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1 TAUP - September 7, 2015S. Blot Investigating ββ decay with NEMO-3 and SuperNEMO Summer Blot, on behalf of the NEMO-3 and SuperNEMO experiments 7 September 2015 Outline Review of double beta decay Recent results from NEMO-3 Status of SuperNEMO Summary
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0νββ decay BSM process that violates ΔL conversation by 2 units Can be mediated by: Light Majorana ν, (V+A) current, SUSY Observed final state identical to 2νββ 2 TAUP - September 7, 2015S. Blot 2νββ Arbitrary units ΣE e = Q ββ 0νββ ΣE e < Q ββ 2νββ decay Occurs if β-decay is forbidden or highly suppressed (35 isotopes) 2 nd order weak process in the Standard Model (SM) (T ½ ~10 18- 21 yrs) Detect 2 electrons with continuous ΣE ΤΟΤ ( ν e ’s escape detection)
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3 TAUP - September 7, 2015S. Blot Why search for 0νββ decay? Observation of 0νββ decay would provide first evidence that lepton number is not conserved (LPV) Test Dirac vs Majorana nature of the neutrino If underlying mechanism is light Majorana neutrino exchange, can determine mass scale of neutrino Experimen t Theoretical input New physics
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The NEMO-3 experiment 4 TAUP - September 7, 2015S. Blot Operated from Feb 2003–Jan 2011 Modane Underground Laboratory (LSM) Passive detector design Source ≠ Detector Cylindrical geometry (R,φ,z) 7 different isotopes investigated Separate tracker-calorimeter systems Ability to reconstruct full kinematics of final state Can disentangle underlying 0νββ mechanisms Measure backgrounds in situ
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The NEMO-3 experiment 5 TAUP - September 7, 2015S. Blot Source foils Central tower Inner calo. wall Outer calo. wall Trackin g volume φ R x z y x y z Operated from Feb 2003–Jan 2011 Modane Underground Laboratory (LSM) Passive detector design Source ≠ Detector Cylindrical geometry (R,φ,z) 7 different isotopes investigated Separate tracker-calorimeter systems Ability to reconstruct full kinematics of final state Can disentangle underlying 0νββ mechanisms Measure backgrounds in situ
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The NEMO-3 detector 6 TAUP - September 7, 2015S. Blot ~10 kg of ββ-decay isotopes 100 Mo, 82 Se, 130 Tl, 116 Cd, 150 Nd, 96 Zr and 48 Ca Produced as thin foils 30- 60mg/cm 2 Typically 2.5 in height, 63-65 mm wide ~10 kg of ββ-decay isotopes 100 Mo, 82 Se, 130 Tl, 116 Cd, 150 Nd, 96 Zr and 48 Ca Produced as thin foils 30- 60mg/cm 2 Typically 2.5 in height, 63-65 mm wide Tracking chamber (both sides of foil) 6180 Geiger cells (50μm) operating in gas mixture of 95 % He, 4 % alcohol, 1 % Ar and 0.1 % H 2 O Vertex resolution σ XY ~3 mm, σ Z ~10mm Tracking chamber (both sides of foil) 6180 Geiger cells (50μm) operating in gas mixture of 95 % He, 4 % alcohol, 1 % Ar and 0.1 % H 2 O Vertex resolution σ XY ~3 mm, σ Z ~10mm Calorimeter (top, bottom, in and out) 1940 optical modules 3” and 5” PMTs coupled to polystyrene scintillator blocks σ E ~14-17 % (FWHM), σ t ~250 ps (1σ) electrons @1 MeV Calorimeter (top, bottom, in and out) 1940 optical modules 3” and 5” PMTs coupled to polystyrene scintillator blocks σ E ~14-17 % (FWHM), σ t ~250 ps (1σ) electrons @1 MeV
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7 TAUP - September 7, 2015S. Blot The NEMO-3 experiment – ββ-decay sources Observation of 0νββ must be confirmed in multiple isotopes NEMO-3 (SuperNEMO) designed with this in mind Largest mass with 100 Mo (6.9 kg) and 82 Se (0.93 kg)
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8 TAUP - September 7, 2015S. Blot Select events with two electrons outgoing from the foil with common vertex Measure all relevant kinematics to reject backgrounds and investigate 0νββ topology if observed B cosθ E1t1E1t1 E2t2E2t2 l2l2 l1l1 Mass mechanism Right-handed Current cosθ between electrons energy difference between electrons (MeV) Theoretical Reconstructed Theoretical Reconstructed Mass mechanism Right-handed Current -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 2.5 3 1 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 Events 1 0.8 0.6 0.4 0.2 0 Events 1 0.8 0.6 0.4 0.2 0 The NEMO-3 experiment – Detection principle
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9 TAUP - September 7, 2015S. Blot Backgrounds External backgrounds from neutrons capture, producing high energy γ-rays Reduced with 4800m water equivalent overburden and extensive passive shielding (wood, iron, borated water) Radon induced backgrounds Reduced by tagging α-particles from 214 Bi- 214 Po cascade Internal background decays e.g. Single β-decay + Møller scattering + conversion electron + γ + Compton scattering 2νββ decay Irreducible – must measure rate with high precision γ γ Internal backgrounds External backgrounds Use background topology to measure expected rates
