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Double Beta Decay review

Double Beta Decay review. Fabrice Piquemal CENBG, University Bordeaux 1 CNRS/IN2P3 and Laboratoire Souterrain de Modane (CNRS/IN2P3-CEA/DSM). Thanks to: G. Gratta, S. Elliot, A. Giuliani, S. Schoenert, T. Kishimito, M. Nomachi, K. Zuber, M. Chen. Double Beta decay: physics case.

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Double Beta Decay review

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  1. Double Beta Decay review Fabrice Piquemal CENBG, University Bordeaux 1 CNRS/IN2P3 and Laboratoire Souterrain de Modane (CNRS/IN2P3-CEA/DSM) Thanks to: G. Gratta, S. Elliot, A. Giuliani, S. Schoenert, T. Kishimito, M. Nomachi, K. Zuber, M. Chen

  2. Double Beta decay: physics case - Leptonic number violation • - Nature of neutrino : Dirac (nn) or Majorana (n=n) • - Absolute neutrino mass and neutrino mass hierarchy • Right-handed current interaction • CP violation in leptonic sector • Search of Supersymmetry and new particles

  3. Neutrino properties m2atm =m231 = (2.3  0.2 ) 10-3 eV2 m2sol =m212 = (7.9  0.3) 10-5 eV2 Oscillations Atmospheric (SK) Accelerators (K2K,Minos) Reactors (CHOOZ) Accelerators (JPARC) Solar (SNO, SK) Reactors (KamLAND) U ,b : CP Majorana phase tan223=1.0 ± 0.3sin2213 < 0.16tan212=0.39 ± 0.05 CP= CP Dirac phase

  4. Neutrino mass m2 m12 m22 m32 Mass hierarchy ? ? Inverted hierarchy m2~m1>>m3 Degenerate m1≈m2≈m3» |mi-mj| Normal hierarchy m3>>> m2~m1 Absolute mass ? 1/2 2 2 Beta decaymv= S |Uei| mi<2.3 eV Double betadecay |<mn>| = |SUei mi| < 0.2 - 0.8 eV Cosmologymi=m1+m2+m3 <~1 eV 2

  5. Double Beta decays Single beta decay forbidden (energy) or strongly suppressed by large angular momentum change Decay to ground state or excited states bb bb bb(2n) bb(0n) e- e- e- e- n n DL =2 2nd order process of weak interaction Already observed for several nuclei bb(0n) Majorana neutrino (n=n)

  6. Neutrinoless Double Beta decay R-parity violation T1/2 depends on (l’111)2, gluino and squarks mass <mn> Light neutrino exchange <mn>,<l>,<h> (V+A) current <gM> Majoron emission l’111,l’113l’131,….. SUSY Nuclear matrix element Phase space factor Phase space factor Nuclear matrix element -1 -1 5 T1/2= F(Qbb,Z)|M|2<mn>2 T1/2= F|MJ|2<gM>2 Effective mass: <mn>= m1|Ue1|2 + m2|Ue2|2.eia1 + m3|Ue3|2.eia2 |Uei|: mixing matrix element a1 et a2: Majorana phase Coupling between Majoron and neutrinos (A,Z) (A,Z+2) + 2 e- Discovery implies DL=2 and Majorana neutrino Process: parameters

  7. bb(0n) observables From G. Gratta

  8. bb(0n) observables Light neutrino exchange V+A current Minimum electron energy MeV MeV Angular distribution betwen the 2 electrons Cosq Cosq

  9. Effective neutrino mass and neutrino oscillations Degenerated Inverted hierarchy Normal hierarchy Degenerate:can be tested Inverted hierarchy:tested by the next generation of bb experiment <mn> in eV Normal hierarchy:inaccessible

  10. bb emitters

  11. Nuclear matrix elements 5 -1 T1/2= F(Qbb,Z)|M0n|2<mn>2 Nuclear matrix elements are calculated using various models: QRPA (RQRPA, SQRPA, …….) Shell model Up to recently no convergence for the results Statement from Bahcall et al. to use the nuclear matrix range as an uncerntainty: « Democratic approach » Does not take into account the improvements of the Models Exchanges between groups to understand discrepencies and to evaluate errors bb(2n) is used by QRPA to fix gpp paramaters for QRPA

  12. Nuclear matrix elements Shell Model (Poves et al) - QRPA Two different QRPA calculations A lot of improvements have been done but still discrepancies Uncertainties for extraction of <mn> In the following, « latest NME » will refer to these Nuclear Matrix Elements

  13. View of the field: present and future Today experiments have a mass of enriched source ~10 kg To reject inverted hierarchy mass scenario, enriched source mass  1 ton All projects have this goal but it is unrealistic to plane to go directly from 10 kg to 1 ton scale (understanding and control of the background) Intermediate step at 100 kg scale is needed (as proposed by each project) Talk focuses on the running experiments, on some 100 kg scale projects starting within 5 years and R&D projects.

