Double beta decay experiments: status and prospects

Transcription

1 Double beta decay experiments: status and prospects Fedor Danevich Institute for Nuclear Research, Kyiv, Ukraine in this presentation: Introduction Status of 2 decay research Goals and prospects Conclusions 1/45

2 Introduction Neutrino oscillations neutrino is massive The experiments with solar, atmospheric, reactor, and accelerator neutrinos have provided compelling evidences for flavour neutrino oscillations transitions in flight between the different flavour neutrinos e, μ, τ, caused by nonzero neutrino masses and neutrino mixing, when flavor neutrinos ll are superposition of left handed massive neutrinos with masses m j : jl U n U ll lj jl j 1 is the unitary Pontecorvo-Maki-Nakagawa-Sakata mixing matrix, l e,, [1] S. Petcov, The nature of massive neutrinos, Advances in High Energy Physics (2013) [2] R. N. Mohapatra, Origin of neutrino masses and mixings, Nucl. Phys. 91 (2001) 313 [3] A. Strumia, F. Vissani, Neutrino masses and mixings and... arxiv:hep-ph/ v /45

3 Introduction neutrino mass the absolute neutrino mass scale Sum of three neutrino masses Σm(ν i ) < ev * Cosmology Average electron neutrino mass : m( e ) = 3 i 1 m U 2 i ei 2 < 2 ev spectra of tritium Effective Majorana 3 2 iα neutrino mass m = mu i ei e <0.1-1 ev ** i 1 2 experiments * The cosmological limits are to some extent model and analysis dependent ** The limits depend on nuclear matrix elements calculations 3 /45

4 Introduction Double beta decay (2 ) Example for isobars with A = 136 Double beta decay was considered by Maria Goeppert-Mayer in 1935 [1] 2 2EC, EC +, 2 + [1] Maria Goeppert Mayer, Double Disintegration, Phys. Rev. 48 (1935) /45

5 Introduction Double beta (2 ) decay and neutrino physics Neutrino considered by Ettore Majorana [1] is identical to its antiparticle:, in contrast to the neutrinos proposed by Dirac Paul Adrien Maurice Dirac 2 2 decay 0 2 decay The neutrinoless (0 ) 2 decay is possible if neutrino is Majorana particle Test of the Lepton number conservation Sensitive to the absolute value of the neutrino mass, the neutrino mass hierarchy, the Majorana CP phases Can be mediated by presence of right handed currents in weak interactions, massless (or very light) Nambu-Goldstone bosons (majorons), and may other effects beyond the Standard Model Majorana neutrino could explain the baryon asymmetry of the Universe Neutrino is only known dark matter particle [1] E. Majorana, Teoria simmetrica dell elettrone e del positrone, Nuovo Cimento 14 (1937) 171 Ettore Majorana 5 /45

6 Introduction 0 2 half-life ( Mass and hierarchy of neutrino masses 0 2 T 1/2 ) depends on the neutrino mass and nuclear structure: Nuclear structure, /2 2 ( T ) G (Q, Z) M m energy of decay m = m j U ej2 effective Majorana neutrino mass m 3 e m 3 atmospheric solar m 2 m 1 m 2 m 1 m 1 m 3 m 2 Useful reviews on 0 2 decay [1-4] normal inverted degenerated [1] J.D.Vergados, H.Ejiri, F.Simkovic, Theory of neutrinoless double-beta decay, RPP 75 (2012) [2] J.Barea, J.Kotila, F.Iachello, Limits on Neutrino Masses from Neutrinoless Double- Decay, PRL 109 (2012) [3] H. Päs and W. Rodejohann, Neutrinoless double beta decay, New J. Phys. 17 (2015) [4] S. Dell Oro et al., Neutrinoless Double Beta Decay: 2015 Review, AHEP 2016 (2016) /45

