S. Blot
TAUP - September 7, 2015
1
Investigating ββ decay
with NEMO-3 and
Summer Blot,SuperNEMO
on behalf of the NEMO-3 and SuperNEMO
experiments
7 September 2015
Outline
Review of double beta decay
Recent results from NEMO-3
Status of SuperNEMO
Summary
2
S. Blot
TAUP - September 7, 2015
2νββ decay
0νββ decay
Occurs if β-decay is forbidden
or highly suppressed (35
isotopes)
nd order weak process in the
 2
Standard Model (SM) (T½ ~101821 yrs)
 Detect 2 electrons with
continuous ΣEΤΟΤ ( νe’s escape
detection)
Arbitrary units

BSM process that violates
ΔL conversation by 2
units
 Can be mediated by:
Light Majorana ν, (V+A)
current, SUSY
 Observed final state
identical to 2νββ

2νββ
0νββ
ΣEe < Qββ
ΣEe = Qββ
S. Blot
TAUP - September 7, 2015
Why search for 0νββ
decay?
Observation
of 0νββ decay would provide first
evidence that lepton number is not conserved (LPV)
Test Dirac vs Majorana nature of the neutrino
If underlying mechanism is light Majorana neutrino
exchange, can determine mass scale of neutrino
(T )
0n -1
1/2
= G0n (Qbb , Z) M 0n h
2
Theoretical
input
2
3
S. Blot
TAUP - September 7, 2015
4
The NEMO-3 experiment
Operated from Feb 2003–Jan
2011
 Modane Underground
Laboratory (LSM)
 Passive detector design
 Source ≠ Detector
 Cylindrical geometry (R,φ,z)
 7 different isotopes
investigated
 Separate tracker-calorimeter
systems
 Ability to reconstruct full
kinematics of final state

S. Blot
TAUP - September 7, 2015
5
The NEMO-3 experiment
y
Central tower
Source
foils
z
z
y
x
φ
R
Operated from Feb 2003–Jan
Inner calo.
2011
wall
Outer
 Modane Underground
calo.
Laboratory (LSM)
wall
 Passive detector design
x
 Source ≠ Detector
Trackin  Cylindrical geometry (R,φ,z)
g
 7 different isotopes
volume investigated
 Separate tracker-calorimeter
systems
 Ability to reconstruct full
kinematics of final state

S. Blot
The NEMO-3
detector
TAUP - September 7, 2015

6
~10 kg of ββ-decay isotopes

100Mo,82Se,130Tl,116Cd,150Nd,96Zr
and 48Ca
 Produced as thin foils 3060mg/cm2
 Typically 2.5 in height, 63-65 mm
 Tracking chamber (both sides
wide
of foil)
6180 Geiger cells (50μm)
operating in gas mixture of 95%
He, 4% alcohol, 1% Ar and 0.1%
H 2O
 Vertex resolution σ
XY~3 mm,in
 Calorimeter (top, bottom,
σZ~10mm

and out)
1940 optical modules
 3” and 5” PMTs coupled to
polystyrene scintillator blocks
 σ ~14-17% (FWHM), σ ~250 ps
E
t

S. Blot
TAUP - September 7, 2015
7
The NEMO-3 experiment – ββ-decay
sources
Observation of 0νββ must be confirmed in multiple
isotopes
 NEMO-3 (SuperNEMO) designed with this in mind

S. Blot
8
TAUP - September 7, 2015
The NEMO-3 experiment – Detection
principle
Select events with two

Right-handed Current
1
1
Theoretical
Reconstructed
Events
electrons outgoing from the
foil with common vertex
 Measure all relevant
kinematics to reject
backgrounds and investigate
0νββ topology if observed
Mass mechanism
0.8
Theoretical
Reconstructed
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
-1 -0.8 -0.6 -0.4 -0.2
0
0.2 0.4 0.6
0.8 1
-1
B
Events
Mass mechanism
E1
t1
l1
cosθ
l2
E2
t2
-0.8 -0.6 -0.4 -0.2
0
0.2 0.4
0.6 0.8
1
cosθ between electrons
Right-handed Current
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
2.5
energy difference between electrons (MeV)
3
S. Blot
TAUP - September 7, 2015
Backgrounds

