Transcript Slide 1

Search for 0-neutrino double beta
decay experiments
1.
2.
3.
4.
5.
6.
Introduction
Overview of Double beta decay experiments
Sn, Zn double beta search with HPGe & CsI(Tl)
Metal Loaded Liquid Scintillators
Ca(Sr)MoO4 Crystal R&D
Prospect
H.J.Kim (KyungPook National U.) for KIMS
Underground and Astroparticle Physics Workshop
MooJu, 2005/02/17
Double beta decay process
(A,Z+1)
(A,Z-1)
(A,Z)
(A,Z+2)
(A,Z) -> (A,Z+2) + 2b +2n
(A,Z)
(A,Z-2)
(A,Z) -> (A,Z-2) + 2b+ +2n
EC+b+ ,2EC also is possible
Excited state
g
b+ -> g g (511 keV)
Ground state
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Signal: good s
Signal: bad s
Probability
Energy
Background
• Run forever! (Not possible)
• Huge mass (If you are rich)
• Find large s process
(Theoy responsibility)
• 100% Efficiency is desired
• 0 background (Not possible)
Background reduction
*Good energy resolution
*Low background ->
Purification
=>Cost optimization is needed
S
M T
Sensitivity 

 Eff  s ( B  S )
B
B
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bb material requirements
Matrix elements: Large s
(ex: Nd, Gd)
~mn1/2
 Enrichment: Gd, Te ~20%; Zr, Nd -> Difficult ~mn1/2
Mo, Se, Ge, Kr, Xe, (Cd, Sn) ->Easy
Expensive : A few hundred $ / 1 g
 Efficiency : ~ 100% for active source technique
~mn1/2
Mass, time ;
~mn1/4
 Resolution; 2n bb background issue
~mn1/4
 Background; Source impurity (U238,Th232)
~mn1/4
Source purification, Time correlation (PSD)
Active shielding to reduce backgrounds

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2n-DBD Candidate and Experimental results
Weighted average of all positive results
Isotope
T1/22n(y)
T1/22n(y)calc
48Ca
(4.2 +2.1-1.0 ) ´ 1019
6 ´ 1018- 5 ´ 1020
76Ge
(1.42 +0.09- 0.07) ´ 1021
7 ´ 1019- 6 ´ 1022
82Se
(0.9 ± 0.1) ´ 1020
3 ´ 1018- 6 ´ 1021
96Zr
(2.1+0.8-0.4) ´ 1019
3 ´ 1017- 6 ´ 1020
100Mo
(8.0 ± 0.7) ´ 1018
1 ´ 1017- 2 ´ 1022
100Mo(0+*)
(6.8 ± 1.2) ´ 1020
5 ´ 1019- 2 ´ 1021
116Cd
(3.3 +0.4-0.3) ´ 1019
3 ´ 1018- 2 ´ 1021
128Te
(2.5 ± 0.4) ´ 1024
9 ´ 1022- 3 ´ 1025
130Te
(0.9 ± 0.15) ´ 1021
2 ´ 1019- 7 ´ 1020
150Nd
(7.0 ± 1.7) ´ 1018
6 ´ 1016- 4 ´ 1020
238U
(2.0 ± 0.6) ´ 1021
1.2 ´ 1019
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0nbb decay half lives uncertainty
A VARIETY OF 0n-DBD CANDIDATE NUCLIDES HAS TO BE STUDIED
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Experimental search for DBD
e-
 Two approaches:

e-

e-
Source  Detector
source
e- detector
Source  Detector
(calorimetric technique)
+ high energy resolution
+100% efficiency
- no event topology
+ event shape reconstruction
- low energy resolution
- low efficiency
 If you use the calorimetric approach
Signature: shape of the two electron
sum energy spectrum
low energy
resolution
1
10-6
2n events can
mask 0n ones
low background
two neutrino DBD
R = 5%
continuum with maximum at ~1/3 Q
10-2
sum electron energy / Q
neutrinoless DBD
peak enlarged only by the detector energy resolution
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detector
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- underground
operation
- shielding
- low radioactivity
of materials
The Best 0n-DBD results with different nuclei
Isotope
T1/20n (y)
Ogawa I. et al., submitted 2002
48Ca
Klapdor-Kleingrothaus et al. 2001
76Ge
> 1.8 ´ 1022
> 1.9 ´ 1025
> 1.57 ´ 1025
> 5.5 ´ 1022
> 1.3 ´ 1023
> 7.7 ´ 1024
> 2.1 ´ 1023
> 7 ´ 1023
Experiment
Aalseth et al 2002
Ejiri et al. 2004*
100Mo
Zdenko et al. 2002
116Cd
128Tegeo
Bernatowicz et al. 1993
Mi DBD n 2002
Belli et al.
