Proposal:
Low Energy Neutrino
Search at Jinping
L i nyan Wa n , Ts i nghua U n i ve rsit yRe p res ent ing Ji nping Group2 0 1 6/10/27

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1Contents
China JinPing underground Laboratory (CJPL)
Detector Concept
Geo-Neutrinos
Other Physics
Status

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JINPING NEUTRINO EXPERIMENT2CJPL: Location

 Near Himalaya mountains.
 Located in Sichuan, China. 2 hours drive from Xichang airport.
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CJPL: Tunnel View Tunnel construction nearly finished.  On average 2,400 m rock shielding; 20 m * 100 m experiment hall;
岩土工程学报, Vol.38 Supp.2, 67
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4CJPL: Depth & Muon Flux
Deepest:2,400 m rockoverburden
Lowest muon rate:(2.0 ± 0.4) ×10−10 / (cm2⋅s)
Extremely lowspallation
background Spallation induced radioactive isotopes 9Li & 8He are the main sourceof non-neutrino background for geo-neutrino detection.
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5CJPL: Reactor Neutrino FluxReactors
Main Neutrino
Observatories

Jinping
Numerical
results later inthis talk.

 Reactor neutrinos are the dominant background overlapping withgeo-neutrino energy range and signal signature.
 More than 900 km away from the nearest nuclear plant.
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6CJPL:A Low Background Laboratory
 Lowest muon rate; Lowest reactor neutrinorate.
 Lowest rock radioactivity
contamination.

Ideal place for low backgroundexperiments: dark matter search,neutrino observatory, …
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JINPING NEUTRINO EXPERIMENT7CJPL Phase I & Phase II CJPL I finished construction in 2010, now hosting 2 dark matter
experiments: CDEX and PandaX.
 CJPL II under construction now, planning to host Jinping Neutrino
Experiment as well as several other low background experiments.

Shift room of CDEX
inside CJPL I
2013/10
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One of the CJPL II experimental
halls under construction
2016/6

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Contents
China JinPing underground Laboratory
Detector Concept
Geo-Neutrino
Other Physics
Status

10/27/2016

JINPING NEUTRINO EXPERIMENT9Neutrino Detection Technique
𝜈𝑒𝑒−

𝜈𝑒𝑒−

Electron elastic scattering

CerenkovScintillation

𝜈𝑒𝑝photon

Photoelectric
converter𝑒+𝑛

Neutron capture

Front-endelectronics

Inverse beta decay (IBD)

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10Detector Concept
 1.5 kton×2 Fiducial for IBD

 PMT coverage >70%
with self-designed light
concentrator
 Energy Resolution: 500 p.e.

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×211

Slow Liquid Scintillator
 Distinguish between
scintillation & Cerenkov
light in time spectrum.
 Enable particle
identification whichsuppresses fake electron
background.
 Now work to improve thescintillation light yield
w/o changing the timing
structure.

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Scintillation
Cerenkov

N.I.M Phys. Res. A 827 (2016) 165-170

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Contents
China JinPing underground Laboratory
Detector Concept
Geo-Neutrino
Other Physics
Status

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Geo Neutrinos:
 Are low energy (< 3.5 MeV) 𝜈𝑒 ’s from natural radioactivity emitted
by U/Th/K heat producing elements.
 Provide constrain on Earth’s thermal budget with geo neutrinomeasured radiogenic earth heat.

 Can be detected via IBD reaction.
TNU:To get avoid of the redundant conversion of target mass / live time etc..
1 TNU = 1 event / 1032 protons / 365 days.

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Reactor Neutrino Background SER: Signal Energy Region
overlapping with geo
neutrino (1.8 ~ 3.3 MeV)
 Reactor neutrino
background in Jinping
mainly come from reactors
in coastal China.
IAEA 201610/27/2016

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Non-Neutrino Background 9Li & 8He
The extremely low muon rate (2.0 ± 0.4) × 10−10 / (cm2⋅s) gives much
lower spallation background compared to other experiments. Thisbackground is estimated to be < 0.1 event / 3 kton / 1,500 days in Jinping.
 (𝛼, 𝑛) reaction
This background is closely related to the level of 210Po contamination
inside the tank. Assuming same level purity as Borexino, we estimate thisbackground to be 1.7 event / 3 kton / 1,500 days in Jinping.

