Search for 0nbb decay with SuperNEMO

1. Search for 0nbb decay with SuperNEMO Ruben Saakyan UCL UCL_HEP/MSSL day out 18 July 2005

2. Outline • Neutrinos • 0nbb decay • NEMO-III • SuperNEMO

3. Why study neutrinos? • 2nd most abundant particle in the Universe photons ~ 107/m3 neutrinos ~ 3  106/m3 protons ~ 0.5/m3 • As many produced in Big Bang as photons. Crucial for element formation. • Only 1% of energy from supernova appears as photons. Other 99% is neutrinos. • Neutrinos are crucial for our understanding how the Sun shines. • Very important for heavy element formation in stars (CNO cycle). • Neutrino astronomy: the only way to study distant objects • Very far-future neutrino beams: search for oil and destroy WMD?

4. Why study neutrinos? • Essential part of the building blocks of matter and the Universe • Fundamental for understanding deep principles of nature • In Standard Model assumed to be massless • We now know they have non-zero mass • Neutrino mass – window beyond Standard Model

9. Absolute neutrino mass • Neutrino oscillations measure Dm2 can not solve this problem • For sure less than 0.0000000000000000000000000000000001 g • 3H decay (look at end point of b-spectrum) • Cosmology • 0nbb decay

10. Weighing neutrino. Cosmology. mi < 0.7 – 2.2 eV

11. Double beta decay and neutrino mass • Neutrino nature  Dirac (n (anti)n vs Majorana (n = (anti)n) • The only way to answer this fundamental question • Absolute neutrino mass • Might be the only way to weigh n in a lab • Important consequences for particle physics, cosmology, nuclear physics

12. Double beta decay and neutrino mass DL=0 DL=2 ! Q

14. 214Bi unknown 214Bi 0nbb 71.7 kgyr A controversial claim by Heidelberg-Moscow group (4.2s)

15. NEMO-3 AUGUST 2001

16. 20 sectors B(25 G) 3 m Magnetic field: 25 Gauss Gamma shield: Pure Iron (e = 18 cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: water + boron) 4 m Able to identify e-, e+, g and a The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e. Source: 10 kg of  isotopes cylindrical, S = 20 m2, e ~ 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

17. Cathode rings Wire chamber PMTs Calibration tube scintillators bb isotope foils

18. bb2n measurement bb0nsearch bb decay isotopes in NEMO-3 detector 116Cd405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV Sensitivity to mn ~ 0.2 – 0.4 eV by 2009 150Nd 37.0 g Qbb = 3367 keV 48Ca 7.0 g Qbb = 4272 keV 130Te454 g Qbb = 2529 keV 82Se0.932 kg Qbb = 2995 keV External bkg measurement natTe491 g 100Mo6.914 kg Qbb = 3034 keV Cu621 g (All enriched isotopes produced in Russia)

19. Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view Vertex emission Vertex emission Drift distance Deposited energy: E1+E2= 2088 keV Internal hypothesis: (Dt)mes –(Dt)theo = 0.22 ns Common vertex: (Dvertex) = 2.1 mm (Dvertex)// = 5.7 mm • Trigger: 1 PMT > 150 keV • 3 Geiger hits (2 neighbour layers + 1) • Trigger rate = 7 Hz Criteria to select bb events: • 2 tracks with charge < 0 • 2 PMT, each > 200 keV • PMT-Track association • Common vertex • Internal hypothesis (external event rejection) • No other isolated PMT (g rejection) • No delayed track (214Bi rejection) bb events selection in NEMO-3 Typical bb2n event observed from 100Mo Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view 100Mo foil 100Mo foil Geiger plasma longitudinal propagation Scintillator + PMT

20. From NEMO-III to SuperNEMO. Motivation. • Very successful technology. > 15 years of experience. • Quick start as a lengthy R&D is not needed • Next generation bb0n experiments should have at least one “bubble chamber”-like detector which will see a signature of bb events

21. SuperNEMO = NEMO3×10(20) + better DE/E • Sensitivity ~0.03 – 0.06 eV in 5 yr • Feasible ifZero BG experiment: • 1)No BG from radioactivity • the only possible BG from • 2n tail (NEMO-III) • 2) Improve DE/E from • existing (14%-16%)/E to • (7%-9%)/E* • *Demonstrated (UCL+ Bordeaux) DE/E = 8% at 1 MeV DE/E = 12% at 1 MeV

22. SuperNEMO. Possible Sites. • Frejus – France (new cavern) • Boulby – UK • Gran Sasso – Italy • Canfranc – Spain

23. Baseline conceptual design. Scintillator blocks SuperNEMO = submodule × 50 100 kg of 82Se (or other) in 2m×4m×40m + shielding 10-20,000 PMts/scintillator blocks

24. Possible alternative scintillator bar design Double sided readout If feasible can reduce the number of PMT’s to 3-5,000 as well as the floor area to ~12x12 m2

25. The UK group is part of the international Super-NEMO collaboration (UCL/MSSL, Manchester) This proposal is part of a coordinated approach with the French to start Super-NEMO UK/French groups have agreed on the sharing of the main work. Other collaborators (Russia, Czech Rep, Japan, US will contribute on a smaller scale) Money request for a 2 yr design study submitted by UK (PPRP), France (IN2P3), US (NUSAG). UK main contributions: Tracking detector Finish up ongoing scinitllator R&D UK involvement

26. MSSL involvement • Large scale production  exploit MSSL technical expertise • New Lab space allows UK to bid for such big construction projects • MSSL main contributions • Tracking detector R&D + Wiring robot • SuperNEMO submodule production

27. Wiring robot The challenge: from 6,000 to ~60,000+ cells • Wires must be • strung • terminated • crimped • This can not be done • manually (~10 min/wire) • Complications • Copper pick-ups • Must be cost effective • Solder can not be used (radiopurity)

28. Tracker Read-out Electronics • Prompt signal from anode • wires (transverse coordinate) • Delayed signal from cathode • rings (longitudinal coordinate • TDC read-out with ~20 ns • resolution • Triggering based on track • parameters • Custom discriminator chip on or close to detector • Challenges: • Large number of channels (~60,000+) • High radiopurity

29. Tracker Front-End ASIC(Application Specific Integrated Circuits) • Design and prototype at UCL/MSSL • Amplifiers and discriminators with programmable threshould and zero suppression • Data collection and triggering/buffering/clock via serial link to minimise number of connections • Exact ASIC specifications need to be developed

30. Tracker Read-Out Boards • Design and prototype in close collaboration with UCL and Manchester HEP • Concentrator boards receive data from ASIC • provide data reduction and concentration • provide trigger data and first stage track reconstruction • Final read-out/track reconstruction/on-line monitoring via a DAQ PC farm. • FPGAs can be used to model ASIC for prototyping

31. SuperNEMO Milestones. • 2004 – 2005: ongoing scintillator R&D in UK, France, Russia, US • March 2005. Design study proposal submitted to UK and French funding agencies. UK answer after 24th August By mid 2007 • Full Technical Design • Prototype • Experimental site • 2007: Full Proposal • 2007 – 2010: Production • 2009-2010: Start taking data • 2014: planned sensitivity ~0.04 eV

32. Conclusions • Very exciting time for neutrino physics in general and 0nbb in particular • A positive signal is now a serious possibility in light of oscillation results • Costs of experiments in the £25M range: this is more than reasonable for the potential scientific gain • SuperNEMO is so far the only project which will look at 0nbb signature • Thanks to MSSL facilities UK (and specifically UCL) can be a crucial player in these and other large HEP projects