DOUBLE BETA DECAY EXPERIMENTS Yeongduk Kim Sejong University
DOUBLE BETA DECAY EXPERIMENTS Yeongduk Kim Sejong University 2 nd Amore Meeting 2010. 7
Outline 2 Introduction to Double Beta Decay. Strategies for detection of 0 Status of Current Projects Upcoming Experiments. Summary
Brief history l 1935 : M. Goeppert–Mayer, “Double beta–Disintegration” Phys. Rev. 48, 512 l 1937: Ettore Majorana 1906 -1938 ? Neutrinos may be identical with its antiparticle. (Majorana neutrino). . 50 years. . . l 1987 : S. R. Elliott : Phys. Rev. Lett. 59 2020 3 First measurements of 2 nub-b- of 82 Se.
Three neutrino mixing and oscillation
Three neutrino mixing and oscillation ~45 me. V ~9 me. V 3 mixing angles & 2 mass square difference 1. Neutrinos are massive ! 2. Neutrino flavors oscillates !
Half-life of 0 process – Doi… e– Helicity -R Nucl e– i i W– W– Nuclear Process Total Lepton number violation. Helicity -L Amplitude for helicity matching Nucl’ Effective Majorana neutrino mass
Mass Hierarchy Depending on the mass hierarchy, the effective neutrino mass to be measured is very different. Hirsch et al, PLB 679: 454 -459, 2009 m 2 Dm. S ~9 me. V m 1 m 3 q 13? m 2 m 1 e m t Dm. A ~45 me. V m 3 NH IH
0 n signal
Strategies for detection of 0 Two approaches: e- e- detector source e- e- detector Source º Detector Source ¹ Detector (calorimetric technique) (Tracking technique) Total Mass Large Mass possible Large Mass Difficult Energy Resolution Excellent Poor Isotopes Fixed by Detector Isotopes can be changed Event Topology No Two tracks
Klapdor’s claim. 76 Ge
Current(2010) best limits for 0 - - 48 Ca Q (ke. V) Abun. (%) T(1/2) (1024 years) mν limit (e. V) Reference 4271 0. 187 >0. 058 <3. 5 -22 S. Umehara et al. , PRC 78 (2008) 058501 H. V. Klapdor-Kleingrothaus et al. , EPJA 12 (2001) 147 H. V. Klapdor-Kleingrothaus Mod. Phys. Lett. A. 21 (2006) 1547 76 Ge 2039 7. 8 >19 =22. 3 <0. 35 -1. 5 =0. 2 -0. 5 82 Se 2995 9. 2 >0. 36 <0. 89 -2. 43 Tretyak AIP 1180 (2009) 135 100 Mo 3034 9. 6 >1. 1 <0. 45 -0. 93 Tretyak AIP 1180 (2009) 135 116 Cd 2809 7. 5 >0. 17 <1. 7 F. A. Danevich et al. , PRC 68 (2003) 035501 130 Te 2530 34. 5 >2. 8 <0. 3 -0. 7 NOW 2010 Bucci presentation 150 Nd 3367 5. 6 >0. 018 <1. 7 -2. 4 A. Barabash, JPCS 173 (2009) 012008 136 Xe 2479 8. 9 >0. 44 <2. 3 R. Luescher et al. , PLB 434 (1998) 407 12
Candidate nuclei for 0 “Golden Nuclei”
Candidate nuclei for 0 130 Te
G : Phase space factor is larger for large Q value. 100 Mo’s G factors are different between calculations by more than factor 2. Doi(85), Boehm&Vogel(91) 150 Nd Suhonen(98) 100 Mo 48 Ca 116 Cd 96 Zr 82 Se
100 Mo’s larger G factor may be questionable. Doi(85), Boehm&Vogel(91) 150 Nd Suhonen(98) 100 Mo 48 Ca 116 Cd 96 Zr 82 Se
Matrix Elements Rodin, 0910. 5866 v 1
from NOW 2010 Giuliani