7 Status of 2 decay research Status of 2 decay research (68 years after the first experiment in 1948 [1]) The two neutrino mode (2 2 ) is detected in 11 nuclei ( 48 Ca, 76 Ge, 82 Se, 96 Zr, 100 Mo, 116 Cd, 128 Te, 130 Te, 136 Xe, 150 Nd, 238 U) with the half-lives in the range T 1/2 = yr (the rarest decay ever observed) The 0νββ decay is still not observed. The best half-life limits are on the level of T 1/ yr By using the experimental limits, the effective Majorana neutrino mass can be limited on the level of m < (0.1 1) ev (the interval is due to uncertainties of the nuclear matrix elements calculations) 2 processes with decrease of nuclear charge (2, +, 2 + ) are not observed, with the best limits on the level of yr. There are indications on two-neutrino double-electron capture in 130 Ba and 78 Kr with the half-lives on the order yr [1] E. Fireman, Artificial Radioactive Substances. Phys. Rev. 74 (1948) /45

8 Status of 2 decay research GERDA: search for 0 2 decay of 76 Ge T 1/2 = yr [1] T 1/2 > yr Schematic view of GREDA T 1/2 ( ) 10 yr Background spectrum, exposure 21.6 kg yr T 1/2 > yr m < ev [2] Unfortunately the statistic is not high enough to disprove or confirm the claim Phase II with 35 (7) kg of enriched (natural) Ge detectors is running from December 2015 [1] H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B 586 (2004) 198 [2] M. Agostini et al., Phys. Rev. Lett. 111 (2013) /45

9 Status of 2 decay research Cuoricino CUORE cryogenic search for 0 2 decay 130 Te Te Cuoricino Exposure 19.7 kg yr ( 130 Te) T 1/2 > yr m < ev [1] First CUORE-0 result: T 1/2 > yr [2] m < ev CUORE cryostat The CUORE is in commissioning stage and should start this year [1] E. Andreotti et al., Astropart. Phys. 34 (2011) 822 [2] K. Alfonso et al., Search for Neutrinoless Double-Beta Decay of Te130 with CUORE-0, Phys. Rev. Lett. 115, /45

10 Status of 2 decay research NEMO-3: search for 0 2 decay of 100 Mo ( 48 Ca, 96 Zr, 82 Se, 116 Cd, 130 Te, 150 Nd) Two-electron energy spectrum and the expected background distributions. The solid histogram represents the spectrum of 2νββ decays and radioactive backgrounds. The dashed histogram represents a hypothetical 0νββ signal. Full reconstruction of ββ events T 1/2 (2νββ) = [ (stat) 0.54(syst)] yr [1] T 1/2 (0νββ) > yr, m < ev [2] SuperNEMO demonstrator, is under construction in the Modane Underground Lab The main isotope is 82 Se ( 150 Nd and 48 Ca could be installed if isotopic enrichment methods will be available) [1] R. Arnold et al., First results of the search for neutrinoless double-beta decay with the NEMO 3 detector, PRL. 95 (2005) [2] R. Arnold et al., Results of the search for neutrinoless double-β decay in 100 Mo with the NEMO-3 experiment, PRD 92 (2015) (2015) 10 /45

11 Status of 2 decay research EXO: search for 0 2 decay of 136 Xe Time-projection chamber with 110 kg of enriched in 136 Xe to 81% exposure 32.5 kg yr T 1/2 > yr m < ev [1] [1] M. Auger et al., PRL 109 (2012) [2] J.B. Albert et al. (The EXO-200 Collaboration) Nature 510 (2014) /45

12 Status of 2 decay research KamLAND-Zen: search for 0 2 decay of 136 Xe 300 kg of enriched 136 Xe dissolved in liquid scintillator T 1/2 > yr m < ev [1] Reduction of 110m Ag [1] A. Gando et al., Search for Majorana Neutrinos near the Inverted Mass Hierarchy region with KamLAND-Zen, arxiv: v1 [hep-ex] 10 May /45

