6th Symposium on Large TPCs for Low Energy Rare Event Detection 17-19 December 2012, Paris

1. Review on double beta decay experiments …for the search of the Majorana neutrino… Xavier Sarazin Laboratoire de l’Accélérateur Linéaire (CNRS-IN2P3, Univ. Paris-Sud 11) 6th Symposium on Large TPCs for Low Energy Rare Event Detection 17-19 December 2012, Paris

2. Majorana Neutrino Massive Majorana n  Violation of the Leptonic Number e- e- • Leptogenesis in the Early Universe through the Majorana neutrino • See-saw mechanism to explain the small mass of the neutrino W- W- neL neR Observation of bb0n decay is the most sensitive way to probe Majorana Neutrino is the only fermion with Q = 0  Neutrino might be a Majoranaparticle n = n ? Only two n states: CPT |nR, h= +1/2 > |nL, h= -1/2 >

3. bb2n and bb0n decay If neutrino is a Majorana particle bb0n Process bb0n V+A mn • Process L = 2 • Majorana neutrino exchange • Right Handed weak current Energy and angular distributions will be different ! For few isotopes, b-decay is forbiden bb2n process (second order b-decay) Qbb Energy Sum of the two electrons • Exchange of SUSY particles • Majoron production

4. Theoretical predictions In the case of an standard exchange of a Majorana neutrino Effective mass Constraint by n oscillations Phase space factor Nuclear Matrix Element  Theoretical uncertainty

5. Nuclear Matrix Elements Nnuclei (76Ge) ≈ 10×Nnuclei (100Mo, 150Nd) Calculated T1/2(bb0n) to start exploring the Inverted Hierarchy in the case of exchange of Majorana neutrino mn 50 meV • QRPA Tüe. Simkovic, Phys. Rev. C 79 (2009); Fang, Phys. Rev. C 82 (2010) • QRPA Jy.Kortelainen, Phys. Rev. C 75 andC 76 (2007) • NSM Shell Model Menendez, Nucl. Phys. A818 (2009); Phys. Rev. C 80 (2009) • IBM Interacting Boson Model Barea, Phys. Rev. C79 (2009) • GCM Generating Coordinate Method Rodriguez, Phys. Rev. Lett. 105 (2010) • PHFB Projected Hartree-Fock-Bogoliubov Rath, Phys. Rev. C 82 (2010) ~ 3 1027 ~ 3 1025 from Duek et al. , Phys. Rev. D 83 (2011)

6. Current best limits obtained in search 1990 – 2010 : ~ 10 kg of bb isotopes, bkg ~ 0.3 – 1 cts/(fwhm.kg.yr) 2012 : New generation ~ 100 kg of 136Xe, bkg ~ 0.025 cts/(fwhm.kg.yr)

7. Limit … or claim ? Heidelberg-Moscow experiment 5 HP 76Ge crystals (~10 kg of 76Ge) running 1990 – 2003  71.7 kg.y Part of the HdM collaboration claims 4.2s bb0n signal T1/2~ 2.1025 years (NIM A 522 2004, PLB 586) Significance of claimed much weaker if background uncertainties included Recent analysis of the origin and description of background done by O. Chkvorets (Dissertation Univ. Heidelberg, 2008, arXiv:0812.1206) Peak significant (without PSA) is only ~ 1.3 – 1.5 s ! Kamland-Zen claims that the HdM hint is rejected if KZ+EXO-200 results are combined. However, NME uncertainties have to be considered…

8. See next talks

9. Ge diodes

10. GERDA 76Ge (Qbb = 2040 keV) • “Bare” Ge crystals in Liquid Argon • - Liq. Argon = cryostat + shield • - Ext. Water tank for shield + m-veto • - Detector arrays using string design for a gradual deployment • Phase 1 (started Nov. 2011) ~ 18 kg 76Ge 8 old 76Ge detectors (HdM, IGEX) 2 detectors OFF  Total 14.6 kg of 76Ge • FWHM ~ 4.5 – 5.2 keV @ 2.6 MeV • Energy peaks stable within  1 keV Target bkg ~ 0.01 cts/(kg.keV.yr) Results in Sping 2013 after 20 kg.yr exposure  T1/2(bb0n) ~ 3 1025 yr

