Marco VignatiINFN Roma
NPB 2012, Shenzhen, 24 Sept. 2012
LUCIFER Low background Underground Cryogenic Installation For Elusive Rates
mmin [eV]
|m``
| [
eV]
NS
IS
Cosm
ological Limit
Current Bound
10<4 10<3 10<2 10<1 110<4
10<3
10<2
10<1
1
1m2m3m
Bolometric searches of 0νDBD
2
KK evidence -76Ge
Bilenky and Giunti, 2012CUORICINO:
11kg 130Tebkg = 0.17 c/keV/kg/y
CUORE:206kg 130Te
bkg ~ 1·10-2 c/keV/kg/y
Needs:1 ton isotope
bkg < 10-3 c/keV/kg/y
CUORICINO
• MC: most of the background in CUORICINO is due to degraded α particles which release only a part of their energy in the detector (surface contaminations, mainly in copper).
• TeO2 bolometers, per se, do not allow to discriminate β and α particles.
‣ α bkg partially reduced by cleaning the detector parts.‣ β/γ smaller in CUORE thanks also to the self-shielding geometry.
CUORE: the α nightmare
3
α’s
TeO2 TeO2
Cu
Scintillating bolometers• Scintillating crystals can be operated as bolometers. Unfortunately
TeO2 does not scintillate, other compounds must be considered.
• The simultaneous read-out of light and thermal signals allows to discriminate the α background thanks to the scintillation yield different from β particles.
4
Thermistor
BolometerEnergy Release
Light detector
• 0νDBD candidates of experimental interest:
• In general, Q > 2615 keV isotopes are preferred because they lie abovethe natural radioactivity edge.
• However the choice has been dominated so far by technology compromises.
130Te 76Ge 100Mo 116Cd
82Se
136Xe
U and Thenvironmental bkg
5
Isotope choice .(arXiv:1201.4916)
Light detectors• Germanium disks (5 cm diameter, 0.1-1 mm thick).
• Calibration with a 55Fe source: 5.9 & 6.5 keV X-rays.
‣ ΔE @55Fe: ~ 130 eV RMS‣ ΔE @baseline: 100 eV RMS
6
Candidate #1: ZnSe
7
DBD Isotope:
Q-value[keV]
isotopic abundance
Light Yield [keV/MeV]
QF
82Se
2995
9%
7-11
4
Largest crystal operated so far: 431g
Detected Light [keV]0 50 100 150 200 250 300 350 400
Ligh
t Dec
ay T
ime
[ms]
7
8
9
10
11
12
13
14 β/γ-background
α-crystal contamination
Energy [keVee]0 1000 2000 3000 4000 5000 6000 7000 8000
Ligh
t Yie
ld [k
eV/M
eV]
5
10
15
20
25
30
35
40
ZnSe• QF > 1 is odd:
‣ Observed only in this compound (CdWO4 ZnMoO4 and other crystals have QF < 1).
‣ not understood.
8
0νDBD
• Excellent separation using light energy and signal shape
Ligh
t dec
ay-ti
me
[ms]
Integral 101
/ ndf 2r 8.021 / 14
A 1.9± 13
mean 0.6± 2615
m 0.594± 5.741
Decorrelated energy [keVee]2590 2600 2610 2620 2630 2640
coun
ts /
2 ke
Vee
0
2
4
6
8
10
12
14
16Integral 101
/ ndf 2r 8.021 / 14
A 1.9± 13
mean 0.6± 2615
m 0.594± 5.741
Integral 101
/ ndf 2r 4.035 / 13
A 1.5± 10.5
mean 1.0± 2614
m 1.116± 7.938
Energy [keVee]2590 2600 2610 2620 2630 26400
2
4
6
8
10
12Integral 101
/ ndf 2r 4.035 / 13
A 1.5± 10.5
mean 1.0± 2614
m 1.116± 7.938
Decorrelated energy [keVee]2590 2600 2610 2620 2630 2640
Det
ecte
d lig
ht [k
eV]
12
13
14
15
16
17
18
19
20
21
Energy [keVee]2590 2600 2610 2620 2630 2640
Det
ecte
d lig
ht [k
eV]
12
13
14
15
16
17
18
19
20
21
ZnSe: Light-Heat correlation
9
ΔE@2615 keV:13 keV FWHM
• Operation of a tower of 32-40 Zn82Se crystals at LNGS.
