Geoneutrino studies with
JUNO detector

Oleg Smirnov, JINR, Dubna
on behalf of JUNO collaboration

International Workshop：Neutrino Research and Thermal
Evolution of the Earth
October 25 – 27, 2016, Sendai, Japan

tryInstituteiam

Yerevan Physics Institute
Universite libre de Bruxelles
PUC
UEL
PCUC
BISEE
Beijing Normal U.
CAGS
ChongQing University
CIAE
DGUT
ECUST
Guangxi U.
Harbin Institute ofTechnology
IHEP
Jilin U.
Jinan U.
Nanjing U.
Nankai U.
NCEPUPekin U.
Shandong U.
Shanghai JT U.
IMP-CAS
SYSU
Tsinghua U.
UCAS
USTCU. of South China
Wu Yi U.
Wuhan U.
Xi'an JT U.

Collaboration established in July 2015
Now: 66 institutions
444 collaborators
8 obervers

China
China
CzechFinland
FranceFranceFranceFranceFranceGermany
Germany
Germany
Germany
Germany
Germany
Germany
Italy
Italy
Italy
Italy
Italy
Italy
Italy
Italy
Pakistan
RussiaRussiaRussiaTaiwanTaiwanTaiwanThailand
USAUSA

Xiamen University
NUDTCharles U.
University of Oulu
APC Paris
CPPM Marseille
IPHC Strasbourg
LLR Palaiseau
Subatech Nantes
Forschungszentrum Julich
RWTH Aachen U.
TUM
U. Hamburg
IKP FZI Jülich
U. Mainz
U. Tuebingen
INFN CataniaINFN di Frascati
INFN-Ferrara
INFN-Milano
INFN-Milano Bicocca
INFN-Padova
INFN-Perugia
INFN-Roma 3
PINSTECH
INR Moscow
JINR
MSU
National Chiao-Tung U.
National Taiwan U.
National United U.
SUT2
UMD1
UMD2

Electronics

Calibration

Filling+
overflow
Top Tracker

Central detector

Acrylic sphere+
20kt Liquid Scin+~18000 20”’ PMT+
~36000 3’’ PMT

AS: ID35.4m

43.5m

SSLS: ID40.1m

Connecting
bars: ~590

Water Cherenkov~2000 20’’ PMT

Pillar:~60
D43.5m

AS: Acrylic sphere; SSLS: stainless steel latticed shellElectronics

Calibration

Filling +Overflow
Top Tracker

Central detector

Acrylic shphere+
20kt Liquid Scin+~18000 20’’ PMT+
~36000 20’’ PMT

AS: ID35.4m

43.5m

SSLS: ID40.1m

Water Cherenkov~2000 20’’ PMT

D43.5m

AS: Acrylic sphere; SSLS: stainless steel latticed shell

44m

••

•
•

6.8 m

Veto system
Top tracker (TT):•
Re-using the Target Tracker walls of the OPERA experiment;•Total number is 62 and cover half of the top area;•3 TT layers spaced by 1 m ,each layer have x,y readout;•A solid bridge support the TT and its mechanical structure;•
Perform a precise muon tracking and provide valuable
information for cosmic muon induced Li9/He8 study.

Water Cherenkov detector:•20 inch MCP-PMT used for veto system with number~2000;•Detector efficiency requirement is expect to be>95%;•
Fast neutron background ~0.1/day.
Compensation coils system used for earth magnet field shielding tokeep PMT performance.
Water system:•
Employ a circulation/polishing water system;•
Keep a good water quality -including radon control.

one wall

top tracker

8

JUNO is mupltipurpose detector“Neutrino physics with JUNO”, J.Phys.G 43 (2016) 030401

