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Double Beta experiment using nuclear emulsions?

Double Beta experiment using nuclear emulsions?. Marcos Dracos IPHC/IN2P3, Université de Strasbourg. Double Beta Decay. Double Beta Decay. Nuclear matrix element. Phase space factor. -1. T 1/2 = F(Q bb ,Z) |M| 2 <m n > 2. 5. Effective mass:

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Double Beta experiment using nuclear emulsions?

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  1. Double Beta experiment using nuclear emulsions? Marcos Dracos IPHC/IN2P3, Université de Strasbourg M. Dracos, Osaka, 26/05/2010

  2. Double Beta Decay M. Dracos, Osaka, 26/05/2010

  3. Double Beta Decay Nuclear matrix element Phase space factor -1 T1/2= F(Qbb,Z)|M|2<mn>2 5 Effective mass: <mn>= m1|Ue1|2 + m2|Ue2|2.eia+ m3|Ue3|2.eib |Uei|: mixing matrix elements, a and b: Majorana phases neutrinoless double beta L=0 L=2 allowed double beta T1/2 ~ 1019-1020 years ! Observed for: Mo100, Ge76, Se82, Cd116, Te130, Zr96, Ca48, Nd150 Qbb = Ee1 + Ee2 - 2me 2 electron energy (keV) M. Dracos, Osaka, 26/05/2010

  4. Neutrino Oscillations MNSP Matrix (Maki, Nakagawa, Sakata, Pontecorvo) reactors accelerators CP violation solar, reactors Majorana phases atmospheric, accelerators Effective mass: <mn>= m1|Ue1|2 + m2|Ue2|2.eia+ m3|Ue3|2.eib |Uei|: mixing matrix elements, a and b: Majorana phases M. Dracos, Osaka, 26/05/2010

  5. Neutrino mass hierarchy m2 m12 m22 m32 ? normal Degenerate m1≈m2≈m3» |mi-mj| Normal hierarchy m3>>> m2~m1 Inverted hierarchy m2~m1>>m3 inverted M. Dracos, Osaka, 26/05/2010

  6. Neutrino mass hierarchy Lower bounds! Degenerate Goal of next generation experiments: ~10 meV Inverted hierarchy Normal hierarchy | mee| in eV Lightest neutrino (m1) in eV M. Dracos, Osaka, 26/05/2010

  7. Possible mechanisms of Double Beta decay M. Dracos, Osaka, 26/05/2010

  8. Possible mechanisms of Double Beta decay • 0nbb can be generated by: • exchange of light Majorana neutrinos • SUSY • LR symmetric model • … • these models are very often differentiated by the 2 electron angular distribution where K varies from -1 to +1 according to the extension of the Standard Model (A. Ali, A.V. Borisov, and D.V. Zhuridov, Phys. Rev. D 76, 093009 (2007)) M. Dracos, Osaka, 26/05/2010

  9. Present detection techniques or under investigation Calorimeter Semi-conductors Source = detector Tracko-calo Source  detector Xe TPC Source = detector Calorimeter (Loaded) Scintillator Source = detector b b b b b b b b e,M e, M e, DE isotope choice better background rejection good energy resolution CANDLES NEMO3 CUORE CaF2(Pure) EXO M. Dracos, Osaka, 26/05/2010

  10. Bolometers (Cuorecino) Heat sink Thermal coupling Thermometer Decay Crystal absorber Q-value for 0νββ in 130Te 2530.3 ± 2.0 keV Double-Beta Decay in Tellurium 130 • 44 5x5x5 cm3 and 18 3x3x6 cm3 TeO2 crystals, • detector mass 40.7 kg, • 130Te mass 11 kg M. Dracos, Osaka, 26/05/2010

  11. Candidate nuclei for double beta decay For most of the nuclei in this list the 2νββ decay has been observed M. Dracos, Osaka, 26/05/2010

  12. The NEMO3 detector(Fréjus tunnel) • Calorimetry combined with electron tracking • Advantage: • detection of the 2 electrons • background rejection • a • b • g • electronic noise • … M. Dracos, Osaka, 26/05/2010

  13. The NEMO3 detector(Fréjus tunnel) with magnetic field expected sensitivity up to mn~0.3 eV plastic scintillator blocks 3m + photomultipliers (Hamamatsu 3", 5") wire chamber (Geiger) energy and time of flight measurements Sources : 10 kg, 20 m2 2 electron tracks low radioactivity materials M. Dracos, Osaka, 26/05/2010

