ZICOS EXPERIMENT FOR NEUTRINOLESSDOUBLE BETA DECAY SEARCH USINGZIRCONIUM-96

TAUP 2019 16th International Conference onTopics in Astroparticle and Underground Physics
Toyama Japan
12 September, 2019
Supported by Grant-in-Aid for Scientific Research on Innovative Areas
19H05093 and Scientific Research (C) 18K03664

Miyagi University of Education

Y. Fukuda, Narengerile, A. Obata,Y. Kamei, D. Anzai

Kamioka Observatory, ICRR, Univ. of Tokyo S. Moriyama, K. Hiraide
Fukui University I. Ogawa
Tokyo University of Science T. Gunji, S. Tsukada, R. Hayami
Institute for Materials Research, Tohoku University S. Kurosawa

Neutrinoless doube beta decay[T1/20ν(0+ ->0+)]-1 =G0ν(E0,Z)|M0ν|2<mν>2 /me2
T1/2~a(Mt/∆E・B)1/2

a: abundance

M: target masst: measuring time ∆E: energy resolution B: BG rate

Requirement : Low BG, Large target mass, High E-resolution
TAUP2019

Sep 12th, 20192

9ZICOSexperiment for neutrinoless double
beta decay using 96Zr
Liquid Scintillator：(1) 10 wt.% Zr(iprac)4 loaded in
Liquid Scintillator(2) 3~4% at 3.35MeV of energy
resolution with 64% photo
coverage and long attenuationlength.

3.5m

Pure water surrounding innerdetector in order to veto muons andexternal backgrounds.
Inner detector with ~64% photo
coverage 20” PMT including 1.7ton
Zirconium loaded 113 tons LS infiducial volume. (Total vol. : 180tons)
TAUP2019

10m
10m

Purpose:① Direct measurement of 0νββ
② Confirm parameter of nuclear
matrix element modelSep 12th, 20193

Liquid Scintillator solving Zr(iPrac)4Zr(CH3COCHCOOCH(CH3)2)4= Zr(iPrac)4mw : 663.87Zr(iprac)4 2242mg, PPO999mg and POPOP 10mg
solved in 20mL Anisole> 70g/L of Zirconium could be solved in anisole.
TAUP2019

Sep 12th, 20194

Performance of liquid scintillator
Measured at several conditions of PPO concentration

48.7±7.1% light yield tostandard cocktail was
obtained at 10wt.%
concentration.
TAUP2019

13.0±2.0%√(64%/9.2%)X(3.35MeV/1.03MeV)= 2.7±0.4% at 3.35MeV
Sep 12th, 20195

Conceptual design of ZICOS detector
Phys.Rev.Lett. 117 (2016) 082503

0𝜈𝜈
NEMO3 : 𝑇𝑇1/2> 9.1 × 1021 yrs

96Zr : 45kg (nat.) → 865kg(50% enrich)→1/20 BG

TAUP20190𝜈𝜈𝑇𝑇1/2> 4 × 1025 yrs → 2 × 1026 yrs → ~1 ×1027yrs
Sep 12th, 20196

Decay scheme of 208Tｌ

The vertex position reconstructedby scintillation might be within
fiducial volume due to gammas.
TAUP2019

Sep 12th, 20197

Discrimination of signal and BG
0νββ event
e-Reconstructed vertex byescintillation light

β decay
2.6MeV γ
Reconstructed vertex
by Cherenkov light
Balloon or
surface ofdetector
TAUP2019

e-Sep 12th, 20198

BG reduction using topological information
Simulated by EGS5

Simulated by EGS5

78%
remainVertex position
Double beta decay event sample
Simulated by EGS593%cut

Topological information from
PMT position which received
PMT hit pattern of 208Tl BG and Cherenkov lights could be
used for the reduction of0νββ signal
208Tl BG event. Sep 12th, 2019
TAUP2019
Vertex position

9

Measurement of pulse shape difference
Photomultiplier : Hamamatsu H2431-50 (R2083)

