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K. Zuber, Uni. Sussex

K. Zuber, Uni. Sussex. IDEA Meeting, Zaragoza 7 Nov. 2005. Status of COBRA. Contents. Introduction Current status of COBRA The 64 detector array Longer term planning Summary. C0BRA. Use large amount of CdZnTe Semiconductor Detectors. Array of 1cm 3

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K. Zuber, Uni. Sussex

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  1. K. Zuber, Uni. Sussex IDEA Meeting, Zaragoza 7 Nov. 2005 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 1cm3 CdTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

  4. + further interested institutes 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 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

  7. Level schemes

  8. Quite a few lines...

  9. ++ -modes n p e In general: Double charged higgs bosons, R-parity violating SUSY couplings, leptoquarks... e p n Q-4mec2 • (A,Z)  (A,Z-2) + 2 e+ (+2e) ++ Q-2mec2 • e- + (A,Z)  (A,Z-2) + e+ (+2e )+/EC Q • 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)

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

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

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

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

  16. The 2x2 prototype Setup installed at Gran Sasso Underground Laboratory 4 naked 1cm3 CdZnTe more than 2.5 kg x days of data

  17. Neutrons Worry (if not enriched in 116Cd): 113Cd (nth,)114Cd 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 cm3, 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 Scalable design for larger masses Delrin holder and kapton foil

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

  24. Physics - 113Cd 113Cd one of only three 4-fold forbidden -emitters known in nature T1/2 = (8.2 ± 0.2 (stat.) +0.2-1.0 (sys)) 1015 yrs C. Goessling et al., nucl-ex/0508016, acc. by Phys. Rev. C

  25. First results H.Kiel, D. Münstermann, K. Zuber, Nucl. Phys. A 723,499 (2003) 0 NPA 723 Current EC-modes Current NPA723 Current results are preliminary T1/2 close to 1020 years obtained

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

  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 Mass is factor 16 higher, about 0.5 kg CdZnTe Include: CoolingNitrogen flushing • Physics: • - Can access • 2ECEC in theoreticallypredicted 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 Introduce tracking properties by using segmented or pixellated electrodes and pulse shape analysis Single electron spectra Angular correlation coefficient 

  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 Solid state TPC 3D - Pixelisation:

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

  35. Back of the envelope T1/2 = ln2 • a•NA• M • t / N (tT) ( Background free) 50 meV implies half-life measurements of 1026-27 yrs 1 event/yr you need 1026-27 source atoms This is about 1000 moles of isotope, implying 100 kg Now you only can loose: nat. abundance, efficiency, background, ...

  36. A real time low-energy solar neutrino experiment? e Threshold energy: 464 keV e e 7Be contribution g.s. alone: 227 SNU 116In  = 14s 116Cd 116Sn K. Zuber, Phys. Lett. B 571,148 (2003) Dimension it right! 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

  40. Join the Party!

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