Neutrino Telescope in Lake Baikal:
Recent Status and Future Perspectives
Rastislav Dvornickýon behalf of the Baikal-GVD collaboration

JINR, Dubna, Russia
Comenius University in Bratislava, Slovakia

Baikal-GVD Collaboration

Collaboration: 10 institutions, ~70 members
1. Institute for Nuclear Research, Moscow, Russia.
2. Joint Institute for Nuclear Research, Dubna, Russia.
3. Irkutsk State University, Irkutsk, Russia.
4. Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia.
5. Nizhny Novgorod State Technical University, Russia.
6. St. Petersburg State Marine University, Russia.
7. EvoLogics Gmbh., Berlin, Germany.
8. Institute of Experimental and Applied Physics, CTU in Prague, Czech Rep.
9. Comenius University, Bratislava, Slovakia.
10. Krakow Institute for Nuclear Research, Krakow, Poland
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Baikal-GVD telescope(under construction)
Objectives:• 1 km3-scale 3D-array of photo sensors• flexible structure allowing an upgrade and/or
a rearrangement of the main building blocks (clusters)• high sensitivity and resolution of neutrino energy,
direction, and flavour content
Physics Goals:• Investigate Galactic and extragalactic neutrino“point sources” in energy range > 100 TeV• Diffuse neutrino flux – energy spectrum, local, andglobal anisotropy, flavour content• Sporadic cosmic sources (GRB, …)• Dark matter and exotic particles searcha tool for multi-messenger astronomy

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Baikal-GVD site

Location: 104o25’ E; 51o46’ N

Shore station

36 km

Baikal’sk
Workshop & Storage facilities• Location ~ 3.6 km from shore• Stable ice cover during
Feb.-April: detector
deployment and maintenance•Baikal water properties:
absorption length ~ 22-24 m
scattering length ~ 30-50 m
low background 15-60 kHzPMT R7081R7081-100 10”
•Absence of high luminosity
bursts from biology andK40 background•The constant depth of the lake
1366-1367 m4

Baikal ambient light field• The increases of the luminescence
activity intermitting periods ofrelatively stable optical background in
2018-2021.
• The luminescent layer propagatedupwards with the maximal speed of 28
m/day in Jan. 2021.

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Baikal-GVD optical module
PMT Hamamatsu
R7081-100
=10 inch
QE ≈ 35% @ 400nm
TTS ~ 3.5 ns
Gain ~107
Dark current ~8-12 kHz

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Optical modules assemble(JINR Dubna)

OM
electronics
Mu-metal cage
PMT
Optical gel
Pressure-resistantglass sphere
VITROVEX (17”)

The new facility allows to
produce and test up to
12 OM per day.
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Baikal-GVD section of OMs
Section• 12 OMs, 15 m spacing, all PMTs look downward.
• 2 acoustic modules (AM) of the positioning system.

12/24VADC 12ch

AM 1, 2control

Optical module

Section control
module

power

pulse

OM 1…12

Commutator

triggerpower

Masterdatacontrol

shDSL

power

Power
supplySection module

COMServer

Section control module• ADC12 ch, 200 MHz sampling;• pulse form measuring.
• Trigger logic, events forming, data filtration.
• Data transmission: shDSL ethernet extender:
5.7 Mbit/sAcoustic module

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Baikal-GVD cluster

Shore hybrid cable,
6 optical fibers,
6 - 7 km length

Section 1525 m

Section 2

Section 3

Cluster: 288 OMs
 24 Sections on 8 strings,
 Cluster DAQ center Shore cable: 6 - 7 km
 Depths from 750 to 1275 m

Cluster
centerCluster

Shore DAQ center

Cluster DAQ• Trigger: 1.5 & 4 p.e. of adjacent optical modules.
• Maximum trigger rate: ~200 Hz.
• Data transferring: shDSL Ethernet extenders: 5.7 Mbit/s• Inter-section synchronization by trigger: ~2 ns accuracy.