 Spectral response ：４００K QE: 25% at peak Dynode structure : linear focused/8 dinodes
 High voltage ：３０００V
 Gain：2.5×106 dark current :100nA (H6410:10nA)
 Time response ：0.37ns(TTS) 0.7ns（rise time）
TAUP2019

Sep 12th, 201910

Measurement of pulse shape difference
FADC digitizer: CAEN V1751

TAUP2019

 10 bit 2 GS/s (interleaved) – 1 GS/s ADC
 4-8 channel
 FPGA for real time Digital Pulse Processing: Pulse Shape Discrimination (DPP-PSD)
 Zero Length Encoding (DPP-ZLEplus)
 0.2 or 1 Vpp input dynamics single ended or 1 Vpp differential
 16-bit programmable DC offset adjustment: ±0.5 V / ±0.1 V
 Trigger Time stamps
 Memory buffer: up to 14.4 MS/ch (28.8 MS/ch @2 GS/s)
 Programmable event size and pre-post trigger adjustment
 Analog Sum/Majority and digital over/under threshold flags for
Global Trigger logic
 Front panel clock In/Out available for multiboard synchronisation(direct feed through or PLL based synthesis)
 16 programmable LVDS I/Os
 Optical Link interface (CAEN proprietary protocol)
 VME64X compliant interface A2818(PCI) / A3818 (PCIe) Controller available for handling up to
8/32 modules Daisy chained via Optical Lin Firmware upgradeable via VME/Optical Link
 Libraries, Demos (C and LabView) and Software tools for Windows andLinuxSep 12th, 201911

Pulse shape using 90Sr/90Y beta decay Electrons from 90Y decay
could have an energy
above Cherenkov threshold.

Possible to measure
pulse shape using highstatistics electrons for
Cherenkov light.
TAUP2019

Sep 12th, 201912

Pulse shape for Cherenkov and Scintillation• Decay time ofscintillation : 6.5ns• Decay time of
Cherenkov : 2.4ns (fast)
2.7ns (slow)• Rise time of scintillation :1.6ns• Rise time of Cherenkov :light : 0.8ns
Possible pulse shapediscrimination for selectionof PMTs whether including
Cherenkov light or not.
TAUP2019

Sep 12th, 201913

R&D and Physics program① R&D（２０１９～２1）• Development of pulse shape discrimination• Energy resolution with 60% photo coverage• Topological info. (averaged angle)• Demonstration of ＢＧ reduction② Physics program I （２０２２～２６）• 2”PMT proto-type detector（R~35cm)• 6.5kg Zr(iPrac)4 ~80g of 96Zr（Nat.）• Use for water veto tank2𝜈𝜈
• 96Zr 2νββ measurement 𝑇𝑇1/2~2.1x1019y0𝜈𝜈
> 9.1 × 1021 yrs• 96Zr 0νββ update NEMO3 𝑇𝑇1/2• 96Zr enrichment→need some techniques
TAUP2019

Sep 12th, 201914

R&D and Physics program① R&D（２０１９～２１）• Development of pulse shape discrimination• Energy resolution with 60% photo coverage• Topological info. (averaged angle)• Demonstration of ＢＧ reduction② Physics program I （２０２２～２６）• 2”PMT proto-type detector（R~35cm)• 6.5kg Zr(iPrac)4 ~80g of 96Zr（Nat.）• Use for water veto tank2𝜈𝜈
• 96Zr 2νββ measurement 𝑇𝑇1/2~2.1x1019y0𝜈𝜈
> 9.1 × 1021 yrs• 96Zr 0νββ update NEMO3 𝑇𝑇1/2• 96Zr enrichment→need some tecniques
TAUP2019

