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Status and perspectives of the COBRA double beta decay experimentx

Status and perspectives of the COBRA double beta decay experimentx. K.Zuber, 3.2.2011. - Double beta decay COBRA (CZT detectors) Status of LNGS data taking The solid state TPC (pixel detectors) Outlook - Summary. -. (A,Z)  (A,Z+2) +2 e - + 2  e 2. Double beta decay.

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Status and perspectives of the COBRA double beta decay experimentx

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  1. Status and perspectives of theCOBRA double betadecayexperimentx K.Zuber, 3.2.2011

  2. - Double beta decay • COBRA (CZT detectors) • Status of LNGS data taking • The solid state TPC • (pixel detectors) • Outlook • - Summary

  3. - • (A,Z)  (A,Z+2) +2 e- + 2e2 Double beta decay • (A,Z)  (A,Z+2) + 2 e-0 Unique process to measure the mass of the neutrino Unique process to measure character of neutrino Requires half-life measurements well beyond 1020 yrs!!!! Thesmallertheneutrinomassthelongerthehalf-life

  4. Double beta decay claim of evidence 1025 yrs 1026 yrs 1027 yrs 1028 yrs 1029 yrs H.V. Klapdor-Kleingrothaus et al. , Mod. Phys. Lett. 2006 (BG free) (BG limited)

  5. COBRA K. Zuber, Phys. Lett. B 519,1 (2001) Use large amount of CdZnTe Semiconductor Detectors CPG technology energy measurement only Pixel technologyenergy measurement and tracking Cape Town, 3.2.2011

  6. Technical University Dresden Technical University Dortmund University of Bratislava COBRA collaboration Material Research Centre Freiburg University of Erlangen-Nürnberg University of Hamburg University of Jyvaskyla University of La Plata Laboratori Nazionali del Gran Sasso Czech TechnicalUniversity Prague Washington University at St. Louis (Louisiana State University) JINR Dubna Cape Town, 3.2.2011

  7. Fedor Simkovic • Source = detector Advantages • Semiconductor (Good energy resolution, clean) Golden isotopes Silver isotopes • Room temperature • Modular design (Coincidences) • Industrial development of CdTe detectors Golden isotopes • 116Cd above 2.614 MeV • Tracking („Solid state TPC“) Silver isotopes COBRA S. Pirro, Milano Cape Town, 3.2.2011

  8. Gran Sasso (Italy) GERDA COBRA CUORE It‘s all about background reduction

  9. Setup at Gran Sasso Lab

  10. Measuredspectrum Data taking with 16 red crystals finished, about 18 kg*d statistics Major background: Red paint on surface, radon Actions: Colourless painting (4 + 4 detectors, nitrogen atmosphere with radon trap) 116Cdpeak region Background at 2.8 MeV around 5 counts/keV/kg/yr ! Cape Town, 3.2.2011

  11. Results: Cd-113 4-fold non-unique beta decay (1/2+9/2+) first time theoretical model based on nuclear structure calculation(thanks to J. Suhonen) first time histogram of 1016yrshalf-lifemeasurements Q-value: J. V. Dawson et al., Nucl. Phys. A 818,264 (2009) Deviations with theory at lower energies Cape Town, 3.2.2011

  12. six half-life limits above 1020 years, one world best, six limits within factor 3 of world best Results: 0νDBD based on 18 kg days of data, J.V. Dawson et al., Phys. Rev. C 80, 025502 (2009)

  13. COBRA - Pixel Idea: Massive background reduction by particle identification Alpha 200 μm pixel simulation For example Bi-214 : Time coincidence of both Electron 3 MeV Space and timecoincidences possible 200 μm pixel simulation Cape Town, 3.2.2011

  14. COBRA – Pixel CZT World largest CZT detector = 36 gramscollaboration with Zhong He (Univ. of Michigan) 20x20x5 mm3 systems8x8 pixels (running at LNGS Jan. –May 2010) 32x32 pixel system 100x100 pixel system Timepix system: 14x14x0.3 mm3 Si ( 2 systems) 14x14x1 mm3 CdTe (2 systems) 256x256 systems128x128 systems 20x20x15 mm3 11x11 pixel system Up to 40 slices in z by pulse information Running at LNGS from Sep. 2009-Jan. 2010 One Si-system running in Felsenkeller Labsince Sep. 2009, one running at LNGSMay-Aug 2010, before in Modane Cape Town, 3.2.2011 Cape Town, 3.2.2011

