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GERDA @ LNGS (GERmanium Detector Assembly

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Background discrimination techniques. Anti-coincidence between different detectors in the setup ... Germanium Test Bench (LArGe-TB) Vol. 1.3 m3. Height 3.6 ... – PowerPoint PPT presentation

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Title: GERDA @ LNGS (GERmanium Detector Assembly


1
GERDA _at_ LNGS(GERmanium Detector Assembly
  • Stefan Schönert
  • MPIK Heidelberg
  • NOW 2004, Sept. 12, 2004

2
Physics goals
Primary Objective
0??? (A,Z) ? (A,Z2) 2e-
(decay generated by (V-A) cc-interaction via
exchange of three Majorana neutrinos)
mee ?i Uei ² mi
Effective neutrino mass
  • Majorana nature, Mass scale, Majorana CP phases

Method
Operation of HP Ge-diodes enriched in 76Ge in
(optional active) cryogenic fluid shield. Line
search at Qßß 2039 keV
3
Range of mee derived from oscillation experiments
?mee f(m1, ?m²sol, ?m²atm, ?12 , ?13, ?-?)
Sensitivity of this project
F.Feruglio, A. Strumia, F. Vissani, NPB 659
4
Status of GERDA
  • Proto-collaboration formed in Feb. 2004
  • LoI discussed at LNGS April 2004
  • Formal collaboration forming completed Sep. 9/10
    (incl. MoU, etc.)
  • Proposal submission to LNGS SC Sep. 17
  • Discussion with LNGS SC Oct. 14-16
  • Funding
  • Kurchatov, INR, ITEP (in-kind contribution of
    Ge-76 diodes)
  • MPG (MPIK Heidelberg MPI Munich) approved
  • INFN (LNGS, Milano, Padova) discussion Sep. 04
  • BMBF (Tuebingen) call for proposal issued

5
Collaboration
  • INFN LNGS, Assergi, Italy
  • JINR, Dubna, Russia
  • MPI für Kernphysik, Heidelberg, Germany
  • Univ. Cracow, Poland
  • Institut für Kernphysik, Univ. Köln, Germany
  • Univ. di Milano Bicocca e INFN Milano, Milano,
    Italy
  • INR, Moscow, Russia
  • ITEP, Moscow, Russia
  • Kurchatov Institute, Moscow, Russia
  • MPI für Physik, München, Germany
  • INFN and Univ., Padova, Italy
  • Physikalisches Institut, Univ. Tübingen, Germany

6
The experimental concept
  • Reduction of backgrounds (bgds) key to
    sensitivity
  • Lifetime limit
  • w/o backgrounds t1/2 ? (MT)
  • with backgrounds t1/2 ? (MT)1/2
  • Bgds in HdM IGEX dominated by external
    activities in the shielding and cladding
    materials
  • Operation of bare Ge diodes in LN2 / LAr shield
    (Heusser, Ann, Rev. Nucl. Part. Sci. 45 (1995)
    543) other proposals based on this idea GENIUS
    (H.V. Klapdor-Kleingrothaus et. al.,
    hep-ph/9910205 (1999)) GEM (Y.G. Zdesenko et
    al., J. Phys. G27 (2001))
  • Shielding against external bgds by high-purity
    cryogenic fluid shield. Optional active
    anticoincidence with scintillation light from LAr

? Goal background free!
7
Phases of the experiment and physics reach
  • Phase I implementation of existing Ge-76 diodes
    (20 kg) of HdM and IGEX in new experiment
    (background free)
  • operation in LN2/LAr with external background
    lt10-3 / keV kg y
  • gt15 kg y (free of background) scrutinize claim
    (97.8 excl. or 5 sigma confirmation)
  • Sensitivity 31025 y, 0.24-0.77 eV
  • Phase II enlarge to 35-40 kg (segmented
    detectors, possibly LAr scintillation readout )
  • within 2-3 years 100 kg y
  • Sensitivity 21026 y, 0.09-0.29 eV
  • Phase III (depending on physics results of Phase
    III and on the understanding of backgrounds)
  • world-wide collaboration 500 kg

8
External shield design
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15
Design Considerationscosmogenic Co-60 in
Ge-diodes
Qßß
  • T0 for cosmic ray exposure completion of
    mono-zone refinement
  • Exposure to cosmic rays above ground for 10 days
    0.17 ?Bq/kg Avignone 92
  • ?0.9 10-3 / keV kg y
  • Kurchatov crystals 5 10-3 / (keV kg y) in 2006

16
Background discrimination techniques
  • Anti-coincidence between different detectors in
    the setup
  • Pulse shape analysis (PSA)
  • Coincidences in the decay chain (Ge-68)
  • Segmentation of one of the readout electrodes
  • Scintillation light detection (LAr)

17
Bgd. summary (Phase II)
18
LAr scintillation readout example 60Co
  • Cosmogenic activities
  • Production after completion of crystal growth
  • Exposure to cosmic rays above ground for 10 days
    0.9 10-3 /(kg keV y)

19
60Co no vs. active suppression
20
Ongoing RD programBare Ge-diode in LAr
simultaneous readout of scintillation light
Wavelength- shifter (WLS)
VM2000 Reflector/WLS foil
54Mn source (E?835 keV)
Ge crystal
Nylon fixture
r10 cm
21
Liquid Argon Germanium Test Bench (LArGe-TB)
Vol. 1.3 m3 Height 3.6 m Diam. 2.5 m Refurbish
of LENS LBF
22
Schedule(provided approval, funding LNGS
refurbishments completed timely)
  • Start construction of infrastructure in 2005
  • Detector commissioning and start physics data
    taking (Phase-I) 2006
  • Procurement of new enriched material 2004/5
  • Start of Phase-II could start early and overlap
    with Phase-I (funding permitted)
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