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Overview of double beta decay experiments at KIMS

Overview of double beta decay experiments at KIMS. Introduction Overview of Double beta decay experiments Sn, Zn double beta search with HPGe & CsI(Tl) Metal Loaded Liquid Scintillators CaMoO4 Crystal R&D and Sensitivity Prospect H.J.Kim (KyungPook National U.) for KIMS

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Overview of double beta decay experiments at KIMS

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  1. Overview of double beta decay experiments at KIMS Introduction Overview of Double beta decay experiments Sn, Zn double beta search with HPGe & CsI(Tl) Metal Loaded Liquid Scintillators CaMoO4 Crystal R&D and Sensitivity Prospect H.J.Kim (KyungPook National U.) for KIMS 2006 Workshop on the Underground Experiment at Yangyang Phoenix, 2006/02/06

  2. 0nbb decay half lives uncertainty A VARIETY OF 0n-DBD CANDIDATE NUCLIDES HAS TO BE STUDIED

  3. Sensitivity of DB • Run forever! (Not possible) • Huge mass (If you are rich) • Find large s process (Theoy responsibility) • 100% Efficiency is desired • 0 background (Not possible) Background reduction *Good energy resolution *Low background -> Purification =>Cost optimization is needed

  4. DB experiment R&D at KIMS (5 years) • Low Cost is highly required (Experimentalist problem) • New method is desired • Other DB Elements ( Theoretical uncertainty) • Unexpected surprise (Unlikely but who knows) • New method for double beta decay R&D -> Metal-Loaded Liquid scintillator (No experiment yet) -> New scintillation crystal ( Ca(Sr)MoO4 etc) • Good News : KIMS experiment experience -> YangYang Underground lab and shielding -> Background reduction technique for Cs -> Experience with Crystal( CsI) and Liquid scintillator -> Crystal growing expert from Russia, Ukraine

  5. Shielding Double beta decay experiment with HPGe • HPGe a) EC+b+ , b+b+ ; No observation yet b) Excited transition to 2nu, 0nu; Sn • HPGe + CsI ( top only) ; Zn,Sn

  6. Sn-124, Sn-122 0-,2-nbb limit * World best limit on Sn-124 (E.Norman PLB 195,1987) • Test of TBSN for a week at CPL , Preliminary results 450cm3 HPGe, 140 hours , 1.0liter TBSN : 400g of Sn • 2+ (603keV) 3.8x1018 year (4.0x1019 year) • 0+ (1156) 1.1x1019 year (2 -n theory : 2.7x1021) • 0+ (1326) 1.3x1019 year (2.2x1018 year) * Sn-122 EC+b+ decay ; 1.5x1018 year (6.1x1013)

  7. Zn EC+b+ decay EC+b+ limit ( b+ -> 2 g decay) 99.7% CL Positve evidence by I.BIKIT et.al, App. Radio. Isot. 46, 455, 1995 <= 25% HPGe + NaI(Tl) with 350g Zn at surface with shielding. -> Need to confirm or disprove!

  8. 511keV g 511keV g Zn EC+b+ decay HPGe + Zn(8x8x1cm)+CsI(Tl) crystal Our advantage: • 100% of HPGe • 350m underground • 10cm low background lead, • 10cm copper and N2 flowing Calibration by Na22 (b+ radioactive source) Efficiency calculation by Geant4; 3% Very Preliminary result with 1 week data; Coincidence cut with 2 sigma range ; 1 event • 2x1020 year by 95% CL • If I.BIKIT’s central value is taken, we would observe 100 events (1.1x1019 y) CsI 7.5x7.5x8 Zn HPGe

  9. Energy dist at HPGe

  10. Why metal loaded liquid scintillator? • Advantage a) high-Z can be loaded to LS (>50% or more) b) Fast timing response (few ns) c) Low cost of LS, Large volume is possible d) U/Th/K background for LS is low and purification is known e) Some elements can’t be made to Scintillator • Disadvantage a) Bigger volume is necessary (C,H in LS, low density) b) Lowerlight output (>15% of NaI(Tl))

  11. Zr2EH + LSC (50% ->Zr 3%) Nd2EH + LSC (50%->Nd 6.25%) TetraButhyl Tin + LSC (50%->Sn 20%) TetraMethyl Tin + LSC (50%->Sn 40%)