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10 TAUP - September 7, 2015S. Blot Background channels External background channels (top right) identified by distinct time sequence of scintillator hits in the event (t i << t j ) Single electron channel (bottom right) provides channel to measure isotopes which undergo single β- decay [arxiv:1506.05825] External e - γ Single e -
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Latest NEMO-3 Results – 100 Mo 11 TAUP - September 7, 2015S. Blot Best 0νββ sensitivity in NEMO-3 using 34.7 kgy 100 Mo No significant excess of data over expected background in region of interest: E TOT = [2.8-3.2] MeV Limits derived on T ½ (0νββ) for various processes Phys. Rev D 89, 111101 (2014). [arxiv:1506.05825] Phys. Rev D 89, 111101 (2014). [arxiv:1506.05825] < 0.33-0.62 eV
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Comparison to other isotopes 12 TAUP - September 7, 2015S. Blot Most stringent half-life limit on 0νββ with 100 Mo from NEMO-3 (top) Translation into effective neutrino mass also shown (bottom) See [arxiv:1506.05825] for references to other isotope results
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Other results from NEMO-3 13 TAUP - September 7, 2015S. Blot Updated results coming soon… Best results of 2νββ T½ measurements for all 7 isotopes investigated Best 0νββ decay limits for many as well See backup slides for details or J.Phys.Conf.Series 375 (2012) 042011 T ½ 2ν ( 100 Mo )= 7.16 ± 0.01 stat ± 0.54 syst
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Moving towards SuperNEMO SuperNEMO shares the same detector design principles as NEMO-3 Modular in design first module (of 20 total) is the demonstrator Demonstrator will house 7kg of 82 Se and with 2.5y will reach sensitivity of ~ 0.2 – 0.4 eV 14 TAUP - September 7, 2015S. Blot *Values in table correspond to the full 20 modules of SuperNEMO 0ν0ν 0ν0ν Full SuperNEMO: m ββ ~ 0.04-0.1 eV
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The SuperNEMO detector 15 TAUP - September 7, 2015S. Blot 7kg of 82 Se per module ( 150 Nd purification studies ongoing, 48 Ca also possible) Thin foils with better radiopurity Factor of x10 decrease in 208 Tl contamination and x30 decrease in 214 Bi 7kg of 82 Se per module ( 150 Nd purification studies ongoing, 48 Ca also possible) Thin foils with better radiopurity Factor of x10 decrease in 208 Tl contamination and x30 decrease in 214 Bi Tracking chamber (both sides of foil) Wire chamber operating in Geiger mode Tracking chamber (both sides of foil) Wire chamber operating in Geiger mode Calorimeter: two main walls 5” and 8” PMTs coupled to scintillator block with optimized geometry σ E ~ 7.8 % (FWHM) for electrons @1 MeV Calorimeter: two main walls 5” and 8” PMTs coupled to scintillator block with optimized geometry σ E ~ 7.8 % (FWHM) for electrons @1 MeV B
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16 TAUP - September 7, 2015S. Blot SuperNEMO demonstrator status – source foils Source foil mounting test ~25% of source foil produced for demonstrator ( 82 Se) Radio-purity measurements underway using the dedicated BiPo detector The BiPo detector
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17 TAUP - September 7, 2015S. Blot Populating a C-section Wiring robot for cell production SuperNEMO demonstrator status – tracker First half of tracker complete First quarter (aka C0) commissioned, ready for shipment to LSM 98.4% of cells fully operational! (504 total) Radon tests for C1 underway, commissioning to follow Bottom seal plate First tracks in C0
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18 TAUP - September 7, 2015S. Blot SuperNEMO demonstrator status – calorimeter Production and testing of optical modules is well underway Energy resolution meeting design specifications Optical module production and testing
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19 TAUP - September 7, 2015S. Blot Radon emanation chamber SuperNEMO demonstrator status – radiopurity All materials screened for radiopurity with HPGe detectors and radon emanation chamber Radon concentration line to measure Rn in tracker gas (Target < 0.15 mBq/m 3) Preliminary measurements of radon in C-sections are very promising!! Radon centration line
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20 TAUP - September 7, 2015S. Blot SuperNEMO demonstrator status – software Many tools already implemented and validated Event generation and simulation of detector components Event reconstruction and particle ID Improved tracking algorithms α –particle ID Advanced γ tracking algorithm
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21 TAUP - September 7, 2015S. Blot Support frame installed at LSM C-section ready for transport to LSM SuperNEMO demonstrator - integration Optical module production underway SuperNEMO Demonstrator starting to take shape Commissionin g by 2016
