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Double beta search : experimental view

Double beta search : experimental view. Laurent SIMARD, LAL - Orsay. 6 th Rencontres du Vietnam, Hanoi, 6 th -12 nd August 2006. W -. n eR. h. n eL. h. ( ). D L = 2 Process Majorana Neutrino n = n and effective mass <m n > Right-handed current in weak interaction

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Double beta search : experimental view

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  1. Double beta search : experimental view Laurent SIMARD, LAL - Orsay 6th Rencontres du Vietnam, Hanoi, 6th-12nd August 2006

  2. W- neR h neL h ( ) • DL = 2 Process • Majorana Neutrino n =n and effective mass <mn> • Right-handed current in weak interaction • Majoron emission • SUSY particle exchange bb(0n) : 2n  2p+2e- p n e- nM e- W- n p 2 2 A=<m>xPSx IMI Nuc. (Qbb ~ MeV)

  3. Tracking + calorimeter NEMO,EXO Calorimeter HPGe, Cd – Te bolometers Very high energy resolution Good efficiency « Compact » detectors (size  10 m) Crystals very pure (surface contamination ?) Direct signature of the 2 electrons 3 observables: - total deposited energy - individual energy - angular corelation Possibility to measure various isotopes No signature of the 2 electrons Only 1 observable: total energy Modest energy resolution and efficiency Large detector  a few 10 m Experimental approaches Both techniques are complementary and at least 2 or 3 experiments are needed to really prove the 0 decay at a level of 5

  4. PURE CALORIMETER

  5. Phase III ~ 100 kg Segmented crystals Liquid Argon 10 years of data-taking Phase III 10-3/(keV·kg·y) 10-2/(keV·kg·y) Phase II ~ 35 kg 76Ge Segmented crystals 3 years of data-taking Phase II (2010) 10-1/(keV·kg·y) Phase I Phase I ~ 15 kg 76Ge (crystals Heidelberg-Moscow + IGEX) (2008) The MAJORANA Project in the US 210 HPGe segmented diodes in a standard shielding (500 kg of enriched 76Ge) The GERDA project (LNGS) • operate with “naked” Ge diodes in a very pure liquid nitrogen shielding (LN2) • possible upgrade with liquid argon(LAr) for active anticoincidence from the scintillation light of LAr • - segmentation of diodes for a greater reduction of backgrounds start with 60 kg

  6. New detectors for Phase II:Procurement of enriched Ge March ’05: procurement of 15 kg of natural Ge (‘test run’) Sep ’05: enrichment of 37.5 kg of Ge-76 completed ! ~ 88% Ge-76 April ’06: enriched material transported to Germany; now stored underground at HADES Specially designed protective steel container reduces activation by cosmic rays by factor 20

  7. Backgrounds in GERDA Muon veto 180 days exposure after enrichment + 180 days underground storage 30 days exposure after crystal growing derived from measurements and MC simulations Target for phase II: B  10-3 cts/(keV kg y)  additional bgd. reduction techniques

  8. Background reduction techniques • Muon veto • Anti-coincidence between detectors • Segmentation of readout electrodes (Phase II) • Pulse shape analysis (Phase I+II) • Coincidence in decay chain (Ge-68) • Scintillation light detection (LArGe)

  9. 130Te

  10. bb (0n)130Te After 5 years of data taking FWHM = 5 keV @ 2528 keV BKG = 0.18 ± 0.01 c/(keV kg y) If background = 0.01 cps/ (keV.kg.year) T1/2() 2.1 x 1026 years (90% C.L.) If background = 0.001 cps/ (keV.kg.year) T1/2() 6.6 x 1026 years (90% C.L.) If background = 0.001 cps/ (keV.kg.year) + enriched crystals T1/2()  1.9 x 1027 years (90% C.L.) Cuoricino T1/20n> 2×1024y @ 90% C.L. a and b degraded particles emitted by 238U and 232Th surface contaminations on the Cu frame and on the crystal surface. Experimental data and simulations suggest one major contribute for CUORE background in the DBD region: Cu TeO2 TeO2 CUORE : 130Te in LNGS (760 kg of Te) Q ~2.5 MeV Goal:() of 130Te ~ 1000 TeO2 bolometers Predictions on the future background expected for CUORE from Cuoricino background analysis and Monte Carlo simulations...

