Post on 14-Jan-2016
description
GERDA
NeutrinolessDouble Beta
Decay
Ludwig Niedermeier, Universität Tübingen NPAE Kiev, 1.6.2006
20 conditions:
Majorana particle
r↔l helicity flip
~(1-(v/c)2) for m>0
Neutrinoless Double Beta Decay
20 decay
n
n p
p
e-
e-
W-
W-
22 decayn p
n p
e-
e-
W-
W-
l
r
_
r
_
r
_
= _
E (e–+e–) in keV
From Decay to Neutrino Mass
• Exp. determination of 20 half life with 76Ge
=> Effective neutrino mass: determination / limit
00
1/ 22 0
01/ 2 20 2
0
32
1
ln 2ln 2 ln 2 ln 2
1
( , )
S
oee
ee en nn
amN N a mtMTS M b EB bmt E
tt t
with TG E Z m
and m U m effective mass
N Number of Ge atomsS 20 signalB Background signalsb Bgr. rate (kg s keV)-1
m Ge massM Ge mol. weighta 76Ge enrichment Detection efficiencyE Energy binningt Measurement time
(inverse)
(normal)
Impact on Neutrino Physics
Hd-Moscow
GERDA I
GERDA II
GERDA III (???)Current status:
m²12 ≈ 8·10-5 eV² (solar )m²23 ≈ 2·10-3 eV² (atm. )
normal hierarchy or inverse hierarchy ? 3 1
1
2
2
3m12
m23
m12
m23
m in
eV
↔meeabsolute mass scale
The Heidelberg-Moscow-Experiment
[Klapdor-K. et al, Phys.Lett. B586(2004)198]
Best fit:T2β0= 1.2·1025 y
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]
76Ge
Gerda – Detector Overview
Water shielding Cherenkov muon veto
LN2 or LAr shield
76Ge crystals
Gran Sasso laboratory3600 mwe
– Check of Hd-Moscow publications– Further improvement of mee sensitivity
Gerda - MotivationHd-
Mos
cowG
ERDA
Reduce background by ultra-pure shielding material LAr or LN2
surrounding Ge crystals 0.17→~10-3(kg·y·keV)-1
Phase I 5 crystals of HD-Moscow, 3 of IGEXm76Ge = 18kg t ≤ 1aBackground requirement: 10-2 (keV kg y)-1
Phase II Additional crystal insertionm76Ge=37.5kg (a>86%) t = 3aBackground requirement: 10-3 (keV kg y)-1
Phase III (?) World-wide collaboration (contact with MAJORANA)
m76Ge ~ 500kgBackground requirement: 10-4 (keV kg y)-1
1.2 · 1025
Gerda – Development
Results!
Gerda – Background
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
(97% veto)
(30d exposure)
Gerda – Ge Crystals
Phase II – ≈20 crystals
1 crystal – 18 segments
Gerda Muon Veto –A Water Cherenkov
Detector
plastic scintillator
photomultiplier
cryo tank + 3.wall
water tank
reflector VM2000
‚lower pillbox‘
Ge crystals
The LArGe Facility as Test Bench
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
Cryostat (1.3m³)
Cu shielding
Pb shielding
Gerda – Schedule
o Ge refurbishment/testing in LArGeo Start of construction in fall 2006o Construction of cryo tank (→ stainless
steel)o Construction of water tanko Insertion of muon vetoo Insertion of first Ge crystals in Gerda
(Phase I)o Towards Phase II: Insertion of more
crystals (37.5kg of enriched 76Ge already produced)
o Final detector fillingo Data taking (3 years)
o Phase III (?)
Construction
Phase I
Phase II
Phase III
Gerda – Conclusion
Test of the Klapdor-Kleingrothaus et al. publication result
Aim to mee determination
Phase I: mee → 0.3 eVPhase II: mee → 0.1 eVPhase III could check inverse hierarchy
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