  14. The NEMO3 detector NEMO3 detector inside aradon tente Sources : 10 kg, 20 m2 M. Dracos, Osaka, 26/05/2010

  15. Isotopes sourcesthicknessmg/cm2) Bckg 82Se (0,93 kg) isotopes used by NEMO3 experiment at Fréjus M. Dracos, Osaka, 26/05/2010

  16. Event Examples • Trigger • 1 PMT > 150 keV • 3 Geiger cells (2 neighbours + 1) • Trigger rate ~7 Hz • Main criteria • 2 tracks with Q < 0 • common vertex • internal event from the foil (TOF cut) • No unassociated PMT ( rejection) • No delayed short tracks ( rejection from 214Bi-214Po cascade) • rate: 1 event / 2.5 minutes Typical ~1 MeV 2nbb candidate event M. Dracos, Osaka, 26/05/2010

  17. Event Examples M. Dracos, Osaka, 26/05/2010

  18. Main sources of Background • Many ways to mimic a bb signal • Natural radioactivity • U/Th chains (Rn), • 40K • Cosmic m • Neutrons • Artificial radioactivity M. Dracos, Osaka, 26/05/2010

  19. Results 82Se Phase I + II 693 days 48Ca 932 g 389 days 2750 even. S/B = 4 T1/2(bb0n) > 5.8 1023 (90 % C.L.)  <mn> <0.6-2.5 eV 100Mo ( 7 kg ) Expected in 2009 T1/2(bb0n) > 2 1024 (90 % C.L.)  <mn> <0.3-1.3 eV 82Se T1/2 = 9.6 ± 0.3 (stat) ± 1.0 (syst)  1019 y 116Cd T1/2 = 2.8 ± 0.1 (stat) ± 0.3 (syst)  1019 y 150Nd T1/2 = 9.7 ± 0.7 (stat) ± 1.0 (syst)  1018 y 96Zr T1/2 = 2.0 ± 0.3 (stat) ± 0.2 (syst)  1019 y 48Ca T1/2 = 3.9 ± 0.7 (stat) ± 0.6 (syst)  1019 y background subtracted M. Dracos, Osaka, 26/05/2010

  20. Improvements: Energy resolution 15%  DE/E = 4% @ 3 MeV Efficiency 15%  20 - 40% @ 3 MeV Source x10 larger 7kg  100 - 200 kg Most promising isotopes 82Se (baseline) or perhaps 150Nd Aim: T1/2 > 2 x 1026 y  Mbb < 40 - 90 meV R&D up to 2010/2011, construction between 2012 and 2014 (if approved) Super NEMO source sheet M. Dracos, Osaka, 26/05/2010

  21. Nuclear Emulsions • Compact objects ("cheap" detectors) • Very high space accuracy (<mm) • 3D information • No need for high tech, nor super trained staff • Very suitable for discoveries 1951 1947 Lattes, Muirhead, Occhialini & Powell observe p→m→e in nuclear emulsions using cosmic rays (few events are significant to make a discovery) M. Dracos, Osaka, 26/05/2010

  22. decay “kink” >25 mrad nt nm 1 mm nt OPERA Experiment τ ne,nm 50 200 50 (μm) ~15 grains/50 mm emulsion “grains”  track segment High spatial resolution is needed (do not forget that large surfaces have to be covered) e, m, h Nuclear Emulsions sqx~ 2.1 mrad sx~ 0.21 mm Pb ES Pb ES M. Dracos, Osaka, 26/05/2010

  23. The OPERA Detector "target" wall (full description in JINST 4, P04018 (2009)) Pb/emulsion brick wall scintillator strips n brick (56 Pb/Em.) Target Tracker + brick walls (2x31) 8 cm (10X0) 150000 bricks (1.25 kt) muon spectrometer (RPC + drift tubes) 8.3 Kg robot Changeable Sheet Doublet M. Dracos, TAUP09

  24. The OPERA Detector "Industrial" production, development, handling, scanning and analysis of emulsions. The BMS (Brick Manipulator System) BAM(Brick Assembling Machine) 5 articulated robots M. Dracos, TAUP09

  25. The OPERA emulsion scanning Based on the tomographic acquisition of emulsion layers. Nominal scanning speed ~20 cm2/h. ~ 20 bricks daily extracted → thousands of cm2/day The European Scanning System The S-UTS (Japan) Customized commercial optics and mechanics Hard coded algorithms (speed higher than 50 cm2/h) M. Dracos, TAUP09

