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The 0-neutrino double beta decay search with Tin-loaded liquid scintillator

The 0-neutrino double beta decay search with Tin-loaded liquid scintillator. 연세대 : 황명진 , 권영준 서울대 : 곽정원 , 김상열 , 김선기 , 김승천 , 명성숙 , 방형찬 , 양혜영 , 이주희 , 이직 , 이현수 , 이명재 , 최정훈 세종대 : 김영덕 , 이정일 경북대 : 김홍주 , 소중호 , 양성철 이화여대 : 박일흥 , 한인식 메릴린드대 : 서은숙 , 이무현 IHEP:J.Li 칭화대 : J.J.Zhu,D.He,Q.Yue.

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The 0-neutrino double beta decay search with Tin-loaded liquid scintillator

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  1. The 0-neutrino double beta decay search with Tin-loaded liquid scintillator 연세대:황명진,권영준 서울대:곽정원,김상열,김선기,김승천,명성숙,방형찬, 양혜영,이주희,이직,이현수,이명재,최정훈 세종대:김영덕,이정일 경북대:김홍주,소중호,양성철 이화여대:박일흥,한인식 메릴린드대:서은숙,이무현 IHEP:J.Li 칭화대:J.J.Zhu,D.He,Q.Yue

  2. Why bb decay is important?

  3. 0n-DBDPresent best experimental limits * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31 Experiment Isotope T1/20n (y) <mn>* (eV) Range <mn> 6.0 48Ca > 1.8 ´ 1022 Ogawa I. et al., submitted 2002 76Ge > 1.9 ´ 1025 0.35 < 0.3 - 2.5 Klapdor-Kleingrothaus et al. 2001 > 1.57 ´ 1025 0.38 < 0.3 - 2.5 Aalseth et al 2002 4.8 < 1.4 - 256 100Mo > 5.5 ´ 1022 Ejiri et al. 2001 1.9 < 1.8 - 6.2 116Cd > 1.3 ´ 1023 Zdenko et al. 2002 128Te > 7.7 ´ 1024 1.0 < 1.0 - 4.4 Bernatowicz et al. 1993 130Te > 2.1 ´ 1023 1.5 < 0.9 - 2.1 Mi DBD n 2002 136Xe > 7 ´ 1023 1.8 < 1.4 - 4.1 Belli et al. submitted PLB

  4. 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 • Disadvantage • a) Bigger volume is necessary (C,H in LS, low density) • b) Lowerlight output (~15% of NaI(Tl))

  5. Passive shielding at Y2L(700m depth) PE shield (5cm) Pb shield (15cm) Mineral Oil shield (30cm)

  6. Double beta decay detector Quartz glass Plastic Dimension R = 5cm H = 14.94cm V = 1.15L Teflon

  7. TMSN40% • TMSN : 347ml (456g, 1.314g/ml) • PC : 753ml (671g, 0.891g/ml) • TMSN40% = TMSN + PC • TMSN : 456g/(456g + 671g) = 40% • Sn = 456g/(456g + 671g) * 119/178 -> 27%

  8. TMSN40% Calibration keV keV -> Resolution 8% , 0.9keV/ADC Channel

  9. Resolution = 1 / sqrt(N) • Resolution 8% -> 156.25 pe • 54Mn 834keV • 156.25pe/834keV = 0.187pe/keV

  10. TMSN40% Energy Spectrum by 500MHz FADC pol3 + gaus fitting keV

  11. Sensitivity • T1/2 = log 2 ´e ´ N ´ T / dS • e : efficiency • N : Number of double beta nuclei • T : Data taken time with year • dS : mean value + 1.64s of Gaussian fitted area • (mean value is Q-value) • T1/2 = 1.71x1019 year by 90% C.L (Preliminary)

  12. Intrinsic radio-impurities b – a coincidence candidates 1. 238U chain • 214Bi : 3.27 MeV b-decay • g 214Po : 7.834 MeV a -decay • Lifetime of 214Po = 164.3 us • 190 keV Energy threshold

  13. 214Po – a sidesubtraction main side

  14. 214Bi - b spectrum 214Po – aspectrum Q=3.27MeV Q=7.834MeV keV 214Po - a decay - Quanching factor = 804/7834 = 10.3% - 4842개/75day = 65개/day

  15. 214Po - a half-life T 1/2 = 163.7us s s T 1/2 = 235.9us * log(2) = 163.5 us

  16. 2. 232Th chain • 212Bi : 2.254 MeV b-decay • g 212Po : 8.784 MeV a -decay • Lifetime of 212Po = 299 ns • 1ch = 2ns 1x 3x a b channel

  17. 212Bi - b spectrum 212Po - a spectrum Q=2.254MeV Q=8.784MeV 212Po - a decay - Quanching factor = 940/8784 = 10.7% - 281개/75day = 3.8개/day

  18. 212Po - a half-life T 1/2 = 299ns ns T 1/2 = 422.9ns * log(2) = 293.1 ns

  19. Summary 1. TMSN40% by 500MHz FADC (75 days) T1/2 = 1.71x1019 year by 90% C.L 2. 214Po - adecay -> 65개/day 3. 212Po - adecay -> 3.8개/day 4. World limit = 2~5x1017 year by 1952

  20. Plan • G4 simulation – intrinsic radio-impurities -> 238U, 232Th decay chains • Background reduction • Nd2EH and Zr2EH study • 2n DB study

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