Comparing with the dominant reactor neutrino background (61.3events / 3 kton / 1,500 days), the above non-neutrino backgroundare not taken into consideration in following analysis.

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Geo-Neutrino Oscillation
Geo-neutrino spectrum

Effective spectrum

KUTh In the present estimationof geo-neutrino flux at
Jinping, 𝑃𝑒𝑒 is employed
as an overall parameter
0.553.
Sci. Rep. 6, 33034 (2016)

 This overall parameter
simplification iscorrected by oscillation
analysis in prediction,
giving a 7% difference.
Electron neutrino survival
probability
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Uncertainty Estimation in GeoNeutrino Flux Prediction
SourceUncertainty

Crustal HPE Modeling*12%Oscillation

Vacuum parameter<1%MSW oscillation<1%Predicted detection precision in Jinping

8%* Sci. Rep. 6, 33034 (2016)10/27/2016

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Prediction:
IBD Events at Jinping
 500 p.e. energy resolution
 The calculation of geo
neutrino signal will becovered in Sramek’s talk.
 Signal/Background ratio > 8in SER.

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Predicted Sensitivity:
With Fixed Th/U Ratio
 With a fixed Th/U ratio in
accordance withtheoretical assumption(3.9),
 And a free reactor fluxparameter, sensitivity for geoneutrinos reaches 4%.
(statistical, 1𝜎)
Live time: 3.0 kton, 1,500 days
Energy resolution: 500 p.e.

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Predicted Sensitivity:
With Free Th/U Ratio
 With free Th/U ratio,
 sensitivity for geo neutrino
reaches 8%. (statistical, 1𝜎)
 Precision of U/Th ratio
measurement reaches 25%.
(statistical, 1𝜎)
Live time: 3.0 kton, 1,500 days
Energy resolution: 500 p.e.

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Contents
China JinPing underground Laboratory
Detector Concept
Geo-Neutrino
Other Physics
Status

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Other Physics Topics:
Jinping is Expected to…
Solar Neutrinos:
Discover CNO flux (5𝜎)Measure the transition phaseDetermine the high/low metallicity hypothesis (7𝜎~10𝜎)

Astro-Neutrinos:Join SNEWS for the supernova burst neutrinos
Reach the discover limit for supernova relic neutrinos
Constrain on galaxy dark matter10/27/2016

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Contents
China JinPing underground Laboratory
Detector Concept
Geo-Neutrino
Other Physics
Status

10/27/2016

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Timeline
2014: CJPL II started construction
2015: Proposal for Jinping Neutrino Experiment2016: Letter of Intent: Jinping Neutrino Experiment
ArXiv:1602.01733
1-ton prototype underway Now here!
2018: 10-ton prototype planned…

1-ton prototype
Design10/27/2016

1-ton prototype
Steel Tank

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1-ton prototype
Acrylic Ball
& Teflon Ball
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Conclusion
1. Experiment setup
 2,400 m rock shielding 2 kton * 2 liquid scintillator
 Lowest reactor neutrino background and muon rate
2. Geo-Neutrinos
 4% (8%) precise measurement of geo neutrino flux for
fixed (free) U/Th ratio
25% sensitivity for U/Th ratio
3. Status
 Now working on 1 ton prototype.
 Welcoming collaborating!
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Thank you!

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Backup: Discussion of MSW
 With lower energy, theMSW effect become
smaller; For 3~3.5 MeV, i.e., themaximum of geoneutrino energy, theMSW oscillation effectis around 1%.

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Solar Neutrinos:
Signal & Background Main background from radioactivity in scintillator, PMT glass,surrounding environment and muon induced isotopes.
 Backgrounds are estimated using Borexino or SNO result.

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Solar Neutrinos:
Numerical Result

 Mainly influenced by
Bi210, C11(muoninduced), and External
Tl208.

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Supernova Burst Neutrino
Doubledetectorcoincidence
reduces thewrong alarmrates.

ArXiv:1602.01733

Galaxy edge

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Supernova Relic Neutrino
With
scintillation/Cerenkov
distinguish technique,backgrounds will begreatly suppressed.
ArXiv:1607.01671

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Galaxy Dark Matter

ArXiv:1602.01733

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