2022-08-07

What can neutrinos dofor geoscience?
Ingrida Semenec (she/her)Queen’s University

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!"#$%&'$(&)*+%,-$(./0+%0$.-,121Liquid Scintillator
Detectors
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The expected signal prediction
Given a certain geological model the antineutrino spectrum at a given position r can be calculated

Decay rate

Geoneutrino flux

ProducVon spectra Survival probability

Geological factor

Distance and Cumulative Flux×106Total 100＜５００kmCrust 80５０％3602Mantle140

Percentage of total (%)

Cumulative flux (1/cm2/sec)

4

sediment
crustmantle
total

20

Sediment
0 0
10101

102
103
Distance from KamLAND (km)neutrino oscillation
Enomoto et al. EPSL 258, 1147 (2007)
P (E, L) ⇠ 1

sin2 2✓

104

About 50% of the expected
geoneutrino signal comesfrom the crust within 500-800
km around the detector, thus
local geology has to be known

120(constant suppression)

12

Current Experimental results
KAMLAND

BOREXINO• 1000t liquid scinXllator• 278 t liquid ScinXllator• 2700 m.w.e depth• 3800 m.w.e depth• Expected event raXo reactor/geo ~6.7 (~0.4 for reactor shutdown)• Expected event raXo reactors/geo ~ 0.3

13

A'2*0-5%0B%;+04+"*-'40%@+)2"-+@+4*22.

Efficien

8060

Selection efficiency

Latest geoneutrino measurements
Data - BG - best-fit reactor ie
Reference geo ie
U contribution
Th contribution

604020KAMLAND
0Events / 0.2MeV

Phys. Rev. D 101, 012009 (2020)

Best-fit reactor ie
Accidental

KamLAND data

180160

BOREXINO

Preliminary

14012010080

13C(_, n)16O60

Best-fit geo ie

40Best-fit reactor ie + BG
+ best-fit geo ie

20
0
1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

Ep (MeV)

Livetime 4397 days (Mar 9, 2002-Apr 15, 2018)1167 candidate events
168.8 +26.3/-26.5 geoneutrino events+15.6/-15.7% uncertainty[KamLAND Information provided by: Dr. Hiroko Watanabe, Tohoku University]

Livetime 3263 days (Dec 9, 2007-Apr 28, 2019)
154 candidate events
52.6 +9.4/ -8.6 (stat) +2.7/-2.1 (syst) geoneutrino events
15+18.3/-17.2% uncertainty

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2021

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Mantle contribuFon(KAMLAND+BOREXINO)Plot by: Ondřej Šrámek, Charles University,Prague, Czech Republic,
ondrej.sramek@gmail.com

KAMLAND: [Watanabe 2019 at NGS Prague]
Measured signal 32.1 ± 5.0 TNU After subtracting crustal prediction:
Mantle signal 6.0+5.6−5.7 TNU Corresponds to ~15 TW in the Earthor ~8 TW in the mantle.
BOREXINO: [Agostini et al 2020 doi:10.1103/PhysRevD.101.012009]
Measured signal 47.0+8.6−8.1 TNU After subtracting crustal
prediction: Mantle signal 21.0+9.6−9.0 TNU Corresponds to38.2+13.6−12.7 TW in the Earth or 30.1+13.5−12.7 TW in themantle.

• Factor of 3.5 difference in mantle radiogenic power• Ongoing effort to understand discrepancy• Multiple groups are looking into the local crustal models

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