DOUBLE BETA DECAY EXPERIMENTS Yeongduk Kim Sejong University 2 nd Amore Meeting

Outline 2  Introduction to Double Beta Decay.  Strategies for detection of   Status of Current Projects  Upcoming Experiments.  Summary

Brief history : M. Goeppert–Mayer, “Double beta–Disintegration” Phys. Rev. 48, : Ettore Majorana ? Neutrinos may be identical with its antiparticle. (Majorana neutrino) years years : S.R. Elliott : Phys. Rev. Lett : S.R. Elliott : Phys. Rev. Lett First measurements of 2nub - b - of 82 Se.

Double beta decay  Even-even 핵들에서 핵자의 pairing effect 때문에 single 베타붕괴가 불가능한 경우 이중 베타붕괴할 수 있다.

Three neutrino mixing and oscillation

3 mixing angles & 2 mass square difference ~45meV ~9meV 1.Neutrinos are massive ! 2.Neutrino flavors oscillates !

Half-life of  process – Doi… Total Lepton number violation. Amplitude for helicity matching i i W–W– W–W– e–e– e–e– Nuclear Process NuclNucl’ Helicity -RHelicity -L Effective Majorana neutrino mass

Mass Hierarchy Hirsch et al, PLB679: ,2009  m A ~45meV  m S ~9 meV m3m2m1m3m2m1 m 2 m 1 m 3 NH IH e      13 ? Depending on the mass hierarchy, the effective neutrino mass to be measured is very different.

 signal

Two approaches: e-e- e-e- source detector Source  Detector (Tracking technique) Strategies for detection of  Source  Detector (calorimetric technique) e-e- e-e- Total MassLarge Mass possibleLarge Mass Difficult Energy Resolution ExcellentPoor IsotopesFixed by DetectorIsotopes can be changed Event TopologyNoTwo tracks

Klapdor’s claim. 76 Ge

12 Current(2010) best limits for     Q (keV) Abun. (%) T(1/2) ( years) m ν limit (eV) Reference 48 Ca >0.058 < S. Umehara et al., PRC 78 (2008) Ge >19 =22.3 < = H.V. Klapdor-Kleingrothaus et al., EPJA 12 (2001) H.V. Klapdor-Kleingrothaus Mod. Phys. Lett. A. 21 (2006) Se >0.36 < Tretyak AIP1180 (2009) Mo >1.1 < Tretyak AIP1180 (2009) Cd >0.17 <1.7 F.A. Danevich et al., PRC 68 (2003) Te >2.8 < NOW2010 Bucci presentation 150 Nd >0.018 < A. Barabash, JPCS 173 (2009) Xe >0.44 <2.3 R. Luescher et al., PLB 434 (1998) 407

Candidate nuclei for  “Golden Nuclei”

Candidate nuclei for  130 Te

Suhonen(98) Doi(85), Boehm&Vogel(91) 48 Ca 150 Nd 96 Zr 100 Mo 116 Cd 82 Se G : Phase space factor is larger for large Q value. 100 Mo’s G factors are different between calculations by more than factor 2.

Suhonen(98) Doi(85), Boehm&Vogel(91) 48 Ca 150 Nd 96 Zr 100 Mo 116 Cd 82 Se 100 Mo’s larger G factor may be questionable.

Matrix Elements Rodin, v1

from NOW2010 Giuliani

Current & Future Experiments  CUORE,LUCIFER,AMORE2 : Cryogenic  GERDA, MAJORANA : HPGe  SNO+,KamLAND : Liquid Scintillator + Mixing  CANDLES, AMORE1 : Inorganic Scintillator  EXO, COBRA, NEXT : Active Tracking  SUPERNEMO, MOON, DCBA : Passive Tracking

NEMO-3 and SuperNEMO A search for zero neutrino double beta decay  Robert L. Flack  University College London

0νββ for 100 Mo(~7kg) and 82 Se (~1kg) [ ] MeV: DATA = 18; MC = 16.4±1.4 T 1/2 (0ν) > 1.0×10 24 yr at 90%CL < ( ) eV V+A: T 1/2 (0ν) > 5.4×10 23 yr at 90%CL λ < 1.4×10 -6 Majoron: T 1/2 (0ν) > 2.1×10 22 yr at 90%CL g ee < 0.5×10 -4 World’s best result! [ ] MeV: DATA = 14; MC = 10.9±1.3 T 1/2 (0ν) > 3.2×10 23 yr at 90%CL < ( ) eV 7 September Robert Flack NOW2010

7 kg 100+ kg isotope mass M 18 % ~ 30 % isotope 100 Mo 82 Se or other NEMO-3 SuperNEMO internal contaminations 208 Tl and 214 Bi in the  foil Rn in the tracker 208 Tl: ~ 100  Bq/kg 214 Bi: < 300  Bq/kg Rn: 5 mBq/m Tl   Bq/kg if 82 Se: 214 Bi  10  Bq/kg Rn ≤ 0.15 mBq/m 3 T 1/2 ( 0ν ) > 2 x y < 0.3 – 0.9 eV T 1/2 ( 0ν ) > 1 x y < eV energy resolution (FWHM) 3 MeV efficiency  7 September 2008 Robert Flack NOW Objectives of the 4 year R&D programme

