Search for neutrinoless double beta decay in NEMO 3 and SuperNEMO Yu. Shitov, IC � Introduction to the ββ ββ -decay theory/experiment ββ ββ � NEMO-3 detector and its results � NEMO-3 detector and its results � SuperNEMO: basic R&D directions and its current status � Conclusion Shitov Yuriy, IC HEP seminar, 16.01.2008 1/54
Double beta decay basic statements ν : allowed SM process T 1/2 ~ 10 20 y ββ 2 ν ββ ββ ββ ν ν (A,Z+1) → (A,Z+2) + 2e - + 2 ν → 2p + 2e - + 2 ν (A,Z) → → → ν ν ( ν ( ( 2n → ( → → ν ν) ν ) ) ) ≥ 10 25 y ββ 0 ν ββ ββ ββ ν ν ν : beyond the SM T 1/2 ≥ ≥ ≥ (A,Z) Q ββ ββ ββ ββ → (A,Z+2) + 2e - ( → 2p + 2e - ) (A,Z) → → → ( 2n → ( ( → → ) ) ) (A,Z+2) Massive Majorana neutrinos (particle ≡ ≡ antiparticle) ≡ ≡ Happiness for theoreticians (many mechanisms proposed to describe the process) p n W − − − − e − − − − ν ν ν ν eR h ν ν M ν ν ν ν eL ν ν h W − − − − e − − − − n p (Q ββ ββ ~ MeV) ββ ββ Shitov Yuriy, IC HEP seminar, 16.01.2008 2/54
Double beta decay basic formulas 2 ν ν − ν 0 0 1 0 0 v 2 2 7 2 0 v 2 = = ( ) ( , ) | | / ~ | | A T G Q Z M m m Q Z M ν 1 / 2 e - effective neutrino Majorana mass M 0ν : nuclear matrix element ������ G 0ν : phase space factor M : mass (g) � : efficiency K C.L. : confidence level N : Avogadro number t : exposition time (y) ~ 69 stable and N Bckg : background events/ (keV/kg/y) 28 α -unstable ββ isotopes ���������� � E : energy resolution (keV) Shitov Yuriy, IC HEP seminar, 16.01.2008 3/54
Resent interest to 0 νββ νββ νββ -decay search νββ Great recent success in neutrino oscillation branch Strong support of 3 light active neutrino mixing theory Hot questions Hot questions Parameters defined Parameters defined ∆ m sol , θ sol , ∆ m atm , θ atm • existence of sterile neutrino(s) • θ 13 measurements New oscillation • precision of oscillation parameters experiments • neutrino nature (Dirac/Majorana) 0 νββ -decay •neutrino absolute scale and hierarchy pattern Shitov Yuriy, IC HEP seminar, 16.01.2008 4/54
Neutrino mass hierarchy patterns and 0 νββ νββ νββ νββ -decay m 2 2 m 1 2 m 2 2 m 3 ? Degenerate Degenerate Inverted hierarchy Inverted hierarchy Normal hierarchy Normal hierarchy m 1 � m 2 � m 3 » |m i -m j | m 2 ~m 1 >m 3 m 3 > m 2 ~m 1 For sin 2 θ θ θ θ chooz = 0.03 Quasi-Degenerated(QD) : |<m ν ν >| < 0.7 eV (cosmology) ν ν ~ Inverted hierarchy (IH) : 20 meV < |<m ν ν >| < 55 meV ν ν ~ ~ Normale hierarchy(NH) : |<m ν ν >| < 20 meV ν ν ~ S. Pascoli, S.T. Petcov and T. Schwetz hep-ph/0505226, Mai 2005 Shitov Yuriy, IC HEP seminar, 16.01.2008 5/54
Experimental difficulties to observe 0 νββ νββ νββ -decay νββ T 1/2 ≥ 10 26 > N A =6 ⋅ 10 23 → → 1 decay per 50 kg per year! → → Large mass of enriched ββ -isotope Now: Nearest future: Long-term future: tens of kg hundreds of kg tons Background Background • Natural background (<2614 keV) - extra-low setup radiopurity NEMO-3 (200 t) activity ~300 Bq, human body (60 kg) ~5000 Bq • Neutrons – active/passive shielding • Cosmics – deep underground sites for setup location Long-time exposition • years of data taking - setup stability required Shitov Yuriy, IC HEP seminar, 16.01.2008 6/54
Resolution as key point (Q ββ ββ ~ MeV) ββ ββ Avignone, King, Zdesenko, New Journal of Physics 7 (2005) 6 Shitov Yuriy, IC HEP seminar, 16.01.2008 7/54
Experimental techniques to observe ββ ββ -decay ββ ββ Experimental methods Tracko-calo TPC Calorimetric Geochemical E E 1 E 2 E 2 β 1 (A,Z-2)daughter θ β ββ -foil B B ββ ββ ββ ββ ββ -sample (A,Z) ββ ββ ββ ββ -foil ββ ββ Experimental output E1, E2, θ θ θ θ ββ ββ -daughter rate E1+E2 spectrum ββ ββ Shitov Yuriy, IC HEP seminar, 16.01.2008 8/54
Calorimeter versus tracko-calo/TPC detectors Calorimetric Tracko-calo/TPC Experimental advantages • Real ββ ββ -observation. ββ ββ • Any ββ ββ -source can be measured ββ ββ • Larger mass • Potentially zero-background exp. • Better resolution • Test of different ββ0ν ββ0ν ββ0ν ββ0ν mechanisms in the • ~ 100% efficiency case of observation. Experimental drawbacks • A few ββ ββ -isotopes can be measured ββ ββ • difficult to accept large mass 76 Ge, 130 Te up to now. • smaller efficiency (for tracko-calo) • Unavoidable natural background. • worth resolution • We don’t see electrons, just energy • background (for TPC) released - no absolute proof, that we see ββ0ν ββ0ν -peak and not something else ( γ ββ0ν ββ0ν γ γ -line)! γ Shitov Yuriy, IC HEP seminar, 16.01.2008 9/54
