Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 1...
-
Upload
julianna-harris -
Category
Documents
-
view
223 -
download
0
Transcript of Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 1...
Béla Majorovits for the GERDA collaboration
1ICHEP 2012, Melbourne, Australia, July 4-11 2012
Béla Majorovits for the GERDA collaboration
Status and plans with the GERDA experiment to probe the nature of neutrinos
Max-Planck-Institut für Physik, München, Germany
O U T L I N E
• 0νββ decay as a probe for neutrino mass and neutrino nature
• The GERDA experiment: Design and construction
• First results with enriched detectors
• Status and plans for phase II: new detectors
~100 physicists 19 Institutes 7 Countries
Béla Majorovits for the GERDA collaboration
2ICHEP 2012, Melbourne, Australia, July 4-11 2012
Neutrino oscillation experiments:Neutrinos have non vanishing rest mass!
invertednormal orhierarchy ?
what is the absolute mass scale?
The quest for the mass of neutrinos
Béla Majorovits for the GERDA collaboration
3ICHEP 2012, Melbourne, Australia, July 4-11 2012
DIRAC: ν=ν Majorana: ν=ν
Neutrinos could be their own anti-particles:
The quest for the nature of neutrinos
Béla Majorovits for the GERDA collaboration
4ICHEP 2012, Melbourne, Australia, July 4-11 2012
DIRAC: ν=ν Majorana: ν=ν
Massive Majorana neutrinos could be responsible for the Baryon asymmetry in the universe (via leptogenesis)
Neutrinos could be their own anti-particles:
The quest for the nature of neutrinos
Béla Majorovits for the GERDA collaboration
5ICHEP 2012, Melbourne, Australia, July 4-11 2012
• Neutrino is a Majorana particle
• Helicity flip can occur in the vertex
1/ = G(Q5,Z) |Mnucl|2 <mee>2
0νββ decay-rate
Phase space-factor
Matrix element
Effective Majorana Neutrino mass
Neutrinoless mode of double beta decay only possible if:
0νββ decay:
n
n
p
pW-
e-
e-
W-
n
n
p
pW-
e-
e-
W-
νe
νe νe= νe νl νr
Lepton flavor
violating: ΔL=2
Effective Majorana neutrino mass contributes to 0νββ decay rate:
2νββ decay:2nd order weak
standard modell
process
Neutrinoless double beta decay
Béla Majorovits for the GERDA collaboration
6ICHEP 2012, Melbourne, Australia, July 4-11 2012
Signature: Sharp peak at Q-value of the decay
2 neutrinos escape the detector undetected: continuous spectrum
Total energy of decay is deposited
within detector:
sharp peak
Peak height not to scale!
Non vanishing CP
violating Majorana
phases βi can supress
<mee> even to zero!
Effective Majorana neutrino mass:
<mee> = |Σ|Uei|2eiβimi|
Neutrinoless double beta decay
Béla Majorovits for the GERDA collaboration
7ICHEP 2012, Melbourne, Australia, July 4-11 2012 Béla Majorovits 7
Mass of lightest neutrino [eV]
Eff
ecti
ve M
ajor
ana
neut
rion
mas
s [e
V] 1
10-1
10-2
10-3
10-4
10-4 10-3 10-2 10-1 10-4
Bilenky and Giunti arxiv:1203.5250
0νββ decay as a probe for neutrino mass and neutrino nature
Observation of 0νββ decay:
• Neutrino must have Majorana nature!
• Determination of absolute mass scale
• Mass hierarchy of Neutrinos
• Information on CP violating phases?
CP violating Majorana phases could be responsible
for Baryogenesis via Leptogenesis
Béla Majorovits for the GERDA collaboration
8ICHEP 2012, Melbourne, Australia, July 4-11 2012
Source = 76Ge = Detector High signal detection efficiency
Detector material very pure (zone refinement, Czochralski growth)
Very low intrinsic internal background
Very good energy resolution Background due to 2νββ decay negligible
Considerable experience Industrial production, improvements possible
Natural abundance of 76Ge 7,83% Enrichment necessary
The quest for the mass of neutrinos
Béla Majorovits for the GERDA collaboration
9ICHEP 2012, Melbourne, Australia, July 4-11 2012
Location: Hall A of LNGS, Assergi, Italy3500 mwe
9
Phase I: Use HdM and IGEX detectors
Phase II: Convert 37.5 kg of enriched germanium (87% 76Ge) into detectors
GERDA : design and construction
Béla Majorovits for the GERDA collaboration
10ICHEP 2012, Melbourne, Australia, July 4-11 2012
Clean room
Water tankwith HP waterand -veto
Detector array
Lock system
HP liquid Ar
Cryostat with internal Cu shield
10
GERDA : design and construction
Béla Majorovits for the GERDA collaboration
11ICHEP 2012, Melbourne, Australia, July 4-11 2012
phase I Detectors (from HdM and IGEX) after dismounting from cryostats:
ANG2: 2833g ANG3: 2391g ANG4: 2372g
ANG5: 2746g RG1: 2110g RG2: 2166g
Tot
al m
ass:
14.