13 Status of 2 decay research 116 Cd is promising 2 candidate Advantages of 116 Cd Large energy of decay Q 2 = (13) kev [1] Large isotopic abundance = 7.49(18)% [2] and possibility of enrichment by centrifugation Promising theoretical estimations of decay probability (see, e.g. [3, 4]) Availability of cadmium tungstate crystal scintillators (CdWO 4 ) as detectors for 2 experiment with 116 Cd [1] S. Rahaman et al., Phys. Lett. B 703 (2011) 412 [2] M. Berglund and M.E. Wieser, Pure Appl. Chem. 83 (2011) 397 [3] J.D.Vergados, H.Ejiri, F.Simkovic, Rep. Prog. Phys. 75 (2012) [4] J. Barea, J. Kotila, and F. Iachello Phys. Rev. Lett. 109 (2012) /45

14 Status of 2 decay research R&D of enriched 116 CdWO 4 crystal scintillators ( 116 Cd) = 82% 116 CdWO 4 scintillator 1868 g Yield of crystal 87% Losses of 116 Cd 2% The crystal was cut into 3 scintillation elements Optical transmission curve of 116 CdWO 4 crystal before and after annealing The excellent optical and scintillation properties of the crystal were obtained thanks to the deep purification of 116 Cd and W, and the advantage of the lowthermal-gradient Czochralski technique to grow the crystal [1] 116 CdWO 4 crystal (510 g) grown in 1986 for the Solotvina experiment [2] [1] A.S. Barabash et al., JINST 06( 2011) p08011 [2] F.A.Danevich et al., JETP Lettt. 49 (1989) /45

15 Status of 2 decay research 116 CdWO 4 scintillation detector PTFE container filled by liquid scintillator High purity quartz lightguide 7 40 cm PMT Hamamatsu 116 CdWO 4 R6233 FWHM 5% at 2615 kev 15 /45

16 Status of 2 decay research Low background DAMA R&D set-up at LNGS Lead 15 cm Copper 10 cm Air-tight Cu box flushed by high purity N 2 gas 116 CdWO 4 detectors An event-by-event data acquisition system based on a 1 GS/s 8 bit transient digitizer (operated at 50 MS/s) records the time of each event and the pulse shape over a time window of 100 s from the 116 CdWO 4 detectors Cadmium 1.5 mm Plexiglas box continuously flushed by high purity N 2 gas Polyethylene 4-10 cm The background rate in the region of interest MeV (after pulse-shape discrimination) is on the level of 0.1 counts/(yr kev kg) 16 /45

17 Status of 2 decay research Two neutrino 2 decay of 116 Cd, 113m Cd, h 40 K, 1461 ext. int. U 40 K Cd 208 Tl, 2615 Q Cd int. Th Sources of the systematic error Source Number of nuclei Contribution yr Live time Efficiency of PSD Model of background, interval of fit 0.1 Simulation Interval of the fit: kev T stat syst / [ (.) 0.14(.)] 10 yr 17 /45

18 T 1/ yr Status of 2 decay research Comparison with other experiments NEMO-2 [3] Solotvina 1995 [2] Solotvina 2003 [5] NEMO-2* [6] NEMO-3 [7] Aurora 2016 ELEGANT V [1] Solotvina 2000 [4] Year of publication [1] H. Ejiri et al., J. Phys. Soc. Japan 64 (1995) 339; [2] F.A. Danevich et al., Phys. Lett. B 344 (1995) 72; [3]R.Arnold et al., Z. Phys. C 72 (1996) 239; [4] F.A.Danevich et al., PRC 62 (2000) ; [5] F.A.Danevich et al., PRC 68 (2003) ; [6] A.S. Barabash, PRC 81 (2010) [7] V.I. Tretyak et al., AIP Conf. Proc (2013) 110; 18 /45

19 Status of 2 decay research Limit on 0 2 decay of 116 Cd 2 2 int.th h Fit in MeV gives area of the effect S = -3.7 ± 10.2 counts lims = 13.3 counts at 90% CL [1] T / yr 210m Ag ext.th Sum of two runs with the background counting rate 0.1 cnt/(yr kev kg) in the energy interval MeV Effective Majorana neutrino mass limits: m 1.6 ev [2] m ( ) ev [3] [1] G.J. Feldman and R. D. Cousins, Phys. Rev. D 57 (1998) 3873 [2] J. Barea, J. Kotila, and F. Iachello Phys. Rev. Lett. 109 (2012) [3] J.D. Vergados, H.Ejiri and F.Simkovic Rep. Prog. Phys. 75 (2012) /45