External backgrounds from
neutrons capture, producing high
energy γ-rays


Reduced by tagging α-particles from
214Bi-214Po cascade
Internal background decays


External backgrounds
γ
Radon induced backgrounds


Reduced with 4800m water equivalent
overburden and extensive passive
shielding (wood, iron, borated water)
Internal backgrounds
e.g. Single β-decay + Møller scattering
+ conversion electron
+ γ + Compton scattering
2νββ decay

Irreducible – must measure rate with
Use background
topology to measure
expected rates
γ
9
S. Blot
Background channels

External background channels (top
right) identified by distinct time
sequence of scintillator hits in the
event (ti << tj)
TAUP - September 7, 2015
10
[arxiv:1506.05825]
External
e-γ
Single
e
Single electron channel (bottom
right) provides channel to measure
isotopes which undergo single β-
S. Blot
11
TAUP - September 7, 2015
Latest NEMO-3 Results –
100Mo
Best 0νββ sensitivity in NEMO-3
Phys. Rev D 89, 111101 (2014).
[arxiv:1506.05825]

using 34.7 kgy 100Mo
 No significant excess of data over
expected background in region of
interest:
ETOT = [2.8-3.2] MeV
 Limits derived on T (0νββ) for
½
various
<mprocesses
> < 0.33-0.62 eV
ββ
0νββ Mechanism
<T1/2 x1024y
@90% CL
Physics parameter
Mass mechanism
1.0
mββ < 0.33-0.62 eV
RH current <λ>
0.6
<λ> < (0.9-1.3)x10-6
RH current <η>
1.0
<η> < (1.6-2.4)x10-8
0
-5
S. Blot
TAUP - September 7, 2015
12
Comparison to other isotopes
Most stringent
half-life limit on
0νββ with 100Mo
from NEMO-3
(top)
 Translation into
effective neutrino
mass also shown
(bottom)
 See
[arxiv:1506.05825]
for references to

S. Blot
TAUP - September 7, 2015
13
Other results from NEMO-3
Best results of 2νββ

T½2ν(100Mo)= 7.16 ± 0.01stat ± 0.54syst
Updated results coming soon…
T½ measurements
for all 7 isotopes
investigated
 Best 0νββ decay
limits for many as
well
 See backup slides
for details or
J.Phys.Conf.Series 375
(2012) 042011
S. Blot
TAUP - September 7, 2015
14
Moving towards SuperNEMO
SuperNEMO shares the same detector design principles as
NEMO-3
 Modular in design  first module (of 20 total) is the
demonstrator
82Se and with 2.5y will reach
 Demonstrator will house 7kg of
Feature
NEMO-3
SuperNEMO
sensitivity ofMo<mββ> ~ 0.2 –Se0.4
eV
Isotope
( Ca, Nd)

100
82
Mass
7 kg
100 kg
Radiopurity
A(208Tl) < 20 μBq/kg
A(208Tl) < 2 μBq/kg
(activity)
A(214Bi) < 300 μBq/kg
A(214Bi) < 10 μBq/kg
A(Rn) < 5 mBq/m3
A(Rn) < 0.15 mBq/m3
Efficiency
18%
30%
σE (FWHM@3MeV)
8%
4%
Sensitivity
0ν
T1/2 > 1 x 1024
mββ < 0.3 – 0.8 eV
0ν
48
150
T1/2 > 1 x 1026
mββ < 0.04 – 0.1 eV
*Values in table correspond to the full 20 modules of SuperNEMO
Full SuperNEMO:
mββ~ 0.04-0.1 eV
S. Blot
TAUP - September 7, 2015
15
The SuperNEMO detector

7kg of 82Se per module (150Nd
purification studies ongoing, 48Ca also
possible)
 Thin foils with better radiopurity
208Tl
 Factor of x10 decrease in
contamination and x30 decrease in
214Bi

Calorimeter: two main walls
5” and 8” PMTs coupled to
scintillator block with optimized
geometry
 σ ~ 7.8% (FWHM) for electrons
E
@1MeV

