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Experimental status of the Double Beta Decay

Experimental status of the Double Beta Decay. Marisa Pedretti INFN Milano Bicocca. OUTLOOK OF THIS TALK. - Neutrinoless Double Beta Decay and Neutrino Physics. - Requirements for a competitive experiment. - Present situation of 0 n DBD. Future experiments.

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Experimental status of the Double Beta Decay

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  1. Experimental status of the Double Beta Decay Marisa Pedretti INFN Milano Bicocca

  2. OUTLOOK OF THIS TALK - Neutrinoless Double Beta Decay and Neutrino Physics - Requirements for a competitive experiment - Present situation of 0nDBD • Future experiments Physics of Massive Neutrinos, Blaubeuren

  3. Double Beta Decay Signature 2 neutrinos Double Beta Decay continuous spectrum  2DBD: (A,Z)  (A,Z+2) + 2e- + 2 Neutrinoless Double Beta Decay peak enlarged by the detector energy resolution ne  sum electron energy / Q 0DBD: (A,Z)  (A,Z+2) + 2e- Allowed by SM new physics beyond the SM two electrons each with a continuous spectrum and a monochromatic sum energy Physics of Massive Neutrinos, Blaubeuren

  4. 0nDBD and neutrino physics Phase space neutrinoless Double Beta Decay rate Nuclear matrix elements Effective Majorana mass In case of dominant mass mechanism: 1/t= G(Q,Z) |Mnucl|2Mbb2 what the experimentalists try to measure parameter containing the physics what the nuclear theorists try to calculate Mbb = ||Ue1 |2M1 + eia1 | Ue2 |2M2 +eia2|Ue3 |2M3 | How0nDBDis connected to neutrino mixingmatrix and masses? Physics of Massive Neutrinos, Blaubeuren

  5. 0nDBD and neutrino physics S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/0505226 76Ge claim excluded by CUORICINO , NEMO3 Mbb = ||Ue1 |2M1 + eia1 | Ue2 |2M2 +eia2|Ue3 |2M3 | Inverted Hierarchy Quasi Degenerate Normal Hierarchy Physics of Massive Neutrinos, Blaubeuren

  6. Target sensitivity S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/0505226 Approach the inverted hierarchy region in a first phase (m>50 meV) Exclude the inverted hierarchy region in a second phase (m>15 meV) Future target sensitivities can be divided in two phases: Physics of Massive Neutrinos, Blaubeuren

  7. Target sensitivity S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/0505226 500 meV 50 meV 15 meV 3 different value of neutrino mass can be seen as future milestones: Physics of Massive Neutrinos, Blaubeuren

  8. Target sensitivity TeO2 enriched Ge natural Ge enriched TeO2 natural Counts / y ton S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/0505226 Rodin et al. 411 1085 50 599 500 meV new calculation TeO2 enriched Ge natural Ge enriched TeO2 natural Counts / y ton Civitarese Suhonen 50 meV 37 434 575 1519 Nucl. Phys. A 729, 867 (2003) Rodin et al. 15 meV 4.11 10.85 0.51 5.99 new calculation Civitarese Suhonen 15 0.37 4.3 5.7 Nucl. Phys. A 729, 867 (2003) Sensitive masses at the 1 ton scale are required TeO2 enriched Ge natural Ge enriched TeO2 natural Counts / y ton Rodin et al. 0.37 0.98 0.046 0.54 new calculation Civitarese Suhonen 0.033 0.39 0.52 1.37 Nucl. Phys. A 729, 867 (2003) In order to give an idea of the amazing challenge of the future sensitivity targhet: The order magnitude of the Bkg is ≤ 1 c / y ton Physics of Massive Neutrinos, Blaubeuren

  9. Experimental parameters b: specific background coefficient [counts/(keV kg y)] b = 0 b  0 live time energy resolution source mass F (MT / bDE)1/2 F MT background level importance of the nuclide choice (but large uncertainty due to nuclear physics) 1/4 1 bDE sensitivity tom (F/Q |Mnucl|2)1/2  |Mnucl| Q1/2 MT How experimentalparameters are connected to the Majorana mass sensitivity of experiment? sensitivity F: lifetime corresponding to the minimum detectable number of events over background at a given confidence level Physics of Massive Neutrinos, Blaubeuren