  12. Double beta decay detector Quartz glass Plastic Dimension R = 5cm H = 15.2cm V = 1.18L Teflon

  13. 214Bib-decay g214Poa-decay s -> T 1/2 = 0.166ms (0.163 ms exp.) U-238 decay chain

  14. 212Bib-decay g212Poa-decay -> T 1/2 = 300ns Th-232 Decay chain

  15. TMSN50% Energy Spectrum pol3 + gaus fitting Ee(keV) Ee(keV)

  16. Current Sn-124 Results * TMSN50% by 500MHz FADC -> 33 days T1/2 = 3.41x1019 year by 90% C.L World best limit = 2.4x1017 years by M.I. Kalkstein • 9 Month data has been collected! => Better results will come out soon. More R&D …… Zr, Nd and Gd loaded LSC for DB R&D (New method under study: Phospohate+XNo3) Purification

  17. Scintillation Crystals for bb (Calorimeter technique) • 300g CdWO4bb search by Kiev group; >0.7x1023 years Enrichment, PSD, active shielding -> successful • CaMoO4 (PbMoO4 , SrMoO4...) ; Mo, Ca bb search 1) Similar to CdWO4 but no hazard with Cd. and low Z 2) Light output; 10-20% of CsI(Tl) at 20o, increase with lower temp. 3) Decay time; 16 micro sec 4) Wavelength; 450-650ns-> RbCs PMT or APD 5) Pulse shape discrimination • CaF2(Eu) (CANDLES) • GSO, ZnSe

  18. Czochralski(CZ) Crystal Growing for DB • Russia *ISTC project is approved *Crystal quality improvement *Large crystal (5x5x20cm) *Powder purification • Ukraine • PSU (Crystal Bank) • KNU (small one for various R&D)

  19. CaMoO4 (SrMoO4) Crystals for R&D 24.8x30x40.8mm (PSU) 18x18x30mm (Russia) 20x20x20mm (PSU) 14.3x15x13.7mm (PSU) New & bigger one! Several SrMoO4 (PSU)

  20. CaMoO4 Pulse shape with 500MHz FADC 60keVg 5.5MeVa

  21. CaMoO4 (14.3x15x13.7mm)with g source - Na22(511keV,1.275keV), Cs137(662keV), Co57(120keV),Cd109(88keV)

  22. Number of photoelectron from 60keV g # of photoelecton from Am-241 Energy distribution # of photoelectron : 0.6 PE/keV => 6% FWHM at 3MeV at 25deg

  23. Alpha response of CaMoO4 Ea/g = 0.2 with 5.5MeV a particle

  24. CaMoO4 2x2x3cm, Pulse Shape discrimination

  25. CaMoO4 2x2x3cm, 1Month data!

  26. Large area with high efficiency R&D 4x4 1.5cm Photodiode ->noise problem PHOTONICS Large Area avalanche photodiode (1.6cm diameter) • Large ared : 5x5cm • Noise : a few hundred RMS noise • High quantum efficiency : 80% (PMT: 15% ) Silicon Drift sensor R&D for crystal DB is ongoing at KNU

  27. mV p2 p0 p4 p5 Micro sec p6 CaMoO4+LAAPD @LowTemp(by Sejong U) • Decay time ~ 100 ms @ -150 oC • But shaping time of AMP is limited by 10 ms • Analyzed PreAmp Signal directly. • Source ; Cs-137 • Temp ; -159.2 oC ± 0.1 Large Area avalanche photodiode (1.6cm diameter) • High quantum efficiency: 80% • (PMT: 15% ) P0 =amplitude, P2=decay time, P4=rising time, P5 = background P6= start time

  28. Compton edge resolution 5.3%(FWHM) energy resolution or better at 3 MeV (0nbb signal) (11% FWHM) • 4.7%(11% FWHM) Resolution with CaMoO4 crystal in low temperature(-159°C)

