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CANDLES for the study of 48Ca double beta decay
T. Kishimoto
RCNP & Physics Dept.
Osaka Univ.
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Contents
• Double beta decay and Majorana Mass –Matter dominated universe–Neutrino mass– Majorana neutrino and double beta decay
• Double beta decay of 48Ca• CANDLES detector
–Concept–CANDLES I, II, III, VI, V
• Prospect
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Baryon density in our Universe• Big bang nucleosynthesis
– 4He, D, 3He, 7Li– Baryon density
B ~ 10 - 10
If particle number is conserved, Particle :Anti-particle :
Matter dominated Univ. →CP + particle # →Double Deta decay
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Relativity + uncertainty →anti-particle
present
future
past
・ no information is faster than light・ interact with any space-time→particle that travels backward in time→anti-particleCarries inverse quantity (charge spin(chirality))
Charge: conservedChirality: violated by mass
distance
timelight
Dirac equation→anti-particle
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Neutrino type
• type Dirac Weyl Majorana• components 4 2 2 x 2• L R
particle
Anti-particle
C, PCP
m=0 m≠0
Lepton numberChirality
Direction of propagation
mL mR
oscillationm
~55 meV ~7 meV
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Direct measurement of m
• 3H – decay (Q: 18.7keV)
• 0 decay
• CMBR– WMAP +
SDSS + …
KATRIN => m ~ 0.2 eV
KATRIN => m ~ 0.2 eV
m < ~ 0.6 eVm < ~ 0.6 eV
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02 decay
n p
e -e
n p
hh
h
hV -A
V -A
e -
m a s s te r m
n p
e - e
n p
e - e
2 m o d e
0 m o d e
Possible in Standard model
Majorana particleparticle⇔anti-particle・ possible only for ・ matter dominated universe
.....||
|)00(|2200
102/1
mMG
T
NM
Phase volume
Nuclear matrix element
Effective mass
2 mode
Sum energy spectrum
0 modeT >1025
yrT ~1019 yr
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has to be a Majorana particle
• Mass term (Dirac)
• Mass term (Majorana)– Only Left (right) handed
mass term can be made– Left and right can have
different mass – We know only left-handed
neutrino – Heavy right-handed
( see-saw mechanism )– Violates lepton number
Chirality flip ( relativity )
Left handed → right handed (anti-particle)
Leptogenesis
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Leptogenesis
• GUT ? (No proton decay?) SK
• Majorana particle ( Lepton number )– particle anti-particle
• CP– Anti-lepton > Lepton (~10-10)
• Instanton effect (t’Hooft)– Standard model– Anti-lepton → baryon
• conserved : B-Lpositron proton
Fukugita, Yanagida (1986)
Proton decay(B-L cons.) is irrelevant to the Baryogenesis : Yanagida
Effective in early universe
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Double beta decay nuclei
• Nuclei – 48Ca, 76Ge, 82Se,100Mo,– 128Te, 130Te, 136Xe, 150Nd– Positron emitter
• Ultra rare process – 1020~25 yr
• Huge natural background sources – High sensitive detector– Low background circumstance⇔Underground
lab.
AZN
AZ+1N-1
AZ+2N-2
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World Experiments
Cla im by KKK
CANDLES
48Ca 76Ge 100Mo82Se 130Te 136Xe 150Nd
0.01
0.1
1
101
IV
V
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Why 48Ca• Highest Q value (4.27 MeV, 150Nd: 3.3 MeV)
– Large phase space factor – Little BG ( : 2.6 MeV, : 3.3 MeV )
• Natural abundance → 0.187%– Isotope separation → expensive (no Gas)
• ~10g x 2 (in the world. only Early studies)• Next generation
– M ~ T-1/2 ~ M-2 (no BG) ~ M-4 ( BG limited )
– 48Ca (no BG so far)• If we want to sense normal hierarchy region,
only 48Ca + enrichment has a chance.
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Nuclear matrix element
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n1
e
p1
p1
n1
e
n1e
p1
p1
n1
e
q1~0q2~0
q2 + q1~0q2 - q1~pF
ifrrqqiedr ))(( 2121
if
i f
2 decay
0 decay
ifdr
2 nucleon correlationNeutrino potential 1/r~A-1/3
F2N(q=0)
F2N(q)
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p n
f7/2
f5/2
Matrix element 48Ca
forbidden if only f7/2(wf) And GT(op)
wf: Configuration mixingOp: Higher partial wave
A=48
・
|M0|2 ~5 ambiguity (accept and challenge) M(48Ca) is well estimated but not perfect yet. It is small though taken to be the minimum.