*
100Mo
130Te
136Xe
: 3.5x1023 years by NEMO3, 2004
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<mn>* (eV) Range <mn>
6.0
0.35
0.38
4.8
1.9
1.0
1.5
1.8
< 0.3 - 2.5
< 0.3 - 2.5
< 1.4 - 256
< 1.8 - 6.2
< 1.0 - 4.4
< 0.9 - 2.1
< 1.4 - 4.1
20 sectors
NEMO3 detector
Installed at the Frejus Underground Laboratory (4800 m.w.e)
Source: 9,5 kg of bb isotopes
(20 m2 with 60 mg/cm2 thickness)
Tracking detector: 6180 cells in
Geiger mode
st=5 mm, sz≤1 cm (vertex)
Best candidate?
100Mo
(6,9 kg)
82Se(0,93
kg)
116Cd
(0,40kg)
130Te
(0,45 kg)
150Nd
(36,5 g)
(9,43 g)
48Ca (6,99g)
96Zr
natTe
(0,61 kg)
Cu (0,62 kg)
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Calorimeter: 1940 plastic scintillators
coupled to low radioactivity PMs :
E/E (FWHM): 14 to 16% at 1 MeV
Time : s=250 ps at 1 MeV
Magnetic field: 25 Gauss
differentiate between (e-e-) and (e+e-)
Shielding:
-18 cm iron (rayt g)
-30 cm water (neutrons)
-28 cm wood
H.J.Kim
Data analysis ~ 890 hours
 Gauss
Iron shielding+B=30
bb - 100Mo
Expected background in bb channel
during 890 hours (simulations) ~ 79 events
Entries=13824
In bb channel : Signal/Noise ~ 170
Data
bb2n+ expected
background
simulations
Very preliminary!
2b2n
T1/2 =(8.40.1(stat)1.3(syst)).1018 years
Consistent with world average:
T1/2 =(8.00.7).1018 years
0
1000
2000
3000
4000
5000
bb0n region
No event E=[2700-3200] keV
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Double beta decay
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0 nbb evidence?
Now claiming
4s significance
By H.V.Klapdor
At 2038.5keV
2004 NIM
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Future projects (2) * Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31
present bkg old/future T1/0n2 (Staudt et al.
Sensitivity (10y)
[c/keV kg y]
mn  10 meV
bkg
Technology
Mass [ton]
GENIUS
HD-M
partially tested
1 – 10
GEM
HD-M
partially tested
1 nat – enr
IGEX
mature
0.5
0.06
150
MI-DBD
tested
0.8 nat
0.33
330
Gotthard Xe
challenging
1 – 10
0.025
1000
MAJORANA
CUORE
EXO
2 - 6 1028 y
1500
0.06
300
2.3 1028 y
0.1 – 1 1028 y
0.4 1028 y
5 1027 y
1 1027 y
0.9 - 13 – 1027
2.2 1028 y
XMASS
DAMA - Xe
tested
10nat – 1.6enr
0.06
10
MOON
ELEGANT
standard
34 nat
~ 0.02
300
1.3 1028 y
1 1027 y
INR - Kiev
needs confirm.