•••••
•
•••
•

Neutrino mass hierarchy study
Precision measurement of neutrino oscillation parameters
Supernova bursts and diffuse supernova neutrinos
Solar neutrinos
R.Han, Y.-F. Li, L.Zhan, W.F.McDonough, J.Cao,
L.Ludhova
Atmospheric neutrino“Potential of geoneutrino measurements at JUNO”
Chinese Phys. C, Vol 40, No3 (2016) 033003
Geoneutrino
V. Strati, M.Baldoncini,I,Callegar, F.Mantovani,Sterile neutrino
W.F.McDonough, B.Ricci,G.Xhixha ”Expectedgeoneutrino signal at JUNO”
Nucleon decays
Progress in Earth and Planetary Science 2, 1 (2015).
Neutrinos from DM
Exotic searches with neutrinos

Detection of geo(anti)neutrino• Earth (in constrast to the Sun) emits
antineutrino.

• Part of antineutrino in the U and Th decay chainsis emitted with E>1.8 MeV (IBD threshold)• Contributions from U and Th are distinguishable• Oscillations are averaged:

ν + p →n+e+<Pee>=0.548+0.012-0.013

Eν>1.8 MeV

Expected antineutrino spectrum

Fig. from R.Han, et al., Chinese Phys. C, Vol 40, No3 (2016) 033003

Expected signals• Expected total reactor signal
1569± 88 TNU*(~90% contrinution from Taishan and Yangjiang nuclear power stations)*1 TNU = 1 event on 1032 protons an year

• Reactor signal in the geoneutrinoenergy window [1.8-3.27 MeV]:
351± 21 TNU• Expected geoneutrino signal:
Stot=39.7+6.5-5.2 TNU(V. Strati, et al.)
SLOC=17.4+3.3-2.8 TNU

Backgrounds for
geo-neutrino measurement1)Reactor antineutrinos (90% of the total
antineutrino signal in geo-nu window):
Geo/Reactor ratio
KamLAND= 0.23 (now much more)
Borexino = 1.8JUNO= 0.112)Cosmic muons induced backgrounds,
including cosmogenic production of(βn)-decaying isotopes (2000 m.w.e.)3)Internal radioactive contamination:
accidental coincidences,(αn) reactions

GeoNu/Backround depends on thethermal power of 2 reactors

Summary of expected rates
Source[1.8-9.0] MeV [1.8-3.3] MeV
ev/yrev/year

Uncertainty

geo408406

reactor

16100

3653

±2.8%(rate)±1%(shape)

8Li/8He657

105±20%(rate)±10%(shape)

fast n36.5

7.7±100%(rate)±20%(shape)

αn

18.2

12.2±50%(rate)±50%(shape)

accidental

401348±1%(rate)

20t->FV(R<17.2m) 18.35t or 12.85·1032 protons
ε=80% detection efficiency assumed in calculations
acrylic vessel (238U: 10 ppt, 232Th: 10 ppt)
LS: 10−15 g/g 238U/232Th

Reactor spectrum :Daya Bay
F. P. An, et al., “Measurement of electron
antineutrino oscillation based on 1230
days of operation of the Daya Bay
Experiment”,
arXiv:1610.04802v1 [hep-ex] 16 Oct 2016
1230 days>2.5 106 antineutrino events
Near detectors 350-600 m

Reactor
spectrum
Y.J. Ko, et al., “A sterile neutrino searchat NEOS Experiment”
arXiv: 1610.05134v1 [hep-ex] 17 Oct 2016

24 m from reactor
R(E)=5% @ 1 MeV
1965 ev/day
46 days reactor OFF
180 days reactor ON
Refers to F. P. An et al. (Daya Bay),(2016), arXiv:1607.05378 [hep-ex](621 days of data)
The differences between the fission
fractions for the NEOS data and theones for Daya Bay are taken into
account and small corrections aremade using the H-M flux model.