Current & Future Experiments CUORE, LUCIFER, AMORE 2 : Cryogenic GERDA, MAJORANA : HPGe SNO+, Kam. LAND : Liquid Scintillator + Mixing CANDLES, AMORE 1 : Inorganic Scintillator EXO, COBRA, NEXT : Active Tracking SUPERNEMO, MOON, DCBA : Passive Tracking
NEMO-3 and Super. NEMO A search for zero neutrino double beta decay Robert L. Flack University College London
0νββ for 100 Mo(~7 kg) and 82 Se (~1 kg) [2. 8 -3. 2] Me. V: DATA = 18; MC = 16. 4± 1. 4 T 1/2(0ν) > 1. 0× 1024 yr at 90%CL <mν> < (0. 47 - 0. 96) e. V T 1/2(0ν) > 3. 2× 1023 yr at 90%CL <mν> < (0. 94 - 2. 5) e. V V+A: T 1/2(0ν) > 5. 4× 1023 yr at 90%CL Majoron: T 1/2(0ν) > 2. 1× 1022 yr at 90%CL 7 September 2008 [2. 6 -3. 2] Me. V: DATA = 14; MC = 10. 9± 1. 3 λ < 1. 4× 10 -6 gee < 0. 5× 10 -4 World’s best result! Robert Flack NOW 2010 21
Objectives of the 4 year R&D programme Super. NEMO-3 100 Mo isotope 7 kg isotope mass M 18 % efficiency ε 208 Tl: ~ 100 μBq/kg 214 Bi: < 300 μBq/kg Rn: 5 m. Bq/m 3 8% @ 3 Me. V or other 100+ kg ~ 30 % 208 Tl ≤ 2 μBq/kg internal contaminations 208 Tl and 214 Bi in the ββ foil if 82 Se: 214 Bi ≤ 10 μBq/kg Rn in the tracker Rn ≤ 0. 15 m. Bq/m 3 energy resolution (FWHM) T 1/2(0ν) > 2 x 1024 y <m> < 0. 3 – 0. 9 e. V 22 82 Se 4% @ 3 Me. V T 1/2(0ν) > 1 x 1026 y <m> < 0. 04 - 0. 11 e. V Robert Flack NOW 2010 7 September 2008
A Super. NEMO module Source 2. 7 m Submodule Source and calibration 4 m • 20 modules having a Planar design. • Each module will have 5 kg of enriched isotope • Making a total of 100 kg. • Drift chamber ~2000 cells in Geiger mode • 550 PMTs + scintillator blocks Submodule calorimeter 6 m Submodule tracker 2 m (assembled, ~0. 5 m between source and calorimeter) 23 Robert Flack NOW 2010 7 September 2008
LUCIFER Low-background Underground Cryogenics Installation For Elusive Rates Principal Investigator: Co-Investigator : Fernando Ferroni Andrea Giuliani ERC-2009 -Ad. G 247115 Double Beta Decay pilot project based on scintillating bolometers
The choice of the isotope 113 Cd beta emitter 113 Cd high neutron cross-section There are 3 main candidates Transition energy does not indicate a preference Q-value Useful LY [ke. V] material [ke. V/Me. V] QF (a/ ) Enrichment [€/g] Cd. WO 4 2809 32% 34 0. 19 > 150 -200 Zn. Mo. O 4 3034 44% 1. 4 0. 16 50 -80 Zn. Se 2995 56% 7. 4 4. 2 50 -80 Pros Cons The baseline: Zn. Se Active isotope: 82 Se Decay: 82 Se -> 82 Kr + 2 e. Q-Value: 2995 ke. V Abundance: 9%
Results @ LNGS (1) a QF > 1: alphas give more light than gammas → risk of leakage in the beta/gamma region? f 4 cm, 1. 7 cm height, 120 g f=2 cm, 3 cm height, 39 g Just an example Q-value of 2615 ke. V: the end of g radioactivity /g 82 Se a ee area r f d n u o Backgr
Gironi et al. , NIMA 617, 478 (2010) Alpha, gamma separation w/o light detection.
