ZICOS – NE W PROJE CT F OR NE UT RINOL E SS DOUBL E BE T A DE CAY E XPE RI ME NT USING ZIRCONI UM COMPL E X IN ORGANI C L IQUI D SCINT I L L AT OR – Supported by Grant-in-Aid for Scientific Research on Innovative Areas No.24104501 and No.26105502 Re ve aling the history of the unive rse with unde rground partic le and nuc le ar re se arc h 2016 Koshiba Hall, T okyo 11 May, 2016 Miyagi Unive r sity of E duc ation Y. F ukuda, Nar e nge r ile , A.Obata Kamioka Obse r vator y, ICRR, Univ. of T okyo S. Mor iyama F ukui Unive r sity I. Ogawa T okyo Unive r sity of Sc ie nc e T . Gunji, S. T sukada, R. Hayami
Ne utrino le ss do ub le b e ta de c a y 0 ν (0 + ->0 + )] -1 = G 0 ν (E 0 ,Z)|M 0 ν | 2 <m ν > 2 / m e 2 [T 1/ 2 1/ 2 ~a (Mt/ ∆ E ・ B) 1/ 2 T a : a b unda nc e M: ta rg e t ma ss t: me a suring time ∆ E : e ne rg y re so lutio n B: BG ra te Requirement : Low BG, Large target mass, High energy resolution Ma y 11, 2016 2 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016
uture 0 νββ e xpe rime nts F 10 27~28 y ~tons of target and ~zero BG detector will be necessary for next generation 0 νββ experiment. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 3
Ba c kg ro unds a ro und 3.35Me V Measured by KamLAND-Zen 208 Tl In balloon I.Shimizu@Neutrino2014 0νββ signal region for 96 Zr Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 4
ZI COS- Zirc o nium Co mple x in Org a nic L iq uid Sc intilla to r fo r ne utrino le ss do ub le b e ta de c a y Goals for development of LS ： (1) Zr should be solved highly in order to make detector small. (2) 3.5% at 3.35MeV of energy resolution, if ZICOS has PMTs 3.0m with 40% photo coverage and long attenuation length (~10m) Pure water surrounding inner detector in order to veto muons and external backgrounds. 10.0m Inner detector with 40% photo coverage 10” PMT including 10m Zirconium loaded 113 tons LS Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 5
Ne utrino ma ss se nsitivity o f ZI COS e xpe rime nt 0 ν > 9.2 × 10 21 y Results from NEMO-3 ( 96 Zr) : T 1/2 <m ν > 7.2 – 10.8 eV (g A =1.25,g pp =1.11,QRPA) (Ref: M.B.Kauer Doctor thesis for UCL(2010)) Assuming same energy resolution, BG rate and measurement time as KamLAND-Zen 0 ν > 2.6 × 10 25 y ) (T 1/2 (Ref: I.Shimizu arXiv:1409.0077 (2014)) Mass : 113 ton 10wt.% Zr(iprac) 4 = 12. ６ ton includes 1.7ton of Zirconium = 45 kg of 96 Zr (natural abundance 2.6%) ( 64kg of 136 Xe = 0.2 × KL-Zen) 0 ν > 1.2 × 10 25 y ← Not enough for 0νββ search T 1/2 Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 6
Ne utrino ma ss se nsitivity o f ZI COS e xpe rime nt 1) Zr enrichment 58.5% enrichment of 96 Zr (e.g. 57.3% for NEMO-3) then 96 Zr will be 1 ton (4.4 times 136 Xe 320kg) 0 ν > 5 × 10 25 y ; <m ν > < 0.09 – 0.15 eV (QRPA) T 1/2 Electromagnetic isotope separation is expensive… 2) Lowering BG ( 208 Tl / 214 Bi) i.e. < 1/20 × KL-Zen (~1.0events/ton/year) 0 ν > 5 × 10 25 y T 1/2 Maybe we can…… Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 7
De ve lo pme nt o f Zr lo a de d L S Zr(CH 3 COCHCOOCH(CH 3 ) 2 ) 4 : Zr(iprac) 4 tetrakis (isopropyl acetoacetate) zirconium mw : 663.87 Solid crystal or powder Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 8
So lub ility o f Zr(ipra c ) 4 fo r a niso le Zr(iprac) 4 2242mg, PPO 999mg Solubility > 31.2 wt.% and POPOP 10mg solved in 20mL Anisole > 70g/L of Zirconium could be solved in anisole. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 9
Ab so rb a nc e spe c tra fo r Zr(ipra c ) 4 Absorption peaks of Zr(iprac) 4 was found around at 278nm. However, overlapped region with emission of anisole was existed. Zr(iprac) 4 works as a quencher for the liquid scintillator system. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 10