20 Status of 2 decay research Results Decay mode Transition, level of 116 Sn limt 1/2 (yr) 90% CL Best previous limit 90% CL 0 g.s [1] (1294 kev) [1] (1757 kev) [1] (2027 kev) [1] (2112 kev) [2] (at 68% CL) (2225 kev) [2] (at 68% CL) 0 M1 g.s [1] 0 M2 g.s [1] 0 M bulk g.s [1] 2 g.s. = see slide (1294 kev) [3] (1757 kev) [3] (2027 kev) [3] (2112 kev) [2] (at 68% CL) (2225 kev) [2] (at 68% CL) [1] F.A. Danevich et al., Phys. Rev. C 68 (2003) [2] A.S. Barabash, A.V. Kopylov, V.I. Cherehovsky, Phys. Lett. B 249 (1990)186 [3] A.Piepke et al. Nucl. Phys. A 577 (1994) /45

21 Status of 2 decay research Segregation of Th, Ra and K in 116 CdWO 4 Activity of 228 Th (mbq/kg)* 10(2) 0.1(1) 0.04(1) 0.02(1) Nuclide Crystal Rest of melt 40 K < (11) 264 g 326 g 589 g 586 g 226 Ra < (4) Rest of the melt after the crystal growth 228 Th 0.04* 10(2)* *Reference date: May Th in the initial powder / crystal 1.4 mbq/kg / 0.04 mbq/kg /45 21

22 Status of 2 decay research Improvement of 116 CdWO 4 crystal radiopurity 326 g 286 g (88%) 2 nd crystallization by the low-thermalgradient Czochralski technique 195 g The thorium contamination of the 116 CdWO 4 crystal was reduced by a factor 10, down to the level 0.01 mbq/kg. The total alpha activity of uranium and thorium daughters was reduced by a factor 3, down to 1.6 mbq/kg [1] [1] A.S.Barabash et al., Improvement of radiopurity level of enriched 116 CdWO 4 and ZnWO 4 crystal scintillators by recrystallization, submitted to NIMA 22 /45

23 Status of 2 decay research ARMONIA: 2 decay of 100 Мо to 0 + excited level of 100 Ru Te Mo 1.2 kg of 100 MoO 3 (99.5%) h Ru Sum spectrum Coincidence spectra T 1/2 = (stat.)±0.7(syst.) yr [1] 0.8 STELLA facility with HPGe gamma spectrometers at Gran Sasso [1] P. Belli et al., Nucl. Phys. A 846 (2010) /45

24 Status of 2 decay research Pm Nd 2 of 150 Nd excited 150 Sm Q 2 =3371 kev Improvement of Nd 2 O 3 radioactive contamination Contamination Before [1] 40 K 46 < Bi ( 226 Ra) 1.1 < Ac ( 228 Ra) 0.9 < Sm 2.38 kg of deeply purified Nd 2 O 3 installed in the GeMulti 4 crystal HPGe spectrometer at LNGS Present HPGe HPGe Samples of Nd 2 O 3 HPGe The experiment is in progress. The acquired statistic for 27 May 2016 is 3987 h [1] A. S. Barabash et al., Investigation of ββ decay in 150 Nd and 148 Nd to the excited states of daughter nuclei, PRC 79 (2009) /45

25 Status of 2 decay research Motivation to study 2, +, 2 + m m m ( T1 / 2 ) Cmn( ) Cm ( ) Cm ( ) C C C m m m 0 e e e Right-handed weak current contribution Half-lives for 0 + decay depend strongly on whether the decay is dominated by the mass mechanism or righthanded weak current [1] Possibility of resonant 0 double electron capture resonant level of 106 Pd can be populated in 2 of 106 Cd [1] M. Hirsch et al., Nuclear structure calculation of + +, +/EC and EC/EC decay matrix elements, Z. Phys. A 347 (1994) /45

