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Probing neutrinos with 0nbb decay

Probing neutrinos with 0nbb decay. Ruben Saakyan UCL Swansea 31 January 2006. Preview. Neutrino oscillations, 0nbb decay and neutrino mass bb decay basics Running experiments Status of “evidence” Future projects. Why study neutrinos?.

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Probing neutrinos with 0nbb decay

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  1. Probing neutrinos with 0nbb decay Ruben Saakyan UCL Swansea 31 January 2006

  2. Preview • Neutrino oscillations, 0nbb decay and neutrino mass • bb decay basics • Running experiments • Status of “evidence” • Future projects

  3. Why study neutrinos? • Essential part of the building blocks of matter and the Universe • Fundamental for understanding deep principles of nature • In Standard Model assumed to be massless • We now know they have non-zero mass • Neutrino mass – window beyond Standard Model

  4. Recall that nm nm ne Neutrino oscillationsSimple case: 2n vacuum oscillations Consider  = 45

  5. Oscillations  mn  0 from 2n to 3n oscillations PMNS matrix (compare CKM matrix for quarks) PMNS – Pontecorvo-Maki-Nakagawa-Sakata CKM – Cabibbo-Kobayashi-Maskawa

  6. First evidence for oscillations from atmospheric neutrinos

  7. SuperKamiokande detector (Japan)

  8. Solar neutrinos SNO – Sudbury Neutrino Observatory

  9. Neutrino oscillation summary Neutrino Mixing Observed ! From KamLAND, solar n and atmospheric n Dm2LMA≈ 5×10-5 eV2 = (7 meV)2 Dm2atm ≈ 2.5×10-3 eV2 = (50 meV)2  at least one neutrino with mi> 0.05 eV! VERY approximately

  10. Neutrino mass. Things we want to know. • Relative mass scale (n-oscillations) • Mass hierarchy (n-oscillations, 0nbb) • CP-violation (n-oscillations, 0nbb) • Absolute mass scale (0nbb, 3H-decay, cosmology) • Dirac or Majorana particle (0nbb only) DL  0? Access to GUT scale (see-saw mechanism) Important consequences for particle physics, cosmology, nuclear physics

  11. Theorists dream: n is Majorana particle MR mL See-Saw: explains smallness of mn Leptogenesis: may shed light on baryon asymmetry of Universe

  12. Standard Model 2nbb Decay Excited state decays possible Qbb Phase space ~Qbb11 NME In many even-even nuclei, b decay is energetically forbidden. This leaves bb as the allowed decay mode. |M| - NME, very hard to calculate but in case of 2nbb can be measured experimentally 2nbb has been observed for 10 nuclei

  13. 0nbb Decay bb spectra. Ee1 + Ee2 DL = 2! Phase space ~Qbb5 NME But there are other mechanisms which could generate 0nbb (V+A, Majoron emission, leptoquarks, extra-dimensions, SUSY, H--…) Q

  14. Effective Majorana Mass(inverted hierarchy case) Ue22 m2 <mee> Ue32 m3 min Ue12 m1

  15. Isotopes • Best candidates: • 76Ge, Qbb = 2.038 MeV • 48Ca, Qbb= 4.272 MeV • 82Se, Qbb= 2.995 MeV • 100Mo, Qbb= 3.034 MeV • 116Cd, Qbb= 2.804 MeV • 130Te, Qbb= 2. 528 MeV • 136Xe, Qbb= 2.48 MeV • 150Nd, Qbb= 3.368 MeV • High Qbb is important (G0n ~ Qbb5, G2n ~ Qbb11) • In most cases enrichment is a must • Different isotopes must be investigated due to uncertainties in NME calculations !

  16. Recent developments in NME calculations Rodin, Faessler, Simcovic, Vogel, PRC 68 (2003) 044303 nucl-th/0503063. Error bars are from experimental errors on Workshop on NME in Durham, May 2005 K. Zuber, nucl-ex/0511009 • gpp fixed from experimentally measured M2n • Different calculations converge • Underlines the importance of 2nbbprecise measurements

  17. The Experimental Problem( Maximize Rate/Minimize Background) Natural Activity: t(238U, 232Th) ~ 1010 years Target: t(0nbb) > 1025 years  Detector Shielding Cryostat, or other experimental support Front End Electronics etc. + Cosmic ray induced activity Extremely radiopure materials + underground Lab