11. GERDA Phase 1 76Ge (Qbb = 2040 keV) Measurement of the bb2n decay In agreement with previous HdM measurement Unexpected background from 42K (b emitter Qb=3.52 MeV, 42Ar progeny) Evidence that charge 42K ions drift in electric field of Ge diodes.  Ge diode screened by a copper “minishroud”

12. GERDA Phase 1 76Ge (Qbb = 2040 keV) Zoom to bb0n energy region Bkg = 0.020 cts/(keV.kg.yr) (excluding blinded region of Qbb 20keV) Only a factor 2 higher than the request of Phase 1 GERDA Phase I expected completion in Spring 2013 (20 kg.yr) Unblinding  expected sensitivity: T1/2(bb0n) ~ 3 1025 yr

13. GERDA 76Ge • LOI between GERDA & MAJORANA Collaborations • Open exchange of knowledge & technologies (e.g. Ge diodes, MC) • • Intention to merge for O(1 ton) exp. selecting the best technologies tested in GERDA and Majorana (Qbb = 2040 keV) Phase 2 : ~ 50 kg 76Ge Bkg reduced by a factor 10  10-3 cts/(keV.kg.yr) T1/2(bb0n) > 2 1026 y in 5 yrs data • 20 kg of Broad Energy 76Ge (BEGe) detectors will be added (30 diodes)  They exhibit superior pulse shape discrimination performances  Single Site (bb0n) / Multi Sites (bkg g interaction) discrimination 3 detectors already installed: FWHM ~ 3 keV @ 2.6 MeV • Detection of Ar scintillation light  Liquid Argon as active shield with the Single site (DEP, bb0n) Multi sites (bkg, g FEP)

14. Bolometers

15. CUORE Bolometers Te natural: 34% of 130Te Typical energy resolution ~ 5 keV @ Qbb Crystal 5×5×5 cm3

16. CUORE-0 (2012 – 2014 ) 40 kg Te02 CUORE (2015 – 2020) 1 ton Te02 (~ 200 kg 130Te) CUORICINO 2003 – 2008 40 kg Te02 (~ 10 kg 130Te) ~ 50 crystals DE/E ~ 6 keV (FWHM) T1/2(bb0n) > 2.8 1024 y (90%C.L.) Expected in 2 years T1/2(bb0n) > 4 1024 y Expected in 5 years T1/2(bb0n) > 1026 y Bkg = 0.17 cts/(keV.kg.yr) Bkg = 0.0.1 cts/(keV.kg.yr) BKG CUORICINO @ Qbb ~ 70% a’s from crystals and Cu surfaces ~ 30% external g from cryostat Qbb(130Te) ~ 2530 keV < g(208Tl) @ 2611 keV Surface treatment of the crystal and Cu Improve the radiopurity of the new cryostat

17. Reduction of the background in CUORE • Surface radiopurity : measured in the CUORICINO cryostat (Three Tower Test, TTT). •  Best results obtained with passive chem. cleaning and polyethylen film or with plasma cleaning • Bulk contamination measured with Cryogenic validation runs (CCVR) • 238U < 5.3 10-14 g/g (0.67 mBq/kg) • 232Th < 2.1 10-13 g/g (0.84 mBq/kg) CUORE request: 3 10-13 g/g Bkg budget in counts/(keV.kg.yr) expected un the bb0n region • CUORE-0 is now running in Cuoricino cryostat since few weeks • Preliminary calibration runs  new Te02 crystals work properly • Current problems in cryostat being fixed • Long Bkg measurement in 2013 STATUS

18. Scintillating bolometers Bkg run with 3×3×6cm3 CdWO4 (400g) - No counts > 2.6 MeV after 44 days - Degraded a > 2.6 MeV are rejected e-,g Expected bkg (GEANT4) using CUORICINO/CUORE measured contaminations (crystal and Cu surface) bkg ~ 10-3 – 10-4 cts/(keV.kg.y) a Above 2.6 MeV: bkg is mainly a surface contamination  Scintillating bolometer to discriminate a to g/e- Ge plate Scintillation signal a / (e-,g)discrimination Heat signal Energy measurement S. Pirro et al. Physics of Atomic Nuclei, 69 (2006)