‣ Option1: use the Cuoricino cryostat in hallA (presently hosting CUORE-0), if CUORE-0 stops in 2015.
‣ Option2: use the cryostat in hallC (presently running the CUORE-0 and LUCIFER R&Ds). Needs cryostat update. Cuoricino cryostat:
• Inner shield:
- 1cm Roman PbA (210Pb) < 4 mBq/Kg
• External shield:
- 20 cm Pb
- 10 cm Borated polyethylene
• Nitrogen flushing to avoid Rn contamination.
Plan for a ZnSe array in 2015
10
LUC
IFER4 crystals
per floor
ZnSe: schedule
11
2012 2013 2014 2015
Light detector R&D
Thermistors prod.
Crystal growth R&D
82Se prod. (15 kg)
Enriched crystalsproduction
Array assemblyThe most crucial part is represented by the crystal growth. The supplier (Ukraine) is presently fine-tuning the complicate procedure (that starts with metal Zn and metal Se). The request of minimizing the 82Se waste is a complicate issue. The target is to reach > 75 % efficiency.
Energy [keVee]1500 2000 2500 3000 3500 4000
Ligh
t Yie
ld [k
eV/M
eV]
9
10
11
12
13
14
15
Do we need a μ-veto?
• The event includes hits on close detectors (multi-site event)
‣ Multiple γ’s produced by μ interactions in the materials close to the detector.
• Easy to remove in this case, but what if one has one hit only?
‣ Montecarlo simulation under development.12
ZnSe data: 1 β/γ event above the 2615 keV line in 580 hours
~ 5x10-2 counts/keV/kg/y
β/γα
Candidate #2: ZnMoO4
13
DBD Isotope:
Q-value[keV]
isotopic abundance
Light Yield [keV/MeV]
QF
100Mo
3034
10%
1.5
0.2
Largest crystal operated so far: 330g
ZnMoO4 .
14 Energy [keV]0 500 1000 1500 2000 2500 3000 3500 4000
TVR
[a.u
.]
-14
-12
-10
-8
-6
-4
-2
0
2
4
Energy [keV]500 1000 1500 2000 2500 3000 3500 4000
LY [k
eV/M
eV]
0.2
0.4
0.6
0.81
1.2
1.4
1.6
1.82
2.2
2.4
Eur. Phys. J. C 72 (2012) 2142
α source
β/γ source
α source
β/γ source
0νDBD
0νDBDH
eat s
igna
l sha
pe p
aram
eter
Ligh
t Yie
ld [k
eV/M
eV]
Discrimination using the shape of the heat signal!
Excellent discrimination using the light signal
Entries 2821
Mean 2742
RMS 1449
Integral 2821
1 2 3 4 5 6 7 8 9 10310×
1
10
210
Po
Energy [keV]
Cou
nts /
9 k
eV 210
226Ra
222Rnsource_ <
Po218
Bi ï Po214 214
ZnMoO4
15
11528
1.153e+04
Energy [keV]500 1000 1500 2000 2500
coun
ts / 3
keV
0
10
20
30
40
50
60
70
80
90
Entries 11528
2.925
2590 2600 2610 2620 2630 26400
10
20
30
40
50
60
70FWHM= 6.3 keV
Energy resolution similar to CUORICINO
(2x better than ZnSe)
β/γ source
Internal contaminations:232Th < 1.4 pg/g
Simulated Čerenkov emission spectrum from
1.5 MeV γ in TeO2 at low temperatures.
Simulated emitted Čerenkov light as a
function of β/γ energy.