  10. Background Sources • Two main sources • Activity in the rock and in surrounding materials • (a, n) processes [0,10] MeV spectrum •  can be shielded • High-energy m induced • complicated problem •  depth •  appropriate shielding / coincidence techniques •  reliable simulations •  “Ad hoc” experiments at muon accelerators could be useful • Levels of < 1 mBq / kg are required • for some materials at the ton scale • Purification techniques • Quality control procedure to establish: • diagnostic is a problem by itself • (traditional gamma counting not sufficient) • Improve alternative techniques: • ICPMS • Neutron Activation Analysis • “Ad hoc” bolometers for alpha self-counting • Full prototype used to measure contamination • (BiPo detector) Common to all tecnhiques and experiments Cooperation (in Europe, ILIAS) Choice of materials Storage of materials underground Partial or full detector realization underground (Ge diodes) Crucial for all experiments and techniques cooperation (in Europe, ILIAS) A challenge for the space-resolving techniques, which normally have low energy resolution (~ 10 %) 1000 present sensitivity Inverted hierarchy 100 10 1 sensitivity to m [meV] 0.1 0.01 0.001 4 3 1 2 Critical in the low energy resolution techniques energy resolution [%] • Natural radioactivity of materials (source itself, surrounding structures) • Neutrons • Cosmogenic induced activity (long living) • 2 n Double Beta Decay Physics of Massive Neutrinos, Blaubeuren

  11. Choice of the nuclide Transition energy (MeV) Isotopic abundance (%) 5 4 40 end of g region 3 20 2 0 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd Nuclear Matrix Element 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd new calculation Physics of Massive Neutrinos, Blaubeuren

  12. Experimental techniques High energy resolution(<2%) No tracking capability SourceDetector Easy to approach the ton scale CUORE -130Te Array of low temperature natural TeO2 calorimeters operated at 10 mK First step: 200 Kg(2011) – LNGS Proved energy resolution: 0.25 % FWHM GERDA -76Ge Array of enriched Ge diodes operated in liquid nitrogen or liquid argon First phase: 18 Kg; second phase: 40 Kg- LNGS Proved energy resolution: 0.16 % FWHM MAJORANA -76Ge Array of enriched Ge diodes operated in conventional Cu cryostats Based on 60 Kg modules; first step: 2x60 Kg modules Proved energy resolution: 0.16 % FWHM COBRA -116Cdcompeting candidate – 9bbisotopes Array of 116Cd enriched CdZnTe of semiconductor detectors at room temperatures Final aim: 117 kg of 116Cd Small scale prototype at LNGS Proved energy resolution: 1.9% FWHM Easy to reject 2nDBD background detector e- e- source Low energy resolution(>2%) Tracking / topology capability e- e- detector Easy to approach zero backround (with the exception of 2nDBD component) SourceDetector Easy to get tracking capability • Even though these experiments do not have tracking capability, some space information helps in reducing the background thanks to: • GRANULARITY of the basic design • - CUORE: 988 closed packed individual bolometers • - COBRA: 64,000closed packed individual detectors • - MAJORANA: 57 closed packed individual diodes per module • PULSE SHAPE DISCRIMINATION • - GERDA / MAJORANA can separate single / multi site events • SEGMENTATION and PIXELLIZATION • Granularity can be achieved through electrodes segmentation •  R&D in progress for GERDA, MAJORANA, COBRA • SURFACE SENSITIVITY in bolometers • R&D in progress in CUORE against energy-degradedaand bbackground • Simultaneous LIGHT and PHONON detection in bolometers • - R&D in progress in CUORE-like detectors fora / g rejection Physics of Massive Neutrinos, Blaubeuren

