Search for neutrinoless double beta decay: from NEMO3 to SuperNEMO Arnaud Chapon on behalf of the NEMO/SuperNEMO collaboration
LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France 11 october 2010
A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
1 / 20
Contents 1
Double beta decay The two decay processes Experimental principle Choice of 2β isotopes
2
NEMO3 experiment Experimental setup Background rejection NEMO3 results
3
From NEMO3 to SuperNEMO SuperNEMO design R&D developments
4
Conclusion Summary Schedule
A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
2 / 20
Double beta decay The two decay processes The allowed 2ν process
The 0ν process beyond the SM
(2ν 2β )
(0ν 2β )
(A,Z)
∆L
→
−
(A,Z+2) + 2e
+ 2ν¯e
= 0
ν 6= ν¯ (T12/ν2 )−1 = G2ν |M2ν |2
T12/ν2 ≈ 1019 − 1021 years u d d
(A,Z)
∆L
→
−
(A,Z+2) + 2e
= 2
ν ≡ ν¯ (T10/ν2 )−1 = G0ν |M0ν |2 |mββ |2
T10/ν2 ≥ 1024 years
u d u
u d d
u d u
−
d d u
W
−
W
−
−
e
ν¯e ν¯e
−
e
u d u
Fig.: 2ν 2β mechanism A. Chapon
Search for neutrinoless double beta decay:
W
−
W
−
e
νe = ν¯e
d d u
−
e
u d u
Fig.: 0ν 2β mechanism from NEMO3 to SuperNEMO
3 / 20
Double beta decay Experimental principle 1
ββ0ν ββ2ν
0.9 0.8
count (a.u.)
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
0.2
0.4
0.6 E/Qββ (MeV)
0.8
1
1.2
Fig.: 2β decay spectrum The tracko-calo technique enables to : measure the energy of the 2 electrons with a good energy resolution (fwhm
≈ 10%
@ 1 MeV)
identify individually the 2 emitted electrons (Ee1 , Ee2 ,
∆t,
cosθ )
measure background components have an e ciency A. Chapon
≈ 30% Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
4 / 20
Double beta decay Choice of 2β isotopes T10/ν2 ≥ k .
Experimentally :
with
t
k=
ln2.NA 1.64
: constant,
: time of measurement,
Nbgr
M .t A Nbgr .r
s
A : molecular weight, M : source mass, : background events and r : energy resolution : e ciency,
Choice of 2β isotopes high Qββ I I
208
Eγ ( Tl) = 2.6 MeV Qβ (214 Bi) = 3.3 MeV
G0ν (low T 2ν high T1/2 (low 2ν 2β ) 0ν 1 /2 )
high
high mass : I I I A. Chapon
natural abundance low atomic mass A enrichment
2β Qββ nat. ab. T1/22ν isotope (keV) (%) (years) 48 Ca 4272 0,187 4.2×1019 82 Se 2995 8,73 9.2×1019 96 Zr 3350 2,8 20.0×1018 100 Mo 3034 9,63 7.1×1018 116 Cd 2805 7,49 3.0×1019 130 Te 2528,9 33,8 9.0×1020 136 Xe 2479 8,9 8.5×1021 150 Nd 3368,1 5,6 7.0×1018
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
G0ν (10−25 yr−1 )
2,44 1,08 2,24 1,75 1,89 1,70 1,81 8,00 5 / 20
NEMO3 experiment Experimental setup Source I
Fig.: NEMO3 sources
A. Chapon
10kg of 2β isotopes
2β isotope 100 Mo 82 Se 130 Te 116 Cd 150 Nd 96 Zr 48 Ca nat TeO 2 Cu
Search for neutrinoless double beta decay:
Qββ enrichment mass (keV) (%) (g) 3034 96.8 6914 2995 96.9 932 2529 89.4 454 2802 93.2 405 3367 91.0 37 3350 57.3 9.4 4271 73.1 6.99 0.9 0.7 from NEMO3 to SuperNEMO
6 / 20
NEMO3 experiment Experimental setup Source (1) I
10kg of 2β isotopes
Tracking detector (4) I
I
Drift wire chamber in Geiger mode (6180 cells) Gas : He + 4% ethyl alcohol + 1% Ar+ 0.1% H2 O
Calorimeter
Fig.: NEMO3 setup
A. Chapon
I
1940 plastic scintillators (2) coupled to low radioactivity PMTs (3)
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
7 / 20
NEMO3 experiment Experimental setup Magnetic eld I
25 Gauss
Shielding I I I
LSM (4800 m.w.e.) Gamma shield : Pure Iron (18 cm) Neutron shield : borated water (30 cm, wall) + Wood (40 cm, top and bottom)
Radon free air around the detector I
I
Fig.: NEMO3 setup A. Chapon
Phase I (Feb 2003 - Oct 2004) : High Radon Phase II (Dec 2004 - Now) : Low Radon (reduced by factor 6)
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
8 / 20
NEMO3 experiment Background rejection
2
Measurement of all kinematics parameters I 1062
Ee1 , Ee2 , ∆t, cosθ
Particles identi cation
432
I
e− , e+ , γ , α
Direct background measurements I
e− , e− γ , e− γγ , e− γγγ , e− α, crossing e− ...
