λ + Cηη η + C m m m ν 0ν λη e e e λ η Half-lives for 0νε νεβ + decay depend strongly on whether the decay is dominated by the mass mechanism or right-handed weak current Search for the 0ν0 modes of 2ε, 2 εβ + and 2β + processes could help for a refined investigation of the neutrino nature and weak interaction [1] [1] M. Hirsch et al., Z. Phys. A 347 (1994)

18 2β decay of 106 Cd TGV experiment to search for 2β decay of 106 Cd in the Modane UL JINR Dubna; CSNSM Orsay Paris; IEAP Prague T 1/2 0νEC/EC > yr T 1/2 2νEC/EC > yr N.I. Rukhadze et al., Bull. Rus. Acad. Sci.: Phys. 73 (2009)

19 Search for 2β decay of 64 Zn INFN Roma 1 & 2; LNGS; INR Kyiv; ISMA Kharkov DAMA R&D, Gran Sasso Low BG PMT ZnWO kg Polystyrene Light-guide in particular: T 2ν2K 1/ yr T 0ν2ε 1/ yr T 2νεβ 1/2 T 0νεβ 1/2 νεβ yr νεβ yr at 90% C.L. Limits on T 1/2 relatively to 2β processes in 70 Zn, 180 W, 186 W on the level of yr P. Belli et al., PLB 658 (2008) 193 P. Belli et al., NPA 825 (2009)

20 Resonant 0ν2ε is possible 2β-decay of 96 Ru 158 h, 483 g of Ru limt 2β 1/ y P.Belli et al., Eur. Phys. J (corr. proof) y? y 20

21 Some best 2ε, 2 εβ +, 2β + experiments Nuclide 40 Ca 54 Fe 58 Ni 64 Zn 78 Kr 92 Mo 96 Ru 106 Cd 130 Ba 132 Ba Channel 2ε, εβ +, 2β 2 > (1-5) Gaseous detector 2ε, εβ + > (0.06-9) HPGe γ spectrometry 2ε, εβ +, 2β 2 + 2ε, εβ +, 2β 2 + 2ε, εβ +, 2β 2 + 2ε Experimental limits 1/2 (yr) T 1/2 2ε > (3-6) CaF 2 (Eu) scintillators 2ε > (4-5) HPGe γ spectrometry 2ε, εβ + > (0.2-7) HPGe γ spectrometry 2ε, εβ + > (0.06-7) ZnWO 4 scintillators > ( ) > (0.01-4) 4) 10 > = (2.2 ± 0.5) 10 > Technique HPGe γ spectrometry HPGe γ spectrometry, NaI(Tl) γ spectrometry CdWO 4 scintillators CdZnTe semiconductor Geochemical Geochemical Geochemical 21

22 Search for 2β decay of 106 Cd 106 CdWO 4 FWHM=10% Crystal boule 231 g mm (87% of mass of initial material) enriched in 106 Cd to 66% Attenuation length 60 cm newer reported Excellent optical and scintillation properties thanks to special R&D to purify raw materials 22

23 Lewis Carroll Through the Looking Glass Sir Charles Lutwidge Dodgson ( Lewis Carroll ) Alice's Adventures in Wonderland Sir John Tenniel Illustrator of Alice s Adwentures The Just White look along King awaits the road, messengers and tell me from if you the can White see Queen. either of He them. asks Alice: I see nobody on the road, said Alice. I only wish I had such eyes, the King remarked in a fretful tone. To be able to see Nobody! And at the distance too! Why, it's as much as I can do to see real people, by this light! 2β experiments only wish to have better sensitivity 23

24 2β projects 24

25 GERDA 76 Ge LNGS, Italy Phase I 20 kg of enriched HP 76 Ge detectors from H-M and IGEX Background expected ~0.01 cnt/(yr kg kev) T 1/2 ~ yr, m ν ~ ev Phase II 100 kg yr exposition BG ~0.001 cnt/(yr kg kev) Phase III 1 t of 76 Ge T 1/2 ~ yr, m ν ~ ev mν ~ 0.01 ev Important advantage: good energy resolution ~ 2-3 kev (0.1%) hep-ex/

