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

Why bb decay is important?

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

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) Lower light output (~15% of NaI(Tl))

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

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

TMSN40% PC : 753ml (671g, 0.891g/ml) TMSN40% = TMSN + PC 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%

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

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

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

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)

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

214Po – a sidesubtraction main side

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

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

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

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

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

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

Plan G4 simulation – intrinsic radio-impurities -> 238U, 232Th decay chains Background reduction Nd2EH and Zr2 EH study 2n DB study