19. Scintillating bolometers Quenching is inversed ! ~ 20 days / No (b,g) > 2.6 MeV  LUCIFER (ZnSe) Qbb (82Se) = 2998 keV Project funded by ERC (Advanced GRANT 2010-2015) • “Cuoricino” tower filled with ~ 50 ZnSe crystals ~ 15 kg of 82Se • Detector installed in Cuoricino cryostat, once CUORE-0 will finish his data taking •  T1/2(bb0n) ~ (0.5 – 1) × 1026 y in 5 yrs Internal contaminations Internal contaminations 2012 2013 2014 2015 Pulse Shape discrimination with light signal provides high (e-,g)/a discrimination R&D on light detectors Thermistor production Natural crystal (growth) R&D Smeared -source 15 kg 82Se production Enriched crystal growth Bkg run with ZnnatSe in LNGS (Hall C) Detector assembling 208Tl calibration source

20. Scintillating bolometers LUMINEU thanks EDELWEISS • First bkg run with large ZnnatMoO4 crystal (300g) •  Heat signal Amplitude ~ TeO2 •  No e-/g counts > 2.6 MeV after 97 hours • Long run foreseen in January 2013 300g ZnnatMoO4 97 hours live-time LUMINEU (ZnMoO4) Qbb (100Mo) = 3035 keV Project funded by ANR (France) • Demonstrator setup with 4 crystals  mid-2014 in Edelweiss cryostat (LSM) • ≈ 0.7 kg 100Mo  T1/2(bb0n) > 1024 yr (in 1 year) • Second setup with ~30 crystals ≈ 7 kg 100Mo (existing)  T1/2(bb0n) > 5.1025 y (in 5 year) • Pulse Shape discrimination with heat signal • bb2n pile-up = limiting bkg for 100 kg scale  R&D on NTD to get faster heat signals AMORE Project (YYUL Korea) with 40CaMoO4 40Ca required to avoid bb2n bkg from 48Ca 3 large 40Ca100MoO4 crystal have been produced for bkg measurement in YYUL

21. Large Liquid Scintillators

22. Kamland-Zen 13 m 3.1 m T1/2(bb2n) = 2.30  0.02(stat)  0.12(syst) 1021 yrs Phys. Rev. C85, 045504 (2012) Update: arXiv:1205.6372 BUT unexpected bkg around Qbb ! • 320 kg of 136Xe loaded in 13 tons Liq. Scint. • Xe concentration ~ 2.45 % • (~700 kg 136Xe available in Kamioka mine) • Energy resolution = 10 % (fwhm) at Qbb • Vertex resolution ~ 10 cm • Fiducial volume ~ 43 % • (FV uncertainty ~ 5% dominant error) • 213.4 days  89.5 kg.yr From K. Inoue, Neutrino 2012

23. Kamland-Zen Peak fitted with bb0n signal only From K. Inoue, Neutrino 2012 Peak position is different from expected bb0n peak bb0n is rejected at 8 s

24. Kamland-Zen Replacing internal ballon with a new one Purification of Liq Scint (to extract 110mAg) 800 kg of load 130Xe T1/2(bb0n) > 1026 yrs in 5 yrs ~ Due to unexpected contamination in 110mAg (T1/2=360 days, Qb=3.01 MeV) (Fallout from Fukushima) 89.5 kg.yr The decrease of the event rate in the [2.2 – 3.2] MeV region is in agreement with 110mAg decay

25. SNO+ SNO detector filled with liquid scint. and load natNd • Expected bkg dominated by • 208Tl contamination (Liq. Scint.) • bb2n tail • 8B n • 0.3% natNd  ~130 kg 150Nd • Fiducial Volume ~ 50% (~ 0.4 kt) • Energy resolution DE ~ 9 % at Qbb = 3.37 MeV 2011 • Acrylic Vessel and hanging system 2012 • First data with air in March 2012 • Sand cleaning of the Acrylic Vessel • Liq. Scint. Purification system • Water fill data • Scintillator fill • Start Scint. Phase (w/o Nd) •  n osc. physics • Data with Nd-loaded scint. 2013 2014 2015

26. NEMO Tracko-Calo

27. NEMO, a tracko-calo approach NEMO detectors combine a tracking chamber and a calorimeter • Direct reconstruction of the two electrons  Can distinguish a possible bb0n signal to a unknown g line • Direct measurement of the various components of background • A modest energy resolution but a high background rejection  Bkg level in the bb0n energy window equivalent with calorimeter detectors