  11. Auxiliary bolometer Main bolometer SSB Classic pulse Event originating inside the main bolometer (DBD event) Classic pulse Event originating outside the main bolometer (degraded a) High and fast pulse Classic pulse Surface Sensitive Bolometers Background reduction may be achieved through both passive and activemethods Surface Sensitive Bolometers Identification of background events Creation of a new kind of detectors able to recognize surface events Idea: cover each face of a classic bolometer by gluing an active layer, in order to provide a 4p shielding Dynamic behavior: The difference between heat capacities generates a difference in pulse height and shape...

  12. Surface events Surface events Bulk events Pulse amplitude on auxiliary NTD [mV] Pulse amplitude on auxiliary NTD [mV] Bulk events Pulse amplitude on main NTD [mV] Pulse amplitude on main NTD [mV] First SSB experimental results (Como) According to the described dynamic behavior, various pulse parameters proved to be effective in discriminating surface events. Amplitude comparison (Scatter plot) -Individual thermistor read-out -Parallel thermistors read-out tr on auxiliary thermistor td on main thermistor (To be investigated)

  13. THE POLISHING SYSTEM • ABRASIVE CLEANING, GRINDING and MECHANICAL POLISHING • SOLVENT CLEANING: Chlorofluorocarbons and Liquid CO2 • SEMI-AQUEOUS CLEANERS: Terpenes; Alcohols; Ketones; Esters; Amines • ULTRASONIC CLEANING • MEGASONIC CLEANING • SAPONIFIERS, SOAPS, AND DETERGENTS • WIPE-CLEAN • SUPERCRITICAL FLUIDS • CHEMICAL ETCHING • ELECTROCHEMICAL POLISHING • ELECTROLESS ELECTROLYTIC CLEANING • DEBURRING: laser vaporization, thermal pulse flash deburring • STRIPPABLE COATINGS • OUTGASSING • REACTIVE CLEANING: Anodic Oxidation and subsequent removal of the oxide • OZONE CLEANING • HYDROGEN CLEANING • REACTIVE PLASMA CLEANING AND ETCHING • PLASMA CLEANING • SPUTTER CLEANING • ION BEAM CLEANING

  14. The CANDLE project • Prototype CANDLE III is in construction • Osaka-JAPAN • Pure CaF2 crystals 103 cm3 • (scintillation) • Energy resolution: • ~ 5% @ 4.2 MeV • CANDLES III: • 60 crystals : Total mass = 191 kg • Crystals natural Calcium • ~ 300 g of 48Ca Technique could be very promising with enriched 48Ca crystals Need to enrich ~ 100-200 kg of 48Ca !...

  15. TRACKING + CALORIMETER

  16. THE EXO PROJECT TPC with Xenon : possibility to use a large mass of isotope Xe noble gaz : centrifugation -> 200 kg of 130Xe avalaible in Stanford T½bb(2n)very high Identification of Ba ion :136Xe  136Ba++ +2e- by laser fluoresence Phase 1: EXO-200, 200 kg of136Xe TPC with liquid Xe, detection of scintillation (FWHM ~ 2% @ 2.5 MeV) No identification of the Ba+ ion Start foreseen end 2007 Expected background : 0.003 cts.keV-1.kg-1.y-1 T½ > 3 1025y Difficulty: neutralisation Ba++ Ba+ collection of ions With identification of the Ba+ion and 1 ton of 136Xe Expected background < 0.0005 cts.keV-1.kg-1.y-1 Date ? T½ > 1027years

  17. 20 secteurs B(25 G) 3 m Magnetic field : 25 Gauss Gamma shielding : Iron (e = 18 cm) Neutron shielding : 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: borated water) 4 m Able to identify e-, e+, geta The NEMO3 detector Frejus Underground Laboratory (LSM) : 4800 m equivalent water Source: 10 kg of isotopes cylindrical shape, S = 20 m2, e ~ 60 mg/cm2 Tracking detector: wire chamber in Geiger regime (6180 cells) Gas: He + 4% ethylic alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low-radioactivity PMTs

  18. 82Se

  19. Preliminary results of NEMO-3 Expected in 2009 T1/2(bb0n) > 2 1024 (90 % C.L.) T1/2(bb0n) > 8 1023 (90 % C.L.) Phase I (with radon) February 2003 - September 2004 : 298 days of data taking Phase II (without radon) December 2004 - March 2006 : 290 days of data taking 82Se, 1 kg 100Mo, 7 kg Phases 1+2 T1/2(bb0n) > 5.8 1023 (90 % C.L.) T1/2(bb0n) > 2.1 1023 (90 % C.L.)

