MPI für Physik, Fachbeirat, Béla Majorovits The GERDA experiment Béla Majorovits

MPI für Physik, Fachbeirat, Béla Majorovits OUTLINE Motivation: neutrinoless double beta-decay The GERDA experiment: Principles The GERDA collaboration GERDA and GeDet at MPI Physik, München Signature: Sharp peak at Q-value of the decay (2039 keV for 76 Ge)

MPI für Physik, Fachbeirat, Béla Majorovits Δm 32 > 0 eV Δm 32 < 0 eV degeneracy F.Feruglio et al., Nucl. Phys. B 637(2002) 90% CL Inverted hierarchy Normal hierarchy In order to discriminate between normal and inverted hierarchy, we need an experiment with sensitivity down to 10 meV ! Lightest neutrino mass [eV] [eV] Motivation: Neutrinoless Double Beta Decay K.K. Claim Width of bands due to unknown CP phases Unknowns about Neutrinos: Nature of the Neutrino (Dirac - Majorana?) Absolute mass scale? Mass hierarchy?

MPI für Physik, Fachbeirat, Béla Majorovits 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

MPI für Physik, Fachbeirat, Béla Majorovits The GERDA collaboration Belgium: IMMR, Geel Germany: MPIK, Heidelberg Univ. Köln MPI, München Univ. Tübingen Italy: INFN LNGS, Assergi Univ. di Milano e INFN Univ. di Padova e INFN Poland: Jagiellonian University, Krakow Russia: INR, Moscow JINR Dubna ITEP Physics, Moscow Kurchatov Institute, Moscow Approved since 2004 Lock Phase II detectors Clean room Suspension

MPI für Physik, Fachbeirat, Béla Majorovits The GERDA collaboration

MPI für Physik, Fachbeirat, Béla Majorovits GERDA and GeDet at MPI für Physik Director Project Scientists Post-Docs Allen Caldwell Infrastructure on tank, Phase II detectors HPGe detector development for GERDA Phase II and beyond B. MajorovitsI. Abt X. Liu, J. Schubert PhD Students M.Jelen, K. Kroeninger, D. Lenz, J. Liu GERDAGeDet

MPI für Physik, Fachbeirat, Béla Majorovits GERDA Infrastructure on top of tank Main challenges met: Severe space constraints due to location in tunnel. Inside the tank we have overpressure. But due to radiopurity requirements we have UHV specifications! (Roughly Rn nuclei allowed in cryo volume at a time). All materials used inside the lock need to be of controlled radiopurity --> Very limited choice of materials. 10 m 13 m 15.4 m Lock with complex detector transfer system. Signal and HV cables Strain relief Towards feed- throughs Pulley Cable winch

MPI für Physik, Fachbeirat, Béla Majorovits SourceEst. Bkg * (MC) [10 -4 Counts/(kg keV y)] Means of bkg reduction Holder, suspension, cabling, electronics (first shot design) 21Minimize materials Screening and cleaning Infrastructure4Segmentation of detectors Pulse shape analysis Cosmogenics in Ge ( 60 Co, 68 Ge, etc.) 5Store underground, in case of 68 Ge: wait Neutrons from GS rock and muon induced 23800mwe at LNGS, Active muon veto Water buffer TOTAL32--> Further R&D MaGe Monte Carlo Activities Detailed Monte Carlo campaign of the GERDA design: Each piece of the setup has been simulated: Joint Majorana-Gerda Monte Carlo Initiative: MaGe based on GEANT 4 Common framework for Majorana and GERDA collaborations MaGe activities: Feb. 2007: Joint MPP (23 participants from GERDA and Majorana collaborations). Regular tel. Conferences with GERDA and Majorana members. MaGe framework has been utilized to perform a detailed Monte Carlo calculation of the GERDA setup. Contribution to bkg from copper on Kapton cable

MPI für Physik, Fachbeirat, Béla Majorovits 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

MPI für Physik, Fachbeirat, Béla Majorovits 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

MPI für Physik, Fachbeirat, Béla Majorovits 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

MPI für Physik, Fachbeirat, Béla Majorovits Phase II Deliverables 1. Enrichment2. Purification3. Crystal growing4. Detector Fabrication  ECP,RussiaGermanyi, Russia isotopic dilution, low yield. asdasfsadf asdas PPM, Germany 20% World supply High yield promised. Test with depleted Ge in April UMICORE: Delivery of few dets until 2008? IKZ,Berlin R&D Contract signed. Test crystals in Canberra-France 37,5 kg enr Ge delivered Few detectors in 2008, Rest ? Prototype delivered 2006

MPI für Physik, Fachbeirat, Béla Majorovits 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) GERDA III K.K. Claim GERDA I,II Different M.E. GERDA sensitivity

MPI für Physik, Fachbeirat, Béla Majorovits

MPI für Physik, Fachbeirat, Béla Majorovits Neutrinoless double beta-decay is a key issue in modern physics MPI Physik is taking a lead role in the GERDA experiment GeDet is developing HPGe detectors for GERDA phase II and beyond Phase II detector development accomplished Infrastructure on top of the GERDA tank well on its way GERDA is well positioned to deliver important data Conclusions