28. The NEMO-3 detector Transverse view 3 m Vertex emission B(25 G)‏ 4 m Running from Feb. 2003 until Jan. 2011 in Modane Underground Laboratory (4800 m.w.e.) bb0n: 7 kg of 100Mo, 1 kg of 82Se bb2n: 0.4 kg 116Cd, 37 g 150Nd, 9 g 96Zr, 7 g 48Ca … Calorimeter: ~ 2000 plastic scint. + 5” PMTs DE/E ~ 15% (FWHM) @ 1 MeV

29. bb0n results with 100Mo and 82Se T1/2 (bb0n) > 1.0 1024 y (90% C.L.) mn < 0.31 – 0.79 eV T1/2 (bb0n) > 3.2 1023 y (90% C.L.) mn < 0.85 – 2.08 eV nM T1/2 (bb0n) > 5.7 1023 y (90% C.L.) l < 1.4 10-6 T1/2 (bb0n) > 2.4 1023 y (90% C.L.) l < 2.0 10-6 V+A Tobs = 4.5 years (Feb. 2003 – Dec. 2009) Phase 1 (1years) + Phase 2 (3.5 years) M(100Mo) = 6.914 kg M(82Se) = 0.932 kg [2.8 – 3.2] MeV Phase 1: 6 events obs., 5.30.6 expected Phase 2: 12 events obs., 11.10.9 expected [2.6 – 3.2] MeV Phase 1: 4 events obs., 3.6 expected Phase 2: 10 events obs., 7.3 expected

30. SuperNEMO Experiment 100 kg of 82Se  to reach T1/2(bb0n) ≥ 1026 years NEMO-3 Extrapolation SN = 20 Modules • Source: ~ 5×3 m2 foil (40 mg/cm2): 82Se, 150Nd, 48Ca • Tracking: Drift cells in Geiger mode • Calorimeter: Polystyrene or PVT scintillators + 8"  PMT’s • 20 modules to be installed in the future extension of LSM Modane.

31. Background reduction for SuperNEMO Demonstrated on prototype with 8” PMTs and large blocks • Energy resolution demonstrated on test bench with cubic (26×26cm2) blocs: FWHM @ 1 MeV = 7.3  0.1 % with PVT (Eljen) = 8.7  0.1 % with polystyrene (JINR Dubna) Requirements to reach T1/2(bb0n) ≥ 1026 y with 100 kg of 82Se NEMO-3 • Reduce  background • - T1/2() = 1020 y for 82Se100Mo 7.1018 y • - Energy resolution Calorimeter FWHM 7% @ 1 MeV15% @ 1 MeV

32. Background reduction for SuperNEMO • BiPo-3 detector (first module) running since July 2012 in Canfranc (Spain) • Ultra high radiopurity of the first module validated: ~ 100 nBq/m2 in 208Tl !!! • Will measure radiopurity of the bb foils in 2013 e- a Requirements to reach T1/2(bb0n) ≥ 1026 y with 100 kg of 82Se NEMO-3 • Reduce  background • - T1/2() = 1020 y for 82Se100Mo 7.1018 y • - Energy resolution Calorimeter FWHM 7% @ 1 MeV15% @ 1 MeV • Reduce 208Tl and 214Bi contamination inside  source foils • A(208Tl) < 2 Bq/kgA=100 Bq/kg • A(214Bi) < 10 mBq/kg

33. Background reduction for SuperNEMO Requirements to reach T1/2(bb0n) ≥ 1026 y with 100 kg of 82Se NEMO-3 • Reduce  background • - T1/2() = 1020 y for 82Se100Mo 7.1018 y • - Energy resolution Calorimeter FWHM 7% @ 1 MeV15% @ 1 MeV • Reduce 208Tl and 214Bi contamination inside  source foils • A(208Tl) < 2 Bq/kgA=100 Bq/kg • A(214Bi) < 10 mBq/kg • Reduce Radon and Thoron contamination inside the detector • A(Radon) < 0.1 mBq/m3A= 5 mBq/m3 • A(Thoron) < 15 mBq/m3 A= 150 mBq/m3 • Tracker closed by Rn-tight thin film • Internal tracker components selected by Rn emanation chamber • Important R&D for Rn-tight seals