  29. CaMoO4 sensitivity and prospect • Ca,Mo purification : 0.01 evt/keV/day/kg at E=3MeV (MC simulation is also on going in Russia) • Active veto(5cm PbWo4(PbMoO4)) + 15cm low bg Pb + 30cm LSC • Time correlation , Pulse shape discrimination • 4% FWHM . • 10kg Mo-100 enriched CaMoO4 with 5 years data Sensitivity: 1025 years by 90% CL (0.15 eV) <- 5 sigma significance if Klapdor claim is right (Current best limit: 3.5x1023 years by NEMO3, 2004) • 100kg Mo-100 enriched CaMoO4 with further background 10 reduction 1026 years (0.05 eV) sensitivity <- next generation experiment

  30. Various Backgrounds and signal estimation with 20kg of CaMoO4 with 5 years data taking (GEANT4) Mo-100 2nu Ca-48 2nu Signal (m=0.3eV) Bi-214 Tl-208

  31. Backgrounds & signal with CaMoO4 (GEANT4 simulation) 5s significance All Backgrounds Signal

  32. LN2 Cooled xMoO4+Photosensor PbWO4 or PbMoO4(5cm) Low background Pb (15cm) Active Muon Veto(LSC), 30cm Conceptual design of experiment

  33. CaMoO4 R&D Summary and Prospect • CaMoO4 (18x18x30mm) :0.6 PE/keV -> 6% FWFM at Q= 3MeV Decay time : g ; 16.5 +-0.5 ms, a ; 15.5 +-0.5 ms at 4.5MeV a • PSD possible, Ea/gratio:0.2 • Currently working on • Temperature dependence study with APD • Background reduction of powder, Crystal growing (ISTC project) • Internal bkg study 2x2x3cm CaMoO4 at Y2L shielding * Study of internal bkg (U238,Th232-> timing correlation, alpha) -> Bigger crystal (powder purification) from Russia will be installed for internal background checking (with 4p CsI(Tl) veto?) 4) SrMoO4, XMoO4( X= Zn, Ba, etc) • Future Plan : 10kg of Mo-10 enriched CaMoO4 crystals installed at YangYang underground Lab in a couple of years. Sensitivity: 1025 years by 90% CL(0.15eV) with 5 years data taking <- 5 sigma significance if Klapdor claim is right

  34. Inviting for the collaboration

  35. An example of double beta decay

  36. (A,Z+1) (A,Z) (A,Z+2) Importanceof 2(0)-n bb processes (A,Z) -> (A,Z+2) + 2b +2n 2(0)-n bb (A,Z) -> (A,Z+2) + 2b

  37. Weighted average of all positive results Isotope T1/22n(y) T1/22n(y)calc 48Ca 6 ´ 1018- 5 ´ 1020 (4.2 +2.1-1.0 ) ´ 1019 76Ge 7 ´ 1019- 6 ´ 1022 (1.42 +0.09- 0.07) ´ 1021 82Se (0.9 ± 0.1) ´ 1020 3 ´ 1018- 6 ´ 1021 96Zr 3 ´ 1017- 6 ´ 1020 (2.1+0.8-0.4) ´ 1019 100Mo (8.0 ± 0.7) ´ 1018 1 ´ 1017- 2 ´ 1022 100Mo(0+*) (6.8 ± 1.2) ´ 1020 5 ´ 1019- 2 ´ 1021 (3.3 +0.4-0.3) ´ 1019 116Cd 3 ´ 1018- 2 ´ 1021 128Te (2.5 ± 0.4) ´ 1024 9 ´ 1022- 3 ´ 1025 130Te (0.9 ± 0.15) ´ 1021 2 ´ 1019- 7 ´ 1020 150Nd (7.0 ± 1.7) ´ 1018 6 ´ 1016- 4 ´ 1020 238U (2.0 ± 0.6) ´ 1021 1.2 ´ 1019 2n-DBD Candidate and Experimental results

  38. Projected/proposed

  39. two neutrino DBD continuum with maximum at ~1/3 Q low energy resolution 2n events can mask 0n ones 1 10-6 Signature: shape of the two electron sum energy spectrum e- low background detector e-   -underground operation • shielding - low radioactivity of materials source R = 5% 10-2 e- e- detector SourceDetector (calorimetric technique) SourceDetector sum electron energy / Q neutrinoless DBD peak enlarged only by the detector energy resolution +event shape reconstruction • low energy resolution • low efficiency +high energy resolution +100% efficiency -no event topology Experimental search for DBD • Two approaches: • If you use the calorimetric approach