M0
M. Horoi (2010)
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Oto Cosmo Observatory
5 03 9 .5 m
第 一 観 測 室第 二 観 測 室 第 三 観 測 室
国 道 168号 線
西 吉 野 村 側
大 塔 村 側
845m
A tunnel constructed for a railroad but never used. It is 60km south from Osaka
ELEGANT VI
C.L.) % (90year 104.1 2202/1 T
C.L.) % (90 eV 7.44~2.7m
NPA 730 ’ 04, 215
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神岡
大 塔 コ ス モ 観 測 所
大阪大学核物理研究センター
大阪大学理学部
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48Ca double beta decay by ELEGANT VI
NPA 730 ’ 04, 215
Not limited by backgrounds
1.76 y
But only 6.4g of 48Ca 16
C.L.) % (90 eV 22~5.3mC.L.) % (90year 108.5 220
2/1 T
PRC78 058501(‘08)
Q of 48Ca
PMT PMT
CaF2(Eu)n = 1.44CaF2(pure)
n = 1.47
Optical greasen = 1.47
Silicon oiln = 1.40
CaF2(Eu)
CaF2(pure)
CaF2(pure)
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How to sense m=1~10-2eV• Big detector
– Huge amount of materials
• Low radioactive background– Active shield– Passive shield– Low background material– BG rejection by signal processing
• High resolution– Backgrounds from 2 decay
• CANDLES is our solution
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CANDLES
CaFCaF22(Pure)(Pure)
200kg, 300kg, 3t, enrichment
48Ca (Q=4.27MeV)
Liquid ScintillatorWave Length Shifter4 Active ShieldPassive shield
PhotomultiplierPhotomultiplier energy resolution
CaF2(Pure)
Liquid Scintillator(Veto Counter)
Buffer Oil
Large PMT
CAlcium fluoride for studies of Neutrino and Dark matrtersby Low Energy Spectrometer
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CANDLES IBackground rejection
Liquid Scintillator
CaF2
ADC(fast)ADC(total)
CaF2(pure)
liquid ScintillatorPMT(5")× 4
ADC(total)
Liquid Scintillator
CaF2
POP(Proof of Principle)
liq. scint. : mineral oil + DPO (3 g/l)+ Bis-MSB (0.3 g/l)
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Reduction 100MHz FADC T > 30ns(3ch) ; ~3% 500MHz FADC (under preparation) . . . T > 5ns ; ~1%
Rejection of Double Pulse
Prompt
Delayed
Typical Pulse Shape(100MHz FADC)
900ns 50ns
212Bi212Po
T1/2 = 0.299sec64%Q = 8.95MeV
Q = 3.27MeV
Q = 2.25MeV
Q = 7.83MeV
208Pb
Sum energy ~ Q value
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Pulse Shape Discrimination
• PSD (Event by Event)PSD (Event by Event)– FADC (100MHz)
– Afast/Aslow (Fast and slow component)
Difference in decay time between and rays
Discrimination between and Events Background Reduction ~ 0.3%
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Development of Low Background CaF2 Crystals
Radioactivities in CaF2(pure) Crystal(-ray measurement)
Radioactivities in CaF2 Powder(HPGe measurement)
U-chain(214Bi) ~41Bq/kg . . . 1/25 of Previous CrystalsTh-chain(220Rn) ~21Bq/kg . . . 1/5 of Previous Crystals
CaF2 Powder
FusedCaF2
Raw MaterialsCaCO3, HF
CaF2 Crystal
Where is the crystals contaminated?
