Supported by Grant-in-Aid for Scientific Research (C) 24540295 andGrant-in-Aid for Scientific Research on Innovative Areas 24104501

ジルコニウム９６を用いたニュートリノを放出しない２重ベータ崩壊事象の探索

新学術領域「先端加速器ＬＨＣが切り拓くテラスケールの素粒子物理学」
研究会
2013年5月24日
宮城教育大学 教育学部
福田 善之

Neutrinoless double beta decay[T1/20n(0+ ->0+)]-1 =G0n(E0,Z)|M0n|2<mn>2
T1/2~a(Mt/DEB) a: abundance M: masst: meas.time DE: energy res. B: BG rate
Requirement : Low BG, Large target mass, High energyresolution
May 24th, 2013

新学術領域研究会

2For future experiments

high energy
resolution
4%@2.5MeV

F.Piquemal@n2012

http://kds.kek.jp/getFile.py/access?contribId=37&sessionId=16&resId=2&materialId=slides&confId=9151~tons of target will be needed for next generation detector
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新学術領域研究会

3Future experiments for Neutrinolessdouble beta decay
Experimental requirement
for BG rate and DE

 To achivemn < 100meV high energy
resolution
4%@2.5MeV low background rate
0.01count kg-1 y-1
 ton scale of target

Liq. Scintillator is easy to scale up target volume
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4Piquemal@n2012

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K.Inoue@n2012

Pseudocumene
20%+Dodecane
80%+
PPO
0.15wt%May 24th, 2013

新学術領域研究会

8Energy spectrum obtained by KamLAND
 Most possible BG

 110mAg (β-γ, βmax=3,02MeV,t=360d)
 214Bi on IB (β-γ,βmax=3,27MeV, t=15d)
 Half-life of 0nββT01/2 > 1.9×1025 y(90%C.L.) neutrino mass limit(conbined by EXO200)
mn < 120 -250mev
PRL 110,062502 (2013)
May 24th, 2013新学術領域研究会

9Detector design for ZICOS experiment

Zirconium Complex in Organic liquid Scintillator(ZICOS) for double beta decay experiment

Assuming 10w.t.% solubility

3m

Zirconium loaded 100ton LS
May 24th, 201310m

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10Zirconium β-diketon complex
 Zirconium(IV) Advantage

acetylacetonate(Zr(acac)4)

 good solubility (over10w.t.%) in Anisole(PhOMe) Stable and cheep Commercial product Disadvantage
 Low scintillation light

Molecular weight : 487.66
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新学術領域研究会

yield11What’s problem
 Absorption spectra ofIn(acac)3 (indium
acetyl acetone) wasoverlapped with theemission spectra from
Anisole （Chem. Phys.
Lett., 435(2007), 252)
Same overlap between the emission
and the absorption could be occurred
even if different metal (Zr) was used.
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新学術領域研究会

12Observed absorption spectra of Zr(acac)4
 Emission peak ofanisole was observed
around 295nm.
 Absorption peak ofZr(acac)4 was observed
around 270nm.
Scintillation light fromanisole (PhOMe) might beabsorbed by Zr(acac)4
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新学術領域研究会

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Simple expectation for quenching Assuming to same cross section

for light
Light yield = L0 ×
s1Nppos1Nppo + s2NZr
L0 : Light yield of anisole +PPO + POPOP
Nppo , NZr : Number ofmolecular for PPO and Zr(acac)4
s1,s2 : cross section of absorbance for
PPO and Zr(acac)4
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新学術領域研究会

14Scintillation Light yield (60Co) withrespect to concentration of Zr(acac)4
concentrationof Zr(acac)4ObservedchannelExpectedchannel

0 mg

3850

3850

50mg
(1.03X10-4)

3175

3138

100mg
(2.05X10-4)

2800

2651

200mg
(4.10X10-4)

2000

2018

300mg
(6.15X10-4)

1600

1613

500mg
(1.03X10-3)

900

1178

PPO 100mg : 4.52X10-4 mol
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新学術領域研究会

15Improvement of scintillation light yield Move absorption peak

to shorter wavelength How to do it?

substituent groups
http://www.hi-ho.ne.jp/hosomi/sotsuron

Courtesy of Prof. Yoshiyuki Kowada(Hyogo University of Education)
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新学術領域研究会

16Absorbance peak for several
substituent groups

Measured absorbancepeaks for several
substituent groups

May 24th, 2013



Expected absorbancepeak for severalsubstituent groups

新学術領域研究会

17Zr b-diketon complex introducing
substituent groups (β-keto ester complex)
Zr(CH3COCHCOOCH(CH3))4 = Zr(iprac)4mw : 711.92

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Zr(CH3CCOCHCOO
CH3)4 = Zr(etac)4
mw : 665.81

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Zr β-keto ester complex
Zr(iprac)4+(iprac)1.5
state: powder