26 Status of 2 decay research R&D 106 CdWO 4 crystal scintillator attenuation length 60 cm was never reported for CdWO CdWO 4 crystal 231 g ( 106 Cd) = 66% yield of crystal = 87% of the initial powder 106 CdWO 4 scintillator 216 g The total irrecoverable losses of 106 Cd = 2.3% FWHM=10% The excellent optical and scintillation properties of the crystal were obtained thanks to the deep purification of 106 Cd and W, and the advantage of the low-thermalgradient Czochralski technique to grow the crystal [1] P. Belli et al., Development of enriched 106 CdWO 4 crystal scintillators to search for double decay processes in 106 Cd, NIMA 615 (2010) /45

27 Status of 2 decay research Experiments and results 1 st stage 2rd stage PbWO 4 from archaeological lead HPGe 225 cm CdWO h h 2 19 T 1/ yr [1] New limits on 2, +, 2 + processes i on the level of T 1/2 > yr [1] P. Belli et al., PRC 85 (2012) [2] P. Belli et al., PRC 93 (2016) T 1/ yr [2] 27 /45

28 Status of 2 decay research A new stage of the 106 Cd 2 experiment the 106 CdWO 4 in CC with two CdWO 4 detectors in close geometry arch PbWO 4 Plastic Quartz Copper PMT Quartz Plastic PMT PMT CdWO CdWO 4 CdWO 4 The measurements are in progress in the DAMA/CRYS set-up at LNGS 28 /45

29 Status of 2 decay research Resonant 0 2 Search for 2 decay of Os Thin source of ultrapure osmium Preliminary results were published in [1] BEGe detector The detection efficiency was significantly improved thanks to the cut of the osmium roads into thin (0.8-1 mm) plates, and use of the Broad Energy Ge detector at the STELLA facility of LNGS High Z atoms are strongly favored to search for resonant 2ε decay [2] The experiment is in progress [1] P. Belli et al., First search for double- decay of 184 Os and 192 Os, Eur. Phys. J. A 49 (2013) 24 [2] Z. Sujkowski, S. Wycech, Neutrinoless double electron capture: A tool to search for Majorana neutrinos, Phys. Rev. C 70 (2004) /45

30 Status of 2 decay research Search for double beta + processes in Ce Cerium contains three potentially 2β active isotopes: 136 Ce, 138 Ce and 142 Ce. The 136 Ce isotope is of particular interest because of one of the highest energies of decay which enables even 2β + decay allowed only for six nuclei Results of the first cerium experiment with HPGe detector were reported in [1] The main contamination in [1] was thorium. After the additional purification of the CeO 2 sample, a hew phase of the experiment is in progress at the STELLA facility of LNGS Important methodological result: radiopure cerium can be used to develop crystal scintillators with Ce and doped by Ce, e.g., GSO(Ce) [1] P. Belli et al., Search for double beta decay of 136 Ce and 138 Ce with HPGe gamma detector, NPA 930 (2014) /45

31 Status of 2 decay research Lewis Carroll Through the Looking Glass Charles Lutwidge Dodgson (Lewis Carroll) Alice's Adventures in Wonderland The White King waiting for two Messengers from the White Queen Sir John Tenniel Illustrator of Alice s Adwentures The Just White look along King the awaits road, messengers and tell from if you the can White see either Queen. of them. He 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! the 0 2 experiments see nothing and only wish to have a better sensitivity 31 /45

32 Goals and prospects The next generation experiments should test the inverted hierarchy of the neutrino mass: m 0.05 ev Theoretical calculations T 1/2 for m 0.05 ev [1] Different nuclear models give rather different predictions To test the inverted scheme of the neutrino mass we need sensitivity on the level of: m 0.05 ев T 1/ yr The possible quenching of the axial vector coupling constant (g A ) could amount to a multiplication of the half-lives by an order of magnitude [2] T 1/ yr [1] J.D.Vergados, H.Ejiri, F.Simkovic, Theory of neutrinoless double-beta decay,rep. Prog. Phys. 75 (2012) [2] J. Barea, J. Kotila, F. Iachello, Limits on Neutrino Masses from Neutrinoless Double- Decay, Phys. Rev. Lett. 109 (2012) /45