26 Majorana 76 Ge At present the collaboration working on a 60 kg prototype set-up material selection detector segmentation pulse shape analysis electro-formation of copper parts and granularity 500 kg of Ge, isotopically enriched to 86% in 76 Ge, in the form of ~200 segmented detectors, equipped by pulse shape analysis electronics T 1/2 ~ yr m ν ~ ev good energy resolution ~ 2-3 kev (0.1%) hep-ex/

27 EXO The EXO 136 Xe ββ decay project using laser tagging PLB 480 (2000) Xe facet 1: EXO-200 is prototype to develop techniques of working with liquid xenon in a time projection chamber (200 kg of enriched to 80% 136 Xe) with a goal to detect 2ν mode and to set a competitive limit on neutrinoless double beta decay facet 2: EXO - a ton scale experiment using 136 Xe to search for 0ν2β decay Large Time Projection Chamber or Scintillation Detector Detecting Ba + ions in the final state of 136 Xe T 1/ yr (1 t of 136 Xe) m ν 0.05 ev Good possibilities to enrich 136 Xe low energy resolution ~ 5-7% 27

28 CUORE From CUORICINO to CUORE (Cryogenic Underground Observatory for Rare Events) CUORE = closely packed array of 988 detectors 19 towers - 13 modules/tower - 4 detectors/module M = 741 kg ~ Te nuclides Compact structure, ideal for active shielding 130 Te Each tower is a CUORICINO-like detector Special dilution refrigerator good energy resolution ~ 5-7 kev (0.3%) 28

29 SuperNEMO 82 Se( 150 Nd) 82 Se foil Track volume Calorimeter 100 kg of enriched 82 Se ( 150 Nd) foil, track reconstruction 20 modules ~5 kg of 82 Se each Radiopurity of 82 Se at the level of a few Bq/kg ~4% of energy resolution at 3 MeV A half-life sensitivity is predicted: T 1/ yr m ν 0.05 ev A track experiment expected energy resolution ~4%, detection efficiency (~30%) 29

30 Design Concepts of CANDLES 48 Ca Liquid Scintillator (Veto Counter) Undoped CaF 2 Scintillator CaF CaF 2 (Pure) Long Attenuation Length (>10m@350nm) Double Beta Decay Source 48 Ca (Q ββ =4.27MeV) Peak Emission at UV Region (280nm) Wave Length Shifter Liquid Scintillator Wave Length Shifter 4 π Active Shield Large Photomultiplier Tube Signals from both scintillators are detected simultaneously CaF 2 (Pure) Buffer Oil Large PMT Active Shielding Technique Different Time Constants CaF 2 (pure) : ~1µsec Liquid Scintillator : a few 10 nsec Courtesy Prof. Saori Umehara High Q ββ energy (4.27 MeV) large mass, low isotopic abundance of 48 Ca (0.187%) 30

31 SNO++ 2β decay of 150 Nd with Nd-loaded liquid scintillator 0.1% Nd in 1000 tons of natural Nd loaded liquid scintillator 56 kg of 150 Nd 150 Nd low energy resolution ~ 6-7%, too large mass ~1 kt 31

32 Advancement of 116 Cd experiment mm An excellent pulse-shape discrimination Energy resolution 3.9% at 2.6 MeV R&D to produce kg of enriched 116 CdWO 4 crystals is in progress in collaboration with the DAMA group, ITEP (Moscow, Russia), NIIC (Novosibirsk, Russia) NIMA 569 (2006) 743; NIMA 556 (2006)

33 Results on the first array of CdWO 4 crystals 2615 kev 208 Tl γ Background-Free area 44 days background α particles The MC simulation predicts a background level of 10-4 c/kev/kg/y in the region of interest Courtesy Dr. Stefano Pirro, INFN - Sezione di Milano Bicocca 33

34 ZnSe an extremely interesting compound Courtesy Dr. Stefano Pirro, INFN - Sezione di Milano Bicocca 34

35 ZnMoO 4 A promising Molibdate A 22 g ZnMoO 4 crystal was grown by Institute for Scintillation Materials (Kharkov, Ukraine) in collaboration with Institute for Nuclear Research (Kiev, Ukraine) βγ 226 Ra, 222 Rn, 218 Po, 214 Bi- 214 Po (56 mbq/kg) 210 Pb (360 mbq/kg) Courtesy Dr. Stefano Pirro, INFN - Sezione di Milano Bicocca 35