Candidate #3: TeO2
16Photon Energy (keV)
0 500 1000 1500 2000 2500
Che
renk
ov li
ght (
eV)
0
100
200
300
400
500
600
700
800
900
1000
/ ndf 2r 3.723 / 5
Prob 0.5899
p0 1.143e-09± -3.111e-08 p1 4.448e-06± 0.0001678
p2 0.00428± 0.1222
p3 0.8393± -10.43
/ ndf 2r 3.723 / 5
Prob 0.5899
p0 1.143e-09± -3.111e-08 p1 4.448e-06± 0.0001678
p2 0.00428± 0.1222
p3 0.8393± -10.43
Prod
uced
Che
renk
ov li
ght[e
V] 867 eV
0νD
BD
β/γ energy [keV]
m)µ (h0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
hdN
/d
0
100
200
300
400
500
600
700
800
dN/dλ
[μm
-1]
λ [μm]
TeO2 does not scintillate, however MeV β’s emit Čerenkov light, unlike α’s [ T. Tabarelli de Fatis, Eur. Phys. J. C 65 (2010) 359].
Heat energy [keV]0 1000 2000 3000 4000 5000
Ligh
t ene
rgy
[keV
]
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4 / ndf 2r 11.9 / 6 [keV] thE 64.47± 360.3
Yield [eV/MeV] 2.846± 48.33
/ ndf 2r 11.9 / 6 [keV] thE 64.47± 360.3
Yield [eV/MeV] 2.846± 48.33
210Po-α contamination
β/γ source
Detected β/γ light: 48 eV/MeV 105 eV @2.527 MeV
0νDBD
Čerenkov from a CUORE crystal
17
• Detected light not sufficient to discriminate α’s event by event.
‣ Needs light detector development: light collection, energy resolution.
Signal/Noise of light detector0 1 2 3 4 5 6 7 8
y]
26D
BD se
nsiti
vity
[10
i68
% 0
0
2
4
6
8
10
12
14
16
18
bkg. [counts/keV/kg/y]_
0.01 with 90% enr.0.04 with 90% enr.0.010.04
CUORE + Čerenkov + enrichment
18
γ bkg. (MC)= 0.001
Signal/Noise of light detector0 1 2 3 4 5 6 7 8
y]
26D
BD se
nsiti
vity
[10
i68
% 0
0
2
4
6
8
10
12
14
16
18
bkg. [counts/keV/kg/y]_
0.01 with 90% enr.0.04 with 90% enr.0.010.04
CUORE + Čerenkov + enrichment
18
Pres
ent:
S =
105
, N =
75
eV γ bkg. (MC)= 0.001
Signal/Noise of light detector0 1 2 3 4 5 6 7 8
y]
26D
BD se
nsiti
vity
[10
i68
% 0
0
2
4
6
8
10
12
14
16
18
bkg. [counts/keV/kg/y]_
0.01 with 90% enr.0.04 with 90% enr.0.010.04
CUORE + Čerenkov + enrichment
18
Pres
ent:
S =
105
, N =
75
eV
Targ
et
γ bkg. (MC)= 0.001
• ZnSe
‣ Target: build a bolometric experiment of ~ 10 kg of 82Se‣ Status: Isotope in production, crystal growth under optimization.
• ZnMoO4
‣ Target: build a bolometric experiment of ~ 10 kg of 100Mo ‣ Status: MoU with IN2P3 and ITEP in consideration.
• TeO2
‣ Target: develop light detectors with S/N improved by a factor 4.‣ Status: KIDs and Neganov-Luke detectors under development.
Overview until 2015
19
• ZnSe
‣ Target: build a bolometric experiment of ~ 10 kg of 82Se‣ Status: Isotope in production, crystal growth under optimization.
• ZnMoO4
‣ Target: build a bolometric experiment of ~ 10 kg of 100Mo ‣ Status: MoU with IN2P3 and ITEP in consideration.
• TeO2
‣ Target: develop light detectors with S/N improved by a factor 4.‣ Status: KIDs and Neganov-Luke detectors under development.
Overview until 2015
19
baseline
CUORICINO data
α’s (+ β/γ’s?)
