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

2. Age of  physics !  What we knew : spin 1/2, no charge 3 type: e      by Z line shape)  What we now know: oscillations ->mass, mixing Solar, Atmospheric, Reactor, K2K, LSND(miniBooNe)  What we still don't know and need to know a) Magnetic moment (Reactor,  source  b) Absolute mass scale (tritium  ) c) Dirac or Majorana ( =? anti ) (  )  Cosmological question Relic, Ultra high energy  Dark matter

3. Neutrino mass limits

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

5. Double beta decay process (A,Z) -> (A,Z+2) + 2  +2  (A,Z) -> (A,Z-2) + 2   +2  EC+  ,2EC also is possible (A,Z) (A,Z+1) (A,Z+2) (A,Z) (A,Z-1) (A,Z-2) Excited state Ground state    ->  keV)

6. Why  decay is important?

7. 2 -DBD Candidate and Experimental results 1  10 17 - 2  10 22 (8.0 ± 0.7)  10 18 100 Mo 6  10 16 - 4  10 20 (7.0 ± 1.7)  10 18 150 Nd 3  10 17 - 6  10 20 (2.1 +0.8 -0.4 )  10 19 96 Zr 1.2  10 19 (2.0 ± 0.6)  10 21 238 U 2  10 19 - 7  10 20 (0.9 ± 0.15)  10 21 130 Te 9  10 22 - 3  10 25 (2.5 ± 0.4)  10 24 128 Te 3  10 18 - 2  10 21 (3.3 +0.4 -0.3 )  10 19 116 Cd 5  10 19 - 2  10 21 (6.8 ± 1.2)  10 20 100 Mo(0 +* ) 3  10 18 - 6  10 21 (0.9 ± 0.1)  10 20 82 Se 6  10 18 - 5  10 20 (4.2 +2.1 -1.0 )  10 19 48 Ca 7  10 19 - 6  10 22 (1.42 +0.09 - 0.07 )  10 21 76 Ge T 1/2 2 (y) calc T 1/2 2 (y) Isotope Weighted average of all positive results

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

9. The Best 0 -DBD results with different nuclei 1.8 * (eV) 6.0 > 1.8  10 22 48 Ca Ogawa I. et al., submitted 2002 Belli et al. Experiment < 1.4 - 4.1 > 7  10 23 136 Xe Range T 1/2 0  (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 2002 < 0.9 - 2.1 > 2.1  10 23 130 Te < 1.0 - 4.4 > 7.7  10 24 128 Te geo < 1.8 - 6.2 > 1.3  10 23 116 Cd < 1.4 - 256 > 5.5  10 22 100 Mo < 0.3 - 2.5 > 1.57  10 25 < 0.3 - 2.5 > 1.9  10 25 76 Ge

10.  evidence?

11. Future projects 0.1 - 1 34 nat 1 - 10 10 nat 1.6 enr 0.8 nat 1 -10 1 nat. enr. 0.5 Mass [ton] 2.3 10 28 y 600 300 1000 10 330 1500 300 150 old/futur e bkg 4.9 10 27 y 1.3 10 28 y 2.2 10 28 y 5 10 27 y INR - Kiev needs confirm. ELEGANT standard Gotthard Xe challenging DAMA - Xe tested MI-DBD tested HD-M partially tested HD-M partially tested IGEX mature Technology 2 - 6 10 28 y 0.1 - 1 10 28 y 0.4 10 28 y 0.06 GENIUS GEM MAJORANA 1 10 27 y0.33CUORE 0.9 - 13 10 27 y 0.5 - 1 10 27 y 0.025 0.06 EXO XMASS 0.1 - 1 10 27 y0.03CAMEO 1 10 27 y~ 0.02MOON Sensitivity (10y) present bkg [c/keV kg y] * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31