0.1 - 1
0.03
600
4.9 1027 y
0.1 - 1 1027 y
CAMEO
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0.5 - 1 1027 y
H.J.Kim
Klapdor-Kleingrothaus HV hep-ph/0103074
Aalseth CE et al. hep-ex/0201021
Zdesenko Y et al. nucl-ex/0106021
GENIUS – MAJORANA - GEM
M = 1 (10?), 0.5, 1 ton (86% enriched 76Ge)
0n-DBD sensitivity
T10y ~ 2, 0.4,1 ·1028 y <mn> ~ 10 – 80 meV
Assumed bkg:
~ 0.04, 0.4, 0.2 count/keV ton y
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CUORE
M = 0.76 ton natural TeO2
0n-DBD sensitivity (1 c/keV ton y)
T10y ~ 1027 y <mn> ~ 30 – 50 meV
Cubic structure, ideal for active shielding
no more inert Cu plates
facing crystals
dilution refrigerator
Each tower is a CUORICINO-like
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H.J.Kim
Danilov M. et al. Phys. Lett. B480 (2000) 12
Moriyama S., XENON01 proc.
Zdesenko Y., XENON01 proc.
EXO – XMASS
Large
TPC (1 – 10 ton)
with single Ba+-ion detection
via laser tagging (optical spectr.)
136Xe
IF
10 ton nat. or 1.6 ton enriched
5 c/keV ton y
Almost no BKG except 2n-DBD
Ton ~ 1027 y <mn>  20 meV
10 ton
T0n > 1.3 x 1028 y (90% C.L.) –
<mn> < 13 - 40 meV in 10 y
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MOON
100Mo
Ejiri H. et al. Phys. Rev. Lett. 85 (2000) 2917
passive source for 0n2b
target for solar neutrinos
34 ton nat. (3.3 ton 100Mo)
Supermodule of scintillator and Mo ensembles
BKG
from 214Bi and 2n-DBD
~ 0.07 c/ keV ton y
Ton ~ 1027 y <mn>  30 meV
1 module prototype
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DB experiment R&D in Korea (4 years)
• Low Cost is highly required (Experimentalist problem)
• New method is desired
• Other DB Elements ( Theoretical uncertainty)
• Unexpected surprise (Unlikely but who knows)
• New method for double beta decay R&D
-> Metal-Loaded Liquid scintillator (No experiment yet)
-> New scintillation crystal (CaMoO4 etc)
• Good News : KIMS experiment experience
-> YangYang Underground lab and shielding
-> Background reduction technique for Cs
-> Experience with Crystal( CsI) and Liquid scintillator
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Double beta; HPGe with CsI crystal
• HPGe
•
•
•
a) EC+b+ , b+b+ ; No observation yet
b) Excited transition to 2nu, 0nu; Mo, Nd (new)
HPGe + CsI ( top only) ; Under study (Zn,Sn, Zr)
HPGe + Full CsI cover ; Improve sensitivity 1 order?
=> Confirm Nd and try for Zr,Sn excited transition
=> Uses 12 6x6x30cm existing crystal
using existing RbCs PMT
HPGe + Active detector( Sn-LSC, CaMoO4....)
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Sn-124, Sn-122 0-,2-n bb limit
* World best limit on Sn-124 (E.Norman PLB 195,1987)
 Test of TBSN for a week at CPL , Preliminary results



*
450cm3 HPGe, 140 hours , 1.0liter TBSN : 400g of Sn
2+ (603keV) 3.8x1018 year (4.0x1019 year)
0+ (1156)
1.1x1019 year (2 -n theory : 2.7x1021)
0+ (1326)
1.3x1019 year (2.2x1018 year)
Sn-122 EC+b+ decay ; 1.5x1018 year (6.1x1013)
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Zn EC+b+ decay
EC+b+ limit ( b+ -> 2 g decay)
99.7% CL
Positve evidence by I.BIKIT et.al,
App. Radio. Isot. 46, 455, 1995
<= 25% HPGe + NaI(Tl) with 350g
Zn at surface with shielding.
-> Need to confirm or disprove!
