Development of InP detector and liquid scintillator containing metal
complexes for pp/7Be solar neutrinos and neutrinoless double beta decay
Neutrino 2012 conference @ Kyoto
Y.Fukudaa M.Asakurad T.Izawad S.Moriyamab T.Muramatsua T.Nambac T.Nakagawaa Narengerilea H.Sekiyabc ICEPP, University of Tokyo d Solid state division, Hamamatsu Photonics K.K.

1. Measurement of pp/7Be solar n◆ Purpose : precise oscillation parameter q12

・ 96%C.L. allowed region obtained by global fit
LMA solution (blue) : Cl + Ga + SK (D/N spectrum)
KamLAND (green) → confirm Dm122

27°< q 12<37°・ mixing angle q12 is not fixed compared with q23 (obtained by Atm. n)
・ survival probability would increase at 5MeV or less in case of LMA
solution, and the shape depends on the value of q12.
pp/7Be solar neutrino spectrum could obtain precise q 12
● on-going solar 7Be experiment

4. Metal complex in liquid scintillator◆ Development of liquid scintillator using metal complexes● goal : solubility : 10wt%, light yield : 60% of BC505● 8-quinolinolate metal complex (organic Electro Luminescence)・ tris(8-quinolinolate) indium (InQ3) C27H18N3O3In (MW. 547.28)
・ tetrakis(8-quinolinolate)zirconium (ZrQ4) C36H24N4O4Zr (M.W. 667.84)
・ InQ3 (for solar n) and ZrQ4 (for bb-decay) have photo luminescence● Solution of organic solvent● Synthesis efficiency

InQ3
primary yield 100%sublimation 77%

・ KamLAND (Liquid scintillator, electron elastic scattering [ES])・ Borexino (Liquid scintillator, ES)

ZrQ4● future solar pp/7Be experiment
・ XMASS (LXe, ES, DARK MATTER)
・ LENS (Liquid scintillator loaded In/Ye, charged current [CC])・ others◆ Technique of low energy solar neutrino detection● Advantage
・ large cross section (~640SNU)
・ direct counting for solar neutrinos
・ sensitive to low energy region (En ≧ 125keV)・ energy measurement (Ee = En － 125keV)・ triple fold coincidence to extract neutrino signal
from huge BG (e1 +g2 + g3 )● Disadvantage
・ natural b-decay of 115In
115In + n → 115Sn* + e (t1/2 = 4.4 × 1014 yr , Ee≧498keV)
e1115Sn*(4.76ms) → 115Sn + g (115keV) + g (497keV)・ possible BG due to correlated accidental
2
3
coincidence by radiative Bremsstrahlung

R.S.Raghavan Phs.Rev.Lett.37(1976)259

2. IPNOS phase-I experiment◆ Indium Project on Neutrino Observation for Solar interior (IPNOS) experiment●Hybrid structure of InP and external scintillator

・InP multi-pixel detector (10mmX10mmX0.2mm cell)・external scintillator (Lxe) to detect g1 and g2●4tons of 115In detector for solar n experiment
・ InP : 5.1tons (2.0X106 modules with DE/E~10% )・ high Z material for external scintillator
・ total size ~5m X ~5m X ~5m (depends on structure)primary yield 96%
sublimation 70%◆ Luminescence of 8-quinolinolate metal complex
AlQ3
InQ3
emission wave length (nm)Y.Suzuki@Neutrino2004

Excitation wave length (nm)

Excitation wave length (nm)O-M = In, n = 3; M = Zr, n = 4

ZrQ4● Setup・ Hamamatsu H6410 2inch photomultiplier・ Fisherbrand 20mL Borosilicate Glass Scintilation Vials
・ Acrylic light guide・ LeCroy 1182 charge sensitive VME ADC
・ Cocktail : PhCN with PPO 100mg and POPOP 10mg
● Response for g-ray from radioactive source

InQ3
Quantum Yield :9.6%(PL : 5.0%)
QE: 0.09
ZrQ4
Quantum Yield :7.6%(PL: 1.1%)
QE:0.10◆ Purpose・ demonstrate LowBG environment
・ long stable operation (1 ppn event will be expected for half year)
・ detect scintillation form g3 by InP detector

Low light yeild
due to small
QY (order ~%)◆ Modify 8-quinolinolate
ligandIn(Q-T)3
QuantumYield :26.0%(P.L.:20%)~2 X InQ3
QE: 0.19~2 X InQ3

Dimethoxy-Tiazine as substitue● Lifetime and neutrino mass

[T1/20n(0+ ->0+)]-1 =G0n(E0,Z)|M0n|2<mn>2● Energy spectrum and lifetime measurement・monochromatic energy = Q-value
・T1/2~a(Mt/DEB) a: abundance M: masst: meas.time DE: energy res. B: BG cnt. rate
Requirement :Low BG, Large target mass, High energy resolution◆ Double beta decay candidatesn◆ Performance of liquid scintillator

・ 30cm cubic chamber (like XMASS 100kg prototype detector)
・ InP multi-pixel detector inside of Liquid Xenon
・ Chamber includes ~10kg InP detector
・ Scintillation could be detected by InP itself◆ Neutrinoless double beta decay

Mn+

Excitation wave length (nm)

◆ IPNOS phase-I detecror

3. Neutrinoless Double Beta Decay

N

Solvent : Benzonitrile (PhCN: C6H5CN)
density : 1.0g/mL flash point : 75℃
Photon emission : 291nm@maximum
Solubility of InQ3 complex: 2wt%
Attenuation length : 66cm (@0.5wt%)

emission wave length (nm)b ICRR, University of Tokyo

emission wave length (nm)a Miyagi University of Education

Tris[5-(4,6-dimethoxy-1,3,5triazine-2-yl)8-quinolinolate]indium
In(Q-T)3 M.W. = 964.62.

Confirm to shorten
emission wavelengthby substitute

L.Y. :
2.7 X InQ3

◆ Experimental limits for neutrino mass

5. Next step
◆ Synthesize Zr(Q-T)4 complex◆ Synthesize Zr-ODZ complex
・large Q.Y. ~0.8

supported by Grant-in-Aid for
Scientific Research (C) 24540295

48Ca, 150Nd, 96Zr, 100Mo,82Se…
00Mo,82Se, 150Nd, 96Zr

● solved in liquid scintillator

formed metal complex
Zirconium (96Zr) is possible candidate

absorption band was overlapped withemission light from anisole （Chem. Phys.
Lett., 435(2007), 252)

expected large L.Y.
・unknown solubility(solvent: PhCN ?)● above 208Tl g line (2.614MeV)● large abundance● emission and absorption problem● high energy resolution

4%@2.5MeV = 100keV● low background rate
Goal:0.01count kg-1 y-1<mn>~10meV● large target mass

~ ton scale◆Synthesize diketon (acetyl acetone)
complex with substitute● beta diketon complex
good solubility (over 10wt.%) foranisole has been reported （J. Radioanal.
Nucl. Chem., 258(2003)255）

R=CH3 : acetylaceton● introduce electron-poor substituteMove absorption bandto shorter wavelength
Dimethoxy-triazine pentafluorophenyl

supported by Grant-in-Aid for
Scientific Research on Innovative
Areas 24104501