  13. Experimental techniques SUPERNEMO -82Seor150Nd Modules with source foils, tracking and calorimetric sections, magnetic field for charge sign Possible configuration: 20 modules with 5 kg source for each module  100 Kg Energy resolution: 4 % FWHM MOON - 100Moor82Seor150Nd Multilayer plastic scintillators interleaved with source foils + tracking section MOON-1 prototype without tracking section Proved energy resolution: 6.8 % FWHM Final target: collect 5 y x ton DCBA -82Se or150Nd Momentum analyzer for b particles consisting of source foils into a drift chamber with magnetic field Prototype under construction: Nd2O3 foils  1.2 g of 150Nd Space resolution ~ 0.5 mm; energy resolution 11% FWHM at 1 MeV  6 % FWHM at 3 MeV Final target: 10 modules with 84 m2 source foil for module (126 through 330 Kg total mass) High energy resolution(<2%) No tracking capability SourceDetector Easy to approach the ton scale Easy to reject 2n DBD background detector e- e- source Low energy resolution(>2%) Tracking capability e- e- detector Easy to approach zero backround (with the exception of 2n DBD component) SourceDetector Easy to get tracking capability Physics of Massive Neutrinos, Blaubeuren

  14. Experimental techniques High energy resolution(<2%) No tracking capability SourceDetector Easy to approach the ton scale EXO –136Xe TPC of enriched liquid Xenon Event position and topology; in prospect, tagging of Ba single ion (DBD daughter)  only 2nDBD background Next step (EXO-200: funded, under construction): 200 kg– will be operated in the WIPP facility Proved energy resolution: 3.3 % FWHM Easy to reject 2nDBD background detector e- e- source Low energy resolution(>2%) Tracking / topology capability e- e- detector Easy to approach zero backround (with the exception of 2nDBD component) SourceDetector Easy to get tracking capability Physics of Massive Neutrinos, Blaubeuren

  15. Experimental techniques High energy resolution(<2%) No tracking capability SourceDetector Easy to approach the ton scale SNO++ –150Nd Liquid scintillator loaded with Nd 1000Ton in SNO detector. Total isotope mass 560 kg. Probable energy resolution: 6.7 % FWHM This experiment compensates the low energy resolution with the huge statistic Easy to reject 2nDBD background detector e- e- source Low energy resolution(>2%) Tracking / topology capability e- e- detector Easy to approach zero backround (with the exception of 2nDBD component) SourceDetector Easy to get tracking capability Physics of Massive Neutrinos, Blaubeuren

  16. Heidelberg Moscow Exp and the 0nDBD claim • 5 Ge diodes with a total statistic of 10.9 kg - ( 86%) 76Ge • location: Underground Gran Sasso Laboratory (Italy) • detectors shielded with lead and N2 fluxed • Reduction of Bkg with Pulse Shape Analysis (PSA) (factor 5) Multi-site events identification (gamma bkg) 7.6  102576Ge nuclei December 2001, 4 authors (KDHK) of HM collaboration claim the 0nDBD of 76Ge Source = Detector Well known Ge diodes technology Spectrumwith 71.7 kg•y Physics of Massive Neutrinos, Blaubeuren

  17. Heidelberg Moscow Exp and the 0nDBD claim Skepticism of scientific community Aalseth CE et al. , Mod. Phys. Lett. A 17 (2002) 1475 Feruglio F et al. , Nucl. Phys. B 637 (2002) 345 Zdezenko Yu G et al., Phys. Lett. B546(2002)206 Comments and analysis HD-M data Klapdor-Kleingrothaus HV hep-ph/0205228 H.L. Harney, hep-ph/0205293 Independent answers of authors Klapdor-Kleingrothaus HV et al., NIM A510(2003)281 Klapdor-Kleingrothaus et al., NIM A 522(2004)371 Other articles • unrecognized peaks • dimension of analyzed energy window Not totally accepted result most probable value: 28.7 in 71.7 kg y exposition KKDC claim: mee= 0.1 - 0.9 eV (0.44 eV b.v.) t1/20n(y) = (0.69 – 4.81)  1025 y (1.19  1025 y b.v.) (99,9973 % c.l.  4.2 σ) H.V. Klapdor-Kleingrothaus et al.NIM. A 522(2004)371 Physics of Massive Neutrinos, Blaubeuren