  26. The OPERA first event   W hadrons charged current Muon momentum: ~7.5 GeV M. Dracos, TAUP09

  27. b decay with emulsions "veto" emulsion, if needed (~50 m like in OPERA?) e e beta source (~50 m in NEMO3 could be less for emulsions) plastic base "b" emulsion thick enough to detect up to 4 MeV electrons (density?) • J. Soc. Photogr. Sci. Technol. Japan. (2008) Vol. 71 No. 5 (http://arxiv.org/abs/0805.3061) • Radiation Measurements 44 (2009) 729–732 M. Dracos, Osaka, 26/05/2010

  28. Tests in Nagoya using OPERA nuclear emulsions A. Ariga, diploma thesis electron spectrometer 50 m M. Dracos, Osaka, 26/05/2010

  29. Electron tracks in emulsions 1 MeV e- simulation 100 m 2 MeV e- simulation (A. Ariga and NIM A 575 (2007) 466) M. Dracos, Osaka, 26/05/2010

  30. b decay with emulsions(comparison with NEMO3/SNEMO) • NEMO3 surface: 20 m2 • Super-NEMO surface: 10x20 m2 • To cover the same isotope source surface with emulsions (both sides to detect the 2 electrons) we need an emulsion surface: 2x200=400 m2. • Just for comparison, one OPERA emulsion has a surface of about 0.012 m2 and one brick 0.680 m2. So 400 m2 is about the equivalent of 600 OPERA bricks over 150000 (but not with the same thickness of course, taking into account the thickness this could be the equivalent in emulsion volume of about 25000 OPERA bricks). • Use the same envelops like the OPERA changeable sheets by introducing at the middle of the two emulsions (or stack of emulsion sheets) a double beta source sheet. • Keep all these envelops for some time (e.g. 6-12 months) in the experiment and after this period start scanning them one after the other. They could be replaced by new envelops during 5 years in order to accumulate something equivalent to what Super-NEMO could do: 5*400 year*m2 • Experiment volume: <5 m3 very compact experiment! M. Dracos, Osaka, 26/05/2010

  31. Previous tentative • 1.28 g 96Zr (powder) • source thickness: 180 m • total exposure time: 3717 hours • scanned surface for electron pairs: 10 mm2 • estimated total efficiency: 18% • Conclusion: • T1/2(96Zr)>1017 years, • decrease the thickness of the isotope layer, • use low radioactivity emulsions, • scanning speed has to considerably be increased (automatic scanning needed). M. Dracos, Osaka, 26/05/2010

  32. Emulsion scanning Scanning Power Roadmap 700 1000 140 60 40 100 1stage 7.0 facility 10 1.2 0.1 / h 1 2 cm 0.1 0.1 0.003 0.01 0.003 0.001 TS(1994) NTS(1996) UTS(1998) SUTS(2006) SUTS(2007-) CHORUS DONUT OPERA • How much time is needed to make a full scan of 2000 m2(full scan in all volume not needed, just follow tracks present in the emulsion layer near the isotope foil)? • If the Japanese S-UTS scanning system is used with a speed of 50 cm2/hour, for one scanning table: 25 m2/year (200 working days/year). By using 16 tables and extracting 100 m2/3 months (1 year exposure at the beginning and putting back new emulsions with the same isotopes), this finally will take less than 5 years (as Super-NEMO). • Probably the emulsion thickness needed to detect these electrons will need more scanning time and the speed would be significantly less than 50 cm2/h. On the other hand, scanning speed increases with time… Nakamura san Nufact07 M. Dracos, Osaka, 26/05/2010

  33. Pending questions • Energy resolution for NEMO: 15% for 1 MeV electrons • Required for Super-NEMO: lower than 8% • Emulsion experiment energy resolution: ??? • Overall reconstruction efficiency for NEMO: 15-18% • Required for Super-NEMO: >30% • Emulsion experiment reconstruction efficiency: ? • Minimum electron energy (~0.5 MeV?, 0.200 MeV for NEMO3), will greatly influence the total efficiency. • Afforded background (fog)?? • Possibility to take thinner isotope sheets (60 m for NEMO3) and have better energy resolution (but also more scanning for the same isotope mass, find good compromise). M. Dracos, Osaka, 26/05/2010

  34. Possible isotopes to be used • For emulsions the electron detection threshold cannot be so low than NEMO3 (200 keV, low density material gas+plastic scintillator)  utilisation of high Q-value isotopes>3 MeV • advantage: low background, high efficiency • problem: low abundance M. Dracos, Osaka, 26/05/2010