63 k
gGERDA : design and construction
Detectors ANG1 and
RG3 started drawing leakage
current after installation
Béla Majorovits for the GERDA collaboration
12ICHEP 2012, Melbourne, Australia, July 4-11 2012
Full phase I infrastructure for deployment of 12 detectors (all HdM and IGEX plus reference detectors) completed in May 2011
GERDA : design and construction
Béla Majorovits for the GERDA collaboration
13ICHEP 2012, Melbourne, Australia, July 4-11 2012
GTF 112
ANG 2
ANG 1
ANG 3
ANG 5
RG 3
ANG 4
RG 1
RG 2
Installation of phase I detectors :
GERDA : Status of phase I
Béla Majorovits for the GERDA collaboration
14ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA phase I of started on 1.11.11 !
Data in Energy RoI is blinded since
9th of Jan. 2012
Installation of phase I detectors :
GERDA : Status of phase I
Béla Majorovits for the GERDA collaboration
15ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status of phase I
Energy calibration of all detectors:
AN
G1 and R
G3 are N
OT
includ
ed
Béla Majorovits for the GERDA collaboration
16ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status of phase I Live time: 152.49 days
Enriched exposure: 6.104 kg∙yDuty cycle Nov. 2011 – May 2012: 78.3%
Béla Majorovits for the GERDA collaboration
17ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status of phase I
PRELIMINARY
Béla Majorovits for the GERDA collaboration
18ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status of phase I Background data for enriched detectors (red) and control
detectors with natural germanium abundance (blue):
Background index in energy RoI for enriched detectors: (2.0+0.6
-0.4) ∙ 10-2 cts/(kg yr keV)
Béla Majorovits for the GERDA collaboration
19ICHEP 2012, Melbourne, Australia, July 4-11 2012
Very pronounced structures for individual energy deposits
Improved multi site recognition efficiency by A/E parameter
BEGe for improved background recognition
we
igh
ing
po
ten
tial
e− h+
D. Budjas et al., JINST 4 P10007 (2009)
GERDA : Status and plans for phase II
curr
en
t
single site event: SSE
time [ns]
multi siteevent: MSE
curr
en
t
time [ns]
Background like event:
Signal like event:
Béla Majorovits for the GERDA collaboration
20ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status and plans for phase II
5 working HPenrGe detectors available at LNGS
Transports in shielded
container, storage
underground
The voyage of the enriched germanium
Béla Majorovits for the GERDA collaboration
21ICHEP 2012, Melbourne, Australia, July 4-11 2012
Signal: Background:
To light detector
Liquid Argon
128nm scintillation light
Background rejection by detection of LAr scintillation light
GERDA : Status and plans for phase II
Béla Majorovits for the GERDA collaboration
22ICHEP 2012, Melbourne, Australia, July 4-11 2012
Background rejection by detection of LAr scintillation light
GERDA : Status and plans for phase II
Two solutions (supported by MC with light tracking):
SiPMs connected to fibres Low background PMTssimulations show: reduction of background to 0.001 cts/(kg yr kev) realistic
Béla Majorovits for the GERDA collaboration
23ICHEP 2012, Melbourne, Australia, July 4-11 2012
Background rejection by detection of LAr scintillation lightGERDA : Status and plans for phase II
Béla Majorovits for the GERDA collaboration
24ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status and plans for phase II
Béla Majorovits for the GERDA collaboration
25ICHEP 2012, Melbourne, Australia, July 4-11 2012
Conclusions:• Observation of 0νββ decay would have far
reaching consequences
• GERDA phase I started on 1.11.11
• Design sensitivity of phase I nearly reached
• Observed 2νββ decay with unprecedented signal to noise ratio
• PSA on BEGe detectors and LAr instrumentation will reduce phase II background by order of magnitude
• First phase II BEenrGe detector crystals available at LNGS
Béla Majorovits for the GERDA collaboration
26ICHEP 2012, Melbourne, Australia, July 4-11 2012
BACKUP
Béla Majorovits for the GERDA collaboration
27ICHEP 2012, Melbourne, Australia, July 4-11 2012
EXO
Béla Majorovits for the GERDA collaboration
28ICHEP 2012, Melbourne, Australia, July 4-11 2012
Béla Majorovits for the GERDA collaboration
29ICHEP 2012, Melbourne, Australia, July 4-11 2012
GERDA : Status and plans for phase II
Uncertainty of EXO 200 90% exclusion limit on 76Ge
due different to matrix element calculations
Béla Majorovits for the GERDA collaboration
30ICHEP 2012, Melbourne, Australia, July 4-11 2012
Plans for phase II: new detectorsBackground recognition powers of BEGes
standard
signals
n+
p+
n+ surface slow
pulses
Data taken with 90Y β-source n+ surface events
Identify surface events:
Low E-fields in “partially” dead layer
Slow pulses
Decrease A/E parameter
90Y source
n+ surfacepulse: NSP
curr
en
t
time [ns]
Béla Majorovits for the GERDA collaboration
31ICHEP 2012, Melbourne, Australia, July 4-11 2012
amplified current amplitude A
PCP
MSE
SSE band
BEGe
Plans for phase II: new detectorsBackground recognition powers of BEGes
p+
At p+ contact also e- are “visible”
Amax/E is increased
D. Budjas et al., JINST 4 P10007 (2009)
M. Agostini et al., JINST 6P03005 (2011)
228Th source
γ