  14. Experimental techniques M . t e A ln2 . N kC.L. (y) > . . NBckg . DE With background: M: masse (g) e : efficiency KC.L.: Confidence level N: Avogadro number t: time (y) NBckg: Background events (keV-1.g-1.y-1) DE: energy resolution (keV) Today, no technique able to optimize all the parameters Calorimeter Semi-conductors Source = detector Tracko-calo Source  detector Xe TPC Source = detector Calorimeter (Loaded) Scintillator Source = detector b b b b b b b b e, M NBckg, isotope choice e,M, (NBckg) e, DE

  15. Calorimeter vs Tracko-calo Tracko-calo Calorimeter High background rejection Modest energy resolution High energy resolution Modest background rejection bb(0n) bb(0n) keV bb(0n) bb(0n) keV MeV

  16. + more specific background for calorimeter Surface or bulk contamination in a emitters cosmogenic production Qbb and background components Natural radioactivity (40K, 60Co,234mPa, external 214Bi and 208Tl…) 214Bi and Radon 208Tl (2.6 MeV g line) and Thoron g from (n,g) reaction and muons bremstrahlung 150Nd 96Zr 100Mo 82Se 130Te 76Ge 48Ca 76Xe 3 4 5 2 Qbb MeV + bb(2n) for tracko-calo or calorimeter with modest energy resolution

  17. bb(0n) search is a very dynamic field

  18. bb(0n): Present situation Ge diode detectors: High energy resolution and efficiency But poor background rejection (pulse shape analysis) Heidelberg-Moscow (2001) ~11 kg of enriched 76Ge (86%) IGEX (2002) ~ 8.4 kg of enriched 76Ge (86%) 35.5 k.yr 8.9 kg.yr without PSA 4.6 kg.y with PSA 0.06 cts/keV/kg/yr T 1/2 >1.9 1025 yr (90% CL) T 1/2 >1.57 1025 yr (90% CL) <mn> <0.35-1.05 eV (90% CL) <mn> <0.33-1.31 eV (90% CL) Eur. Phys. J., A 12 (2001) 147 Phys. Rev. D65 (2002) 092007

  19. bb(0n) signal ? HM claim 2006: Improvement of PSA (6s) 2004 (4s) +0.44 T1/2=2.231025 yr T1/2= (0.69 – 4.18) 1025 <mn>= 0.28-0.58 (90%) -0.31 <mn> = 0.32 ± 0.03 eV

  20. Ge detector improvements crystal anti-coincidence Detector segmentation segments detector e-  pulse shape analysis R&D: liquid argon anti-coincidence Liquid argon e- scintillation Strategies:Ge detectors in liquid nitrogen to remove materials Active shielding and segmentation of detectors to reject gamma-rays

  21. GERDA (Germany, Italy, Belgium, Russia) Removal of matter Use of liquid nitrogen or argon for active shielding Segmentation Improvement of Pulse Shape Analysis PHASE I:17.9 kg of enriched 76Ge (from HM and IGEX) In 1 year of data if B=10-2 cts/keV/kg/yr (check of Klapdor’s claim) Start 2009 at Gran Sasso, results 2010 T1/2 > 3 1025 yr <mn> < 250 meV PHASE II:40 kg of enriched 76Ge (20 kg segmented) if B=10-3 cts/keV/kg/an T1/2 > 2 1026 yr in 3 years of data <mn> < 110 meV PHASE III:if PHASE I and II succeed 1 tonif B=10-3 cts/keV/kg/yr T1/2 > 5 1027 yr in 3 years of data <mn> < 20 meV

