1. K. Zuber, Uni. Sussex Status of COBRA IDEA Meeting, Zaragoza 7 Nov. 2005

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

5. COBRA 2005 some are missing...

6. Isotopes nat. ab. (%)Q (keV)Decay mode COBRA: CdZnTe semiconductors

7. Level schemes

8. Quite a few lines...

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

10. Neutrino mass vs. right handed currents (eV) Possible evidence M. Hirsch et al., Z. Phys. A 347,151 (1994) EC/ß +

11. Advantages Source = detector Semiconductor (Good energy resolution, clean) Room temperature Tracking („Solid state TPC“) Modular design (Coincidences) Industrial development of CdTe detectors Two isotopes at once 116 Cd above 2.614 MeV

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

13. Running periods Running at LNGS since February 2004 Scheme driven by money/manpower CAMAC DAQ - 4 detector prototype CAMAC DAQ - 4 detector prototype mod. VME DAQ - 4 detector prototype modified

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

15. 2  - decay + Tracking option S. Elliott, P. Vogel, Ann. Rev. Nucl. Part. Sci. 2002 Energy resolution important  semiconductor Fraction of 2  in 0  peak: Signal/Background: 2  is ultimate, irreducible background

16. The 2x2 prototype 4 naked 1cm 3 CdZnTe more than 2.5 kg x days of data Setup installed at Gran Sasso Underground Laboratory

17. Neutrons Worry (if not enriched in 116 Cd): 113 Cd (n th,  ) 114 Cd MCNP simulation of the full set-up

18. Calibration 2.4% energy resolution at 2614 keV Much better ones available A little bit of cooling helps

19. Comparison of measurements 0.5 cm 3, surface, no shielding „old“ prototype, LNGS, no shielding „old“ prototype, LNGS, shielding, no veto

20. The background model Input: Pertinax (grid, base), detectors, paint and copper Currently limiting background: Passivation paint on detectors

21. Strategies We started a long term R&D with eV-Products to find another passivation (they have alternatives) Alternative providers not using the paint (Freiburg Material Research Centre)

22. Redesigned prototype Delrin holder and kapton foil Scalable design for larger masses

23. New versus old prototype Measuring time: 2630 hours, about 0.71 kg x days, Det1 only

24. Physics - 113 Cd T 1/2 = (8.2 ± 0.2 (stat.) +0.2 -1.0 (sys)) 10 15 yrs 113 Cd one of only three 4-fold forbidden  -emitters known in nature C. Goessling et al., nucl-ex/0508016, acc. by Phys. Rev. C

25. First results  1/2 close to 10 20 years obtained 70 Zn1.3 x 10 16 2.9x10 17 116 Cd8.0 x10 18 1.1x10 19 130 Te3.3x10 19 8.2x10 19 106 Cd 0  + EC 3.8x10 17 1. 6x10 18 64 Zn 0  + EC 2.8x10 16 2.6x10 17 120 Te 0  + EC 2.2x10 16 9.3x10 16 0  NPA723 Current EC-modes H.Kiel, D. Münstermann, K. Zuber, Nucl. Phys. A 723,499 (2003) Current results are preliminary

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

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

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

29. Signatures -  + /EC High granularity  A lot of patterns, interesting to investigate

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

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

32. First own measurements Two detectors: 4x4 pixel, 2mm x 2mm 16x16 pixel, 1.6 mm x 1.6 mm  -  plot Source location Two pixel events

33. Pixellated detectors 3D - Pixelisation: Solid state TPC

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

35. Back of the envelope  1/2 = ln2 a N A M t / N  (   T) ( Background free)  50 meV implies half-life measurements of 10 26-27 yrs 1 event/yr you need 10 26-27 source atoms This is about 1000 moles of isotope, implying 100 kg Now you only can loose: nat. abundance, efficiency, background,...

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

37. Sensitivity 50 meV

38. 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

39. Einstein was right