  20. From NEMO-3 to SuperNEMO Me Tobs Navo T1/2(bb0n) > ln2   A Nexcluded SuperNEMO NEMO-3 7 kg Isotope mass M 100kg Energy resolution FWHM(calo)=8% @3MeV FWHM(calo)=4% @3MeV Efficiency e e(bb0n) = 8 % e(bb0n) =25 % Background 214Bi < 300 mBq/kg 208Tl < 20mBq/kg 214Bi < 10 mBq/kg 208Tl < 2mBq/kg Internal contaminations 208Tl and 214Bi in the bb foil (208Tl, 214Bi) ~ 1 evt/ 7 kg /y (208Tl, 214Bi) ~ 1 evt/ 100 kg /y bb2n ~ 2 evts / 7 kg / y bb2n ~ 1 evt / 100 kg/ y bb(2n) T1/2(bb0n) > 2. 1024 y <mn> < 0.3 – 1.3 eV T1/2(bb0n) > 1026 y <mn> < 0.05 – 0.1 eV SENSITIVITY

  21. View of the detector in its shielding 4 m New cavity ~ 70m x 15m x15m 5,7 m • 2009-2010: construction of the 1st • module • 2010: commissioning of the 1st module • measurement of the background level • 2010 – 201N: construction of the other • modules • 201N: full detector 13 m Shielding : Water aganist  and neutron Source foil ~ 2 000 tons of water for 20 modules

  22. 1 2 0n T1/2 = G0nM0n‹mn›2 Choice criteria for the isotope: • High phase space factor • Favorable nuclear matrix element… but uncertain calculations… • High Qbb for the background rejection • Possibility of enrichment !... Which isotope for SuperNEMO ? Half-life of the bb0n decay Effective mass of the Majorananeutrino Nuclear matrix element Uncertainties from the theoretical calculations Phase space factor

  23. Which isotope for SuperNEMO ? T1/2(0n) with mn=50meV Only phase space factor (M0n=1) 100 kg of 150Nd is equivalent to: ~ 410 kg of 82Se ~ 410 kg of 130Te ~ 1700 kg of 76Ge ~ 400kg of 136Xe With QRPA nuclear matrix elements calculations, 100 kg of 150Nd is equivalent to: ~ 340 kg of 82Se ~ 720 kg of 130Te ~ 1010 kg of 76Ge ~ 2640 kg of 136Xe But value ofM0 2 ? Shell Model: Caurier et al. QRPA: Faesller Rodin Simkovic Vogel 2005

  24. Enrichment by laser photoionisation • SILVA Infrastructure in Pierrelate (France) • In 2003: enrichment of 200 kg of 235U in 2 weeks ! • 235U + 3 photons  235U+ + e- • Possibility of enrichment of 200 kg of 150Nd in few weeks ! • Simulations done par Alain Petit (DEM, CEA) • Enrichment of 96Zr and of 48Ca could be considered : to be studied… • Main goal : maintain the installation for an enrichment of 100 kg of 150Nd •  “Statement” of the SuperNEMO collaboration Enrichment of bb isotopes Enrichment by centrifugation: 82Se: 100 kg in 3 years in ECP Zelenogorsk (Siberia) price ~ 50 keuros / kg Agreement for 1.5 kg (ILIAS funding)