  18. Experiments From the ApPEC roadmap… Physics of Massive Neutrinos, Blaubeuren

  19. Running experiments Physics of Massive Neutrinos, Blaubeuren

  20. NEMO 3 (Neutrino Ettore Majorana Experiment) sourcesthicknessmg/cm2) Other sources  Bckg 82Se (0,93 kg) →100Mo Qbb = 3034 keV Detector: tracking detector with different sources Energy resolution: 8% @ Qvalue Location: Modane Underground Laboratory (France) Multi-source detector Physics of Massive Neutrinos, Blaubeuren

  21. NEMO 3 (Neutrino Ettore Majorana Experiment) 2n spectrum E1 event e- Vertex E1+E2= 2088 keV t= 0.22 ns (vertex) = 2.1 mm e- E2 1 Source plane 2 Tracking volume (3-D readout wire drift chamber with 6180 cells) 3 Calorimeter volume (1940 plastic scintillator block) Physics of Massive Neutrinos, Blaubeuren

  22. NEMO 3 (Neutrino Ettore Majorana Experiment) Present limit on 100Mo 0nDBD bkg ~ 0.3 c/y/kg [2.8-3.2] MeV t1/20n(y) > 5.8  1023 y (90% CL) Expected sensitivity @ end 2009 t1/20n(y) ~ 2  1024 y mee < 0.64 – 2.4 eV mee ~ 0.3 – 1.3 eV 1 Source plane 2 Tracking volume (3-D readout wire drift chamber with 6180 cells) 3 Calorimeter volume (1940 plastic scintillator block) Physics of Massive Neutrinos, Blaubeuren

  23. Cuoricino Experiment Heat bath Thermal coupling Thermometer incident particle Crystal absorber →130Te Qbb = 2530 keV ~ 34% natural abundance Detector: array of 62 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvin Energy resolution: 0.28% @ Qvalue Location: LNGS (Italy) Thermal signal DT = E/C Detector works at low temperature Physics of Massive Neutrinos, Blaubeuren

  24. Cuoricino Experiment →130Te Qbb = 2530 keV ~ 34% natural abundance Detector: array of 62 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvin Energy resolution: 0.28% @ Qvalue Location: LNGS (Italy) Physics of Massive Neutrinos, Blaubeuren

  25. Cuoricino Experiment Present limit on 130Te 0nDBD bkg ~ 0.18 ± 0.01 c/keV/kg/y t1/20n(y) > 3  1024 y (90% CL) mee < 0.2 – 0.98 eV →130Te Qbb = 2530 keV ~ 34% natural abundance Detector: array of 62 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvin Energy resolution: 0.28% @ Qvalue Location: LNGS (Italy) Expected sensitivity t1/20n(y) ~ 6.1  1024 y mee ~ 0.1 – 0.6 eV Physics of Massive Neutrinos, Blaubeuren

  26. Future (but not so far) experiments Physics of Massive Neutrinos, Blaubeuren

  27. CUORE (Cryogenic Underground Observatory for Rare Event) Expansion of Cuoricino →130Te Qbb = 2530 keV ~ 34% natural abundance Detector: array of 988 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvin (total mass = 741 kg) 90 cm Energy resolution: 0.28% @ Qvalue Location: Hall A at LNGS (Italy) 19 towers Cuoricino-like Physics of Massive Neutrinos, Blaubeuren

  28. CUORE (Cryogenic Underground Observatory for Rare Event) M< 7 – 38 meV enriched CUORE Montecarlo simulations of the background show that b = 0.001 counts / (keV kg y) is possible with the present bulk contamination of detector materials The problem is the surface background (alpha, beta energy-degraded) it must be reduced by a factor 10 – 100 with respect to Cuoricino work in progress! (only a factor 2 from the conservative assumption) 5 y sensitivity (1 s) with conservative Assumption: b = 0.01 counts/(keV kg y) 5 y sensitivity (1 s) with aggressive assumption: b = 0.001 counts/(keV kg y) F0n = 9.2 ´ 1025´ ( T [ y ] )1/2 F0n = 2.9 ´ 1026´ ( T [ y ] )1/2 M< 11 – 60 meV M< 20 – 100 meV Physics of Massive Neutrinos, Blaubeuren