34. Background reduction for SuperNEMO Requirements to reach T1/2(bb0n) ≥ 1026 y with 100 kg of 82Se NEMO-3 • Reduce  background • - T1/2() = 1020 y for 82Se100Mo 7.1018 y • - Energy resolution Calorimeter FWHM 7% @ 1 MeV15% @ 1 MeV • Reduce 208Tl and 214Bi contamination inside  source foils • A(208Tl) < 2 Bq/kgA=100 Bq/kg • A(214Bi) < 10 mBq/kg • Reduce Radon and Thoron contamination inside the detector • A(Radon) < 0.1 mBq/m3A= 5 mBq/m3 • A(Thoron) < 15 mBq/m3 A= 150 mBq/m3 • Total bkg:0.01 cts/(FWHM.kg.y)0.5 cts/(FWHM.kg.y)

35. SuperNEMO demonstrator • First SuperNEMO module in Modane with 7 kg of 82Se • Demonstrate the feasibility of a large scale detector production with low background • Validation of the Radon purity inside the tracking detector • Validation of the background from the detector components • Construction of the tracking detector started in 2012 in UK • Construction of the calorimeter in 2013 – 2014 • Start Data in 2015 in Modane • Expected sensitivity : T1/2(bb0n) > 7 1024 years after 2.5 years of data collection • In the mean time: R&D for 150Nd and 48Ca enrichment

36. 136Xe TPC Experiments • Several advantages to study Xenon • Simplest and least costly bb isotope to enrich • High bb2n half-life T1/2(136Xe) ~ T1/2(76Ge) ~ 2 1021 yrs • Natural candidate for TPC - Liq. TPC: EXO-200 (See R. Gornea’s talk) - Gas TPC: NEXT (See J.J. Gomez-Cadenas’s talk) (see also C. Oliveira’s talk for Micromegas readout)

37. EXO-200 (WIPP, USA) Liq. Xe TPC (200 kg Xe, 80% enrich. 130Xe) Active mass 98.5 kg LXe (79.4 kg 136Xe) DE = 3.4 % FWHM @ Qbb (DE ~ 100 keV) Start running in 2012 120.7 days, 32.5 kg.yr Phys. Rev. Lett. 109, 032505 (2012) T1/2(bb0n) > 1.6 1025 yrs (90% C.L.) T1/2(bb2n) = (2.23  0.017stat  0.22syst) 1021 yrs Very low bkg : 1 cts in 1s  3.6 cts/(FWHM.yr) (14.4 expected) 50% bkg due to Radon surounding the TPC  will be suppressed for next runs

38. NEXT (CANFRANC, SPAIN) Gas Xe TPC ~ 100 – 150 kg Xe gas, >90% enrich. 130Xe Electroluminescence technique for the TPC readout TDR, JINST 7 (2012) T06001 • Better Energy resolution • Target: DE = 1 % FWHM @ Qbb (DE ~ 25 keV) • Results of the NEXT-DEMO (a worst geometry): • 1.7% FWHM at 511 keV (extrapolating to 0.77% FWHM at 2.5 MeV) has been obtained • Electron tracking by topological detection of the characteristic blob at the end of the track • NEXT-DEMO (a worst geometry): • electrons are identified in 98.5% of the cases arXiv:1211.4838

39. CONCLUSIONS • 2010 – 2020: New generation of bb experiments with ~ 100 kg of isotope • Experiments using 136Xe provided already first results in 2012 ! • Kamland-Zen (using available large liquid scint. detector) : contamination in 110mAg • EXO-200 Liq. TPC obtained low bkg ~ 4 cts/(fwhm.yr) (15 cts expected) • New experiments started • GERDA Phase 1: results in Spring 2013 • Target GERDA Phase 2: 50 kg, 0.15 cts/(fwhm.yr) • CUORE-0 to validate bkg then CUORE • …or in construction… • LUCIFER & LUMINEU: should reduce bolometer bkg by factor at least 10 • SNO+ with natural Nd • SuperNEMO module 1 • NEXT-100

40. SUMMARY X* = obs. value T1/2( bb0n) 1026 yrs 5 yrs data Bkg at Qbb cts/(fwhm.yr) Efficiency bb0n DE (fwhm) at Qbb mee (meV) Start Data min.–max.

41. Constraints from neutrino oscillations Inverted hierarchy 10 < mn < 50 meV Degenerate masses mn > 50 meV ~ ~ Normal hierarchy mn ??? In the case of an standard exchange of a Majorana neutrino  Prediction for the best-fit values of the oscillation parameters and for the 3s ranges A. Merle, and W. Rodejohann Phys. Rev. D 73, 073012 (2006)

42. Nuclear Matrix Elements B. Schwingenheuer, Annalen des Physik (2012)