B

Tracking chamber (both sides
of foil)

Wire chamber operating in Geiger
S. Blot
TAUP - September 7, 2015
16
SuperNEMO demonstrator status –
source foils
~25% of source foil
produced for
demonstrator (82Se)
 Radio-purity
measurements
underway using the
dedicated BiPo
detector

Source foil
mounting test
The BiPo detector
S. Blot
TAUP - September 7, 2015
17
SuperNEMO demonstrator status –
tracker
Wiring robot for cell production
First half of tracker complete
 First quarter (aka C0)
commissioned, ready for
shipment to LSM
Populating a C-section



First tracks in C0
98.4% of cells fully operational! (504 total)
Radon tests for C1 underway,
commissioning to follow
Bottom seal plate
S. Blot
TAUP - September 7, 2015
18
SuperNEMO demonstrator status –
calorimeter
Production and testing of
optical modules is well
underway
 Energy resolution meeting
design specifications

Optical module production and testing
S. Blot
TAUP - September 7, 2015
19
SuperNEMO demonstrator status –
radiopurity
All materials screened for radiopurity
with HPGe detectors and radon
emanation chamber
 Radon concentration line to measure
Rn in tracker gas (Target < 0.15
mBq/m3)
 Preliminary measurements of radon in
C-sections are very promising!!

Radon centration line
Radon emanation chamber
S. Blot
TAUP - September 7, 2015
20
SuperNEMO demonstrator status –
software
Many tools already
implemented and
validated
 Event generation and
simulation of detector
components
 Event reconstruction
and particle ID

Improved tracking algorithms
 α –particle ID
 Advanced γ tracking
algorithm

S. Blot
TAUP - September 7, 2015
21
SuperNEMO demonstrator integration
Support frame installed at LSM
C-section ready for transport to LSM
SuperNEMO
Demonstrator
starting to
take shape
Optical module production underway
Commissionin
g by 2016
S. Blot
TAUP - September 7, 2015
22
<mββ> = |m1|Ue1|2 +m2|Ue2|2eiα + m3|Ue3|2eiβ|
Sensitivity of next generation 0νββ
experiments
Current best limit at mββ < 130 - 310 meV
(90% CL)
SNO+,
SuperNEMO,
CURORE< EXO+,
GERDA,
KAMLAND-Zen+
(2017– )
SNO+ ungraded,
nEXO, SuperKamLAND-Zen
Assumes
3 neutrino
mixing model
P. Guzowski et al., Submitted to PRD (2015). arXiv:1504.03600v1 [hep-ex]
S. Blot
TAUP - September 7, 2015
23
Summary
The NEMO-3/SuperNEMO experiments offer a
unique
way to search for 0νββ decay and disentangle
underlying mechanisms
 Analysis of full data set from NEMO-3 is ongoing


Best results with 100Mo yield mββ < 0.33-0.62 eV
82Se, 116Cd 150Nd, 96Zr
Coming
soon:
new
results
from
 Construction of SuperNEMO demonstrator is
and 48Ca
well underway
Many of the most challenging design specifications
have been achieved or are very close to being met
 Commissioning of demonstrator should begin next
year (2016)
 Goal is to reach m
ββ < 0.2-0.4 eV in just 2.5 years of
running
Thank you for your attention!

S. Blot
TAUP - September 7, 2015
BACKUP SLIDES
24
S. Blot
TAUP - September 7, 2015
Dirac vs Majorana
Schechter-Valle theorem
Image from Neutrino Physics Kai Zuber, IoP Publishing 2004
25
S. Blot

DESY seminar 2015
26
Experimental considerations
for
0νββ
Choice of isotope
Large G0ν and M0ν for shorter T1/2
 Large Q
ββ for background rejection
 Large mass of isotope of interest



Enrichment, purification, abundance
GERDA
Detector design
Good energy resolution
 Radio-pure materials
 Active or passive


Choice of location

Experiments underground and protected
by
many layers of passive and active
shielding to protect from cosmic muon
NEMO-3
SuperNEMO
SNO+
S. Blot
DESY seminar 2015
27
NEMO-3 tracker

