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Prospect of bb experiment in Korea

Prospect of bb experiment in Korea. Presented by H.J.Kim Yonsei Univ., 10/25/2003 KPS 2003 fall meeting Contents 1) Introduction of n 2) Theory and Experiments of 0 n , 2 n bb 3) EC+ b + and transition to excited state with

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Prospect of bb experiment in Korea

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  1. Prospect of bb experiment in Korea Presented by H.J.Kim Yonsei Univ., 10/25/2003 KPS 2003 fall meeting Contents 1) Introduction of n 2) Theory and Experiments of 0n, 2nbb 3) EC+b+ and transition to excited state with HPGe and CsI crystal with coincidence (Zn, Sn study) 4) Metal Loaded Liquid Scintillator R&D for bb 5) 0n, 2nbb R&D with Crystals. 6) Prospect

  2. Age of n physics ! • What we knew : spin 1/2, no charge 3 type: ne, nm, nt (2.981+-0.08 n by Z line shape) • What we now know: n oscillations ->mass, mixing Solar, Atmospheric, Reactor, K2K, LSND(miniBooNe) • What we still don't know and need to know a) Magnetic moment (Reactor, n source) b) Absolute mass scale (tritium b, bb) c) Dirac or Majorana (n =? anti n) (bb) • Cosmological question Relic n, Ultra high energy n, Dark matter

  3. Neutrino mass limits

  4. n mass limits from high energy But it is difficult to reach ~eV sensitivity

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

  6. Why bb decay is important?

  7. 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

  8. 0nbb decay half lives uncertainty A VARIETY OF 0n-DBD CANDIDATE NUCLIDES HAS TO BE STUDIED

  9. 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 > 5.5 ´ 1022 4.8 < 1.4 - 256 100Mo Ejiri et al. 2001 1.9 < 1.8 - 6.2 116Cd > 1.3 ´ 1023 Zdenko et al. 2002 128Tegeo > 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. The Best 0n-DBD results with different nuclei

  10. 0 nbb evidence?

  11. * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31 old/future bkg present bkg [c/keV kg y] Technology Mass [ton] Sensitivity (10y) HD-M partially tested HD-M partially tested IGEX mature GENIUS GEM MAJORANA 1 -10 1 nat. enr. 0.5 0.06 0.06 1500 300 150 2 - 6 1028 y 0.1 - 1 1028 y 0.4 1028 y 2.3 1028 y MI-DBD tested CUORE 0.8 nat 0.33 330 5 1027 y 1 1027 y 1 - 10 10nat 1.6enr Gotthard Xe challenging DAMA - Xe tested EXO XMASS 0.025 0.06 1000 10 0.9 - 13 1027 y 0.5 - 1 1027 y 2.2 1028 y ELEGANT standard MOON 34 nat ~ 0.02 300 1.3 1028 y 1 1027 y INR - Kiev needs confirm. CAMEO 0.1 - 1 0.03 600 4.9 1027 y 0.1 - 1 1027 y Future projects

  12. detector e- e- source e- e- detector SourceºDetector (calorimetric technique) Source¹Detector +event shape reconstruction -low energy resolution +high energy resolution -no event topology 1 10-6 Signature: shape of the two electron sum energy spectrum R = 5% 10-2 sum electron energy / Q Experimental search for DBD • Two approaches: • If you use the calorimetric approach

  13. bb material requirements • Matrix elements: good one (ex: Nd) ~mn1/2 • Enrichment: Gd, Te ~20%; Zr, Nd -> Difficult ~mn1/2 Mo, Se, Ge, Kr, Xe, (Cd, Sn) ->Easy • 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

  14. Why high-Z loaded scintillator for bb • Advantage a) Some high-Z can't be used for inorganic scintillator. (Sn) b) high-Z can be loaded to LS (>50% or more) c) Fast timing response (few ns) d) Low cost of LS, Large volume is possible e) U/Th/K background for LS is low and purification is known f) a/g separation can be possible • Disadvantage a) Bigger volume is necessary (C,H in LS, low density) b) Moderate light output (~15% of NaI(Tl))

  15. Background of homemadeLSC

  16. Tin loading study • Tin compound 1) 2-Ethyl hexanoate (144g/mole), Tin 15% w 50% loading (CH3(CH2)3CH(C2H5)CO2)2Sn ( FW405) => Quanching 2) Tetramethyl-tin (40%w50%) : flammable,expensive 3) Tetrabutyl-tin (19%w50%) 4) Dibutyltin diacetate, Dibutylphenyltin, tetrapropyltin, Tetraethyltin, Dimethyldiphenyltin • LS : Solvent+Solute * Solvent ; PC, 1,2-MN, o-,p-Xylene, Tolune, Benzene.. * Solute ; POP, BPO, PBD, Butyl-PBD, Naphthalene.. * Second-solute ; POPOP, M2-POPOP, bis-MSB... * PSD possible? -> Need a study * Others ; Nd2-ethylhexanoate, Zr4-ethylhexanoate. Ce2-ethylhexanoate, Sr2-ethylhexanoate, Pb2-ethylhex.

