Double beta decay Ruben Saakyan UCL 25 March

Double beta decay Ruben Saakyan UCL 25 March 2004 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

Outline o o o 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? ne n 1 Ue 12 n 3 Ue 22 Ue 32 Mixing normal ~0. 01 e. V 25/03/2004 inverted ~0. 05 e. V n oscillations 0 nbb only Superbeams n-factories degenerate preferred by theorists • • Hierarchy (n-osc and 0 nbb) CP-violation (n-osc, 0 nbb+3 H) Relative mass scale (n-osc) Absolute mass scale (0 nbb+3 H+cosmology) > 0. 1 e. V Ruben Saakyan, UCL PPAP meeting at RHUL 3

Double beta decay 2 nbb Main candidates: 48 Ca, 76 Ge, 82 Se, 100 Mo, 136 Xe, 116 Cd, 130 Te, 150 Nd 0 nbb ~2 -3 Me. V ü Neutrino nature (Dirac vs Majorana) ü Absolute neutrino mass scale. Possible sensitivity ~0. 01 e. V (3 H – 0. 2 e. V, KATRIN) IF degenerate hierarchy, we can measure “everything” 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 4

The Experimental Problem ( Maximize Rate/Minimize Background) Natural Activity: t(238 U, 232 Th) ~ 1010 years Target: t(0 nbb) > 1024 years Detector Shielding Cryostat, or other experimental support Front End Electronics Cosmic ray induced activity ü Low-energy, ultralow-background eperiment. ü Overlap in experimental techniques with dark matter, solar n’s ü UK expertise exists 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 5

Where are we now? <mn> < 0. 35 – 0. 9 e. V mscale ~ 0. 05 e. V mass scale from oscillation experiments normal ~0. 01 e. V inverted ~0. 05 e. V degenerate >0. 1 e. V (S. King et al. hep-ph/0402121) 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 6

Heidelberg-Moscow experiment claim (end 2001) <mn> = 0. 4 e. V ? ? ? 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 76 Ge double beta experiment in Gran Sasso 1990 -2003 accepted for publication in NIM A • Data reanalyzed with improved 214 Bi binning/summing 0 nbb • Peak visible • Effect reclaimed with 4. 2 s • <m> = (0. 2 – 0. 6) e. V, 0. 4 e. V best fit <m> = (0. 1 – 0. 9) e. V (due to NME) Problems (my view) 71. 7 kg yr 25/03/2004 • Looks more like 2. 5 s of effect • Unknown peak at 2030 ke. V? • 214 Bi line intensities do not match Ruben Saakyan, UCL PPAP meeting at RHUL 8

Situation in the UK o o 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 o o o 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 -50 me. V? A Great Number of Proposals UK steering group suggested roadmap 10 CAMEO Cd-116 1 t Cd. WO 4 crystals DCBA Nd-150 20 kg Nd layers between tracking chambers Super. NEMO Se-82, Various 100 kg of Se-82(or other) foil COBRA Te-130, Cd-116 Cd. Te semiconductors CANDLES Ca-48 Several tons Ca. F 2 crystals in liquid scint. CUORE Te-130 750 kg Te. O 2 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 Gd 2 Si. O 5: 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 Majorana $50 M 76 Ge, CUORE $30 M Sensitivity to T 1/2 (y) Sensitivity to <mn> (e. V)* 500 kg 3× 1027 0. 03 – 0. 07 130 Te, 2× 1026 0. 04 – 0. 17 EXO $50 M-100 M 136 Xe 8× 1026 0. 05 – 0. 12 Super. NEMO $30 M 82 Se(or other) 2× 1026 0. 04 – 0. 11 25/03/2004 * 750 kg(nat) 1 ton 100 kg Ruben Saakyan, UCL PPAP meeting at RHUL 5 different latest NME calculations 12

Super. NEMO-III (25 G) 3 m B 4 m COBRA Cd. Te, Cd. Zn. Te 25/03/2004 Criteria for choosing projects • Competitiveness • UK role • Complementarity Ruben Saakyan, UCL PPAP meeting at RHUL 13

Suggested Future UK programme Two steps: Super. NEMO and COBRA o Super. NEMO n n o Quick start due to >15 yr of R&D experience; 40 -50 me. V by ~2014, likely to be first; if observed, disentangle mechanism of 0 nbb decay UK one of the main proponents; suggested to host in Boulby mine COBRA n n Novel approach; potential for large masses; possibility 10 -20 me. V by ~2020 -2025; possibility to disentangle 0 nbb mechanism Idea of Kai Zuber (Sussex) Highly complementary! 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 14

Summary o o 0 nbb 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 0 nbb research We may be not far away from the effect… 25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL 15