The physics reach …but has a remarkable sensitivity by itself From the LUCIFER proposal: Half Life limit Sensitivity* to 26 (10 y) mee (me. V) 116 Cd 15. 1 kg Cd. WO 4 32% 1. 15 65 -80 100 Mo 11. 3 kg Zn. Mo. O 4 44% 1. 27 67 -73 Zn. Se [baseline] 82 Se 17. 6 kg 56% 2. 31 52 -65 Zn. Se [option 1] 82 Se 20. 5 kg 56% 2. 59 49 -61 Zn. Se [option 2] 82 Se 27. 8 kg 56% 3. 20 44 -55 * The 1 s sensitivity is calculated with the Feldman Cousins approach for 5 y running and a background index d. Gb/d. E = 10 -3 c/ke. V/Kg/y. The matrix elements come from the two most recent QRPA calculations [ME 08]; the energy window is taken as 5 ke. V, compatible with the resolution achieved in Te. O 2 macrobolometers and in scintillating-bolometer R&D. Crystal Isotope weight Useful material More realistic evaluation: Optimistic evaluation, assuming full success for several difficult tasks: 10 kg of isotope Ø negotiate a good contract for enrichment → Zelenogorsk (Russia), URENCO ( ~100 me. V as <m > Ø get radiopure and chemically pure isotope after enrichment sensitivity Ø efficient crystallization → Institute for Single Crystals, Kharkov, Ukraina Ø optimize bolometric performance of Zn. Se crystals
Kam. LAND-Zen (0 with 136 Xe) (Zero neutrino double beta decay) 136 Xe can be dissolved into liquid scintillator up to ~ 3 wt%.
Some best 2 , +, 2 + experiments Even 2 ECEC Not detected for any nucleus ! Nuclide Channel Experimental limits T 1/2 (yr) Technique 40 Ca > (3 -6) × 1021 > (4 -5) × 1020 > (0. 2 -7)× 1020 > (0. 06 -7)× 1020 > (1 -5) (1 -5 × 1021 > (0. 06 -9)× 1020 > (0. 2 -1. 3) (0. 2 -1. 3 × 1019 > (0. 01 -4)× 1020 Ca. F 2(Eu) scintillators HPGe spectrometry Zn. WO 4 scintillators Gaseous detector HPGe spectrometry 106 Cd 2 2 2 , +, 2 + 2 , +, 2 + 130 Ba 2 , +, 2 + > 4× 1021 = (2. 2 ± 0. 5) × 1021 132 Ba 2 > 2. 2× 1021 Geochemical 54 Fe 58 Ni 64 Zn 78 Kr 92 Mo 96 Ru HPGe spectrometry, Na. I(Tl) spectrometry Cd. WO 4 scintillators Cd. Zn. Te semiconductor 43 F. A. Danevich Workshop on Double Beta Decay Search, SNU 15 Oct 2009
TGV II Location: Modane Underground Laboratory (4800 m. w. e. ) Copper > 20 cm Airtight box Lead >10 cm Boron filled polyethylene 16 cm HPGe Cd
Belli, NIMA 615 (2010) 106 Cd is most promising nucleus to detect 2 ECEC. Yangyang : 92 Mo experiment
Summary 0 experiment is still the best experiment to confirm Majorana nature of neutrinos. At present, the most sensitive half-life limit is Т 1/2 ~ 2 X 1025 yr, with m 0. 3 – 3 e. V. GERDA, MAJORA will begin data taking shortly. Background level should be confirmed. 2 ECEC could be detected with 106 Cd. WO 4.
Backup
Results @ LNGS (2) g n i r Sp 0 1 0 2 Pulse shape discrimination in light detector (very preliminary) Final surprise: pulse shape discrimination in the heat signal There are no enough data to conclude that pulse shape discrimination is sufficient to reject alphas at the desired level, but it is surely crucial to investigate this opportunity.
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