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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. - PowerPoint PPT Presentation


  • Double Beta Decay reviewFabrice PiquemalCENBG, University Bordeaux 1 CNRS/IN2P3and 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

  • - 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

    Double Beta decay: physics case- Leptonic number violation

  • Neutrino propertiesAtmospheric (SK)Accelerators (K2K,Minos)Reactors (CHOOZ)Accelerators (JPARC)Solar (SNO, SK)Reactors (KamLAND) tan223=1.0 0.3 sin2213 < 0.16 tan212=0.39 0.05 CP= CP Dirac phaseU,b : CP Majorana phase


  • Neutrino massBeta decay mv = S |Uei| mi
  • Double Beta decays2nd order process of weak interactionAlready observed for several nucleibbSingle beta decay forbidden (energy) or strongly suppressed by large angular momentum change

    Decay to ground state or excited statesbbe-e-nnbb(2n) bb(0n) e-e-DL =2 bb(0n) Majorana neutrino (n=n)

  • (A,Z) (A,Z+2) + 2 e-Process: parametersNeutrinoless Double Beta decayDiscovery implies DL=2 and Majorana neutrino

  • bb(0n) observablesFrom G. Gratta

  • bb(0n) observablesLight neutrino exchangeV+A currentMinimum electronenergyAngular distributionbetwen the 2 electronsMeVMeVCosqCosq

  • Effective neutrino mass and neutrino oscillationsDegenerate: can be testedInverted hierarchy: tested by the nextgeneration of bb experimentNormal hierarchy: inaccessible in eV

  • bb emitters

    IsotopeQ (MeV)Isotopic abundance (%)G0(yr-1) x 102548Ca4.2710.1872.4476Ge2.0407.80.2482Se2.9959.21.0896Zr3.3502.82.24100Mo3.0349.61.75116Cd2.8027.51.89130Te2.52833.81.70136Xe2.4798.91.81150Nd3.3675.68.00

  • T1/2= F(Qbb,Z) |M0n|2 2-15Nuclear matrix elementsNuclear 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

  • A lot of improvements have been done but still discrepanciesUncertainties for extraction of Nuclear matrix elementsIn the following, latest NME will refer to these Nuclear Matrix ElementsShell Model (Poves et al) - QRPATwo different QRPA calculations

  • 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 scaleprojects starting within 5 years and R&D projects.View of the field: present and future

  • Experimental techniquesToday, no technique able to optimize all the parametersM: masse (g)e : efficiencyKC.L.: Confidence levelN: Avogadro numbert: time (y)NBckg: Background events (keV-1.g-1.y-1)DE: energy resolution (keV)CalorimeterSemi-conductorsSource = detectore, DEbbbbCalorimeter(Loaded) ScintillatorSource = detectore, MTracko-caloSource detectorNBckg, isotope choiceXe TPCSource = detectorbbe,M, (NBckg)bbWith background:

  • Calorimeter vs Tracko-calobb(0n)bb(0n)bb(0n)bb(0n)CalorimeterTracko-caloHigh energy resolutionModest background rejectionHigh background rejectionModest energy resolutionkeVkeVMeV

  • 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

    Qbb MeV23476Ge130Te76Xe100Mo 82Se5150Nd 96Zr48CaQbb and background components+ bb(2n) for tracko-calo or calorimeter with modest energy resolution

  • bb(0n) search is a very dynamic field

    ExperimentsIsotopesTechniquesMain caracteristicsNEMO3100Mo,82SeTracking + calorimeterBckg rejection, isotope choiceSuperNEMO82Se, 150NdTracking + calorimeterBckg rejection, isotope choiceCuoricino130TeBolometersEnergy resolution, efficiencyCUORE130TeBolometersEnergy resolution, efficiencyGERDA76GeGe diodesEnergy resolution, eficiencyMajorana76GeGe diodesEnergy resolution, efficiencyCOBRA130Te, 116CdZnCdTe semi-conductorsEnergy resolution, efficiencyEXO136XeTPC ionisation + scintillation Mass, efficiency, final state signatureMOON100MoTracking + calorimeterCompactness, Bckg rejectionCANDLES48CaCaF2 scintillating crystalsEfficiency, BackgroundSNO++150NdNd loaded liquid scintillatorMass, efficiencyXMASS136XeLiquid XeMass, efficiencyCARVEL48CaCaWO4 scintillating crystalsMass, efficiencyYangyang124SnSn loaded liquid scintillatorMass, efficiencyDCBA150NdGazeous TPCBckg rejection, efficiency