L ig ht yie ld q ue nc hing b y Zr(ipra c ) 4 σ 1 N ppo Light yield = L 0 × σ 1 N ppo + σ 2 N Zr L 0 : Light yield of anisole N ppo : Number of PPO molecular in mole N Zr : Number Zr complex molecular in mole σ 1 : absorbance of PPO (mol -1 ) σ 2 : absorbance of Zr complex (mol -1 ) PPO would help the recovering light yield. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 11
Re c o ve ring the lig ht yie ld Measured at several conditions of PPO concentration 5wt.% PPO helps actually recovering the scintillation light yield. 48.7 ± 7.1% light yield to standard cocktail was obtained at 10wt.% concentration. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 12
Re c o ve ring the e ne rg y re so lutio n Measured at several conditions of PPO concentration 5wt.% PPO helps again the energy resolution 35% → 13%. at 10wt.% of Zr(iprac) 4 . 13.0 ± 2.0% √ (40%/9.2%)X(3.35MeV/1.03MeV) = 3.5 ± 0.5% at 3.35MeV Achieved goal ! Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 13
Sta b ility o f liq uid sc intilla to r Mar. 14, 2016 Feb. 27,2015 Keep transparent liquid and no precipitate is found. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 14
Me a sure me nt o f b a c kg ro unds fro m L S Measured by lowBG CsI 1.120MeV ( 214 Bi) 0.609MeV ( 214 Bi)+ 0.583MeV ( 208 Tl) 1.765MeV ( 214 Bi) 2.204MeV ( 214 Bi) 2.615MeV ( 208 Tl) Using subtracted # of events around 2.6MeV and 2.2MeV 214 Bi < 4.9x10 -20 g/g 208 Tl < 2.7x10 -22 g/g ( 238 U < 6.4x10 -6 g/g) ( 232 Th < 7.4x10 -7 g/g) (c.f. KL 10 -18 g/g) Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 15
Ma in b a c kg ro unds fo r ZI COS Main backgrounds evaluated by KamLAND-Zen are mainly 208 Tl inside the balloon film. Need additional technique except energy spectral shape obtained by scintillation light in order to reduce those backgrounds drastically. Can we use Cherenkov lights for background reduction ? Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 16
Pro pe rty o f Che re nko v lig ht Refractive index of anisole : n=1.518 Cherenkov angle is determined by cos θ = 1/n’ β (Ee>0.7MeV) n’>n Assuming 1.65MeV electron, then β =0.972 and Cherenkov angel θ =47.3 degree are expected. Number of Cherenkov photon : 100 photon/MeV (400nm – 600nm) c.f. Light yield of Scintillation : ~12000photon/MeV Cherenkov light = ~1% of scintillation light Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 17
Me a sure me nt o f L Y fo r Che re nko v lig hts 90% SC-37 filter 50% 400nm 500nm 600nm Cherenkov light yield ( λ >400nm) Scintillation light yield of std. LS 159/0.15/0.95 = ~0.02 = 255/0.046/0.098 Consistent with expectation. Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 18
Sig nific a nt b a c kg ro unds 208 Tl : β and 2.6MeV γ s 214 Bi : β and multi γ s (609keV,1.12MeV) 164 µ s No Cherenkov lights (scintillation only) α -particle and low energy e/ γ • Observed Cherenkov lights • Can we check the consistency of vertex position obtained by scintillation and Cherenkov? (if we can reconstruct vertex position using Cherenkov lights.) Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 19
208 T l b a c kg ro unds 0νββ event e- Reconstructed vertex by e- scintillation only Real position 2.6MeV γ Reconstructed vertex e- by Cherenkov Balloon film Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 20
E le c tro n kine tic e ne rg y spe c trum For calculation of 2 νββ , k i , electron momenta ε i =sqrt(k i 2 +m e 2 ) : electron energy W 0 =Q+2m e : total release energy Q : Q value m e : electron mass θ : opening angle F : Fermi func. ε i can generate independently within energy conservation. For calculation of 0 νββ , 2e emit Cherenkov Same calculation but ε i can only lights generate with ε 1 + ε 2 =W 0 . Ma y 11, 2016 Re ve a ling the histo ry o f the unive rse with und e rg ro und p a rtic le a nd nuc le a r re se a rc h 2016 21
Recommend
More recommend
