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Double beta decay Ruben Saakyan UCL 25 March 2004 Outline Motivation bb status Situation in the UK Future projects and UK involvement Sensitivity and time scale 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 2 Neutrino mass. What do we want to know? e 1 Ue12 2 3 Ue22 Ue32 Mixing normal ~0.01 eV 25/03/2004 inverted ~0.05 eV ( Dirac) oscillations OR (Majorana) Superbeams -factories degenerate 0bb only preferred by theorists • • • • Hierarchy (-osc and 0bb) CP-violation (-osc, 0bb+3H) Relative mass scale (-osc) Absolute mass scale (0bb+3H+cosmology) > 0.1 eV Ruben Saakyan, UCL PPAP meeting at RHUL 3 Double beta decay 2bb 1 T1/02 (0 0 ) G 0 ( E0 , Z ) M m 2 2 N U mi 2 ei i N 0 2 m 2 i U e ei mi 2 Main candidates: 48Ca,76Ge,82Se, 100Mo,136Xe,116Cd, 130Te,150Nd 0bb 2 i ~2-3 MeV Neutrino nature (Dirac vs Majorana) Absolute neutrino mass scale. Possible sensitivity ~0.01 eV (3H – 0.2 eV, KATRIN) IF degenerate hierarchy, we can measure “everything” The Experimental Problem ( Maximize Rate/Minimize Background) Natural Activity: t(238U, 232Th) ~ 1010 years Target: t(0bb) > 1024 years Detector Shielding Cryostat, or other experimental support Front End Electronics Cosmic ray induced activity Low-energy, ultralow-background eperiment. Overlap in experimental techniques with dark matter, solar ’s UK expertise exists 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 5 Where are we now? <m> < 0.35 – 0.9 eV mscale ~ 0.05 eV mass scale from oscillation experiments normal ~0.01eV inverted ~0.05eV degenerate >0.1eV (S. King et al. hep-ph/0402121) 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 6 Heidelberg-Moscow experiment claim (end 2001) <m> = 0.4 eV ??? 2.5-3 s bb community immediate response: Claim is at least premature 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 7 Heidelberg claim. Recent developments unknown hep-ph/0403018. Data acquisition and analysis of the 76Ge double beta experiment in Gran Sasso 1990-2003 accepted for publication in NIM A • Data reanalyzed with improved 214Bi 214Bi binning/summing 0bb • Peak visible • Effect reclaimed with 4.2s • <m> = (0.2 – 0.6) eV, 0.4 eV best fit <m> = (0.1 – 0.9) eV (due to NME) Problems (my view) 71.7 kgyr 25/03/2004 • Looks more like 2.5s of effect • Unknown peak at 2030 keV? • 214Bi line intensities do not match Ruben Saakyan, UCL PPAP meeting at RHUL 8 Situation in the UK At least 4 bb experts in UK (3 academics, 1 postdoc) UCL in NEMO – one of two experiments currently taking data Sussex, Warwick – COBRA, new approach R&D Meeting at RAL, Sep 2003 – Interest bb decay group > 40 people from particle and nuclear communities 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 9 Situation in the UK bb steering group: Sacha Davidson, Brian Fulton, Sean Paling, Ruben Saakyan, James Stirling (chair), Kai Zuber IPPP workshop 21-23 April. Think about tackling NME problem bb strategy for UK suggested by steering group 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 10 Where to go from here to reach 10-50 meV? A Great Number of Proposals UK steering group suggested roadmap CAMEO Cd-116 1 t CdWO4 crystals DCBA Nd-150 20 kg Nd layers between tracking chambers SuperNEMO Se-82, Various 100 kg of Se-82(or other) foil COBRA Te-130,Cd-116 CdTe semiconductors CANDLES Ca-48 Several tons CaF2 crystals in liquid scint. CUORE Te-130 750 kg TeO2 bolometers EXO Xe-136 1 ton Xe TPC (gas or liquid) GEM Ge-76 1 ton Ge diodes in liquid nitrogen GENIUS Ge-76 1 ton Ge diodes in liquid nitrogen GSO Gd-160 2 t Gd2SiO5:Ce crystal scint. in liquid scint. Majorana Ge-76 500 kg Ge diodes MOON Mo-100 Mo sheets between plastic scint., or liq. scint. Xe Xe-136 1.56 t of Xe in liq. Scint. XMASS Xe-136 10 t of liquid Xe 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 11 Future experiments expected to start in 2008/10 (5 yr exposure) Experiment, Source and cost Mass estimate Sensitivity to T1/2 (y) Sensitivity to <m> (eV)* Majorana $50M 76Ge, 500kg 3×1027 0.03 – 0.07 CUORE $30M 130Te, 2×1026 0.04 – 0.17 EXO $50M-100M 136Xe 8×1026 0.05 – 0.12 SuperNEMO $30M 82Se(or other) 2×1026 0.04 – 0.11 * 750kg(nat) 1 ton 100 kg 5 different latest NME calculations SuperNEMO NEMO-III (25 G) 3m B COBRA CdTe, CdZnTe Criteria for choosing projects • Competitiveness • UK role • Complementarity Suggested Future UK programme Two steps: SuperNEMO and COBRA SuperNEMO Quick start due to >15 yr of R&D experience; 40-50 meV by ~2014, likely to be first; if observed, disentangle mechanism of 0bb decay UK one of the main proponents; suggested to host in Boulby mine COBRA Novel approach; potential for large masses; possibility 10-20 meV by ~2020-2025; possibility to disentangle 0bb mechanism Idea of Kai Zuber (Sussex) Highly complementary! 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 14 Summary 0bb decay is indispensable for solving neutrino mass puzzle Great interest in particle and nuclear physics community. Highly complimentary to existing UK neutrino programme An opportunity for UK to lead 0bb research We may be not far away from the effect… 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 15