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

13.  material requirements  Matrix elements: good one (ex: Nd) ~ m 1/2  Enrichment: Gd, Te ~20%; Zr, Nd -> Difficult ~ m 1/2 Mo, Se, Ge, Kr, Xe, (Cd, Sn) ->Easy  Efficiency : ~ 100% for active source technique ~m 1/2 Mass, time ; ~m 1/4  Resolution; 2  background issue ~m 1/4  Background; Source impurity (U238,Th232) ~m 1/4 Source purification, Time correlation (PSD) Active shielding to reduce backgrounds

14. Why high-Z loaded scintillator for   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)  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 (CH 3 (CH 2 ) 3 CH(C 2 H 5 )CO 2 ) 2 Sn ( 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+  +,  +  + ; No observation yet b) Excited transition to  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. W/o shielding 10cm Pb + 10 cm Cu+ N2 (16 days data taking) 100% HPGe installed in CPL  Background measurement Shielding

21. Sn-124, Sn-122 0-,2-  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) 3.8x10 18 year (4.0x10 19 year)  0+ (1156) 1.1x10 19 year (2 - theory : 2.7x10 21 )  0+ (1326) 1.3x10 19 year (2.2x10 18 year) * Sn-122 EC+  + decay ; 1.5x10 18 year (6.1x10 13 )

22. Zn EC+  + decay EC+  + limit (  + -> 2  decay) 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! 99.7% CL

23. Zn EC+  + 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 (  + radioactive source) Efficiency calculation by Geant4; 3% Very Preliminary result with 1 week data; Coincidence cut with 2 sigma range ; 1 event  2x10 20 year by 95% CL  If I.BIKIT’s central value is taken, we would observe 100 events (1.1x10 19 y) Sn (8x8x1cm) data is available and we can set 5 orders better limit 511keV  CsI 7.5x7.5x8 Zn HPGe

24. Energy dist at HPGe

25. Crystals for   300g CdWO4  search by Ukrine group; >0.7x10 23 years Enrichment, PSD, actvie shielding -> successful  CaMoO4 (PbMoO4, SrMoO4...) ; Mo, Ca  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 8x10 24 years (0.2eV) <- explore Klopder’s claim region. (Current best limit: 5x10 22 years by Ejiri group) 10% Ca-48 enriched 10kg CaMoO4: 0 background, 1.5x10 24 years (0.6eV) sensitivity (Current best limit : 2x10 22 years) 1ton Mo-100 enriched CaMoO4 with further factor 100 background rejection. 8x10 26 years (0.02eV) sensitivity <- next generation goal.

28. CaMoO 4 R&D CaMoO4 crystal *5x5x5mm * 부산대 결정성장연구소 Pulse shape spectrum by Am-251 source

29. CaMoO4 and SrMoO4 S.B. Mikhrin et.al, NIMA 486 (2002) 295 1: SrMoO 4 2: CaMoO 4

30. Red-sensitive high efficiency silicon sensor Large area Avalanche Photo diode (1.6cm diameter) 4x4 1.5cm 2 Photo diode

31. Summary  A R&D with HPGe, we already achieved world the best limit for 2-, 0- Sn-124 excited level and Sn-122 transition.  With a pilot experiment with HPGe + Zn + CsI crystal, we ruled out Zn-64 EC+  + positive evidence claimed by I.BIKIT et al. and set the limit to 2x10 20 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  search with active detector technique.

32. Prospect  New 700m underground site at Yangyang : This will allow us to compete with world wide dark matter &  experiment.  1 liter enriched Sn loaded Liquid Scintillator: First Observation of 2  and T 1/2 > 10 22 years for 0  in Sn- 124  10kg Mo-100 enriched CaMoO4 (SrMoO4, PbMoO4..) 8x10 24 years (0.2eV), 10% Ca-48 enriched 10kg CaMoO4: 1.5x10 24 years (0.6eV) sensitivity  One ton Mo-100 enriched CaMoO4. 8x10 26 years (0.02eV) sensitivity

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

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

35.  candidates