Zr(etac)4
state : dry solid

Synthesized by Prof. Takahiro Gunji (Tokyo University of Science)

Solubility > 10 w.t.% for anisole
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19Absorbance spectra (Solvent effect)
Solution : Hexane

Solution : acetonitrile

solvent effectAbsorption peak moves to shorter wavelength,
however it depends on the polarity of solvent.
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20Absorbance in liquid scintillator
Solution : Diethyl Ether

Solvent effect could
depend on the polarity(dielectric const.)
 Acetonitrile : 37.5
 Hexane : 1.89
 Anisole : 4.3



Need solution which hassame polarity as anisole Diethyl ether : 4.33

Still solvent effectremains around 270nm
May 24th, 2013

新学術領域研究会

21Light yield of Zr β-keto ester scintillator
Zr(iprac)5.5 in anisoleZr(etac)4 in anisole

0%0%

1w.t.%

1w.t.%

5w.t.%

5w.t.%

Same quenching as Zr(acac)4 was observed
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22Requirement of scintillator solvent

Low polarity (lowdielectric constant) No absorption ~270nm

Aromatic compounds
 luminescence >270nm

Keep high solubility >~10%
 Keep luminescence fromsolventPossible solvent:Toluene / Xylene
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23Zirconium complex with luminescence Zr-ODZ complex

 Photo luminescencem.w. = 1040.18
Solvent : Acetonitrile
Concentration : 3.0×10-5 mol/L
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Emission and absorption spectrum ofZr(ODZ)4• Emission wavelength :430nm
emission

PMT sensitive• Absorption wavelength:
270nm and 320nm
absorption

May 24th, 2013

different from excitation W.L.

• Solvent : PhCN(Benzonitrile)• Solubility : ~5w.t.%
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25Response for g-irradiation
Most of emission light fromPhCN was not used for theemission of Zr(ODZ)4.
 third excitation of ~340nm
from PPO was used for theemission of Zr(ODZ)4.
 Estimated Quantum yield
was obtained ~30% at firstexcitation of ~240nm.
Need another solvent
which has shorter emission
wavelength than PhCN.
May 24th, 2013

新学術領域研究会

26Summary High solubility of Zirconium β-keto ester in Anisole(>~10w.t.%) was achieved.
 Confirmed absorption peak moves to shorter
wavelength (275nm → 245nm) by introducing ester
substituent groups.
 Observed scintillation light yield decreased inproportion to the concentration of Zr β-keto ester
complex due to solvent effect
Need lowpolarity solvent
 To avoid solvent effect, we will synthesize newcomplex tetrakis (diethyl malonato) zirconium.

May 24th, 2013

新学術領域研究会

27Tetrakis (diethyl malonato) Zr compex
Zr(CH3CH2OCOCHCO
OCH2CH3)4 = Zr(demｌ)4mw : 727.84

May 24th, 2013

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Zr(CH3CCOCHCOO
CH3)4 = Zr(etac)4mw : 665.81

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Absorbance spectrum for β-ketoester ligands

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BACKUPMay 24th, 2013

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30Tetrakis 8-quinolinolate Zr complex loaded
scintillator
Tetrakis (8-quinolinolate)
Zirconium complex (ZrQ4)

ZrQ4 50mg in PhCN-POPOPQuantum
Yield=1.1%
obtained by
optical method

NMn+O-n

M = In, n = 3; M = Zr, n = 4

Light Yield toBC505:=7.3%

ZrQ4 m.w. = 689.07
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Scintillation light yield (137Cs) withrespect to concentration of Zr(acac)4

May 24th, 2013

concentrationof Zr(acac)4ObservedchannelExpectedchannel

0 mg

2450

2450

50mg

1800

1997

100mg

1400

1687

200mg

950

1284

300mg

650

1038

500mg

300

750

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Photo Luminescence and absorption of PPO
Photo luminescence Fluorescence device: HORIBAFluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 2,5-Diphenyloxazole
 Molecular mass : 221.26
 Max. emission wavelength :368.0nm
 Max. absorption wavelength :309.7nm
May 24th, 2013

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Photo Luminescence and absorption ofPOPOP

Photo luminescence Fluorescence device: HORIBA

FluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 1,4-Bis(5-phenyloxazol-2-yl)benzene
 Molecular mass : 364.40
 Max. emission wavelength :423.6nm
 Max. absorption wavelength :364.1nm
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Photo Luminescence and absorption of bisMSBPhoto luminescence Fluorescence device: HORIBA

FluoroMax-4
 Absorbance device : HITACHI
U-3000 Solvent : Benzonitrile (PhCN) Concentration : 1.0×10-5 mol/L 1,4-Bis(2-methylstyryl)benzene
 Molecular mass : 310.44
 Max. emission wavelength :426.6nm
 Max. absorption wavelength :355.3nm
May 24th, 2013新学術領域研究会

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