  29. The GERDA Experiment →76Ge Qbb = 2039 keV Detector: Array of enriched (~86%) Ge Good energy resolution: < 0.19% at Qbb Location: Hall A at LNGS (Italy), 3400 mwe the mountain provides a passive cosmic ray reduction Physics of Massive Neutrinos, Blaubeuren

  30. The GERDA Experiment: detector The detectors, arranged in strings, will be put in LAr in order to cool down them and also shield them. Physics of Massive Neutrinos, Blaubeuren

  31. The GERDA Experiment: setup Steel-tank + Cu lining Clean room / lock Liquid argon (nitrogen) Germanium detectors Ge Array Water / Muon-Veto (Č) Additional water shielding: - neutron moderator - Cerenkov medium for 4p muon veto Physics of Massive Neutrinos, Blaubeuren

  32. The GERDA Experiment Tools for the bkg reduction: • muon veto (Cerenkov detector) • anticoincidence among the detectors • pulse shape analysis • segmented crystals • active veto with LAr scintillation Physics of Massive Neutrinos, Blaubeuren

  33. GERDA goal and phases Bkg Goal: 10-3 count/(keV kg y) improvement of a factor 100 with respect HM Phase I: test claim 8 crystals from HM and IGEX (18 Kg) exposure: 15 kg·y bkg:10-2cnt/(keV kg y) (exclude 99% c.l. or confirm 5 the 0nDBD claim) Phase II: new segmented detectors exposure: 100 kg·y (it was 71 kg·y in HM) bkg:10-3count/(keV kg y) 37 Kg of enriched 76Ge already bought for the construction of 2nd phase detectors claim Further Possible Phase Collaboration with Majorana Experiment to construct a single larger experiment Physics of Massive Neutrinos, Blaubeuren

  34. SuperNEMO Top view 1m 5 m Expansion of NEMO-3 →82Se Qbb = 2995 keV →150Nd Qbb = 3367 keV Detector: tracking detector with different sources Location: Modane (Fr) / Canfranc (SP) Tracking: drift chamber ~3000 cell (Gaiger mode) Calorimeter: scintillators + PM ~ 1000 if sc. blocks ~ 100 scint. bars Physics of Massive Neutrinos, Blaubeuren

  35. SuperNEMO Improvement with respect to NEMO-3: NEMO-3SuperNEMO 100Mo Choice of isotope150Nd or 82Se 7 kg Isotope Mass 100 -200 kg 8% Efficiency 30% 208Tl < 20 mBq/Kg 214Bi < 300 mBq/Kg 208Tl < 2 mBq/Kg 214Bi < 10 mBq/Kg Internal contamination 8% @ 3MeV Energy resolution 4% @ 3MeV t1/20n(y) ~ 2  1024 y <m> ~ 0.3 -1.3 eV t1/20n(y) ~ 1026 y <m> ~ 50 meV SENSITIVITY Full experiment running at the end of 2012 Physics of Massive Neutrinos, Blaubeuren

  36. EXO-200 (Enriched Xenon Observatory) →136Xe Qbb = 2458 keV 200 kg of Xe enriched to 80% in 136 Detector: TPC of enriched liquid Xenon able to reconstruct the event position and topology. In this phase the Ba tagging technique (for the reduction of the background) will not be used GOALS - search for 0nDBD with competitive sensitivity (and test the claim) - measure 2nDBD half life (best limit currently set by Bernabei et al. 1x1022y) - Understand the operation of a large LXe detector • Understand bkg / characterize detectors materials • Learn about large scale Xe enrichment • Understand Xe handling, purification Physics of Massive Neutrinos, Blaubeuren

  37. EXO-200 (Enriched Xenon Observatory) Improve energy resolution via simultaneous collection of ionized electrons and scintillation light Physics of Massive Neutrinos, Blaubeuren

