The Search for Neutrinoless Double Beta Decay: From NEMO-3 to SuperNEMO

1. A search for neutrinoless double beta decay: from NEMO-3 to SuperNEMO Yuri Shitov Imperial College London On behalf of the NEMO Collaboration • Outline: • Physics of double beta decay • Latest results from NEMO-3 experiment • Status of the SuperNEMO project • Summary of world status in the field • Conclusion Moriond EW 2010, 6-13.03.2010

2. Double beta decay basic statements (A,Z)(A,Z+2) + 2e- + 2n (A,Z)(A,Z+2) + 2e- 0: beyond the SM, T1/2 1025y 2: allowed SM process, T1/2 ~ 1020y Experimental patterns (E1+E2)/Qbb Other scenarios (Majoron emission, Right-handed (V+A) current, SUSY, etc.) are possible Light neutrino exchange

3. Double beta decay basic formulas where: T0n: half-life of the process <mn>: effective neutrino Majorana mass M0n: Nuclear matrix element (NME) G0n: phase space factor THEORY where: M : source mass ε : efficiency W : molecular weight t : time of measurement a :Isotope abundance or enrichment NBGR : background events ΔE : energy resolution EXPERIMENT

4. 0nbb and neutrino fundamental properties Probe of neutrino nature. Neutrinos are Majorana fermions (particle  antiparticle) if 0 takes place  See-Saw mechanism, Leptogenesis, Baryon asymmetry, CP violation Neutrino mass hierarchy. 0 measurements might help to establish the right one. Absolute mass scale. 0 experiments are among the most sensitive ones. Spreads are due to variations of unknown CP phases

5. Real bb-observation. • Any bb-source can be measured • Potentially zero-background • Test of bb0n mechanisms • Larger mass • Better resolution • High (~ 100%) efficiency bb-daughter rate E1+E2 spectrum E1, E2,  Experimental techniques to observe bb-decay Geochemical & Radiochemical Calorimetric Source  detector Tracking + Calorimetric TPC Time Projection Chamber There is no “ideal” method to meet all requirements!

6. Claim of 0nbb observation A.M. Bakalyarov et al. Part. and Nucl., Lett. 125, 21 (2005) 0nbb? 4.2 s evidence of 0nbbin 76Ge(Qbb=2039 keV) has been claimed by Klapdor-Kleingrothaus group (KGC) analyzing data of Heidelberg-Moscow (HM) experiment: Exposure: 71 kgy (1995-2003) T1/20nbb=1.51025 y <mn>=0.2-0.45 eV The same spectrum from Moscow group of HM. 1995-2001 data without problematic Det.3,5. 1)KGC has triggered a huge discussion 2) The best answer is the measurement! Check of KGC is now the target for all next generation 0nbb projects

7. NEMO-3/SuperNEMO collaboration Neutrino Ettore Majorana Observatory (Neutrino Experiment on MOlybdenum – historical name) 80 physicists / 30 institutions

8. B(25 G) 3 m Magnetic field: 25 Gauss Gamma shield: Pure Iron (18 cm) Neutron shield: borated water (~30 cm) + Wood (Top/Bottom/Gaps between water tanks) 4 m Able to identify e-, e+, g and a-delayed The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e. 20 sectors Source: 10 kg of  isotopes cylindrical, S = 20 m2, 60 mg/cm2 Tracking detector: drift wire chamber operating in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs

9. NEMO3 unique features Multi-source detector Multisourcebb-detector Measurement of full bb-event pattern Self-determination of ALL background components measuring independent channels

10. 100Mo 2 Results Sum energy spectrum Single electron energy spectrum Angular distribution 100Mo • • Data • MC ββ2 • background • subtracted NEMO-3 ’’2n-factory’’ in action 100Mo 100Mo 219 000 events 389 days S/B=40 Unique spectra from tracko-calo technique Latest results:

11. 100Mo 2 Results Summary of NEMO-3 2n-results Systematic studies of 2nbb process provide crucial knowledge for 0nbb search!

12. 100Mo 2 Results 0n-results

13. From NEMO to SuperNEMO NEMO-3 successful experience allows to extrapolate tracko-calo technique on larger mass next generation detector to reach new sensitivity level. SUPERNEMO R&D is in progress since 2006

14. SuperNEMO basic design SuperNEMO module 20 modules, each of them hosts: - 5 kg of source foil (82Se, 40mg/cm2) - 2000-3000 Geiger channels - 600 Calorimeter channels: PVT Scintillator + 8’’ PMT SuperNEMO is the favorite project to be hosted in the new LSM laboratory (hall A) planned to be opened at 2013

15. SuperNEMO demonstrator Source: 6.3 kg of 82Se Tracker R&D Calorimeter R&D Simulations Low background R&D BiPo setup • SuperNEMO demonstrator (first module) being finalizing, which will: • Prove the concept • Test 0nbb at level of KGC • Start in 2012

16. World leading 0nbb projects I CUORE Bolometer EXO-200 TPC GERDA HPGe

17. 0nbb experiments overview World leading double beta-decay projects II * Pure mass of bb-isotope. Efficiencies are NOT included. Others concepts and/or R&D:CANDLES (48Ca), COBRA (116Cd, 130Te), DCBA (150Nd), CARVEL (48Ca), CAMEO (116Cd), XMASS (136Xe), GEM (76Ge), GSO (76Ge), NEXT (136Xe), MOON (100Mo)

18. Roadmap for double beta-decay projects NEMO 3 CUORICINO, EXO-200 KGC GERDA SuperNEMO CUORE,EXO 2015-2020, 1t experiments (1 or 2) >2020, >10t experiment

19. Conclusion • - The 0nbb-decay is a test of physics beyond the Standard Model, fundamental neutrino properties: nature, absolute mass scale and neutrino hierarchy. • NEMO-3 detector is very efficient “bb-factory”, which is producing world leading results in the bb-field. • SuperNEMO R&D program has confirmed that NEMO-3 technique can be successfully extrapolated to 100 kg experiment with sensitivity compatible with other world leading projects. • SuperNEMO team is finalizing the design of SuperNEMO Demonstrator (first module) which will prove the workability of technique and check KGC. The Demonstrator will be started in 2012. • Positive signal from 2-3 experiments with different sources and different techniques would be guaranteed confirmation of the existence of 0nbb-process. • - Only tracko-calo and gas TPC can directly register 0nbb-decay. In the case of discovery only direct methods will allow to determine the process leading to bb(0n) : light neutrino exchange, right-handed current, supersymmetry, etc.