Geoneutrino signal extraction precision
fixed M(Th)/M(U)=3.9

Fig. from R.Han, et al.
In JUNO publication the sensitivity was estimated as 18% for 1 yr with -4% syst.bias

Geoneutrino signal extraction precision
free Th and U components
Figs. from R.Han, et al. : no bias

1 year: 1,2 and 3σ

Table from JUNO publication

10 years: 1,2 and 3σ

U/Th ratio reconstruction

Distribution of the ratio reconstructed-to-generated U/Th ratio for 1 (blue line) and10 (red line) years of lifetime after cuts. The simulations resulting in zero Thcontribution are not plot here (fig. from JUNO publication).

Radiogenic heat

GeodynamicalGeochemical
Cosmochemical

Fig. from R.Han, et al.

Signal from the mantle
Type equation here.Can be extracted from the measurement if crust contribution
is known

R(Mantle)=R(Geo, measured)-R(Crust, predicted)

Current prediction (V. Strati, et al.) for the R(Crust) has 18% uncertainty –blue line in the plot
Red line : 8% crust contribution knowledge (KamLAND level)𝜺𝜺𝑮𝑮𝑮𝑮𝑮𝑮 𝑵𝑵𝑮𝑮𝑮𝑮𝑮𝑮 𝟐𝟐 + 𝜺𝜺𝑪𝑪 𝑵𝑵𝑪𝑪 𝟐𝟐 + 𝑵𝑵𝑪𝑪

∆𝑵𝑵𝑴𝑴 =𝟏𝟏𝜺𝜺𝑴𝑴 = 𝟏𝟏−𝒓𝒓

𝑪𝑪𝒓𝒓𝜺𝜺𝑮𝑮𝑮𝑮𝑮𝑮 𝟐𝟐 + 𝜺𝜺𝑪𝑪 𝒓𝒓𝑪𝑪 𝟐𝟐 + 𝑵𝑵 𝑪𝑪

𝑵𝑵𝑪𝑪𝒓𝒓𝑪𝑪 ≡𝑵𝑵𝑮𝑮𝑮𝑮𝑮𝑮

𝑮𝑮𝑮𝑮𝑮𝑮∆𝑵𝑵𝜺𝜺 ≡𝑵𝑵

Importance of local contribution prediction

local (<500 km) crust contributes 50% of geoneutrino signal

Directionality?
••

•

•

The average forward shift of neutrons in the direction of incoming
antineutrinos have been observed by reactor experiments (i.e. by CHOOZ).
The basic idea is to search for the small statistical displacement of thecapture vertex of the neutron with respect to the vertex of the prompt
positron event.
The neutron from the inverse beta decay of geoneutrino carries energy up
to tens of keV and is emitted in a relatively narrow range (below ∼ 55degrees) of angles around the incoming antineutrino. The average forward
displacement of the neutron capture vertex is about 1.7 cm, as observed by
CHOOZ for reactor neutrinos, while the spread due to neutron drifting isabout 10 cm.
Given the small displacement (∼1.7 cm) and the large intrinsic smearing(∼25 cm), the direction of the reconstructed antineutrino is only meaningfulstatistically and needs large statistics. Because the direction to the reactors
in JUNO is known, it looks promising exploiting the fit of displacement
distribution with predicted separate distributions from geo and reactor
antineutrinos in conjunction with the spectral fit. An attempt to separate thecrust and mantle geoneutrino components could be made. Both tasks needextensive MC studies.

Summary• JUNO represents a new opportunity to measure geoneutrinos,recording of 300 to 500 geoneutrino interactions per year. In
approximately six months JUNO would match the present
world sample of recorded geoneutrino interactions, which isless than 150 events.
• Using a well constrained estimate of the reactor signal andreasonable estimates of the non-antineutrino sources, theconclusion is that geoneutrinos are indeed observable atJUNO.
• Maximizing the precision of the mantle geoneutrino
measurement at JUNO requires detailed knowledge of theuranium and thorium content in the crust within several
hundreds of kilometers to JUNO.
• The statistical power of the geoneutrino signal at JUNO enables
a measurement of the thorium to uranium ratio, which provides
valuable insight to the Earth’s origin and evolution.