NEMO-3/SuperNEMO collaboration N eutrino E ttore M ajorana O bservatory ( N eutrino E xperiment on MO lybdenum – historical name) Japan Morocco U Saga USA Fes U MHC KEK INL U Osaka (U Texas) (U Texas) UK Finland Poland Russia JINR Dubna UCL U Jyvaskyla U Warsaw ITEP Moscow U Manchester Imperial College Kurchatov Institute Ukraine INR Kiev France ISMA Kharkov CEN Bordeaux IReS Strasbourg Slovakia LAL ORSAY (U. Bratislava) Spain LPC Caen U Valencia Czech Republic LSCE Gif/Yvette U Saragossa Charles U Praha U Barcelona IEAP CTU Praha ~ 80 physicists, 12 countries, 27 laboratories Shitov Yuriy, IC HEP seminar, 16.01.2008 10/54
The NEMO3 host laboratory LABORATOIRE SOUTERRAIN DE MODANE Main hall 30 x 10m 2 (h 11m ) 2 smaller halls ( 18 m 2 and 21 m 2 ) gamma hall (70 m 2 ) Operators CEA/DSM & CNRS/IN2P3 Location Fréjus Tunnel (Italian-French border) Excavation 1983 Underground area main hall (30x10x11 m) + γ γ γ -spectroscopy γ hall (70 m 2 ) + 2 secondary halls of 18/21 m 2 Depth 1700 m (4800 mwe) > 400 m 2 Surface Permanent staff 8 Scientists users 100 Shitov Yuriy, IC HEP seminar, 16.01.2008 11/54
The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e. 20 sectors Source : 10 kg of ββ ββ ββ ββ isotopes cylindrical, S = 20 m 2 , 60 mg/cm 2 Tracking detector : drift wire chamber operating in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H 2 O Calorimeter : Calorimeter : 1940 plastic scintillators 3 m coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: Pure Iron (18 cm) Neutron shield: borated water (~30 B (25 G) cm) + Wood (Top/Bottom/Gapes between water tanks) Able to identify e − − − − , e + + + + , γ γ and α γ γ α α α− − − − delayed Shitov Yuriy, IC HEP seminar, 16.01.2008 12/54
NEMO3 sector Cathodic rings Wire chamber PMTs Calibration tube scintillators ββ ββ isotope foils ββ ββ Shitov Yuriy, IC HEP seminar, 16.01.2008 13/54
Assembling of NEMO 3 August 2001 Location: LSM wood shield (Modane, France) water tanks magnet coil/shield Start taking data iron shield 14 February 2003 Opening Day, July 2002 Shitov Yuriy, IC HEP seminar, 16.01.2008 14/54
ββ ββ ββ decay isotopes in NEMO-3 detector ββ 05 04 06 03 ββ2ν measurement ββ2ν ββ2ν ββ2ν 02 07 116 Cd 405 g 08 01 Q ββ = 2805 keV 96 Zr 9.4 g 09 00 Q ββ = 3350 keV 150 Nd 37.0 g 19 10 Q ββ = 3367 keV Q ββ = 3367 keV 18 11 48 Ca 7.0 g Q ββ = 4272 keV 17 12 130 Te 454 g 13 16 Q ββ = 2529 keV 14 15 External bkg 100 Mo 6.914 kg 82 Se nat Te 491 g 0.932 kg measurement Q ββ = 3034 keV Q ββ = 2995 keV Cu 621 g ββ0ν ββ0ν ββ0ν ββ0ν search (All enriched isotopes produced in Russia) Shitov Yuriy, IC HEP seminar, 16.01.2008 15/54
ββ ββ -events selection in NEMO-3 ββ ββ ν event observed from 100 Mo Typical ββ ββ ββ 2 ν ββ ν ν Transverse view Run Number: 2040 Longitudinal Event Number: 9732 view Date: 2003-03-20 Vertex emission Vertex emission Deposited energy: E 1 +E 2 = 2088 keV Internal hypothesis: ( ∆ ∆ ∆ ∆ t) mes –( ∆ ∆ ∆ ∆ t) theo = 0.22 ns ( ∆ ∆ vertex) // = 5.7 mm ∆ ∆ Common vertex: ( ∆ ∆ vertex) ⊥ ∆ ∆ ⊥ = 2.1 mm ⊥ ⊥ Criteria to select ββ ββ ββ ββ events: Trigger : at least 1 PMT > 150 keV • 2 tracks with charge < 0 •external event rejection by TOF ≥ ≥ 3 Geiger hits (2 neighbour layers + 1) ≥ ≥ • 2 PMT, each > 200 keV • No other isolated PMT hit Trigger rate = 7 Hz • PMT-Track association ( γ rejection) • Common vertex ββ ββ events: 1 event every 2.5 minutes ββ ββ • No delayed track ( 214 Bi rejection) Shitov Yuriy, IC HEP seminar, 16.01.2008 16/54
Background tagging in NEMO-3 2e - event Τ l 208 208 Τ 208 208 e - N γ γ event to measure γ γ Τ Τ → → → → β β - α β β α α -delayed event 214 Bi → α → → → 214 Po → → → → 210 Pb e + – e - pair event B rejection Shitov Yuriy, IC HEP seminar, 16.01.2008 17/54
Background Unprecedented understanding, control and rejection of backgrounds Shitov Yuriy, IC HEP seminar, 16.01.2008 18/54
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