GERDA, the GERmanium Detector Array for the search of neutrinoless bb decay in 76Ge - PowerPoint PPT Presentation

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GERDA, the GERmanium Detector Array for the search of neutrinoless bb decay in 76Ge

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INFN, Gran Sasso National Laboratories. for the GERDA Collaboration ... Phase III: worldwide new collaboration O(ton) experiment 1027 y Cooperation with Majorana ... – PowerPoint PPT presentation

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Title: GERDA, the GERmanium Detector Array for the search of neutrinoless bb decay in 76Ge


1
GERDA, the GERmanium Detector Array for the
search of neutrinoless bb decay in 76Ge
L. Pandola INFN, Gran Sasso National
Laboratories for the GERDA Collaboration
PANIC Conference, Santa Fe, NM, October 24th 2005
2
Motivations for 0n2b
3
GERDA experiment at Gran Sasso
The GERmanium Detector Array experiment will look
for 0n2b decay in 76Ge using HP-Ge detectors
enriched in 76Ge
GERDA Collaboration
60 physicists 12 institutions
Italy, Germany, Russia
4
What do we look for?
Ge-76 source detector (diode)
5
The current situation
Heidelberg-Moscow at Gran Sasso
5 Ge detectors (m 10.9 kg, a 86) S 71
kg y , B 0.2 c/keV kg y
Positive evidence
(0.69 4.2) 1025 y (3s) (2004)
lt meegt 0.1 0.9 eV
GERDA goal confirm or reject this claim with
high statistical confidence within 1 year
IGEX at Canfranc
3 Ge detectors (m 6 kg, a 86) S 8.8 kg
y , B 0.2 c/keV kg y
Gonzales et al. Nucl. Phys. B (P.S.) 87 (2000)
278
Projects with other isotopes (e.g. 130Te) are
also ongoing
6
Phases and physics reach of Gerda
Our Goal background index 10-3 cts/(keV kg y)
10-3 / (keVkgy)
21026 (90 CL)
10-1 / (keVkgy)
  • Phase I existing detectors of HM IGEX,
    establish background reduction
  • Phase II new detectors
  • Phase III worldwide new collaboration O(ton)
    experiment ? 1027 y Cooperation with Majorana

31025 (90 CL)
H-M bck
Phase-I HdM IGEX
Phase-II HdM IGEX new diodes
KK claim
2007/8
2010
7
... how to reach 10-3 cts/keV kg y?
The background index of 10-3 counts/keVkgy is 2
orders of magnitude smaller than the current
state-of-the-art !
Learn from Borexino!
? 0.06 /cm²s (2.6 MeV ?)
Heusser, Ann, Rev. Nucl. Part. Sci. 45 (1995) 543
5.6 m
Shield against external g operating naked Ge
crystals suspended in high purity liquid N2/Ar lt
0.3 ?Bq 222Rn/m3
10-3 (kg keV y) -1
(same concept of GENIUS and GEM)
LN2, ?0.8 g/cm3
Too large for GS ? graded shielding (water buffer)
8
Gerda baseline design
Clean room lock
Water tank / buffer/ muon veto
Advantages of water
- better shielding than LNitrogen - cheaper -
safer - neutron moderator - Cerenkov medium for
4p muon veto
Vacuum insulated copper vessel
Liquid N/Ar
External background lt 10-3 cnt/(keV kg y) for
LN2, factor 10 smaller for LAr
Ge Array
9
Backgrounds in Gerda
180 days exposure after enrichment 180 days
underground storage
derived from measurements and MC simulations
30 days exposure after crystal growing
For Phase II B ? 10-3 cts/(keV kg y) ?
additional reduction
10
Background reduction techniques
  • Muon Veto
  • Anti-coincidence between detectors
  • Segmentation of readout electrodes (Phase II)
    (6? ? 3z)
  • Pulse shape analysis (Phase III)
  • Coincidence in decay chain (68Ge)
  • Scintillation light detection (LAr option)
  • Wait for decay of isotopes (68Ge)

11
Location of Gerda
Hall A of the Gran Sasso Laboratory, in front of
LVD
12
Outlook and conclusions
The GERDA experiment will search for 76Ge 0n2b
decay at Gran Sasso (Italy) with background level
of 10-3 counts/keV kg y Experiment approved by
LNGS substantial funding from MPI, Russia
(in-kind), INFN, BMBF Start of construction in
2006 detector commissioning/start data taking
2007 Test the result from Klapdor-Kleingrothaus
in 1 year (phase I). Then phase II ? 2 1026
y Co-operation with Majorana (MC, LArGe) very
positive mutual benefit! ? Phase III
13
Phases and physics reach of Gerda
Phase I
Phase II
Phase III
F.Feruglio, A. Strumia, F. Vissani, NPB 659
mee in eV
Lightest neutrino (m1) in eV
To test inverted degenerate hierarchy need
sensitivity lt50 meV
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