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Activities on double beta decay search experiments in Korea

Activities on double beta decay search experiments in Korea. Yangyang Underground laboratory Double beta decay search with HPGe & CsI(Tl) Metal Loaded Liquid Scintillators EC/ b +, b+b+ search with 4 p CsI(Tl) shielding CaMoO4 Crystal R&D for 0 n-bb R&D Prospect

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Activities on double beta decay search experiments in Korea

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  1. Activities on double beta decay search experiments in Korea Yangyang Underground laboratory Double beta decay search with HPGe & CsI(Tl) Metal Loaded Liquid Scintillators EC/b+, b+b+ search with 4p CsI(Tl) shielding CaMoO4 Crystal R&D for 0n-bb R&D Prospect H.J.Kim (KyungPook National Univ.) for KIMS The 16th International Conference on Supersymmetryand the Unification of Fundamental Interactions 2008/06/17

  2. 2νββ 0νββ e e e e ν ν ν ν N N B A N’ N’ 0-, 2-n bb decay 2-n bb decay 2nd order beta decay Rare nuclear decay (>1018 years) 0-n bb decay n mass>0 & Majorana particle 2) New Physics

  3. Environment Parameters in Y2L Gneiss (2 Gyr )

  4. Normal Water Pure water Ultra pure 100% HPGe at Y2L and bb decay search • Background measurement : Cs137,shielding • EC+b+ , and Excited transition to 2n, 0n a) EC+b+ of Sn-122, Zn-64 new limits b) Excited transition of Sn-124: new limits H.J.Kim et al., Nuclear Physics A 793 (2007) => Currently working on 0n-EC/EC resonance and EC/b+, b+b+search NIMA 552(2005) 456

  5. CsI 7.5x7.5x8 511keV g Zn HPGe 511keV g 64Zn EC+b+ decay search HPGe + Zn(8x8x1cm)+CsI(Tl) crystal Our advantage: • 100% of HPGe • 10cm Pb, 10cm copper and N2 flowing Calibration by 22Na (b+ radioactive source) Efficiency calculation by Geant4; 3% Result with 2 weeks data; Coincidence cut with 2 sigma ; 1 event • 2x1020 yearsby 95% CL • If I.BIKIT’s central value is taken, we would observe 100 events (1.1x1019 y)

  6. 0n bb search with Sn-loaded LSC 1.1 liter 30% Tin-loaded Liquid scintillator 124Sn g 124Te + 2b-decay 9Month data at Y2L inside of Pb shielding • NIMA 570 (2007) 454 Submitted to Astroparticle phys. T1/2 < 2.4x1017 yr at 90% C.L T1/2 < 4x1019 yr at 90% C.L 2287keV

  7. 2n EC+b+ , b+b+ ; No observation yet Interest : 1) Sr-84 : SrCl2 (7x1013 yr) 2) Ce-136 : CeBr3 (4x1016 yr) 3) Mo-92 : CaMoO4 (2x1020 yr) 4) Cd-116 : CdWO4 (4x1020 yr) 511keV g EC+b+ , b+b+ Crystal 511keV g CsI(Tl) 6cm Low background Pb (10cm) 0,2n EC+b+ , b+b+ Experiment at Y2L

  8. b+/EC setup with 4pCsI crystals at Y2L

  9. CaMoO4 & SrCl2 : 0n EC/b+ search 92Mo Search near 628 keV Very Preliminary limit: 3x1019 y 84Sr Search near 765 keV Very Preliminary limit: 1x1017 y Grown at KNU

  10. Ca(x)MoO4 scintillation crystal for 0-n bb search -> Active source technique (first presented at new view in particle physics in 2004) CaMoO4 based 100Mo 0-n bb Difference from other 100Mo experiment • Energy resolution 5% (3.03 MeV) • Avalanche photodiode ( 4 times Q.E.) • Detection efficiency : ~ 100% • Pulse shape discrimination : 238U, 232Th background removal First developed 2003 (5x5x5mm3)

  11. 12.5 cm 2.2 cm 2.2 cm CaMoO4 crystal development Korea(2004) Ukraine(2006) Russia(2006) 30x30x200mm Russia (2007), ISTC project

  12. Number of photoelectron from 60keV g # of photoelecton from Am-241 Crystals tested 0.6PE/keV : Ukraine 0.6PE/keV : Russia 0.5PE/keV : Korea * The size of crystals are different 0.6 PE/keV => 6% FWHM at 3MeV

  13. Alpha response of CaMoO4and PSD Ea/g = 0.2 with 5.5MeV a

  14. PMT1 PMT2 Long CaMoO4 crystal test Size: 30x30x200 mm Attenuation Length >50 cm

  15. CaMoO4 background measurement at Y2L * Two 22x22x60mm CaMoO4 crystal + RbCs PMT • 10 cm Pb shielding • Active Veto (4p CsI ) • 400Mhz FADC • Data taking and analysis on going 238U : 30 ppt(0.4mBq/kg) 231us expected

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

  17. Backgrounds and signal for 20kg of CaMoO4 with 5 years data taking (GEANT4) Sensitivity • 10kg (100Mo) • 5% FWHM resolution • 0.05 mBq/kg for 208Tl, 214Bi • *5 years  7.1x1024 y (90% CL) • (0.18~0.71 meV) • *1.6x1025 y with Ca depletion • *1tonCaMoO4 : 7 x1026 y (~0.02eV) (Ca depletion, further bg reduction) Mo-100 2n Ca-48 2n Signal (m=0.4eV) Bi-214 Tl-208 10s significance • Current best limit on 100Mo : 4.6x1023 by NEMO3 with 6.9kg 100Mo • Claim by Klapdor-Kleingrothaus et al.  ~ 400 meV  Assuming optimistic theoretical value

  18. Conceptual 100Mo bb decay experimental setup Ca(x)100MoO4 : 20kg CsI/PbMoO4 (5cm) Low activity Pb(15cm) Liquid scintilaltor (30cm) (Inside Pb : LN temperature) Avalanche photodiode

  19. Summary and Prospect CaMoO4 R&D • 0.6 PE/keV -> 6% FWHM at Q= 3MeV (5% at low temp) • PSD possible, Ea/g ratio:0.2 • Currently working on • Temperature dependence study with APD • Internal background study of CaMoO4 • SrMoO4, XMoO4( X= Zn, Ba, Pb etc) R&D • Low temperature (LTD) development with CaMoO4 • Future Plan : Ukraina, Russia and China collaboration 10kg of Mo-100 enriched CaMoO4 crystals could be installed at YangYang underground Lab in a couple of years. Sensitivity: ~1025 years by 90% CL with 5 years data taking • 64Zn: Rule out I.Bikit’s claim : 2x1020 year by 95% CL • Tin-loaded LSC (33%): 124Sn : T1/2 > 4x1019 yr at 90% C.L • 0-n b+/EC search with 4p CsI : 92Mo, 84Sr -> Promising

  20. Thank you

  21. CaMoO4 2x2x3cm, Cs137 source

  22. 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!

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