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-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
<
> 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
<
> 2.1 ´ 1023
130Te
<
> 7.7 ´ 1024
128Te
<
> 1.3 ´ 1023
116Cd
<
> 5.5 ´ 1022
100Mo
<
> 1.57 ´ 1025
> 1.9 ´ 1025
76Ge
* Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31

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

5. Mineral Oil shield (30cm)
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% 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%

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

9. Resolution = 1 / sqrt(N)
Resolution 8% -> 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 s 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
U chain
214Bi : 3.27 MeV b-decay
g 214Po : MeV a -decay
Lifetime of 214Po = us
190 keV Energy threshold

13. 214Po – a sidesubtraction
main
side

14. 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

15. 214Po - a half-life
T 1/2 = 163.7us s s
T 1/2 = 235.9us * log(2) = 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 212Po - a decay
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 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 - a decay -> 65개/day
3. 212Po - a decay -> 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 Zr2 EH study
2n DB study