33 Goals and prospects What does it mean T 1/ yr? Nucleus T 1/2 to reach m = 0.02 ev [1] Detector Number of 2 nuclei in 1 ton detector Number of decays over 5 years 48 Ca (3 28) yr 48 CaF 2 (20%) Ge (3 17) yr HP 76 Ge Se (1 4) yr Zn 82 Se Mo ( ) yr Zn 100 MoO Ca 100 MoO Li MoO Cd ( ) yr 116 CdWO Te (0.7 3) yr 130 TeO Xe (1 4) yr 136 Xe [1] Table 3 in J.D.Vergados, H.Ejiri, F.Simkovic, Rep. Prog. Phys. 75 (2012) /45

34 Goals and prospects Significant background reduction is requested 116 Cd 82 Se 100 Mo CdWO kg no shield CdWO kg 10 cv Cu, 5 cm Pb 2 2 decay 116 CdWO kg DAMA R&D at LNGS Next generation experiments CUPID 34 /45

35 Goals and prospects The most promising 2 nuclei Natural Isotopic abundance (%) kev 208 Tl 130 Te T 1/ 2 Sensitivity (half-life T 1/2 ) of 2 experiments: m t R BG detection efficiency concentration of 2 isotope m mass of detector t time of measurements R energy resolution BG background Large Q 2 > 2615 kev Ge 136 Xe 82 Se 100 Mo 116 Cd 150 Nd 96 Zr 48 Ca Energy of decay, Q 2 (MeV) Enrichment kg High detection efficiency Low background High energy resolution 35 /45

36 Goals and prospects Energy resolution in 0 2 experiments FWHM = 1% FWHM = 3.5% FWHM = 10% KamLAND-Zen 2016 Background in the ROI due to 2 2 decay [1] Visibility of 2 2 peak [2] FWHM 17% / E(MeV) A poor energy resolution is acceptable if one give a limit on 0 2 decay, while it is not a case if one claim detection of the process [1] Yu.G. Zdesenko, F.A. Danevich, V.I. Tretyak, Sensitivity and discovery potential of the future 2β decay experiments, J. Phys. G: Nucl. Part. Phys. 30 (2004) 971 [2] J.J. Gómez-Cadenas and J. Martín-Albo, Phenomenology of Neutrinoless Double Beta Decay, PoS (GSSI14) /45

37 Goals and prospects Cryogenic bolometers a promising technique for 0 2 experiments Optical detector (Ge disk) mk Scintillating crystal / energy resolution (a few kev) Temperature sensor (Ge-NTD) Excellent particle discrimination (10-15 ) High registration efficiency (70% - 90%) High energy resolution Low background counts/ (yr ton) in at Q 2 37 /45

38 Goals and prospects Photons collector film AMoRE: search for 0 2 decay of 100 Mo with cryogenic scintillation bolometers depl Ca 100 MoO 4 [1] Light detector 2 inch Ge wafer + Metal Magnetic Calorimeter CaMoO 4 crystal scintillator / High energy resolution Full / discrimination [1] G.B. Kim et al., A CaMoO 4 Crystal Low Temperature Detector for the AMoRE Neutrinoless Double Beta Decay Search, Advances in High Energy Physics (2014) [2] V. Alenkov et al., Technical Design Report for the AMoRE 0 Decay Search Experiment, arxiv: v1 [physics.ins-det] 18 Dec /45

39 Goals and prospects AMoRE pilot Detector was assembled in July 2015 at the Yangyang Underground Lab in Korea Check overall status of detector performances, cryostat, shielding, DAQ system, etc: 26 Aug Oct 2015 (63 days) Calibration measurement with external 232 Th source at 10, 20, 30, 40 mk. Background measurements are in progress At present measurements are in progress with 1.5 kg of 48depl Ca 100 MoO 4 Center of Underground Physics is purchasing 120 kg of 100 Mo from the ECP company (Russia) directly, the material is expected to be delivered until 2018 ( 11 M$) 39 /45