120 m
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Automatic data processing• 40 Gb/cluster/day send and stored at the shore centre• 300 Mbit/s radio link over the lake to Baikal’sk• Data send to JINR servers over the internet• Data stored on EOS• Recently (2021), completely automatic data processing(100s of cores) + alert production system• Raw waveforms stored →possible reprocessing• Pulse extractions• White Rabbit synchronization ofindependent cluster data transfers• Data Quality Monitoring10

Calibration devices
Section calibration: 2 LEDs in each OM, 470 nm, 1 - 108 ph., 5 ns.
String calibration: LED beacons in 12 OMs of a cluster.
Cluster calibration: 2 Lasers per station, 532 nm, 1012 - 1015 ph., 1 ns.

Calibration LEDs
- 2 vertical LEDs;

LED beacons- 2 vertical and 10
horizontal LEDs

Laser event

Calibration accuracy ~2 ns11

Acoustic positioning system•••••

OM drift can reach tens of meters, depending on season and elevation.
OM coordinates are acquired via an acoustic positioning system.
It consists of a network of acoustic modems (AMs) installed along strings
4 AMs per string in a standard configuration.
OM coordinates are obtained by interpolating AM coordinates, error < 0.2 m
12Baikal-GVD construction status and schedule
Status 2021: 8 clusters, 3 laser stations, 2 experimental strings
Deployment schedule
Year
2016
2017

Number Numberofof OMs
clusters
1288
2576

2018

3864

2019

51440

2020

7

2016

2021

82304

2022

1028802023

1234562024

144032

Effective volume 2021: 0.40 km3 (cascade mode)
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Selected results Muons detection mode: atmospheric neutrinos
 Multi-messenger studies
 Cascades detection mode: HE cascades

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Muons – track analysis
Present status: technique for neutrino events selecting and reconstructing is currently
being developed.

Reconstruction: noise hit suppression and fit track with quality function:

Data sample: data taken between Apr 1 and Jun 30, 2019; 5 clusters.
Event selection: 8 hit OMs on at least two detector strings.
late

Neutrino selection cuts:- Zenith angle >120
- Fit quality Q/ndf < 32-Visible track length L >75 m- Average distance to OMs < 18 m
- Charge of all hits > 18 p.e.
- Estimated zenith angle error < 2Upgoing: θzenith > 120 deg.

early15

Muon neutrino: single-cluster analysis• 9.8 million reconstructed events for the combined dataset from the 5 clusters.
• Single-cluster equivalent live time 323 days.

MC expected: 43.6 ±6.6 (stat.)Observed: 44

The median energy of the neutrino
events 500 GeV.

Fair agreement with MC prediction
for atmospheric neutrino

Angular resolution: (single cluster)~ 1° or better16Multi-messenger studies
BAIKAL-GVD alerts
Since Sept. 2020: data processing with a delay ofseveral hours. Nearest plans: HE alerts processing
with delay less than tens of minutes.
ANTARES alerts
Since the end of Dec. 2018 Baikal-GVD follows
ANTARES alerts. Processed 48 alerts, among
which 3 possible coincidences were found incascade mode within 5° and T = ±1 day and areunder investigation with ANTARES.

IceCube alerts
Starting Sept. 2020 Baikal-GVD follows ICalerts (GCN) , 22 alerts.
Upper limits at 90% c.l. on the neutrino fluence:~1÷2 GeV cm-2 for energy range 1TeV– 10PeV.
E-2 spectral behavior; equal fluence in all flavors.

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Cascades detection with Baikal-GVD
Neutrino effective area for 7 GVDclusters

Expected number of events in 7 GVD clusters
from astrophysical neutrinos for 1 yr.

3-4 events/yr Esh >100 TeV

Energy resolution : δE/E ~ 10%-30%

Directional resolution for cascades:
2°- 4° - median value of mismatch angles 18

Preliminary!

High energy cascades (data and MC)
Data from 2019-2020 , live-time: 2915 days (in terms of one cluster)
MC atmospheric muons - Corsika 7.74, Sybill 2.3c, protons, E p>100 TeVIThanks to Jakob van Santen for modification of DYNSTACK CORSIKA.
72 events with E > 40 TeV and Nhit > 19

10 events with E > 100 TeV and Nhit >19:
Energy distribution

One upgoing cascade: E ≈ 91 TeV
Cosine of zenith angle

EventsDatalogE/Tev

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619

Final selection requirements:

Preliminary!