  25. Sensibility of SuperNEMO : discussion • Simulation Monte Carlo with 5 years of data taking • 82Se T1/2> 1026 years mais constrain on 214Bi, Radon et 208Tl are very strong • 150Nd T1/2> 6 1025 years equivalent to 5 1026y(82Se) because of the phase space factor. bb2n background similar for 82Se whereas T1/2 is lower (Fermi factor : coulombian effect due to the high Z) No constraint on 214Bi and radon (Qbb = 3.367 MeV) • 48Ca T1/2 1.5 1026 years equivalent to 5 1026 y (82Se) because of the phase space factor. No constrain on 214Bi and radon Constrain on 208Tl much less stronger (Qbb = 4.271 MeV) 150Nd: T1/2(bb2n) = 1019 y 82Se: T1/2(bb2n) = 1020 y

  26. Expected sensitivities COBRA 418 <56 <0.001 ~ 60-180 ~1026 ? 116Cd Nuclear Matrice elements: Shell Model: Caurier (2004) private com. Stoica et al. (2001) Suhonen et al. (1998 and 2003) QRPA Rodin, Simkovic, Faessler (2005)

  27. Current experiments Current experiments Next generation Next generation Constrain on <mbb> Cosmology Cosmology (Figure from C. Giunti)

  28.  Cuoricino and NEMO3 are running ~ for 5 years : range ≈ a few 100 meV • R&D for new experiments with a mass of ≈ 100 kg of enriched isotopes. aim : a few 10 meV with at least 3 isotopes  Coordination in Europe (ILIAS)  Neutrinoless double beta decay could be one of the experimental key for understanding neutrino physics : it is along way but promising ?

  29. 222Rn (3.8 days) a b- 214Bi  214Po (164 ms)  210Pb Two independent measurements of radon in NEMO-3 gas 214Po 218Po b • Radon detector at the input/output of the NEMO-3 gas ~ 20 counts/day for 20 mBq/ m3 • (1e- + 1 a) channel in the NEMO-3 data: • Delayed tracks (<700 ms) to tag delayed a from 214Po 214Bi  214Po (164 ms)  210Pb • ~ 200 counts/hour for 20 mBq/m3 a 164 ms 214Bi b- Decay in gas 210Pb 214Pb delayed a Good agreement between the two measurements A(Radon) in NEMO-3  20-30 mBq/m3 ~ 1 bb0n-like events/year/kg with 2.8 < E1+E2 < 3.2 MeV Radon in the NEMO-3 gas of the wire chamber Due to a tiny diffusion of the radon of the laboratory inside the detector A(Radon) in the lab ~15 Bq/m3

  30. May 2004 :Tent surrounding the detector

  31. Starts running Oct. 4th 2004 in Modane Underground Lab. 1 ton charcoal @ -50oC, 7 bars Activity: A(222Rn) < 15 mBq/m3 !!! Flux: 125 m3/h a factor 1000

  32. Time (days) 5.8 11.6 17.4 23.1 Level of radon measured inside the wire chamber, by analysing (1e- + 1 a) channel in the NEMO-3 data Without tent: A ~ 1.5 Bq Residual level to be understood sources ? After flushing radon-free air inside the tent: A ~ 0.15 Bq Radon level reduced by a factor of 10 Thanks a lot to S.K especially M.Nakahata,S.Tasaka

  33. if mn0 and n = n double beta bb0n Arbitrary scale The double beta process Allowed process bb2n Experimentally : a peak for The energy sum of the 2 e- E/Qbb Qbb : end-point energy ~ 2-4 MeV

  34. Two different approaches TRACKING+CALORIMETER • identification of the 2 e- • measurement of the 2 electrons energies, and of the angular distribution • measurement of each background amount BUT • reduced efficiency and energy resolution NEMO/SuperNEMO, EXO PURE CALORIMETER • only measurement of the energy sum of the 2 e- Esum • high efficiency • high precision for the measurement of Esum BUT • sensitive to an unknown gamma line Semi-conductors : GERDA,MAJORANA (Ge) CANDLE (Cd,Te) Bolometer : CUORICINO/CUORE IDENTIFICATION OF THE NATURE OF THE PROCESS (Majorana n, right current…)

  35. Water tank / buffer/ muon veto Vacuum insulated Copper or steel vessel Liquid N/Ar Ge Array GERDA : 76Ge in LNGS Phase I : 17.9 kg of enriched Ge-detectors underground at LNGS (from IGEX and Heidelberg-Moscow) IGEX HdM

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