  • 1.9 1025 yr (90% CL) Eur. Phys. J., A 12 (2001) 14735.5 k.yr0.06 cts/keV/kg/yrHeidelberg-Moscow (2001) ~11 kg of enriched 76Ge (86%) 8.9 kg.yr without PSA4.6 kg.y with PSAPhys. Rev. D65 (2002) 092007IGEX (2002)~ 8.4 kg of enriched 76Ge (86%) T 1/2 >1.57 1025 yr (90% CL)
  • bb(0n) signal ? HM claimT1/2 = (0.69 4.18) 1025 = 0.28-0.58 (90%)2006: Improvement of PSA (6s)+0.44-0.31 = 0.32 0.03 eV2004 (4s)T1/2 = 2.23 1025 yr

  • Ge detector improvementsStrategies: Ge detectors in liquid nitrogen to remove materials Active shielding and segmentation of detectors to reject gamma-rays

  • (Germany, Italy, Belgium, Russia)GERDARemoval of matterUse of liquid nitrogen or argon for active shieldingSegmentationImprovement 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 Klapdors claim) Start 2009 at Gran Sasso, results 2010 T1/2 > 3 1025 yr < 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 < 110 meV PHASE III: if PHASE I and II succeed 1 ton if B=10-3 cts/keV/kg/yr T1/2 > 5 1027 yr in 3 years of data < 20 meV

  • MajoranaVery pure material(Electroformed cooper)

    SegmentationPSD improvement Deep undergroundGoal 500 kg of 76Ge (modules of 60 kg)R&D phase 30-60 kg of 86% enriched 76Ge crystals

    Some of the crystals segmentedT1/2 > 1. 1026 yr < 140 meV (could confirme or refute Klapdors claim)Bckg goal ~ 1 count/ROI/t-yr (after analysis cuts)

    30 kg of enriched Ge, running 3 yr. Data taking scheduled for 2011 Collaboration with Gerda for 1 ton detector(USA, Russia, Japan)

  • Bolomtres: CUORICINOCuoricino Heat sinkCrystal absorberSignal:T = E/CHigh energy resolution 5-7 keV (FWHM)Natural abundance for 130Te: 34%High efficiency: 86%

    But no electron identificationBackground from internal and surfacecontamination in a emittersBolometers of TeO2 (Qbb= 2.528 MeV) Running at Gran Sasso since 200310.4 kg of 130Te

  • 60Copile up130Te0vBBT1/2 > 3. 1024 yr (90% CL) < 0.2 1 eV (90% CL)Expected final sensitivity ~2009: T1/2 > 6. 1024 yr < 0.1 0.7 eVEnergy (keV)11.83 kg.yrCuoricino resultsBckg: 0.18 cts/keV/kg/yr

  • 750 kg of TeO2 203 kg of 130TeArray of 988 TeO2 5x5x5 cm3 crystalsImprovement of surface event rejection CUOREData taking foreseen in 2011Nbckg=0.01 > 2.1 1026 yr < 0.03 0.17 eVNbckg=0.001 T > 6.6 1026 yr < 0.015 0.1 eV Goal :Nbckg=0.01 sensitivities (5 years of data)(Italy, USA,Spain)(Factor 20 compared to Cuoricino)(R&D on other bolometers like 116CdWO4)

  • 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 2003Vertex bb eventsE1E2e-e-NEMO 3Multi-isotopes (7 kg of 100Mo, 1 kg of 82Se,)Identification of electronsVery good bckg rejection (< 10-3 cts/keV/kg/yr)Angular distribution and single electron energy(necessary to distinguish the mechanism in caseof discovery)But modest energy resolution and efficiency(France, UK, Russia, Spain, USA, Japan, Czech Republic,Ukraine, Finland)Tracko-calo detector

  • T1/2(bb0n) > 5.8 1023 yr (90 % C.L.) < 0.6 1.3 eVPhases I + IIPhase I, High radon7.6 kg.yr [2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 8.1 events Nobserved = 7 eventsNumber of events / 40 keVPhase II, Low radon5.7 kg.yr[2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 3.0 events Nobserved = 4 eventsNumber of events / 40 keVNumber of events / 40 keVNEMO3: bb(0n) results 100Mo [2.8-3.2] MeV: e(bb0n) = 8 % Expected bkg = 11.1 events Nobserved = 11 events

  • SuperNEMO projectTracko-calo with 100 kg of 82Se or 150Nd(possibility to produce 150Nd with the French AVLIS facility)3 years R&D program: improvement of energy resolution Increase of efficiency Background reduction .2009: TDR2011: commissioning and data taking of first modules in Canfranc (Spain)201


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