  18. detector e-   source e- detector SourceDetector (calorimetric technique) SourceDetector • scintillation • gaseous TPC • gaseous drift chamber • magnetic field and TOF • scintillation • cryogenic macrocalorimeters (bolometers) • solid-state devices • gaseous detectors e- e- high efficiency and energy resolution event reconstruction bb signature Experimental approaches to direct searches Two approaches for the detection of the two electrons:

  19. A History Plot Current best limit comes from 76Ge experiments: Heidelberg-Moscow and IGEX <mn> < 0.35 – 0.9 eV mscale~ 0.05 eV from oscillation experiments

  20. Hieldeberg-Moscow (Gran Sasso) First claim (end 2001) <mn> = 0.4 eV ??? • 5 HPGe 11 kg, 86% 76Ge • DE/E 0.2% • >10 yr of data taking <mn> < 0.3 – 0.7 eV If combine HM and IGEX

  21. Heidelberg claim. Recent developments hep-ph/0403018, NIMA, Phys. Rev… Data analysed for 1990 – 2003 • Data reanalyzed with improved • binning/summing • Peak visible • Effect reclaimed with 4.2s • <m> = (0.2 – 0.6) eV, • 0.4 eV best fit • <m> = (0.1 – 0.9) eV (due to NME) 214Bi 214Bi unknown 0nbb Personal view • Looks more like 2.5s of effect • 214Bi line intensities do not match 71.7 kgyr

  22. Current Experiments NEMO-3 (Tracking calorimeter) CUORICINO (bolometer) Until ~2008 results are only from these two Sensitivity ~ 0.2 eV – 0.6 eV

  23. Today:CUORICINO • Located in LNGS, Hall A CUORE R&D (Hall C) CUORE (Hall A) Cuoricino (Hall A)

  24. heat bath Thermal sensor absorber crystal Incident particle Today: CUORICINO 40.7kg total 2modules, 9detector each, crystal dimension3x3x6 cm3 crystal mass330 g 9 x 2 x 0.33 = 5.94 kg of TeO2 11modules, 4detector each, crystal dimension5x5x5 cm3 crystal mass790 g 4 x 11 x 0.79 = 34.76 kg of TeO2

  25. Today:CUORICINO • Operation started early 2003 • BG = 0.19 counts/kev/kg/y • DE/E = 4 eV @ 2 MeV mn < 0.3 – 1.6 eV (all NME)

  26. Today: NEMO-III AUGUST 2001

  27. bb2n measurement bb0n search bb decay isotopes in NEMO-3 detector 116Cd405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV 150Nd 37.0 g Qbb = 3367 keV 48Ca 7.0 g Qbb = 4272 keV 130Te454 g Qbb = 2529 keV External bkg measurement natTe491 g 100Mo6.914 kg Qbb = 3034 keV 82Se0.932 kg Qbb = 2995 keV Cu621 g (All enriched isotopes produced in Russia)

  28. Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view Vertex emission Vertex emission Drift distance Deposited energy: E1+E2= 2088 keV Internal hypothesis: (Dt)mes –(Dt)theo = 0.22 ns Common vertex: (Dvertex) = 2.1 mm (Dvertex)// = 5.7 mm • Trigger: 1 PMT > 150 keV • 3 Geiger hits (2 neighbour layers + 1) • Trigger rate = 7 Hz • bb events: 1 event every 1.5 minutes Criteria to select bb events: • 2 tracks with charge < 0 • 2 PMT, each > 200 keV • PMT-Track association • Common vertex • Internal hypothesis (external event rejection) • No other isolated PMT (g rejection) • No delayed track (214Bi rejection) bb events selection in NEMO-3 Typical bb2n event observed from 100Mo Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view 100Mo foil 100Mo foil Geiger plasma longitudinal propagation Scintillator + PMT

  29. Latest results, 100Mo PRL 95, 182302 (005) T1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst)  1018 y, SSD mechanism! T0n > 4.6  1023 y , mn < 0.7-2.8 eV

  30. Strategy for future.An Ideal Experiment • Large Mass (0.1t) • Good source radiopurity • Demonstrated technology • Natural isotope • Small volume, source = detector • Tracking capabilities • Good energy resolution or/and Particle ID • Ease of operation • Large Q value, fast bb(0n) • Slow bb(2n) rate • Identify daughter • Event reconstruction • Nuclear theory • All requirements can NOT be satisfied • Red – must be satisfied

