K. Zuber, Uni. Sussex NNR 05, Osaka Status of COBRA

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1 K. Zuber, Uni. Sussex NNR 05, Osaka Status of COBRA

2 Contents Introduction Current status of COBRA The 64 detector array Longer term planning Summary

3 C0BRA Use large amount of CdZnTe Semiconductor Detectors Array of 1cm 3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

4 Cobra - The people + further interested institutes C. Gößling, H. Kiel, D. Münstermann, S. Oehl, T. Villett University of Dortmund J. Dawson, C. Montag, D. Palzeaird, C. Reeve, J. Wilson, K. Zuber University of Sussex P.F. Harrison, B. Morgan, Y. Ramachers, D. Stewart University of Warwick A. Boston, P. Nolan University of Liverpool B. Fulton, A. Smith, R. Wadsworth University of York T. Bloxham, M. Freer University of Birmingham P. Seller Rutherford Appleton Laboratory M. Junker Laboratori Nazionali del Gran Sasso

5 COBRA 2005 some are missing...

6 Isotopes COBRA: CdZnTe semiconductors nat. ab. (%) Q (kev) Decay mode Zn ß-ß- Cd ß-ß- Cd ß-ß- Te ß-ß- Te ß-ß- Zn ß+/EC Cd ß+ß+ Cd EC/EC Te ß+/EC

7 Quite a few lines...

8 β + β + - modes In general: Double charged higgs bosons, R-parity violating SUSY couplings, leptoquarks... (A,Z) (A,Z-2) + 2 e + (+2ν e ) n n p e p e β+β+ Q-4m e c 2 e - + (A,Z) (A,Z-2) + e + (+2ν e ) β+/ec 2 e - + (A,Z) (A,Z-2) (+2ν e ) EC/EC Q-2m e c 2 Q Important to reveal mechanism if 0νββ is discovered Enhanced sensitivity to right handed weak currents (V+A)

9 Neutrino mass vs. right handed currents H int j L J + L + κj L J + R + ηj R J + L + λj R J + R EC/ß + <λ> λ,η <<1 Possible evidence <m n > (ev) M. Hirsch et al., Z. Phys. A 347,151 (1994)

10 Advantages Source = detector Semiconductor (Good energy resolution, clean) Room temperature Modular design (Coincidences) Two isotopes at once Industrial development of CdTe detectors 116 Cd above MeV Tracking ( Solid state TPC )

11 Background 116 Cd (Q=2805 kev) Alphas, Betas, Gammas Cosmogenics Measurement: E. Porras et al., NIM B 111, 325 (1996) neutrons 2νββ 113 Cd (n th,γ) 114 Cd muon induced neutrons

12 2νββ - decay 2νββ is ultimate, irreducible background Energy resolution important semiconductor Fraction of 2νββ in 0νββ peak: F = 8Q( E /Q)6 m e = 3.7 *10 10 S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci Signal/Background: S B 1 F T 2ν 1 /2 = = 0ν T1/ ν 19 T1 / 2 = yrs 0ν 26 T1 / 2 = 2 10 yrs + Tracking option

13 The 2x2 prototype Setup installed at Gran Sasso Underground Laboratory 4 naked 1cm 3 CdZnTe more than 3.2 kg x days of data

14 Calibration 2.4% energy resolution at 2614 kev Much better ones available A little bit of cooling helps

15 Comparison of measurements 0.5 cm 3, surface, no shielding old prototype, LNGS, no shielding old prototype, LNGS, shielding, no veto

Physics - 113 Cd 113 Cd one of only three 4-fold forbidden β-emitters known in nature T 1/2 = (8.

16 Physics Cd 113 Cd one of only three 4-fold forbidden β-emitters known in nature T 1/2 = ( (stat.) (sys)) 1015 yrs C. Goessling et al., nucl-ex/ , acc. by Phys. Rev. C

17 First results H.Kiel, D. Münstermann, K. Zuber, Nucl. Phys. A 723,499 (2003) COBRA 0νββ 70Zn 1.3 x x Cd 8.0 x x Te 3.3x x1019 EC-modes 106Cd 64Zn 64Zn Τ1/2 close to 1020 years obtained Current COBRA 0nb+ 3.8x1017 EC + 0nb 2.8x1016 EC 0nECEC 2.2x1016 Current 2.5 x x x1016 Current results are preliminary 64Zn limits world best

18 Coincidences Aim: Coincidences among crystals should significantly reduce gamma background 2614 kev gamma (MC) About 0.2 % of events are coincidences Array too small to prove power of coincidences Larger Array

The 64 detector array Aim for next 2 years: The next step towards a large scale experiment, Scalable modular design, explore coincidences All detectors are at Dortmund Mass is

19 The 64 detector array Aim for next 2 years: The next step towards a large scale experiment, Scalable modular design, explore coincidences All detectors are at Dortmund Mass is factor 16 higher, about 0.5 kg CdZnTe Include: Cooling Nitrogen flushing Physics: - Can access 2νECEC in theoretically predicted region -Precision measurement of 113Cd - New limits

20 Signatures - β + /EC High granularity A lot of patterns, interesting to investigate

21 Dimension it right! Current idea: 40x40x40 CdZnTe detectors = 420 kg, enriched in 116Cd A real time low-energy solar neutrino experiment? ν e 116Cd 116In e e τ = 14s Threshold energy: 464 kev 7Be contribution g.s. alone: 227 SNU 116Sn K. Zuber, Phys. Lett. B 571,148 (2003)

22 Sensitivity 50 mev

23 Single electron spectra The solid state TPC Introduce tracking properties by using segmented or pixellated electrodes and pulse shape analysis Angular correlation coefficient α

24 First own measurements Two detectors: 4x4 pixel, 2mm x 2mm 16x16 pixel, 1.6 mm x 1.6 mm Two pixel events θ - ϕ plot Source location

25 Pixellated detectors We have two 2D pixellated detectors running Solid state TPC 3D - Pixelisation:

26 Nobody said it was going to be easy, and nobody was right George W. Bush

27 Summary COBRA plans to use a large amount of CdZnTe semiconductors for double beta searches Collaboration of about 25 people established Currently preparing a 64 detector array (about 0.5 kg), to be installed at LNGS end of 2005 Design changed to allow easy upgrade to larger scales Work on signal enhancer/active veto and pixellated detectors has started Progress is fast

28 Einstein was right

Contents. General Introduction Low background activities Pixel activities Summary and Outlook. Kai Zuber

Contents. General Introduction Low background activities Pixel activities Summary and Outlook. Kai Zuber Contents General Introduction Low background activities Pixel activities Summary and Outlook COBRA Use large amount of CdZnTe Semiconductor Detectors Large array of CdZnTe detectors K. Zuber, Phys. Lett.