  22. Majorana (USA, Russia, Japan) Very pure material (Electroformed cooper) Segmentation PSD improvement Deep underground Goal 500 kg of 76Ge (modules of 60 kg) R&D phase 30-60 kg of 86% enriched 76Ge crystals Some of the crystals segmented • Bckg goal ~ 1 count/ROI/t-yr (after analysis cuts) • 30 kg of enriched Ge, running 3 yr. Data taking scheduled for 2011 T1/2 > 1. 1026 yr <mn> < 140 meV(could confirme or refute Klapdor’s claim) Collaboration with Gerda for 1 ton detector

  23. Cuoricino Thermometer Double beta decay 5.3 kg.an 208Tl (232Th chain) T1/2 > 1. 1024 ans (90%) <mn> <0.5 – 2.4 eV 60Co pile up 214Bi (238U chain) bb(0n) Energy (keV) Bolomètres: CUORICINO Bolometers of TeO2 (Qbb= 2.528 MeV) Heat sink Signal:∆T = E/C Crystal absorber High energy resolution 5-7 keV (FWHM) Natural abundance for 130Te: 34% High efficiency: 86% But no electron identification Background from internal and surface contamination in a emitters 10.4 kg of 130Te Running at Gran Sasso since 2003

  24. Cuoricino results 0DBD Gamma region, dominated by gamma and beta events, Alpha region, dominated by alpha peaks (internalorsurfacecontaminations) Bckg: 0.18 cts/keV/kg/yr 60Co pile up 130Te 0vBB 11.83 kg.yr Energy (keV) T1/2 > 3. 1024 yr (90% CL) <mn> < 0.2 – 1 eV (90% CL) Expected final sensitivity ~2009:T1/2 > 6. 1024 yr <mn> < 0.1 – 0.7 eV

  25. CUORE (Italy, USA,Spain) 750 kg of TeO2 203 kg of 130Te Array of 988 TeO2 5x5x5 cm3 crystals Improvement of surface event rejection Goal :Nbckg=0.01 cts.keV-1.kg-1.yr-1 (Factor 20 compared to Cuoricino) Data taking foreseen in 2011 (R&D on other bolometers like 116CdWO4) Expected sensitivities (5 years of data) Nbckg=0.001 cts.keV-1.kg-1.yr-1 T½ > 6.6 1026 yr <mn> < 0.015 – 0.1 eV Nbckg=0.01 cts.keV-1.kg-1.yr-1 T½ > 2.1 1026 yr <mn> < 0.03 – 0.17 eV

  26. NEMO 3 E1+E2= 2088 keV t= 0.22 ns (vertex) = 2.1 mm (France, UK, Russia, Spain, USA, Japan, Czech Republic,Ukraine, Finland) Tracko-calo detector Central source foil (~50 mm thickness) Tracking detector (6180 drift cells) t = 0,5 cm, z = 1 cm ( vertex ) Calorimeter (1940 plastic scintillators + PMTs) Efficiency 8 % Running at Modane Underground lab since 2003 E1 e- Vertex Multi-isotopes(7 kg of 100Mo, 1 kg of 82Se,…) Identification of electrons Very good bckg rejection(< 10-3 cts/keV/kg/yr) Angular distribution and single electron energy (necessary to distinguish the mechanism in case of discovery) But modest energy resolution and efficiency e- E2 bb events

  27. NEMO3: bb(0n)results 100Mo Phase I + II 13.3 kg.yr T1/2(bb0n) > 2. 1024 yr (90 % CL) <mn> < 0.3 –0.7 eV Expected in 2009 Phase I, High radon 7.6 kg.yr Phase II, Low radon 5.7 kg.yr Number of events / 40 keV Number of events / 40 keV Number of events / 40 keV [2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 11.1 events Nobserved = 11 events [2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 3.0 events Nobserved = 4 events [2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 8.1 events Nobserved = 7 events T1/2(bb0n) > 5.8 1023 yr (90 % C.L.) <mn> < 0.6 – 1.3 eV Phases I + II

  28. SuperNEMO project (France, UK, Russia, Spain, USA, Japan, Czech Republic,Ukraine, Finland) Tracko-calo with 100 kg of 82Se or 150Nd (possibility to produce 150Nd with the French AVLIS facility) T½ > 2. 1026 yr <mn> < 0.05 – 0.09 eV Modules based on the NEMO3 principle Measurements of energy sum, angular distribution and individual electron energy 3 years R&D program: improvement of energy resolution Increase of efficiency Background reduction ……. 100 kg 20 modules R&D funded by France, UK and Spain 2009: TDR 2011: commissioning and data taking of first modules in Canfranc (Spain) 2013: Full detector running