40 Goals and prospects AMoRE: schedule AMoRE Pilot, kg of depl Ca 100 MoO 4 AMoRE phase I, kg of depl Ca 100 MoO 4 AMoRE phase II, kg of molybdates Stage Start Background (yr/kev/kg) Sensitivity limt 1/2 (yr) m (ev) AMoRE pilot ~10 24 < AMoRE I ~ AMoRE II ~ /45

41 Goals and prospects LUMINEU: search for 0 2 decay of 100 Mo with Zn 100 MoO 4 cryogenic scintillating bolometers The main purpose of LUMINEU is to prepare the construction of a next-generation 0 2 decay experiment, capable exploring the inverted hierarchy region of neutrino mass based on Zn 100 MoO 4 scintillating bolometers to search for 0 2 decay of 100 Mo [1] FWHM=6 kev High energy resolution 5-7 kev (0.2%) High registration efficiency (70% - 90%) Powerful particle discrimination ( 15 ) potential to reject background to almost a zero level, [1] [M. Tenconi, for the LUMINEU collaboration, Physics Procedia 61 (2015) /45

42 Goals and prospects Ultra-radiopure ZnMoO 4 crystal scintillators 2008 (IGP, Moscow, Russia) [1] ZnMoO 4 crystals 5 4 cm (0.33 kg), 2013 [2] first Zn 100 MoO 4 crystal from enriched 100 Mo (0.17 kg), 2014 [3] [1] LI. Ivleva et al., Crystallography Reports, 2008, Vol. 53, No. 6, pp [2] E. Armengaud et al., JINST 10 (2015) P05007 [3] A.S. Barabash et al., Eur. Phys. J C 74 (2014) 3133 [4] F.A. Danevich et al., to be published in MEDEX 15 proceedings Zn 100 MoO 4 crystal from enriched 100 Mo (1.4 kg), 2015 [4] Radioactive contamination of ZnMoO 4 crystals is extremely low: 226 Ra, 228 Th < 5 Bq/kg Yield of crystal boule: more than 80%, Irrecoverable losses: less than 4% 42 /45

43 Goals and prospects LUCINEU Li MoO 4 enriched in 100 Мо High energy resolution 5-7 kev First Li MoO 4 1 kg (18 January 2016, NIIC, Novosibirsk), Excellent particle discrimination High radiopurity (< 6 Bq/kg of 228 Th) One more Li MoO 4 1 kg (end of May) Data taking in the Modane underground laboratory, 4800 m w.e. 43 /45

44 Goals and prospects Perspective: CUPID CUORE Upgrade with Particle IDentification [1, 2] CUPID is a proposed tonne-scale bolometric 0 2 decay experiment to probe the Majorana nature of neutrinos and inverted hierarchy region of the neutrino mass. CUPID will be built on experience, expertise and lessons learned in CUORE, and will exploit the current CUORE infrastructure as much as possible. CUPID aims to increase the source mass and reduce the backgrounds in the region of interest Nuclei Detector m (mev) 130 Te TeO Mo ZnMoO Se ZnSe Cd CdWO Léon Perrault ( ) Les flèches de Cupidon CUORE [1] G.Wang et al., CUPID: CUORE (Cryogenic Underground Observatory for Rare Events) Upgrade with Particle Identification, arxiv: v1 [2] G.Wang et al., R&D towards CUPID ( CUORE Upgrade with Particle IDentication), arxiv: v1 44 /45

45 conclusions Investigation of the neutrinoless double beta (0 2 ) decay has a unique potential to clarify the nature of the neutrino (Majorana or Dirac particle?), check the lepton number conservation, determine the absolute scale and the neutrino mass hierarchy The 0 2 decay is still not observed: the most sensitive experiments give half-life limits at the level of T 1/2 > yr and provide a test of the degenerate region of the neutrino mass hierarchy: m (0.1 1) ev 2 experiments using crystal scintillators and HPGe detectors study at new level 2 - and 2 + processes in range of nuclei The goal of the next generation 2 experiments is to explore the inverted hierarchy of the neutrino mass ( m 0.05 ev, T 1/2 ~ yr) Cryogenic scintillators are promising detectors to explore the inverted hierarchy and even go toward the normal hierarchy of the neutrino mass pattern 45 /45