Fig.: reconstruction of a simulated 2ν 2β decay from 100Mo
A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
9 / 20
NEMO3 experiment Background rejection1 channel
background category
radio-contaminants
external background e− γext , crossing e− internal background e− γ , e− γγ , e− γγγ from γ -emitters internal background 1e− from pure β-emitters radon daughters deposited e− α(Nγ ) on wires and source foils
K, 60 Co, 226 Ra... 208 Tl, 207 Bi... 234m Pa, 40 K, 90 Y... 214 Bi, 214 Po... 40
elaborate a full background model in the 500keV-3MeV region Can measure : internal backgrounds in foils external backgrounds from detector components radon in gas cross check with Cu foils.
1 NIM A606 (2009) 449-465
A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
10 / 20
NEMO3 experiment NEMO3 results - 2ν 2β from 100Mo (7kg)2
Phase II (≈ 3.5 yr,
S B
= 76) :
T12/ν2 = (7.17 ± 0.01(stat ) ± 0.54(sys ) ) × 1018 years Phase I (≈ 1 yr,
S B
= 40) :
T12/ν2 = (7.11 ± 0.02(stat ) ± 0.54(sys ) ) × 1018 years
2 PRL 95 (182302) 2005 A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
11 / 20
NEMO3 experiment NEMO3 results - 2ν 2β from other isotopes 82Se - 932g
130Te - 454g
T12/ν2 (1019 years ) = 9.6 ± 0.1(stat ) ± 1.0(sys )
T12/ν2 (1020 years ) = 7.0 ± 1.0(stat ) ± 1.0(sys )
150Nd - 37g
T12/ν2 (1019 years ) = 2.88 ± 0.04(stat ) ± 0.16(sys )
96Zr - 9.4g
T12/ν2 (1018 years ) = 9.11 ± 0.25(stat ) ± 0.63(sys ) A. Chapon
116Cd - 405g
48Ca - 6.99g
T12/ν2 (1019 years ) = 2.35 ± 0.14(stat ) ± 0.16(sys )
Search for neutrinoless double beta decay:
T12/ν2 (1019 years ) = 4.4 ± 0.5(stat ) ± 0.4(sys )
from NEMO3 to SuperNEMO
12 / 20
NEMO3 experiment NEMO3 results - 0ν 2β from 100Mo (7kg) and 82Se (1kg) 82Se - 932g
100Mo - 6914g
[2.8-3.2] MeV : DATA = 18 ; MC = 16.4±1.4
T10/ν2 > 1 × 1024 yr
@ 90%
[2.6-3.2] MeV : DATA = 14 ; MC = 10.9±1.3
CL
hmν i < (0.47 - 0.96) eV3
T10/ν2 > 3.2 × 1023 yr
@ 90% hmν i < (0.94 - 2.5) eV3
CL
3 Using NME from : - E. Caurieret al., PRL 100 (2008) 052503 - Simkovicet al., PRC 77 (2008) 045503 - Suhonnenet al., J. Mod. Phys E 17 (2008) 1 A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
13 / 20
NEMO3 experiment NEMO3 results - other measurements 100 43
Decays to excited states4
Tc
T12/ν2 (0+ → 0+1 ) =
E2
Qβ − = 3203
.8
0 1 13 539 0.3 E .5 5 0
Mo
100 42 Q2β = 3035
9.5
E2
90
+ 1 .3 ± 0.8(sys ) ) × 1020 yr (5.7− 0.9(stat )
1130.3
0 5 3
+
01
+
21
100 44
539.5
T10/ν2 (0+ → 0+1 ) > 8.9 × 1022 yr T12/ν2 (0+ → 2+1 ) > 1.1 × 1021 yr T10/ν2 (0+ → 2+1 ) > 1.6 × 1023 yr
8.2 ps
12.56 ps
Ru u d d
Right Handed Currents V+A
T
0ν 1 /2
> 5.4 × 10
23
yr
@ 90%
CL
@ 90%
CL
u d u −
−
WR
d d u
ν¯R νR −
eR
u d u
@ 90%
u d d
eL
−
WL
CL CL @ 90% CL @ 90%
u d u −
W
−
W
−
eL
νL νL
d d u
J
−
eL
u d u
Majoron emission5
T10/ν2 > 2.7 × 1022 yr
4 Nucl. Phys. A781 (2007) 209 5 Nucl. Phys. A765 (2006) 483 A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
14 / 20
From NEMO3 to SuperNEMO SuperNEMO design
NEMO3 100
208
Tl :
214
SuperNEMO 82
or 48Ca or 150Nd
7kg
isotope mass
100kg
18%
e ciency
30%
≈
100µBq/kg
Bi : < 300µBq/kg
3
Rn : 5 mBq/m
208
internal contaminations in the
ββ
214
foils
Rn in the tracker
Bi :
≤2µBq/kg ≤10µBq/kg
≤
0.15 mBq/m
Rn :
Tl :
8% @ 3MeV
energy resolution
4% @ 3MeV
T10/ν2 > 2 × 1024 yr
sensitivity
T10/ν2 > 1 × 1026 yr
m i < (0.3 - 0.9) eV
h
Se
isotope
Mo
ν
A. Chapon
Search for neutrinoless double beta decay:
h
3
m i < (0.04 - 0.11) eV ν
from NEMO3 to SuperNEMO
15 / 20
From NEMO3 to SuperNEMO SuperNEMO design 20 modules surrounded by passive shielding
20 modules Source I
I
I
5kg per module (40 mg/cm2 , 4 × 2.7 m2 ) 82 Se rst (High Qββ , long T10/ν2 , proven enrichment technology) 48 Ca and 150Nd under consideration
Tracking detector I
Drift wire chamber in Geiger mode (2000 cells)
Calorimeter I
Fig.: SuperNEMO module A. Chapon
Search for neutrinoless double beta decay:
600 plastic scintillators coupled to low radioactivity PMTs from NEMO3 to SuperNEMO
16 / 20
From NEMO3 to SuperNEMO R&D developments Calorimeter Scintillator and PMT R&D : requires resolution demonstrated with 28cm hexagonal blocks (≥10cm thick) directly coupled to 8 PMT.