(N Type_2 = 0, Erec  60 TeV) or (N Type_2 = 1, Erec  100 TeV)
7 data events have been selected.
4 events are expected from atm. muons
5 events are expected from E-2.46 astrophys. flux with IC normalization
Cumulative distributions of data and events fromatm. muons and astrophys. flux after final cuts

2020Preliminary!

Parameters of 10 selected events (2018-2020)
E, TeV z,degree

,degree

R.A.

Dec

GVD2018_354_N

105

37

331

118.2

72.5

GVD2018_383_N

115

73

112

35.4

1.1

GVD2018_656_N

398

64

347

55.6

62.4

GVD2019_112_N

1200

61329

217.7

57.6

GVD2019_114_N

91

109

92

45.1

-16.7

GVD2019_663_N

83

50

276

163.6

34.2

GVD2019_153_N

12950

321

33.7

61.4

GVD2020_175_N110

71

185

295.3

-18.9

GVD2020_332_N

74929223.035.4

GVD2020_399_N

246

5749

131.9

50.2
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Sky map with 10 events

Preliminary!

Small (large) circle stands for 68 % (95%) C.L.
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GVD_2019_112_N event

Preliminary!

• Energy E = 1 200 TeV (±30%)• Distance from central string r = 91 m
• Zenith angle = 6123

Gamma sources nearby the event

Fermi sources in 5 circle:
1ES 1421+582
RBS 1409
2MASS J14363365+6149514
OQ 530 = J1419+5423
brightest radio-blazar (1.1 Jy)
S4 1427+543
87GB 135720.6+555936
FIRST J150106.2+552750
FIRST J150229.0+555204

E> 30 GeV
RBS 1409 BL Lac z=unknown.
1ES 1421+582 z=unknown.
both with hard spectrum

24Two close events at distance 10.3: GVD_2018_656_N and GVD_2019_153_N
Sky map of Fermi sources

LSI +61 303 and the two events

LSI +61 303 – at 3.1 and 7.4 from GVD_2019_153_N and GVD_2018_656_N
LSI +61 303 – -ray active micro-quasar
Using PSFs of all 10 events chance probability to observe such configuration was estimated:p-value = 0.007 or 2.7  ! (conservative, preliminary!!!)25

Preliminary!

The first clear cascade event from the interaction of an
upward moving electron- or a tau-neutrino at ~ 100 TeV
Contained event
Reconstructed energy E = (91 ± 11) TeVZenith angle
z = 109GVD2019_1_114_N

Sky plot of -ray sources(D.Semikoz, A.Neronov)

91.2 TeV (from below) no good known sources in 3
PKS 0302-16 unknown type of source
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PMN J0301-1652 unknown type of sourceRadio-loud blazars – promising neutrino sources
A. Plavin et al., ApJ 894, 101 (2020)A. Plavin et al., ApJ 908, 157 (2021)

OQ 530

GVD2019_1_114_N
Radio blazar J0301-1812

Sky plot of radio-bright blazars nearby neutrino event

Light curves of J0301-1812 measured by RATAN-600

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GVD2020_3_175_N
Radio blazar J1938-1749
Sky plot of radio-bright blazars nearby neutrino event

Light curves of J1938-1749 measured by OVRO

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Acknowledgements
We sincerely thank to Y. Kovalev, A. Neronov, A. Plavin, D. Semikoz,
and S. Troitsky who performed comparing of our results withastrophysical data.

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Conclusions
Baikal-GVD is now the largest neutrino telescope in the Northern
Hemisphere: 0.4 km3 and still growing.

Modular structure of the Baikal-GVD design allows a search for HE neutrinos andmulti-messenger studies at the early phases of the array construction.
Observations of atmospheric neutrinos by Baikal-GVD agree with expectations,first astrophysics neutrino candidate events have been selected.

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Future plansImprovements in pulse extraction: Pulse ﬁtting, Double Pulse
identiﬁcation, pulse separation
Alerts: Shorten the time from a few hours to a few tens of minutes

Multi-cluster track reconstruction, search for high-energy starting events
Experimental strings with optical DAQIncreasing the effective volume about 2 clusters per winter expedition

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Thank you for your attention!

http://baikalgvd.jinr.ru