  31. A Great Number of Proposals

  32. Clean room lock Water tank / buffer/ muon veto Vacuum insulated copper vessel Liquid N/Ar Ge Array GERDA. 76Ge. “Naked” 76Ge detectors in LN2/LAr Original idea from GENIUS (Klapdor)

  33. GERDA. 76Ge • Phase I: collect 76Ge detectors from HM(11kg)+IGEX(8kg) • 15kgy+BG@0.01 c/keV/kg/y  sens-ty: 3·1025 y, 0.24-0.77 eV  Confirm Klapdor with 5s OR rule out • Phase II: increase to ~35-40 kg • BG < 10-3 c/keV/kg/y • within 4 yr ~ 100 kgy  • 2·1026 y, 0.09-0.29 eV  • Phase III: 0.5 -1 ton • Possible merge with Majorana • >1027 y, ~ 0.03 eV- 0.09 eV GERDA Phase I and Phase II approved Site: Gran Sasso Mostly European project

  34. New 130Teexperiment, evolution of CUORICINO Closely packed array of 988 bolometers at 10 mK 19 towers - 13 modules/tower - 4 detectors/module M = 741 kg ~ 265 kg of 130Te Compact structure, ideal for active shielding Each tower is a CUORICINO-like detector Special dilution refrigerator CUORE. 130Te Site: Gran Sasso Euope +US

  35. CUORE • Current CUORICINO background 0.2 c/keV/y/kg • Two scenarios: • I: BG down to 0.01 c/keV/y/kg • II: BG down to 0.001 c/keV/y/kg • Sensitivity I: 2×1026 y, 0.03 – 0.1 eV • Sensitiviry II: 6.5×1026 y, 0.017 – 0.06 eV 5 year exposure Approved

  36. SuperNEMO (UK, France, Russia, Spain, US, Czech Rep…) Evolutionof NEMO 3  same technique, larger mass, lower background better efficiency, higher energy resolution 82Seexperiment (high Qbb, slower 2n rate) as baseline. Basic points: Planargeometry • Modularstructure • Isotope Mass 100-200 kg • Instrumentation ~20 submodules, 40,000 – 60,000 tracking channels • ~ 5,000 – 20,000 PMTs (depending on the design) • Sensitivity T1/2: 2 x1026 y Mbb< 40 - 70 meV

  37. source tracker calorimeter 1 m 4 m 5 m Top view Side view SUPERNEMO. Tracking calorimeter

  38. Majorana. 76Ge Mostly US • 0.5 ton of 86% enriched 76Ge • Very well known and successful technology • Segmented detectors using pulse shape discrimination to improve background rejection. • Prototype ready (14 crystals, 1 enriched) • Possible merger with GERDA at later stage Sensitivity: T1/2 ~ 3×1027 y <mn> ~ 0.03 – 0.09 eV

  39. EXO. 136Xe Mostly US • 1-10 ton, ~80% enriched 136Xe • Gas TPC or LXe chamber • Optical identification of Ba ion. • Drift ion in gas to laser path or extract on cold probe to trap. • 200-kg enrXe prototype (no Ba ID) being built • Isotope in hand Sensitivity with 1 ton: 8×1026 y 0.04 – 0.08 eV

  40. Sussex Oxford Dortmund Warwick Cadmium-Telluride O-neutrino double-Beta Research Apparatus. COBRA • CdTe or CdZnTe semiconductor detectors • Good DE/E • Two isotopes 116Cd and 130Te • Operate at room temperature • New approach

  41. Next generation experiments Plan to reach this sensitivity by ~2015

  42. C O S M O L O G Y • degeneracy will be deeply probed • inverted hierarchy will be soon attacked Mb [eV] PLANCK + larger surveys Strumia-Vissani hep-ph/0503246 KDHK claim D O U B L E b (HM,CUORICINO, NEMO3) S I N G L E b CUORE, GERDA, SUPERNEMO, ... KATRIN, MARE S [eV] Mbb [eV] Neutrino mass scaleExpected limits from 0n-DBDA. Giulliani, 1st Astroparticle EU town meetingMunich, 23-25 Nov

  43. Concluding Remarks • Very exciting time for neutrino physics in general and 0nbb in particular • From oscillations: positive signal is a serious possibility • “Good value”: ~$50M for great potential scientific gain • At least one measurement which must be done but can not be done by any other approach (nature of n mass) • Several experiments with different isotopes are needed (recall NME uncertainties)

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