Wire tracking chamber with 6180 cells operating in
Geiger mode

95% He, 4% alcohol, 1% Ar, 0.1% H2O
Vertex resolution: σXY ~ 3 mm, σZ ~ 10 mm
+  25 G magnetic field for discrimination between e /e

Ground wire
Cathode
ring
Gaps for top/bottom
calorimeter
Single tracker cell
anatomy
Source foil
Anode
4-2-3 layout on each
side of source foil
S. Blot
DESY seminar 2015
Optical module
anatomy
NEMO-3 calorimeter
1940 optical modules
 3” and 5” low-radioactivity
PMTs coupled to large
(10x10x10) scintillator
blocks
 ~15% / √E @ 1 MeV
 Dedicated studies for PMT
monitoring to ensure high
quality modules used in
analysis
28
PMT base
electronics
Magnetic
shielding
Optical fibre
Light-tight
sleeve

Interface
light guide
PMT
Light guide
External wall
of sector
Iron ring
Scintillator
block
Particle entrance
0
50
100 mm
Aluminized
Mylar coating
PMT stability
monitoring
S. Blot
DESY seminar 2015
29
NEMO-3 calibrations
Monthly absolute calibration runs
with 207Bi sources + runs with 90Sr
source for calibrating up to 3 MeV
 Check PMT stability with daily
laser survey (82% of PMTs stable
for entire lifetime of experiment)

207Bi
C.E.
peaks
Laser survey validation
90Sr (90Y)
endpoint
S. Blot
TAUP - September 7, 2015
30
Measuring backgrounds: 214Bi-214Po
cascade
Electronics store Geiger hits
information up to 700μs after
event trigger
214Bi-214Po cascades with
 Tag
one electron and one cluster
of delayed Geiger hits (α)

1e1α event display
214Po
half-life is
164.3μs
arxiv:1506.05825
S. Blot
TAUP - September 7, 2015
31
Measuring backgrounds: Crossing
electrons
+ -
High energy external γ-flux can produce e e pairs
in foil
 Use passive shielding to reject most events (slide
9)
NIM A 606: 449-465, 2009
 Use calo timing information to tag and
characterize external events

Crossing electron
S. Blot
TAUP - September 7, 2015
32
Measuring backgrounds: electron +
gammas
Many internal
background decay to
excited states of their
daughter isotopes
 Tag γ rays emitted
100in
Mo 1e2γ & 1e3γ
de-excitation to
identify these
backgrounds
 Channel selects
one electron and
N scintillator hits
without tracks

arxiv:1506.05825
S. Blot
TAUP - September 7, 2015
33
Results from NEMO-3
Mass
(g)
2νββ T1/2 (x1019 y)
0νββ T1/2
(90% CL)
Reference
82Se
932
9.6 ± 0.1stat ± 1.0syst
> 3.2 x
1023
PhysRevLett 95 (2005)
182302
150Nd
37.0
0.91+0.025-0.022stat ±
0.063syst
> 1.8 x
1022
PhysRevC 80 (2009) 032501
Isotop
e
Nucl.Phys.A847 (2010) 168
9.4 2.35 ± 0.14stat ± 0.16syst
> 9.2 x
21 82Se for full exposure!
New results soon for 150Nd, 48Ca, 116Cd 10
and
96Zr
130
PhysRevLett 107 (2011)
S. Blot
100Mo
TAUP - September 7, 2015
34
0νββ result
Event break-down
 Dominant systematic is
absolute normalization on
0νββ efficiency

Contribution
External
background
N2e events
ETOT = [2.8-3.2]
MeV
Systemati
cs
< 0.2
0νββ
efficiency
214Bi
from radon
5.2 ± 0.5
214Bi
214Bi
internal
1.0 ± 0.1
internal
208Tl
internal
3.3 ± 0.3
208Tl
2νββ
8.45 ± 0.05
Total Expected
18.0 ± 0.6
internal
%
Estimation method
7.0 Activity of 207Bi
calibration sources
HPGe v NEMO
10. Variation of activity
0 between bkg. channels
10. Activity of 232U
0 calibration sources
HPGe v NEMO