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Zn EC+b+ decay
HPGe + Zn(8x8x1cm)+CsI(Tl) crystal
Our advantage:
 100% of HPGe
 350m underground
 10cm low background lead,
 10cm copper and N2 flowing
CsI
7.5x7.5x8
Calibration by Na22 (b+ radioactive source)
Efficiency calculation by Geant4; 3%
Very Preliminary result with 1 week data;
Coincidence cut with 2 sigma range ; 1 event
Zn
HPGe 511keV g
2x1020 year by 95% CL
If I.BIKIT’s central value is taken, we would
observe 100 events (1.1x1019 y)
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511keV g
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Energy dist at HPGe
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Why metal loaded liquid scintillator?
• Advantage
a) high-Z can be loaded to LS (>50% or more)
b) Fast timing response (few ns)
c) Low cost of LS, Large volume is possible
d) U/Th/K background for LS is low and purification
is known
e) Some elements can’t be made to Scintillator
• Disadvantage
a) Bigger volume is necessary (C,H in LS, low density)
b) Lower light output (>15% of NaI(Tl))
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LSC test sample
HV + LSC
Setup
VME
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Zr2EH + LSC (50% ->Zr 3%)
Nd2EH + LSC (50%->Nd 6.25%)
TetraButhyl Tin + LSC (50%->Sn 20%) TetraMethyl Tin + LSC (50%->Sn 40%)
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Double beta decay detector
Quartz glass
Plastic
Dimension
R = 5cm
H = 15.2cm
V = 1.18L
Teflon
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214Bi
b-decay g
214Po
a-decay
s
-> T 1/2 = 0.166ms (0.163 ms exp.)
U-238 decay chain
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212Bi
b-decay g
212Po
a-decay
-> T 1/2 = 300ns
Th-232 Decay chain
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TMSN50% Energy Spectrum
pol3 + gaus fitting
Ee(keV)
Ee(keV)
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Current Sn-124 Results
* TMSN50% by 500MHz FADC -> 33 days
T1/2 = 3.41x1019 year by 90% C.L
World best limit = 2.4x1017 years by M.I. Kalkstein
* More data taking is on-going
More R&D ……
Zr, Nd and Gd loaded LSC
Purification
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H.J.Kim
Scintillation Crystals for bb (Calorimeter technique)
 300g CdWO4 bb search by Ukrine group; >0.7x1023 year
Enrichment, PSD, active shielding -> successful
 CaMoO4 (PbMoO4 , SrMoO4...) ; Mo, Ca bb search
1)
2)
3)
4)
5)
Similar to CdWO4 but no hazard with Cd. and low Z
Light output; 20% at 20o, increase with lower temp
Decay time; 16 micro sec
Wavelength; 450-650ns-> RbCs PMT or APD
Pulse shape discrimination
 GSO, ZnSe, CaF2
 New Crystal R&D : NdCl3(X), GdCl3(?) New idea??
 New Method R&D : LSC + CaF2 powder (?)
2005/02/18
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Czochralski(CZ) Crystal Growing for DB
• Russia, Ukrine
• PSU (Crystal Bank)
• KNU (small one for R&D)
2005/02/18
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H.J.Kim
CaMoO4 R&D Crystals
PSU crystals in Korea:
CaMoO4, 5x5x6mm,
8x7x11mm
8x6x10mm
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CaMoO4 from Russia
18x18x35mm, 10x10x10mm
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H.J.Kim
CaMoO4 R&D Crystal from Crystal Bank in PSU
New One
14.3x15x13.7mm
10.73g (small)
20x20x20mm
24.27g (middle)
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24.8x30x40.8mm
93.13g (large)
H.J.Kim
CaMoO4 Pulse shape with 500MHz FADC
60keV g
5.5MeV a
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Number of photoelectron from 60keV g
# of photoelecton from Am-241
Energy distribution
# of photoelectron : 0.6 PE/keV => 6% FWHM at 3MeV at
25deg
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CaMoO4 2x2x3cm, Pulse Shape discrimination
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CaMoO4 2x2x3cm, 1Month data!