Powder selection Crystal making
CaF2(Eu) in ELEGANT VI U-chain(214Bi) : 1100Bq/kg Th-chain(220Rn) : 98Bq/kg
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Radioactive impurities
0
5
10
15
20
25
30
35
40
45
50
0 - 0.01
- 0.02
- 0.03
- 0.04
- 0.05
- 0.06
- 0.07
- 0.08
- 0.09
- 0.10
- 0.12
- 0.14
- 0.16
- 0.18
- 0.20
(mBq/ kg)不純物濃度
U系列
Th系列
3t 600k 300kCANDLES III(U.G.)CANDLES IV
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Energy resolution and BG rejection (2 phase system)
CaF2(Pure)
• BG from 2
• Energy resolution
• CaF2 : UV – PMT
• 2 phase system 9.14%(FWHM)
Energy (keV)
Cou
nts
137Cs (662keV)
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UV
Visible light
Veto phase (absorves UV)
Conversionphase
CaF2(pure)
Liquid ScintillatorCANDLES I (WLS phase)
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H2O
15”PMT
Mount System
CaF2(Pure)10cm cube
Liquid Scintillator
CANDLES-II
• Prototype
45cm
Cosmic-ray Events (High Energy)
Index 1.44@586nm (CaF2)
Index 1.46@586nm (Mineral Oil)
S.Umehara
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CANDLES III@Osaka
Tank: Φ2.8×h2.6 m
PMT:13”×3215”× 8
CaF2: 191 kg103 cm3×60
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Rejection ofexternal BG
Observation at sea levelUnderground OK
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Kamioka Experimental hall D
CANDLES III(UG)3m ×4m h
CANDLES III ( UG )
Lab D
Super Kamiokande
KamLAND
CANDLES
Kamioka
4m3m
CANDLES III(UG)
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CANDLES III ( UG )
CANDLES III ( UG )62 PMT’s
96 CaF2(pure) crystals
(CaF2 crystals)
Almost completed
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Mile stone• ELEGANTS VI
– Best 48Ca 0limit
• CANDLES I, II
• CANDLES III+ III(UG)– 100 x10cm3 CaF2 (~30Bq/kg) ~0.5 eV
– Start running in this October.
• CANDLES IV – 3t CaF2 (3.5 kg 48Ca) (~3Bq/kg) ~0.1 eV
• CANDLES V– Enrichment and 0.3~1t of 48Ca (m≦10meV)
achieved
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Characteristic of CANDLES
• BG rate (events/weight)– So far the best
• 2~3 orders
• Scale up: – CANDLES IV, V
• Enrichment – more nuclei– BG reduction
Target Project Abund. (%)
Background rate (counts/kg/year)
48Ca ELEGANT VI 0.187 0 (measured)0.075 (expected)
CANDLES III 0.187 5x10-4
CANDLES IV 0.187 5x10-5
76Ge HDM ~86 0.61
130Te CUORICINO 33.9 2.4
CUORE 33.9 0.8 (CUORE-0)10-2~10-3(Goal)
136Xe EXO-200 ~80 0.1
+ Ba tagging
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Achieve both simultaneously
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Enrichment of 48Ca• Increase nuclei
• BG reduction
• Crown ether– Sep. coeff. ε~ (3.5±0.5)x10-3
– Crown ether resin
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O
O O
O
OO
C C
C
C
C
C
C C
Dicyclohexano 18-crown-6
DC18C6Ca2+
- -
- -
- -
48Ca : 0.2% => 5~10 %
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Enrichment for long migrationEnrichment for long migration
~7 hours~7 hours1m1m
~70~70 hourshours20m20m
~250~250 hourshours200m200m
Enrichment due to crown ether
・ long migration length ・ higher enrichment and larger amount ~7 時間 (1m) → ~250 時間 (200m) amount: ×17, enrichment: ×8
P r e l i m i n a r ymaximum: 0.0026(original:0.0019)
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Ca ions in CE
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• Why CE absorbs 40Ca more than 48Ca? – CE: Harmonic oscillator pot.
• Heavier Ca is in a lower energy state.
– Water: (pH: 10-14 mol/ℓ)• H2O: polar molecule: HO pot.
• Partition function ⇔ distribution
– Mass dependence
)2
1( nEn
CE
water
E
14848
48
2
)(31
kTExp
nWCE
WCE
m
k
2.0)12.1( meV~1% effect
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Other enrichment methods
• Laser ionization – Plant for Uranium enrichment– KAERI 1kUS$/g (~1/100 of current CM value)
• Centrifuge: high (0.6 MG) (JAERI)• Electrophoresis • Others
• We will clarify the separation method in an year.
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Thank you.