Source 2.7m Submodule tracker Submodule calorimeter Submodule Source and cali bration 6 m 4 m 2 m (assembled, ~0.5m between source and calorimeter) 7 September 2008 Robert Flack NOW A SuperNEMO module 20 modules having a Planar d esign. Each module will have 5kg of enriched isotope Making a total of 100 kg. Drift chamber ~2000 cells in Ge iger mode 550 PMTs + scintillator blocks

LUCIFER Low-background Underground Cryogenics Installation For Elusive Rates Principal Investigator: Fernando Ferroni Co-Investigator : Andrea Giuliani ERC-2009-AdG Double Beta Decay pilot project based on scintillating bolometers

The choice of the isotope There are 3 main candidates The baseline: ZnSe Active isotope: 82 Se Decay: 82 Se -> 82 Kr + 2e - Q-Value: 2995 keV Abundance: 9% Q-value [keV] Useful material LY [keV/MeV] QF   Enrichment [€/g] CdWO %340.19> ZnMoO % ZnSe299556% Cons Pros Transition energy does not indicate a preference 113 Cd beta emitter 113 Cd high neutron c ross-section

LNGS (1)   4 cm, 1.7 cm height, 120 g  2 cm, 3 cm hei ght, 39 g  QF > 1: alphas give more light than gammas → risk of leakage in the beta/gamma region? Q-value of 82 Se   2615 keV: the end of  radioactivity Background free area Just an example

Gironi et al., NIMA617, 478 (2010) Alpha, gamma separation w/o light detection.

From the LUCIFER proposal: CrystalIsotope weightUseful material Half Life limit (10 26 y) Sensitivity* to m ee (meV) CdWO Cd 15.1 kg32% ZnMoO Mo 11.3 kg44% ZnSe [baseline] 82 Se 17.6 kg56% ZnSe [option 1] 82 Se 20.5 kg56% ZnSe [option 2] 82 Se 27.8 kg56% * The 1  sensitivity is calculated with the Feldman Cousins approach for 5 y running and a background index d  b /dE = c/keV/Kg/y. The matrix elements come from the two most recent QRPA calculations [ME08]; the energy window is taken as 5 keV, compatible with the resolution achieved in TeO 2 macrobolometers and in scintillating-bolometer R&D. Optimistic evaluation, assuming full success for several difficult tasks:  negotiate a good contract for enrichment → Zelenogorsk (Russia), URENCO (NL)  get radiopure and chemically pure isotope after enrichment  efficient crystallization → Institute for Single Crystals, Kharkov, Ukraina  optimize bolometric performance of ZnSe crystals The physics reach …but has a remarkable sensitivity by itself More realistic evaluation: 10 kg of isotope ~100 meV as sensitiv ity More realistic evaluation: 10 kg of isotope ~100 meV as sensitiv ity

KamLAND-Zen (0  with 136 Xe) (Zero neutrino double beta decay) 136 Xe can be dissolved into liquid scintillator up to ~ 3 wt%.

43 Some best 2 ,  +, 2  + experiments NuclideChannel Experimental limits T 1/2 (yr) Technique 40 Ca 22 > (3-6) ×10 21 CaF 2 (Eu) scintillators 54 Fe 22 > (4-5) ×10 20 HPGe  spectrometry 58 Ni 2 ,  + > (0.2-7)×10 20 HPGe  spectrometry 64 Zn 2 ,  + > (0.06-7)×10 20 ZnWO 4 scintillators 78 Kr 2 ,  +, 2  + > (1-5× > (1-5)×10 21 Gaseous detector 92 Mo 2 ,  + > (0.06-9)×10 20 HPGe  spectrometry 96 Ru 2 ,  +, 2  + > ( × > ( )×10 19 HPGe  spectrometry 106 Cd 2 ,  +, 2  + > (0.01-4)×10 20 HPGe  spectrometry, NaI(Tl)  spectrometry CdWO 4 scintillators CdZnTe semiconductor 130 Ba 2 ,  +, 2  + > 4×10 21 = (2.2 ± 0.5) ×10 21 Geochemical 132 Ba 22 > 2.2×10 21 Geochemical F.A. Danevich Workshop on Double Beta Decay Search, SNU15 Oct 2009 Even 2 ECEC  Not detected for any nucleus !

TGV II Location: Modane Underground Laboratory (4800 m.w.e.) Copper > 20 cm Airtight box Lead >1 0cm Boron filled p olyethylene 1 6cm HPGe Cd

106 Cd is most promising nucleus to detect 2 ECEC. Belli, NIMA 615 (2010) Yangyang : 92 Mo experiment

Summary  0  experiment is still the best experiment to co nfirm Majorana nature of neutrinos. Т 1/2  ~ 2X10 25 yr, with  m   0.3 – 3 eV.  At present, the most sensitive half-life limit is Т 1/2  ~ 2X10 25 yr, with  m   0.3 – 3 eV.  GERDA, MAJORA will begin data taking shortly. Background level should be confirmed. ECEC could be detected with 106 CdWO4.  2 ECEC could be detected with 106 CdWO4.  Fugure projects, EXO, CUORE, LUCIFER would cover most of the inverse mass hierarchy region.

Backup

LNGS (2) Pulse shape discrimination in light detector (very preliminary) Spring 2010 There are no enough data to conclude that pulse shape discriminat ion is sufficient to reject alphas at the desired level, but it is sur ely crucial to investigate this opportunity. Final surprise: pulse shape discrimination in the heat signal