  35. Low energy cut and efficiency • The higher the Q-value the better the detection efficiency • For Ecut=0.5 MeV: • ECa~94% • ENd~86% • EMo~84% • From all detection points of view 48Ca is the best, but very low abundance… light majorana neutrino model 0.5 MeV seams a reachable limit, is it possible to go even lower? M. Dracos, Osaka, 26/05/2010

  36. Low energy cut and efficiency • For this model the efficiency will be lower than the previous one • For Ecut=0.5 MeV: • Eca~72 (94) % • ENd~54 (86)% • EMo~50 (84)% right handed current model (heavy majorana neutrino) M. Dracos, Osaka, 26/05/2010

  37. Thick Emulsions are needed • To stop up to 48Ca isotope electrons ~5 mm thick emulsions are needed, • A stack of 10 emulsion layers 0.5 mm thick could be used. M. Dracos, Osaka, 26/05/2010

  38. Feasibility studies 207Bi source with well known activity (EICe-=976, 482 keV) emulsion sheets 0.6 mm thick (3-4 layers) • Reconstruction efficiency: by counting the number of reconstructed electrons from both energy lines after scanning (this would also help to tune the algorithms). • Electron threshold: the reconstruction efficiency for both electrons (mainly those at 482 keV) would give a good idea about the threshold. • Energy resolution: by counting the associated grains to the track, by measuring the track range. • Afforded background: perform the above tests with different backgrounds. • Needed • scanning tables, • low radioactivity lab (Gran Sasso, Baksan, Fréjus…), • thick emulsions (provided by Fuji?) M. Dracos, Osaka, 26/05/2010

  39. Limitations • high multiple scattering for low energy electrons • de/dx fluctuations • bremsstrahlung gammas (energy lost) • lost -electrons • electron backscattering 0.7 MeV e- (10 tracks) d=2.7 g/cm3 (Geant 3.2) better to use low density emulsions? (by chance OPERA emulsions could be the best) M. Dracos, Osaka, 26/05/2010

  40. Extra Ideas e e e e decreasing density (25 m layers) emitter in powder (diluted in an emulsion layer ~25 mm) better vertex and energy reconstruction? (few isotopes are anyway in powder form) to minimize the emulsion thickness and better energy resolution at the end of the track M. Dracos, Osaka, 26/05/2010

  41. Extra Ideas top • Tests of dilution of Mo powder into 75 mm nuclear emulsion • high size granules go down during the emulsion production, but this is not a problem, • the optical properties are not affected, • the maximum afforded Mo density has been determined (keeping high detection efficiency). e e bottom (http://lanl.arxiv.org/abs/1002.2834) M. Dracos, Osaka, 26/05/2010

  42. BACKGROUND EVENTS OBSERVED BY NEMO-3which could be easily rejected in emulsions Electron crossing > 4 MeV Neutron capture Electron + a delay track (164 ms) 214Bi 214Po 210Pb end of tracks easily recognised in emulsions  rejection alpha tracks easily recognised in emulsions  rejection M. Dracos, Osaka, 26/05/2010

  43. BACKGROUND EVENTS OBSERVED BY NEMO-3and rejection in emulsions  Electron – positron pair B rejection Electron + N g’s 208Tl (Eg = 2.6 MeV) cannot be rejected in absence of magnetic field  good emulsion shielding no vertex or very good vertex resolution in emulsions  rejection M. Dracos, Osaka, 26/05/2010

  44. NEMO3 main background configurations Proportion of types of events in raw data: M. Dracos, Osaka, 26/05/2010

  45. Emulsion R&D done by Fuji R&D to remove 40K from gelatine to decrease the fog → very promising results Tadaaki Tani (Frontier Res. Labs, FUJIFILM) M. Dracos, Osaka, 26/05/2010

  46. Conclusion • Technology allows today the investigation about observation of neutrinoless double beta decays using nuclear emulsions, advantages of the method: • tracking and calorimetry, • very high resolution detector, • very compact volume easily shielded against external radioactivity, • flexibility to change isotopes at any time, • no fluids, • cost effective technique (easy to operate). • To prove the experiment feasibility few questions have to be answered: • what is the energy resolution? • what is the afforded background? • what is the overall efficiency? • The above questions could be answered with relatively low investment. M. Dracos, Osaka, 26/05/2010

  47. END Thank you for your kind attention M. Dracos, Osaka, 26/05/2010

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