  29. EXO (USA, Canada, Switzerland, Russia) Liquid Xe TPC Energy measurement by ionization + scintillation Tagging of Baryum ion (136Xe  136Ba++ + 2 e-) Large mass of Xe Identification of final state  background rejection But no e- identification Poor background rejection without Ba ion tagging R&D for Ba ion tagging in progress Prototype EXO-200 200 kg of 136Xe, no Ba ion tagging Installation in progress in WIPP underground lab 2007 Could measure bb(2n) of 136Xe EXO 200 (2 years) T½ > 6.4 1025 yr (90% CL) <mn> < 0.27- 0.38 eV

  30. CANDLES Liquid Scintillator (Veto Counter) CaF2(Pure) Buffer Oil Large PMT (Japan) Pure CaF2 crystals Wave length shifter in LS PSD to reject g and a Efficiency, 48Ca (background) But mass of isotope, no e- identification CANDLES III :Prototype 103 cm3 × 60 crystals 191 kg (~ 350g of 48Ca) In test in Osaka University Full detector103 cm3 × 96 crystals 305 kg Installation in spring 2008 at Kamioka Expected BG: 0.14 event/yr (30 mBq/kg) <mn> ~0.5 eV CANDLES IV :3 tons of CaF2 (3 mBq/kg) 6 yr <mn> ~0.1 eV

  31. MOON (Japan, USA) Compact tracko-calo Compactness Multi-isotopes Electron identification But energy resolution and bckg rejection (ToF) Moon 1:Data acquisition with 142 g of 100Mo (40 mg/cm2) In progress: Improvement energy resolution Waveform readout Design of a module Module: 2011 20 kg of bb source <m> ~100 meV

  32. DCBA (Japan) Drift Chamber beta-ray Analyser Electron identification Multi-isotopes But Efficiency, Energy resolution Prototype with 207Bi : 10% (FWHM) energy resolution X position s= 0.5 mm Y position s= 0.02 mm X position s= 6 mm

  33. COBRA (UK, Germany, Italy, poland, Slovaquia, Finland, USA) Array of 1cm3 CdZnTe detectors Good energy resolution Several isotopes at the same time Efficiency But background rejection Cd-113 beta decaywith half-life of about 1016 yrs 4x4x4 detector array = 0.42 kg CdZnTe Installed at LNGS Test of coincidence rejection Measure of 113Cd

  34. SNO++ Scintillator loaded with Nd. Mass Efficiency But energy resolution No e- identification Test of light attenuation Study of Nd purification (factor 1000 per pass in Th and Ra) 56 kg of 150Nd (0,1 % of natural Nd) 4 yr of data <mn> ~80 meV 500 kg of 150Nd 4yr <mn> ~30 meV 500 kg of 150Nd 1 year <mn> = 150 meV only internal Th and 8B solar neutrino backgrounds are important Similar prospect in KamLAND

  35. Summary Summary * Calculation with NME from Rodim et al., Suhonen et al., Caurier et al. PMN07

  36. <mn> current and future limits . Klapdor claim HM Cuoricino NEMO3 Limits in 2009 HM,NEMO3, Cuoricino Expected limits 2009 – 2015 CUORE,GERDA, Majorana, SuperNEMO, EXO,…. Degenerated Inverted hierarchy Normal hierarchy Use of « latest NME » for all experiments

  37. Summary Summary Very active field. A claim to be checked Current experiments will reach a sensitivity on<mn> ~(0.2 – 0.7) eV in 2009 Need to measure several nucleus with different techniques (only tracko-calo could distinguish the mechanism in case of discovery) Next generation ~ source mass 100 – 200 kg.<mn> ~ (0.03 – 0.1) eV Will cover partially the inverted hierarchy mass scenario (2011 – 2015) Essential step for 1 ton scale experiment ( background considerations) Need improvements for Nuclear Matrix Element calculations

  38. bb(0n): Present situation Pulse shape analysis with Ge detectors SSE (Multiple Site Event) (Single Site Event) SSE MSE

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