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Sensitivity of next generation 0νββ experiments 22 TAUP - September 7, 2015S. Blot = | m 1 |U e1 | 2 +m 2 |U e2 | 2 e i α + m 3 |U e3 | 2 e i β | SNO+, SuperNEMO, CURORE< EXO+, GERDA, KAMLAND-Zen+ (2017– ) SNO+, SuperNEMO, CURORE< EXO+, GERDA, KAMLAND-Zen+ (2017– ) SNO+ ungraded, nEXO, Super- KamLAND-Zen P. Guzowski et al., Submitted to PRD (2015). arXiv:1504.03600v1 [hep-ex] Current best limit at m ββ < 130 - 310 meV (90% CL) Assumes 3 neutrino mixing model
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Summary The NEMO-3/SuperNEMO experiments offer a unique way to search for 0νββ decay and disentangle underlying mechanisms Analysis of full data set from NEMO-3 is ongoing Best results with 100 Mo yield m ββ < 0.33-0.62 eV Coming soon: new results from 82 Se, 116 Cd 150 Nd, 96 Zr and 48 Ca 23 TAUP - September 7, 2015S. Blot Thank you for your attention! Construction of SuperNEMO demonstrator is well underway Many of the most challenging design specifications have been achieved or are very close to being met Commissioning of demonstrator should begin next year (2016) Goal is to reach m ββ < 0.2-0.4 eV in just 2.5 years of running
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BACKUP SLIDES 24 TAUP - September 7, 2015S. Blot
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25 TAUP - September 7, 2015S. Blot Dirac vs Majorana Schechter-Valle theorem Image from Neutrino Physics Kai Zuber, IoP Publishing 2004
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Experimental considerations for 0νββ 26 DESY seminar 2015S. Blot Choice of isotope Large G 0ν and M 0ν for shorter T 1/2 Large Q ββ for background rejection Large mass of isotope of interest Enrichment, purification, abundance Detector design Good energy resolution Radio-pure materials Active or passive Choice of location Experiments underground and protected by many layers of passive and active shielding to protect from cosmic muon spallation, uranium fission, etc GERDA NEMO-3 SuperNEMO SNO+
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NEMO-3 tracker 27 DESY seminar 2015S. Blot Wire tracking chamber with 6180 cells operating in Geiger mode 95% He, 4% alcohol, 1% Ar, 0.1% H 2 O Vertex resolution: σ XY ~ 3 mm, σ Z ~ 10 mm 25 G magnetic field for discrimination between e + /e - Ground wire Anode Cathode ring Source foil Gaps for top/bottom calorimeter Single tracker cell anatomy 4-2-3 layout on each side of source foil
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NEMO-3 calorimeter 28 DESY seminar 2015S. Blot 1940 optical modules 3” and 5” low-radioactivity PMTs coupled to large (10x10x10) scintillator blocks ~15% / √E @ 1 MeV Dedicated studies for PMT monitoring to ensure high quality modules used in analysis Optical module anatomy PMT base electronics Magnetic shielding Light-tight sleeve PMT Interface light guide Light guide Iron ring Aluminized Mylar coating Particle entrance Scintillator block External wall of sector Optical fibre 0 50 100 mm PMT stability monitoring
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NEMO-3 calibrations 29 DESY seminar 2015S. Blot Monthly absolute calibration runs with 207 Bi sources + runs with 90 Sr source for calibrating up to 3 MeV Check PMT stability with daily laser survey (82% of PMTs stable for entire lifetime of experiment) Laser survey validation 207 Bi C.E. peaks 90 Sr ( 90 Y) endpoint
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30 TAUP - September 7, 2015S. Blot 1e1α event display Measuring backgrounds: 214 Bi- 214 Po cascade Electronics store Geiger hits information up to 700μs after event trigger Tag 214 Bi- 214 Po cascades with one electron and one cluster of delayed Geiger hits (α) 214 Po half-life is 164.3 μs arxiv:1506.05825
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Crossing electron 31 TAUP - September 7, 2015S. Blot Measuring backgrounds: Crossing electrons High energy external γ-flux can produce e + e - pairs in foil Use passive shielding to reject most events (slide 9) Use calo timing information to tag and characterize external events NIM A 606: 449-465, 2009
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32 TAUP - September 7, 2015S. Blot Measuring backgrounds: electron + gammas Many internal background decay to excited states of their daughter isotopes Tag γ rays emitted in de-excitation to identify these backgrounds Channel selects one electron and N scintillator hits without tracks pointing to them 100 Mo 1e2γ & 1e3γ arxiv:1506.05825
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Results from NEMO-3 33 TAUP - September 7, 2015S. Blot New results soon for 150 Nd, 48 Ca, 116 Cd and 82 Se for full exposure!
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100 Mo 0νββ result 34 TAUP - September 7, 2015S. Blot Event break-down Dominant systematic is absolute normalization on 0νββ efficiency
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