  17. Tin loading

  18. Tin loading (TBSN 50%->20%Sn)

  19. Double beta; HPGe with CsI crystal • HPGe a) EC+b+ , b+b+ ; No observation yet b) Excited transition to 2n, 0n;Mo, Nd (new) • HPGe + CsI (top side only) ; Under study (Zn,Sn, Zr) • HPGe + Full CsI cover ; Improve sensitivity 1 order? => Confirm Nd and try for Zr,Sn excited transition => at Y2L, Uses 12 6x6x30cm existing crystal and existing RbCs PMT • HPGe + Active detector (Sn-LSC, CaMoO4, ZnSe)

  20. Shielding g Background measurement 100% HPGe installed in CPL W/o shielding 10cm Pb + 10 cm Cu+ N2 (16 days data taking)

  21. 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)

  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!

  23. 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) Sn (8x8x1cm) data is available and we can set 5 orders better limit CsI 7.5x7.5x8 Zn HPGe

  24. Energy dist at HPGe

  25. Crystals for bb • 300g CdWO4 bb search by Ukrine group; >0.7x1023 years Enrichment, PSD, actvie shielding -> successful • CaMoO4 (PbMoO4 , SrMoO4...) ; Mo, Ca bb search Similar with CdWO4 Light output; 20% at 20deg, increasing with lower temp, Decay time; weak 4ns and 16.6micro sec Wavelength; 450-650ns-> RbCs PMT or APD PSD?; -> Crystal growth issue; no commercial -> PSU -> Active (CsI) shielding inside of Y2L • GSO, ZnSe • CdZnTe ; R&D, 0.5x0.5x05cm(1g) <-100$ -> expensive • Liquid Xenon (not a crystal)

  26. Double beta decay

  27. CaMoO4 sensitivity • Ca,Mo purification, Active shield( 6cm CsI), Time correlation (PSD), 5% FWHM assumed. • 10kg Mo-100 enriched CaMoO4(100kg natural) Depleted Ca-48 or uses SrMoO4, PbMoO4 8x1024 years (0.2eV) <- explore Klopder’s claim region. (Current best limit: 5x1022 years by Ejiri group) • 10% Ca-48 enriched 10kg CaMoO4: 0 background, 1.5x1024 years (0.6eV) sensitivity (Current best limit : 2x1022 years) • 1ton Mo-100 enriched CaMoO4 with further factor 100 background rejection. 8x1026 years (0.02eV) sensitivity <- next generation goal.

  28. CaMoO4 R&D Pulse shape spectrum by Am-251 source CaMoO4 crystal *5x5x5mm * 부산대 결정성장연구소

  29. CaMoO4 and SrMoO4 S.B. Mikhrin et.al, NIMA 486 (2002) 295 1: SrMoO4 2: CaMoO4

  30. Red-sensitive high efficiency silicon sensor Large area Avalanche Photo diode (1.6cm diameter) 4x4 1.5cm2 Photo diode

  31. Summary • A R&D with HPGe, we already achieved world the best limit for 2-, 0-n Sn-124 excited level and Sn-122 transition. • With a pilot experiment with HPGe + Zn + CsI crystal, we ruled out Zn-64 EC+b+ positive evidence claimed by I.BIKIT et al. and set the limit to 2x1020 years by 95%CL . • Tin loaded LSC can be used for the double beta decay experiment. (up to 36% Sn loading successful) • Crystal R&D of CaMoO4, ZnSe, GSO started for bb search with active detector technique.

  32. Prospect • New 700m underground site at Yangyang : This will allow us to compete with world wide dark matter & bb experiment. • 1 liter enriched Sn loaded Liquid Scintillator: First Observation of 2n bb and T1/2 > 1022 years for 0n in Sn-124 • 10kg Mo-100 enriched CaMoO4 (SrMoO4, PbMoO4..) 8x1024 years (0.2eV) , 10% Ca-48 enriched 10kg CaMoO4: 1.5x1024 years (0.6eV) sensitivity • One ton Mo-100 enriched CaMoO4. 8x1026 years (0.02eV) sensitivity

  33. Tl-208 (Q=5MeV) background

  34. Mo-100 2n+0n with 5% FWHM

  35. bb candidates

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