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Outline of the MOON detector Background rejection & Expected sensitivity R&D Summary

TAUP2007, Sendai, September 11-15, 2007. MOON for next-generation neutrino-less double beta decay experiment ; present status and perspective. T. Shima Research Center for Nuclear Physics, Osaka University for the MOON collaboration. Outline of the MOON detector

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Outline of the MOON detector Background rejection & Expected sensitivity R&D Summary

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  1. TAUP2007, Sendai, September 11-15, 2007 MOONfornext-generation neutrino-less double beta decay experiment ;present status and perspective T. Shima Research Center for Nuclear Physics, Osaka University for the MOON collaboration Outline of the MOON detector Background rejection & Expected sensitivity R&D Summary

  2. MOON collaboration • H. Ejiri* (CTU-Praha, RCNP/Osaka and NIRS) • T. Itahashi, K. Matsuoka, M. Nomachi, S. Umehara (Phys./OULNS, Osaka Univ.) • T. Shima (RCNP, Osaka Univ.) • K. Fushimi, K. Yasuda, Y. Kameda (GAS, Univ. of Tokushima) • R. Hazama (Hiroshima Univ.) • H. Nakamura (NIRS) • S. Yoshida (Tohoku Univ.) • T. Kii (IAE, Kyoto Univ.) • P.J. Doe, R.G.H. Robertson*, D.E. Vilches, J.F. Wilkerson, D.I. Will (CENPA, Univ. Washington) • S.R. Elliott, V. Gehman (LANL) • J. Engel (Phys. Astronomy, Univ. North Carolina) • M. Finger, M. Finger, K. Kuroda, M. Slunecka , V. Vrba (Phys. Charles Univ. and CTU-Praha) • M. Greenfield (ICU, Tokyo) • A. Para (FNAL) • A. Sissakian, V. Kekelidze, V. Voronon, G. Shirkov, A. Titov (JINR) • V. Vatulin, P. Kavitov (VNIIEF) * Contact persons.

  3. QD:100~200 meV NEMO3 CUORITINO IH: 50~25 meV Next-generation: Super-NEMO, MOON NH: 4~2 meV Future experiment KKDC440meV Goal of next-generation DBD experiments • Thermal Leptogenesis scenario favors 1meV < mn < 0.1eV • Astronomical observations (PLANCK, Ly-a, weak lensing etc.) will provide constraints of 25~65meV on mn. q132

  4. 0nbb nuclear matrix element

  5. MOON Mo/Majorana Observatory Of Neutrino 10~30mm 15mm 20~40mg/cm2 1 unit = 42 modules = 20kg bb source

  6. Detectors • Plastic scintillators (2m×1m×15mm/layer) : • b-ray energy & time, g-ray veto • FWHM DE/(E1+E2) = 7%@3MeV → 5% • Wire chambers (2m×1m×10~30mm/layer) : • gas mixture; Ar+CO2 • particle ID; b/g • correction for position dependent response of PLs • delayed anti-coincidence with a, b • position separation of 5mm×5mm (wire-spacing + charge-division or anode×cathode) • Active shieldings: thick PL or NaI

  7. Features Multi-layers of source foils, scintillators and wire chambers • capability to measure different bb nuclei • sensitivity to bb energy- and angular- correlations • good selectivity of bb and BG with information of E,t,position Compact and modular structure • scalable from sub-tons to multi-tons • easy to shield against external & internal BG’s • large acceptance

  8. Real-time detection of low-energy solar n 8B pep 7Be pp

  9. Backgrounds • RI impurities with large Qb : 214Bi, 208Tl • (n,n’g), (n,g) by m-induced neutrons • 2nbb : t2n/t0n > ~1/105

  10. 208Tl (Qb=4.999MeV) : b-g-g in source foil b g1 g2 --- to be rejected with • anti-coincidence by g1 • coincidence with MWPCs on both sides of source

  11. Response for 1.8MeV b+583keV g+2614keV g 20mBq/ton 208Tl in 100Mo ~0.3 events for 1 ton·yr measurement

  12. Neutron-induced g-rays Main components of MOON detector; 12C, 1H, 100Mo, etc. 1H(n,g)2H ; Q=2.225MeV << Qbb of 100Mo, 82Se, 150Nd…

  13. Production rates of neutron-induced g Fn (En < 20MeV) ~10-8 n/cm2/MeV/s at 2000m w.e. (Gaitskell 2001)

  14. Response for 5MeV g 0nbb window ~0.2 events for 1 ton·yr measurement at 2000m w.e.

  15. Estimated background rates ; summary

  16. Sensitivity for <mn> ; 100Mo 0nbb

  17. Sensitivity vs. Energy resolution MOON-1 MOON-1 (correct for position)

  18. H. Ejiri, Czeck. J. Physics, 56 (2006) No 5, 459. H. Nakamura, et al., nucl-ex/0609008 MOON-1 6-layers of PL 53×53×1cm3, Mo-Foil142g @20mg/cm2×2 PLs Mo foils PMTs DE/E(FWHM) = 7% at 3MeV → 5% with correction for position dependence

  19. R&D; prototype NaI(Tl) scintillator • provided by Horiba, Ltd. • 150mm×150mm×10mm slab, three PMTs on each side • better energy resolution for bb and BG gs • sensitivity for bb to excited states

  20. Summary MOONis one of the feasible solutions for next-generation 0nbb experiment, because of its high efficiency, good resolutions (E, x, t), compactness, scalarbility, etc. - Road map - FWHM= 5% or 4% @3MeV Cf. Next-generation 76Ge experiments ; 1ton×4yr ⇒ ~40meV

  21. 214Bi (Qb=3.27MeV) : single b --- rejected with • energy losses in both PLs > 500keV • b-ray track positions in MWPCs (5mm×5mm)

  22. Response for 214Bi single b 20mBq/ton 214Bi in 100Mo ~0.002 events for 1 ton·yr measurement

  23. 214Bi (Qb=3.27MeV) : b-g --- rejected with • anti-coincidence by Compton-scattered g • coincidence with MWPCs on both sides of source

  24. Response for 214Bi b-g 20mBq/ton 214Bi in 100Mo ~0.1 events for 1 ton·yr measurement

  25. m-induced neutrons Energy spectrum: Fn (En < 20MeV) ~10-8 n/cm2/MeV/s

  26. 12C+n cross sections

  27. Inelastic g ( for one unit (42 modules, 20kg 100Mo) )

  28. Capture g Assuming all neutrons are thermalized and captured inside the detector…. 374 40 73000 [b·mole/unit] ( i = 12C, 100Mo, or 1H )

  29. Accidental Coincidence of external 2614keV g-rays Response for 2614keV single g-ray (0.1Bq/kg 232Th in PMTs)

  30. Coincidence rate

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