  15. Polaris system (U Mich) preliminary Latest development on CZT 36 gram detector, 6 times larger than current COBRA detectors

  16. Polarissystem Together with University of Michigan (group Zhong He) The power of pixels! Running at LNGS from Sep. 2009-Jan. 2010 Cape Town, 3.2.2011

  17. Polarissystem 116Cd peakregion No survivor after 125 days of data taking!!! Corresponds to a background between 2700-3000 keV of 0.9 counts/keV/kg/yr Detector not tuned for low background, no z-analysis Cape Town, 3.2.2011

  18. 55 μm pixel Si Timepix device Timepix It reacts on environment, ie. not completely dominated by internalbackground

  19. A nicemuon A nice muon...

  20. Timepix 256x256 pixels, 55mm Alphas Muons Electrons Particle identification as background reduction tool works!

  21. Picture show NO event in 117.5 days in energy range between 2.7 and 3 MeV which looks like 1(2) electrons

  22. COBRA - Pixel Idea: Massive background reduction by particle identification Alpha 200 μm pixel simulation Bi-214 = Time coincidence of both Electron 3 MeV 55 μm pixel real event alpha electron alpha electron 200 μm pixel simulation

  23. COBRA Upgrade 2010/11 Upgrade to 64 CZT 1 cm3 detectors, about 0.42 kg (all detectors at hand) Single grid readout , i.e. pulse shaping (done end of Aug. 2010) Improved shielding , readout (new DAQ) , material selection Active veto (CsI), strongly enhances physics potential Aim : Background below 1 count/keV/kg/yr for CPGs Good news: Got a new location at LNGS (former HdM building) Running CZT in LSci Produce enriched CZT detectors Running larger scale Polaris and pixel systems

  24. Pulse shapes - I J. McGrath et al. , NIM A 615,57 (2010) Much more information in pulse shape 60Co pulse CPG detector works like a Frisch grid in wire chambersP. Luke , IEEE Trans. NS 42, 207 (1995) Single site event Multiple site event Experiment TCAD simulation Modification of preamps necessary... DoneFirst new preamps and 16 FADCs installed at LNGS

  25. Pulse shapes - II 8 detectors FADC readout About 1 kg*d 116Peak position

  26. COBRA Upgrade Aim : Improve excited state and positron decay sensitivity by factor 10-30 128Te 1st excited state 116Cd 1st excited state Done for : NaI, CsI , BGO, CdWO4 Exploring various readout concepts Note: Can tolerate some impuritiesbecause of coincidencerequirement

  27. Material screening chain Dortmund Low Background Facility): Factor of 1000 reduction with respect to unshielded 1 2 3

  28. Bare crystals in LScintillator I

  29. Bare crystals in Lscintillator II

  30. Crystal growing done within the collaboration Crystal growing Preparation for growing enriched crystal/detector

  31. King Cobra Measurement of less than 50 meV neutrino mass would require about 420 kgof CZT, isotopically enriched in Cd-116 Shielding (+ pixel) must be able to reduce background to less than 10-3 events /kg/keV/yr Plan is to have TDR by end of 2012

  32. Conclusion COBRA is a promising next generation experiment to explore double beta decay of Cd-116. First scientific results have been obtained , major upgrades ongoing/planned this year Unique option would be the semiconductor tracker (solid-state TPC)in form of a pixel CZT, first measurements are very promising  The plan is to have a proposal for the large scale experiment ready by end of 2012 IWORID2010

  33. This is the 50 meV option, just add 0‘s to moles and kgs if you want smaller neutrino masses Back of the envelope T1/2 = ln2 • a•NA• M • t / N (tT) ( Background free) For 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, ...

  34. Why more than 1 isotope? - I 2012-13: Imagine GERDA is seeing a clear peak -> Is it really double beta decay or something Ge-specific? Imagine GERDA is NOT seeing a peak -> GERDA/MAJORANA 1 tonne experiment -> more promising isotopes (K. Zuber, ECFA workshop „European Strategy for future neutrino physics“, CERN, Okt. 1-3, 2009, arXiv:1002.4313)

  35. Why more than 1 isotope? - II Uncertainties in nuclear matrix elements („conversion factor“) Observation in one isotope results in „predicted ranges“ for others T.R. Rodriguez, G. Martinez-Pinedo, PRL 2010

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