Sep 12th, 201915

BACK SCATTERING METHODNaI detector

60Co

sourceLiquid scintillator

PMTTAUP2019

Single peak could be usedeven in liquid scintillator.
Sep 12th, 201916

Measurement for energy resolution with
60 % photo coverage

TAUP2019

Sep 12th, 201917

R&D and Physics program① R&D（２０１９～２１）• Development of pulse shape discrimination• Energy resolution with 60% photo coverage• Topological information (averaged angle)• Demonstration of ＢＧ reduction② Physics program I （２０２２～２６）• 2”PMT proto-type detector（R~35cm)• 6.5kg Zr(iPrac)4 ~80g of 96Zr（Nat.）• Use for water veto tank2𝜈𝜈
• 96Zr 2νββ measurement 𝑇𝑇1/2~2.1x1019y0𝜈𝜈
> 9.1 × 1021 yrs• 96Zr 0νββ update NEMO3 𝑇𝑇1/2• 96Zr enrichment→need some techniques
TAUP2019

Sep 12th, 201918

Measurement of topological information• Measurement of averaged angle by HUNI-ZICOSTAUP2019

Sep 12th, 201919

R&D and Physics program① R&D（２０１９～２１）• Development of pulse shape discrimination• Energy resolution with 60% photo coverage• Topological info. (averaged angle)• Demonstration of ＢＧ reduction② Physics program I （２０２２～２６）• 2”PMT proto-type detector（R~35cm)• 6.5kg Zr(iPrac)4 ~80g of 96Zr（Nat.）• Use for water veto tank2𝜈𝜈
• 96Zr 2νββ measurement 𝑇𝑇1/2~2.1x1019y0𝜈𝜈
> 9.1 × 1021 yrs• 96Zr 0νββ update NEMO3 𝑇𝑇1/2• 96Zr enrichment→need some techniques
TAUP2019

Sep 12th, 201920

Demonstration of BG reduction• Direct reduction for βγ events by UNI-ZICOS

ThO2

TAUP2019

Sep 12th, 201921

R&D and Physics program① R&D（２０１９～２１）• Development of pulse shape discriminaiton• Energy resolution with 60% photo coverage• Topological info. (averaged angle)• Demonstration of ＢＧ reduction② Physics program ZICOS-I （２０２２～２６）• 2”PMT proto-type detector（R~35cm)• 6.5kg Zr(iPrac)4 ~80g of 96Zr（Nat.）• Use for water veto tank2𝜈𝜈
• 96Zr 2νββ measurement 𝑇𝑇1/2~2.1x1019y0𝜈𝜈
> 9.1 × 1021 yrs• 96Zr 0νββ update NEMO3 𝑇𝑇1/2• 96Zr enrichment→need some techniques
TAUP2019

Sep 12th, 201922

③ Physics program ZICOS-II（２０２７～）• Goal : T1/2>1027years mν~3meV• Detector design• Kamioka mine/need radisu12ｍ water tank
• 96Zr enriched Zr(iPrac)4• International collaboration?
• Budget（total 10M$）① 96Zr enrichment : a few M$??
② First 20” PMT (rise time<1ns)
650 PMTs X 6000$ = 4M$③ Detector (no excavation)＋electronics :less 10M$④ Synthesis of 12ton Zr(iPrac)4 : a few M$
TAUP2019

Sep 12th, 201923

Summary• High Zr concentrated liquid scintillator is available.
• Expected energy resolution ~3％＠３．３５ＭｅV→ need to confirm with 60% Photo coverage• Need reduction technique for backgrounds from208Th decay→ topological info using Cherenkov lights① Pulse shape discrimination for selection ofPMT which receives Cherenkov lights.
② Confirmation of topological information③ Demonstration of βγ events reduction using
topological information• Physics program with proto-type detector will start
within 3~4 years. Stay tuned!
TAUP2019

Sep 12th, 201924

Backup slides

TAUP2019

Sep 12th, 201925

Topological info. : averaged angle
Average directione- = Σ didi θi

Averagedangle= Σ θiNhit

Average angle with respect to averaged direction
for single electron seems to have a peak at 48
degree which is almost same as Cherenkov angle.
TAUP2019

Sep 12th, 201926

Time profile of scintillation

TAUP2019

Time profile distribution
was obtained by singlepeak.
27
Sep 12th, 2019

Time profile of Cherenkov light

Time profile distribution wasseparated by two peaks.
TAUP2019

Sep 12th, 201928