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GERDA Neutrinoless Double Beta Decay

GERDA Neutrinoless Double Beta Decay. Ludwig Niedermeier, Universität Tübingen NPAE Kiev, 1.6.2006. _. _. _.  r.  r.  r. _.  = . Neutrinoless Double Beta Decay. 2  2  decay. 2  0  decay. n. p. n. p. W -. W -. e -. e -. e -.  l. e -. W -. W -. n. p.

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GERDA Neutrinoless Double Beta Decay

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  1. GERDA Neutrinoless Double Beta Decay Ludwig Niedermeier, Universität Tübingen NPAE Kiev, 1.6.2006

  2. _ _ _ r r r _  =  Neutrinoless Double Beta Decay 22 decay 20 decay n p n p W- W- e- e- e- l e- W- W- n p n p 20 conditions: Majorana particle r↔l helicity flip~(1-(v/c)2) for m>0 E (e–+e–) in keV

  3. From Decay to Neutrino Mass • Exp. determination of 20 half life with 76Ge=> Effective neutrino mass: determination / limit N Number of Ge atomsS 20 signalB Background signalsb Bgr. rate (kg s keV)-1m Ge massM Ge mol. weighta 76Ge enrichment Detection efficiencyE Energy binningt Measurement time

  4. Impact on Neutrino Physics GERDA I Hd-Moscow GERDA II GERDA III (???) Current status: m²12 ≈ 8·10-5 eV² (solar ) m²23 ≈ 2·10-3 eV² (atm. )normal hierarchy or inverse hierarchy ? (inverse) (normal) 3 1 m12 2 m23 m23 2 m in eV m12 3 1 ↔mee absolute mass scale

  5. The Heidelberg-Moscow-Experiment 76Ge Best fit:T2β0= 1.2·1025 y [Klapdor-K. et al, Phys.Lett. B586(2004)198] A.M. Bakalyarov, A. Ya. Balysh, S. T. Belyaev, V. I. Lebedev, S. V. Zhukov (Kurchatov Institute, Moscow): T1/2(2β0ν) >1.55 · 1025 y (90% C.L.) [Письма в ЭЧАЯ. 2005. T.2, No.2(125). C.21-28]

  6. Gerda – Detector Overview Gran Sasso laboratory3600 mwe Water shielding Cherenkov muon veto LN2 or LAr shield 76Ge crystals

  7. Gerda - Motivation – Check of Hd-Moscow publications– Further improvement of mee sensitivity Reduce background by ultra-pure shielding material LAr or LN2surrounding Ge crystals 0.17→~10-3(kg·y·keV)-1 Hd-Moscow GERDA

  8. 1.2 · 1025 Gerda – Development Phase I 5 crystals of HD-Moscow, 3 of IGEX m76Ge = 18kg t ≤ 1a Background requirement: 10-2 (keV kg y)-1 Phase II Additional crystal insertion m76Ge=37.5kg (a>86%) t = 3a Background requirement: 10-3 (keV kg y)-1 Phase III (?) World-wide collaboration (contact with MAJORANA) m76Ge ~ 500kg Background requirement: 10-4 (keV kg y)-1 Results!

  9. Gerda – Background (97% veto)(30d exposure) anti-coincidencepulse-shapedecay chain coinci- dence for 68Ge anti-coincidence with crystal segmentation Required background level (phase I): 10-2 (keV kg y)-1(phase II): 10-3 (keV kg y)-1 Compare Hd-Moscow 0.17 (keV kg y)-1

  10. Gerda – Ge Crystals Phase II – ≈20 crystals 1 crystal – 18 segments

  11. Gerda Muon Veto – A Water Cherenkov Detector plastic scintillator photomultiplier cryo tank + 3.wall Ge crystals water tank reflector VM2000 ‚lower pillbox‘

  12. The LArGe Facility as Test Bench Pb shielding Cu shielding Cryostat (1.3m³) Test bench at LNGS for refurbished Ge detectors and Liquid Argon solution LAr LN2 better  shield better n shieldscintillation veto less scattered n no 39Ar contam.TEST! easier handling

  13. Gerda – Schedule Construction Phase IPhase II Phase III • Ge refurbishment/testing in LArGe • Start of construction in fall 2006 • Construction of cryo tank (→ stainless steel) • Construction of water tank • Insertion of muon veto • Insertion of first Ge crystals in Gerda (Phase I) • Towards Phase II: Insertion of more crystals (37.5kg of enriched 76Ge already produced) • Final detector filling • Data taking (3 years) • Phase III (?)

  14. Gerda – Conclusion • Test of the Klapdor-Kleingrothaus et al. publication result • Aim to mee determination • Phase I: mee → 0.3 eV • Phase II: mee → 0.1 eV • Phase III could check inverse hierarchy

  15. Gerda – Collaboration • INFN Laboratori Nazionali del Gran Sasso, Assergi, Italy • Joint Institute for Nuclear Research, Dubna, Russia • Max-Planck-Institut für Kernphysik, Heidelberg, Germany • Jagellonian University, Krakow, Poland • Università di Milano Bicocca e INFN Milano, Milano, Italy • Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia • Institute for Theoretical and Experimental Physics, Moscow, Russia • Russian Research Center Kurchatov Institute, Moscow, Russia • Max-Planck-Institut für Physik, München, Germany • Dipartimento di Fisica dell’Università di Padova e INFN Padova, Padova, Italy • Physikalisches Institut, Universität Tübingen, Germany • EC-JRC-IRMM, Geel, Belgium

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