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December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 The Germanium Detector Array (GERDA) for the search.

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Presentation on theme: "December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 The Germanium Detector Array (GERDA) for the search."— Presentation transcript:

1 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 The Germanium Detector Array (GERDA) for the search of neutrinoless double Beta Decay Neutrinos and the Neutrinoless Double Beta-Decay Present Experimental Status Principles of the GERDA Experiment Status and Prospects of GERDA

2 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Neutrinos in the Universe Neutrinos are nearly as abundant in our universe as photons! Even a small rest mass has large cosmological influence! Most prominent Neutrino sources: Relic from Big Bang: 100 per cm3 Neutrinos from the sun at earth: cm2s-1 Neutrinos from 1GW nuclear reactors: cm2s;1 in 100m Supernova Neutrinos;Up to 1059 emitted within 10s

3 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Neutrino-oscillation experiments have taught us: Neutrinos must have a non vanishing rest mass! Neutrino Mass Hierarchy Normal hierarchy Δm 32 > 0 eV Inverted hierarchy Δm 32 < 0 eV But we do not know the sign of Δm 32 Mass hierarchy is still unknown We only have information on the squared mass difference between the eigenstates Absolute mass scale still unknown Are Neutrinos their own Antiparticles, ie Majorana particles? Nature of the Neutrinos still unknow

4 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Signature: Sharp peak at Q-value of the decay Neutrinoless Double Beta-Decay Double Beta-Decay is an allowed 2 nd order weak process Its half life is of the order times the age of the universe If Neutrinos are massive and their own anti-particles, ie Majorana particles, the process could occur without the emission of Neutrinos 1/ = G(Q,Z) |M nucl | 2 2

5 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Δm 32 > 0 eV Δm 32 < 0 eV degeneracy F.Feruglio et al., Nucl. Phys. B 637(2002) 90% CL In order to discriminate between normal and inverted hierarchy, we need an experiment with sensitivity down to 10 meV ! Lightest neutrino mass [eV] [eV] K.K. Claim Neutrinoless Double Beta-Decay and the Mass Hierarchy

6 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Present Experimental Status ExperimentUnderground Laboratory IsotopeT 1/2 [10 21 y] [eV] Elegant VIOto (Japan) 48 Ca> 95< Heidelberg- Moscow Gran Sasso (Italy) 76 Ge>19000 evidence: < IGEXCanfranc (Italy) 76 Ge> 16000< NEMO-IIIFrejus (France) 82 Se> 140< NEMO-III 100 Mo> 460< CdWO 4 scintillator Solotvina (Ukrain) 116 Cd> 170< CuoricinoGran Sasso 130 Te> 1800< DAMAGran Sasso 136 Xe> 1200< 2.9

7 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week kg of enriched Ge detectors 71.7 kg yrs of data Upper limit: T 1/2 1.9 * years (90% C.L.) 4.2 σ claim: T 1/2 = 1.19 * years = 440 meV (KK matrix el.) Evidence for Neutrinoless Double Beta-Decay HPGe-detectors, enriched in 76 Ge in conventional low background copper cryostat. Data taking: The Heidelberg - Moscow Experimet:

8 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 The principle idea of the GERDA experiment: Use the cryo-liquid as cooling medium and shield simultaneously: GERmanium Detector Array: GERDA Increase sensitivity in order to confirm or refute the claim --> Reduce bkg-index by at least two orders of magnitude to Cts/(kg keV year) --> Increase target mass G. Heusser, Ann. Rev. Nucl. Part. Sci. 45(1995)543 --> Radioactive background can be drastically reduced - LN and LAr can be produced with very high purity - Materiel of conventional cryostat is removed from detector surrounding

9 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Germanium detectors Water / Myon-Veto (Č) Clean room / lock Steel-tank + Cu lining Liquid argon GERmanium Detector Array: GERDA Place array of naked HPGe-detectors enriched in 76 Ge in the center of a stainless steel cryostat filled with LAr. Inner copper lining as radiation shield against gammas from cryostat. Surround the whole setup with water tank to shield against external gammas, neutrons and muons (water Cerenkov). 10 m

10 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 GERmanium Detector Array: GERDA Phase IPhase II Target mass of enriched material [kg] 18 kg from Hd- Mo and IGEX detectors Additional 20 kg Envisioned background [Counts/(kg keV y)] 0.01 (limited by cosmogenic 60 Co) (improvement by segmentation and further material selections) Exposure15 kg y100 kg y Confirm or refute claim Push sensitivity, prove low background capability of technique Discov. potential: T 1/ yrs, Limit setting: to yrs. For Rodin et al. matrix element, mass sensitivity about 200 meV

11 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Heidelberg-Moscow detectors IGEX detectors Phase I Detectors: Acquired HdMo and IGEX detectors Constructed detector holder out of low level materials Dismounting of detectors from cryostats without problem Prototype (nat.) detector works well in LAr Detectors being refurbrished by Canberra

12 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Germanium detectors can be segmented --> Background identification through identification of multiply Compton-scattered photons by coincidences Signal: Background: PhaseII detectors: Segmentation Phase II detectors will be 18 fold segmented: 3-fold in height, 6-fold in φ

13 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Phase II: Detector development 18-fold segmented prototype detector works fine. New contacting scheme verified in conventional surrounding: Good energy resolution for core and 18 all segments: MeV --> 0.2% I. Abt. et al, nucl-ex/ , Accepted for publication in NIM A Novel low mass contacting scheme with Cu on Kapton. Material balance: 31g Cu, 7g Teflon, 2.5 g Kapton cable

14 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Phase II: Results with Prototype Compton Background recognition works as expected: Photon Peak is reduced in single segment spectrum, whereas Double Escape Peak remains Suppression factors (SF) as expected from MC All events Single segment events Double Escape Peak (mostly SSE) Photon Peak (mostly MSE) All events Single segment events I. Abt. Et al, nucl-ex/ , Submitted to NIM A

15 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Gran Sasso Underground Laboratory 1400 m rock overburden : ~3500 mwe to shield against cosmic radiation Laboratori Nationale di Fisica Nucleare

16 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Status: Cryostat Production

17 December 4, 2007Béla Majorovits,MPI für Physik, München Excellence Cluster Universe – Science Week 2007 Inverted hierarchy Normal hierarchy Degenerate Lightest neutrino (m 1,m 3 ) in eV m ee in eV 1.We will confirm or rule out the Klapdor-Kleingrothaus et al. claim (Phase I) 2.If not confirmed and background reduction to the level /(kg yr keV) demonstrated (Phase II), go for 3.Phase III (ca. 1 ton, 20 meV level) K.K. Claim GERDA IIIGERDA I,II Different M.E. GERDA sensitivity


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