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Various Backgrounds and signal estimation with
20kg of CaMoO4 with 5 years data taking (GEANT4)
Mo-100 2nu
Ca-48 2nu
Bi-214
Signal (m=0.3eV)
Tl-208
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Backgrounds & signal with CaMoO4 (GEANT4 simulation)
5s significance
All Backgrounds
Signal
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결정섬광 검출기를 이용한 0-n bb 실험
CaMoO4 (PbMoO4, SrMoO4, ZnMoO4) ;
Mo, Ca 0-n bb 탐색 <= 새로운 아이디어
10kg Mo-100 CaMoO4
8x1024 년 (0.2eV)
(현재 3.5x1023 년)
10% 10kg Ca-48
1.5x1024 년 (0.6eV)
(현재 2x1022 년)
1톤 Mo-100 CaMoO4
8x1026 년 (0.02eV)
이론 예측: 0.01-1.0 eV
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감사합니다
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H.J.Kim
CaMoO4 sensitivity and prospect
• Ca,Mo purification : 0.01 evt/keV/day/kg at E=3MeV
• Active veto (6cm CsI) + 15cm low bg Pb + 30cm LSC
• Time correlation , Pulse shape discrimination
• 4% FWHM .
• 10kg Mo-100 enriched CaMoO4 with 5 years data
Sensitivity: 1025 years by 90% CL (0.15 eV)
<- 5 sigma significance if Klapdor claim is right
(Current best limit: 3.5x1023 years by NEMO3, 2004)
• 100kg Mo-100 enriched CaMoO4 with further
background 10 reduction
1026 years (0.05 eV) sensitivity
<- next generation experiment
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CaMoO4 R&D Summary and Plan




1)
2)
3)

CaMoO4 (18x18x30mm) : 0.6 PE/keV -> 6% FWFM at Q= 3MeV
Decay time : g ; 16.5 +-0.5 ms, a ; 15.5 +-0.5 ms at 4.5MeV a
PSD possible: Th232, U238 background reduction
Ea/g ratio: 0.2
Currently working on
Temperature dependence
Background reduction study of powder, Crystal growing (Russia)
Internal bkg study 2x2x3cm CaMoO4 at Y2L shielding
* Study of internal bkg (U238,Th232-> timing correlation, alpha)
Future Plan :
10kg of Mo-10 enriched CaMoO4 crystals installed at YangYang
underground Lab in Korea in two years.
Sensitivity: 1025 years by 90% CL(0.15eV) with 5 years data taking
<- 5 sigma significance if Klapdor claim is right
2005/02/18
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H.J.Kim
Large area with high efficiency R&D
4x4 1.5cm Photodiode
->noise problem
Large Area avalanche
photodiode (1.6cm diameter)
• Large ared : 5x5cm
• Noise : a few hundred RMS noise
• High quantum efficiency : 80%
(PMT: 15% )
anodes
z
y
x
n
k
ul
-b
+
n
p
+
y = v .t
d
d
X-rays
Silicon Drift sensor
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CdWO4 experiment (Zdsenko)
Double beta decay
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H.J.Kim
0 -, 2-n bb decay processes
(A,Z+1)
(A,Z)
(A,Z+2)
(A,Z) -> (A,Z+2) + 2b +(2n
2005/02/18
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H.J.Kim
CaMoO4 2x2x3cm, Cs137 source
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H.J.Kim
Alpha response of CaMoO4
Ea/g = 0.2 with 5.5MeV a particle
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H.J.Kim
U238
aa
ab
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H.J.Kim
Th232
aa
a-a
a-a,a-b
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H.J.Kim
CUORICINO
CUORICINO proposal:
1 tower of 14 modules, 4 detector (760 g) each
Mass ~ 40 kg
Final configuration: 11 modules, 4 det. (790 g) each
2 special planes, 9 det. (330 g) each
+
T5y ~ 1025 y <mn> 0.1 – 0.3 eV
Expected bkg
~ 0.1 c/keV kg y
NOW ASSEMBLING!
Plane section
Tower
Lead shield
Test of anticoinc.
for BKG reduction
2005/02/18
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Same cryostat
and similar
structure
as Mi DBD
H.J.Kim