FWHM = 4% @ 3MeV
Tracker Basic cell design developed and veri ed. Required performances demonstrated using cosmic muon data.
Geiger
A. Chapon
> 98%
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
17 / 20
From NEMO3 to SuperNEMO R&D developments BiPo6 : ββ source foils measurement Enrichment 100kg by centrifugation is feasible Radio-purity Chemical and physical puri cation requirements :
beta
≈
alpha
t0 t
BiPo
(t ~ 300 ns)
214
I
214
Tl : < 2 µBq/kg Bi : < 10 µBq/kg
40 mg/cm
2 composite foil
Tl : Required sensitivity demonstrated after 3 months Bi : investigating Bi/radon sensitivity
208
BiPo
(t ~ 164 us) t
214
6 NIM A 622 (2010) 120128 A. Chapon
208
Foil production
Scintillator Source
212
I
Search for neutrinoless double beta decay:
214
from NEMO3 to SuperNEMO
18 / 20
Conclusion Summary Nemo experiments use tracking + calorimetry technique I I I I
Full event reconstruction Clear ββ event signature Excellent background rejection New physics studies using event topology
NEMO3 is a running 2ν 2β factory I I
T12/ν2 = (7.17 ± 0.01(stat ) ± 0.54(sys ) ) × 1018 years in 100Mo
7 isotopes studied (100Mo,
82
Se,
130
Te,
116
Cd,
150
Nd,
96
Zr,
48
Ca)
NEMO3 provides competitive 0ν 2β limits I
T10/ν2 > 1 × 1024 yr
@ 90%
CL (hmν i < (0.47 - 0.96) eV)
SuperNEMO is next generation experiment I I I I
A. Chapon
R&D objectives reached : energy resolution, BiPo sensitivity Demonstrator module sensitive to Klapdor claim by 2015 Full detector sensitivity by 2019 : T10/ν2 > 1 × 1026 yr (hmν i < (0.04 - 0.11) eV) Possibility to probe 0ν 2β mechanism Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
19 / 20
Conclusion Schedule
A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
20 / 20
Backgrounds for ββ decays Backup slide γ Origin : natural radioactivity of the detector or neutrons Main background for 2ν 2β but negligeable for 0ν 2β (100Mo and 82Se : Qββ ≈ 3MeV > Eγ (208Tl) = 2.6MeV)
External I I
208
Tl and
214
Bi contamination inside the
ββ
source foils
Radon inside the tracking detercor I I
A. Chapon
Deposits on the wires near the ββ foils Deposits on the surface of the ββ foils Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
21 / 20
Radon trapping facility Backup slide Radon trapping facility
o
1 ton of charcoal @ -50 C, 9 bars air ux = 150 m3/h
222 Rn) 15 Bq/m3 222 Rn) < 15 mBq/m3 ! ! ! Output : A( Input : A(
reduction factor of 1000 Inside the NEMO3 tent : factor of 100 - 300 Inside NEMO3 : almost factor of 10 A(
3 mBq/m
A. Chapon
Search for neutrinoless double beta decay:
222 Rn) : 6
from NEMO3 to SuperNEMO
22 / 20
Probing new physics7 Backup slide In case of observaton, measure energy dierence and cosine of separating angle between electrons to identify mechanism of 0ν 2β .
Fig.:
Fig.:
70% MM + 30 % RHCA admixture
pure MM
Fig.:
pure RHCA
Combination of half-life measurement (blue contour) and topological parameter reconstruction (green contours) leads to parameter space restriction (red contour) at 1 standard deviation.
7 arXiv :1005.1241, accepted by EJP C for publication A. Chapon
Search for neutrinoless double beta decay:
from NEMO3 to SuperNEMO
23 / 20