36 Scintillators for double β decay search Good Scintillation light Poor Scintillation light No Scintillation light PbMoO 4 ZnSe CdMoO 4 ZrO 2 Li 2 MoO 4 MgMoO 4 TeO 2 SrMoO 4 CdWO 4 CaF 2 CaMoO 4 ZnMoO 4 The energy resolution needed to go towards normal hierarchy can be achieved only by bolometers and semiconductors Different nuclei can be studied Li 2 Zn 2 (MoO 4 ) 3 Courtesy Dr. Stefano Pirro, INFN - Sezione di Milano Bicocca 36

37 Normal hierarchy? Is it possible to go toward normal hierarchy? m ν ev Т 1/ / yr 30 yr 37

38 Energy resolution Should be better than ~1% (FWHM) HPGe, cryogenic bolometers Y.G. Zdesenko et al., J. Phys. G, 30 (2004)

39 Exposition Mass of detector t Time of experiments 10 years Detection efficiency 100% Y.G. Zdesenko et al., J. Phys. G, 30 (2004)

40 Background 0 counts / (10 yr 10 t 30 kev) ~ cnt / (yr kev kg) At present achieved background counting rate: cnt / (yr kev kg) 48 Ca, CaF(Eu) 0.01 cnt / (yr kev kg) 136 Xe, TPC 0.04 cnt / (yr kev kg) 116 CdWO 4, Solotvina 0.1 cnt / (yr kev kg) HP 76 Ge, H-M, IGEX (no PSA) 0.2 cnt / (yr kev kg) Te0 2, CUORICINO Problems and possible solutions: 2ν-mode energy resolution only U, Th, Radon < ( ) g/g, «wise» detector (pulse shape analysis, etc) Cosmogenic activation: choice of nuclei (high Q ββ ), production of detector deep underground Background from neutrino: minimal volume of detector, energy resolution Special radiopure technology is needed 40

41 0ν2β experiments can: conclusions I measure m ν ев and establish hierarchy of the neutrino mass determine nature of neutrino (Dirak or Majorana) test lepton number conservation The most sensitive 2β-2 experiments give limits on half-lives lives of nuclei ( 48 Ca, 76 Ge, 82 Se, 100 Mo, 116 Cd, 130 Te, 136 Xe, 150 Nd) and on the effective neutrino Majorana mass: Т 1/ yr m ν ev 25 yr The best 2ε, 2 εβ+, 2β+ 2 experiments give only limits on half-lives lives of nuclei ( 40 Ca, 54 Fe, 58 Ni, 78 Kr, 92 Mo, 96 Ru, 10 6 Cd, 130 Ba, 13 2 Ba): Т 1/2 1/ yr Even 2ν2 mode is still not detected clearly. Further development of experimental methods is required 41

42 conclusions II 100 кг 0ν2β-experiments 0 ( 48 Ca, 76 Ge, 82 Se, 130 Te, 136 Xe, 100 Mo, 150 Nd, ) to test inverted hierarchy of neutrino mass is in preparation to test inversed hierarchy of the neutrino mass Т 1/ yr m ν эв Mo, 116 Cd, 116 Cd, 0ν2β-experiment able to detect m ν of the normal hierarchy should have a sensitivity Т 1/ / yr 30 yr Background of a detector looks the most complicated and exciting problem 42

43 43

44 2β decay - history M. Goeppert Mayer, Double β Disintegration Phys. Rev. 48 (1935) 512 G. Racah, Nuovo Cimento. 14 (1937) 322 Ettore Majorana ? Majorana neutrino is identical with its antiparticle ν ν Paul Adrien Maurice Dirac Neutrinoless double beta decay is only possible if neutrino is a massive Majorana particle 44

45 2β decay of 100 Мо to excited level of 100 Ru sample γ ~0.8 kg of 100 Mo T 1/2 = (6.5 ) yr yr of measurements by the ultra-low background HP Ge γ spectrometer Ge-Multi at LNGS P.Belli et al., in preparation to PRC 45