46 46

47 Backup slides 47

48 Introduction 2 decay two modes: 2 and 0 effective Majorana mass of neutrino m = U 2 ej m j can be estimated by measuring the 0 2 decay half-life G (Q, Z) T 1/ /2 2 0 M ( T ) G (Q, Z) M m where is the phase space integral, is the nuclear matrix 2 element J.D.Vergados, H.Ejiri, F.Simkovic, Theory of neutrinoless double-beta decay, Rep. Prog. Phys. 75 (2012) W. Rodejohann, Neutrinoless double-beta decay and neutrino physics, Int. J. Mod. Phys. E 20 (2011) J.Barea, J.Kotila, F.Iachello, Limits on Neutrino Masses from Neutrinoless Double- Decay, Phys. Rev. Lett. 109 (2012) /33

49 Introduction Presence of light sterile neutrino Allowed mass intervals m in absence of sterile neutrino Allowed mass intervals m if one sterile neutrino exists [1] J.D.Vergados, H.Ejiri, F.Simkovic, Theory of neutrinoless double-beta decay,rep. Prog. Phys. 75 (2012) /45

50 Status of 2 decay research Claim on 0 2 decay of 76 Ge 55 kg year 71 kg year T 1/2 = yr [1] T 1/2 = yr [2] The claim was strongly criticized [3-5] [1] H. V. Klapdor-Kleingrothaus et al., Mod. Phys. Lett. A. 16 (2001) 2409 [2] H. V. Klapdor-Kleingrothaus et al., Phys. Lett. B 586 (2004) 198. [3] C.E. Aalseth et al., Mod. Phys. Lett. A 17 (2002) 1475 [4] F. Feruglio, A. Strumia, F. Vissani, Nucl. Phys. B 637(2002) 345 [5] Yu.G. Zdesenko, F.A.Danevich, V.I.Tretyak, Phys. Lett. B 546 (2002) /45

51 Experiment Data analysis pulse-shape discrimination ( h) 8397 h Raw data Q Cd, Bi-Po Activity of 238 U: 0.69(2) mbq/kg 210 Po: 0.57(3) mbq/kg F.A. Danevich Search for double beta decay of 116 Cd with enriched 116 CdWO 4 crystal scintillators TAUP 2015, Sep 7, Turin 51

52 Experiment Data analysis front edge and time-amplitude analyses ( h) 220 Rn 216 Po 212 Pb 55.6 s s h T 1/2 = 0.131(12) s Activity 228 Th: 0.027(3) mbq/kg* Activity of 228 Th: 0.027(4) mbq/kg* *Reference date: November F.A. Danevich Search for double beta decay of 116 Cd with enriched 116 CdWO 4 crystal scintillators TAUP 2015, Sep 7, Turin

53 Experiment Radioactive contamination of 116 CdWO 4 Chain Nuclide Activity (mbq/kg) 232 Th 232 Th Th 0.027(4)* 238 U 238 U 0.69(2) 226 Ra Po 0.57(3) Total 2.25(7) 40 K 0.9 *Reference date: November 2014 F.A. Danevich Search for double beta decay of 116 Cd with enriched 116 CdWO 4 crystal scintillators TAUP 2015, Sep 7, Turin 53

54 Estimation of systematic errors Conditions of the Fit: Variation of bounds for rad. contaminations Model of background Interval of fit Quenching for (non proportional light response) [1,2] Interval of fit Model of BG Source T 1/2 = yr 53 fits in ( ) - ( ) kev Number of nuclei Contribution yr Live time Efficiency of PSD Model of background, interval of fit 0.1 Simulation [1] PRC 76(2007) [2] NIMA 696(2012) F.A. Danevich Search for double beta decay of 116 Cd with enriched 116 CdWO 4 crystal scintillators TAUP 2015, Sep 7, Turin