130Te 82Se 100Mo
α’s + β/γ’sso far:82Se and 100Mo arrays will answerCUORE (130Te) will measure
the reduction
Ultimate background: β/γ• So far, we do not have a measure of the β/γ background above
2615 keV with bolometric arrays à la CUORICINO, and of the CUORE β/γ background at the 130Te Q-value.
20
• To cover the entire inverted hierarchy of neutrino masses a bolometric experiment operated in the CUORE cryostat will require:
Crystal R&D Status ΔE(keV)
Bkg. reach
Enrichment cost (€/g)
Zn82Se
Zn100MoO4
130TeO2 (Čerenkov)
Isotope/crystals in preparation 13 likely 75
(contract)
MoU to be signed 6 likely 100-130(estimate)
CUORE experience Light Detectors 5 to be
proved10-20(estimate)
✓1 ton isotope✓Bkg < 1 count/keV/ton/y✓ΔE ~ 5 keV FWHM
Conclusion: which one after CUORE?
21
Backup
• natTeO2 bolometers (34% 130Te), 750g each (ΔE =5 keV FWHM)
• Past: Cuoricino ‣ 62 bolometers
11 kg (130Te)×2y, Bkg: 0.16 cpy/keV/kg
‣ T0ν1/2 > 2.8×1024 years (90% CL)〈mββ〉< 300~700 meV
• Future: Cuore (data taking in 2015)‣ Expected bkg: 0.01~0.04 cpy/keV/kg‣ Exp. T0ν1/2 > 1.6 ×1026 years 〈mββ〉< 40~94 meV
• Present: Cuore-0, a CUORE-like tower.‣ same mass of Cuoricino, 0.05 cpy/keV/kg.
Energy [keV]2480 2500 2520 2540 2560 2580
Rat
e [c
ount
s/ (1
keV
)]
05
101520
253035
404550
Best Fit68% C.L.90% C.L.
0νDBD
60Co γ + γ Cuoricino
130Te CUORE
23
CUORE - @LNGS
CUORE: 988 bolometers
750 kg TeO2
200 kg 130Te
• The spread in the values does not influence the isotope choice.
• Generates problems when comparing exclusions and evidences from experiments running different isotopes.
March 26, 2012 0:7 WSPC/INSTRUCTION FILE bb0
16
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
M0ν
QRPAEDFPHFBIBM-2LSSM
76Ge 82Se 96Zr 100Mo116Cd124Sn 130Te 136Xe48Ca 150Nd128Te
Fig. 3. Values of the NME calculated with the methods in Tab. 2 55.
and we do not discuss the advantages and disadvantages of each of them. We onlypresent the references to the original papers in Tab. 2 and the latest results in Fig. 3.
From Fig. 3 we reach the following conclusions:
(1) The LSSM value of each NME is typically smaller than the corresponding onecalculated with other approaches. Moreover, the LSSM value of each NMEdepends weakly on the nucleus, except for the double-magic nucleus 48Ca. If0νββ-decay of different nuclei will be observed in future experiments, this char-acteristic feature of the LSSM can be checked, because the LSSM predicts thefollowing ratio of half-lives of different nuclei:
T 0ν1/2(Z1, A1)
T 0ν1/2(Z2, A2)
!G0ν(Q2, Z2)
G0ν(Q1, Z1)(68)
(2) There is a large discrepancy between the values of NMEs calculated with dif-ferent approaches. The ratios of the maximal and minimal values of each NMEare 3.1 (48Ca), 2.4 (76Ge), 2.0 (82Se), 3.7 (96Zr), 1.8 (100Mo), 1.3 (116Cd), 1.8
Table 2. Methods of calculation of nuclear matrix elements of0νββ-decay.
Method References
Quasi-particle Random Phase Approximation (QRPA) 49,50
Energy Density Functional method (EDF) 51
Projected Hartree-Fock-Bogoliubov approach (PHFB) 52
Interacting Boson Model-2 (IBM-2) 53
Large-Scale Shell Model (LSSM) 54
NME .
24