candles for the study of 48 ca double beta decay
DESCRIPTION
CANDLES for the study of 48 Ca double beta decay. T. Kishimoto RCNP & Physics Dept. Osaka Univ. Contents. Double beta decay and Majorana Mass Matter dominated universe Neutrino mass Majorana neutrino and double beta decay Double beta decay of 48 Ca CANDLES detector Concept - PowerPoint PPT PresentationTRANSCRIPT
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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.