  40. Double beta; HPGe with CsI crystal • HPGe a) EC+b+ , b+b+ ; No observation yet b) Excited transition to 2nu, 0nu; Sn • HPGe + CsI ( top only) ; Under study (Zn,Sn, Zr) • HPGe + Full CsI cover ; Improve sensitivity 1 order? => Confirm Nd and try for Zr,Sn excited transition => Uses 12 6x6x30cm existing crystal using existing RbCs PMT • HPGe + Active detector( Sn-LSC, CaMoO4....) • Full CsI(Tl) Cover (6cm) + Active detector; R&D going on

  41. LSC test sample HV + LSC Setup VME

  42. CaMoO4 R&D Summary and Plan • CaMoO4 (18x18x30mm) :0.6 PE/keV -> 6% FWFM at Q= 3MeV Decay time : g ; 16.5 +-0.5 ms, a ; 15.5 +-0.5 ms at 4.5MeV a • PSD possible:Th232, U238 background reduction • Ea/gratio:0.2 • Currently working on • Temperature dependence • Background reduction study of powder, Crystal growing (Russia) • Internal bkg study 2x2x3cm CaMoO4 at Y2L shielding * Study of internal bkg (U238,Th232-> timing correlation, alpha) • Future Plan : 10kg of Mo-10 enriched CaMoO4 crystals installed at YangYang underground Lab in Korea in two years. Sensitivity: 1025 years by 90% CL(0.15eV) with 5 years data taking <- 5 sigma significance if Klapdor claim is right

  43. CaMoO4 sensitivity and prospect • Ca,Mo purification : 0.01 evt/keV/day/kg at E=3MeV • Active veto (6cm CsI) + 15cm low bg Pb + 30cm LSC • Time correlation , Pulse shape discrimination • 4% FWHM . • 10kg Mo-100 enriched CaMoO4 with 5 years data Sensitivity: 1025 years by 90% CL (0.15 eV) <- 5 sigma significance if Klapdor claim is right (Current best limit: 3.5x1023 years by NEMO3, 2004) • 100kg Mo-100 enriched CaMoO4 with further background 10 reduction 1026 years (0.05 eV) sensitivity <- next generation experiment

  44. CdWO4 experiment (Zdsenko) Double beta decay

  45. 10kg Mo-100 CaMoO4 8x1024년 (0.2eV) (현재 3.5x1023 년) 10% 10kg Ca-48 1.5x1024년 (0.6eV) (현재 2x1022 년) 1톤 Mo-100 CaMoO4 8x1026년 (0.02eV) 이론 예측: 0.01-1.0 eV 결정섬광 검출기를 이용한 0-n bb실험 CaMoO4 (PbMoO4, SrMoO4, ZnMoO4) ; Mo, Ca 0-n bb탐색 <= 새로운 아이디어

  46. (A,Z+1) (A,Z) (A,Z+2) 0 -, 2-n bb decay processes (A,Z) -> (A,Z+2) + 2b +(2n)

  47. Double beta decay process (A,Z) -> (A,Z+2) + 2b +2n (A,Z) -> (A,Z-2) + 2b+ +2n EC+b+ ,2EC also is possible (A,Z+1) (A,Z-1) (A,Z) (A,Z) (A,Z+2) (A,Z-2) Excited state g b+-> g g (511 keV) Ground state

  48. CaMoO4 2x2x3cm, Cs137 source

  49. bb material requirements • Matrix elements: Large s (ex: Nd, Gd) ~mn1/2 • Enrichment: Gd, Te ~20%; Zr, Nd -> Difficult ~mn1/2 Mo, Se, Ge, Kr, Xe, (Cd, Sn) ->Easy Expensive : A few hundred $ / 1 g • Efficiency : ~ 100% for active source technique~mn1/2 Mass, time ; ~mn1/4 • Resolution; 2n bb background issue ~mn1/4 • Background; Source impurity (U238,Th232) ~mn1/4Source purification, Time correlation (PSD) Active shielding to reduce backgrounds

  50. U238 a-a a-b

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