  38. EXO-200 – the LXe TPC Central HV plane Supporting ring X and Y plane APD plane Teflon light reflector Physics of Massive Neutrinos, Blaubeuren

  39. EXO-200 (Enriched Xenon Observatory) In the first part of this year the cryostat has been commissioned and it has successfully liquefied 30 kg of natural Xenon Now they are moving all their structures from Stanford to WIPP Physics of Massive Neutrinos, Blaubeuren

  40. EXO-200 (Enriched Xenon Observatory) Low but finite radioactive background: 20 counts/year in ±2σ interval centered around the 2.458 MeV endpoint No Ba tagging capability Negligible background from 2νDBD (T1/2> 1·1022 yr R.Bernabei et al. measurement) Rodin et al Phys Rev C 68(2003)044302 Courier et al. Nucl Phys A 654 (1999) 973c • In case that the Klapdor’s claim is correct EXO-200 in 2 year will see: • 15 events on top of 40 events of bkg in the worst case (QRPA – upper limit) -> 2s • 162 events on top of 40 of bkg in the best case (NSM, lower limit) -> 11s Physics of Massive Neutrinos, Blaubeuren

  41. SNO++ →150Nd Qbb = 3368 keV Nd enriched to 56% in 150 Detector: refill SNO detector with liquid scintillator (linear alkylbenzene - LAB) loaded at 0.1% with enriched Nd (not enough light output in SNO+ if using 1% Nd loading) 560 kg of 150Nd (compared to 37 g in NEMO-III) Location: Sudbury (Canada) En resolution: 6.4% @ Qvalue Physics of Massive Neutrinos, Blaubeuren

  42. SNO++ Simulation: <mv>=150 meV 1 year of data a liquid scintillator detector has poor energy resolution; but enormous quantities of isotope (high statistics) and low backgrounds help compensate - Test on stability of Nd-LAB: no change in optical properties after > 1 year - Small Nd-LS detector with a, b, g, source demonstrates it works as scintillator Sensitivity assumed background levels (U, Th) in the Nd-LS to be at the same level as KamLAND scintillator 2011: below 100 meV sensitivity reached if natural Nd and below 50 meVreached if enriched Nd Physics of Massive Neutrinos, Blaubeuren

  43. COBRA (CZT 0-neutrino Beta-decay Research Apparatus) →116Cd Qbb = 2809 keV Enriched to 90% Detector: 64000 1 cm3 CZT detectors for a total mass of 418 kg → 183 kg of interesting isotope Location: LNGS (Italy) Physics of Massive Neutrinos, Blaubeuren

  44. COBRA (CZT 0-neutrino Beta-decay Research Apparatus) The collaboration has mounted the first layer of a 4x4x4 1cm3 new array (without enriched crystals) that is now running. They will complete the 64 detector array in autumn. Resulting Energy Resolution: 1.9% @ Qvalue Possibility to study the coincidence to make a Bkg reduction Reduction at least of a factor 10 of Bkg (10 c/(keV Kg y) R&D on pixellisation of detector electrodes (200mm pixel) to make a particle ID for a Bkg reduction solid state TPC 2x2x0.5 cm3 with 64 pixels Physics of Massive Neutrinos, Blaubeuren

  45. Future scenarios The future scenarios can be divided in possible steps: • I step [100-500 meV]: • to test of HM claim and to probe the QD region of neutrino mass • SuperNEMO, CUORE, GERDA, EXO-200, SNO++ • if the neutrino mass is in this range different experiment could see it with different isotopes. Precision measurement era for 0nDBD • II step [15-50 meV]: • to probe the IH region of neutrino mass. 1 ton scale and 10 y • SuperNEMO (especially with 150Nd), • CUORE (especially if enriched), GERDA-III, SNO++ (enriched) • discovery in 3-4 isotopes is necessary to confirm the observation • III step [2-5 meV]: • For this big leap in sensitivity new approaches are required. • Next generation experiments are precious for the selection of the future approaches • 100 tons of isotopes • Unpredictable time scale and large investment in enrichment Physics of Massive Neutrinos, Blaubeuren

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