# VLVnT 2021 - Very Large Volume Neutrino Telescope Workshop Valencia, 18 - 21 May 2021

Valencia

#### Valencia

Description

The workshop is a forum where the latest developments in neutrino astronomy are discussed together with the recent progress on the technological and instrumentation aspects of current and future large scale neutrino detectors in water and ice.

 CATALOG FLIP CHIP TECHNOLOGY PoP TECHONOLOGY PHOTOMULTIPLIER TUBES PHOTONIC DEVICES 2021

Participants
• aart heijboer
• Abdelilah Moussa
• Abhinav Choudhury
• Abigail Vieregg
• Agustín Sánchez Losa
• Alba Domi
• Albrecht Karle
• Aleksandr Doroshenko
• Alexander Avrorin
• Alexander Avrorin
• Alexander Trettin
• Alexandre creusot
• Alfonso Garcia
• Alfred Mishi
• Alice Paun
• Allan Hallgren
• AMAN Gupta
• Amani Besma BOUASLA
• Anastasiia Omeliukh
• Andreas Gaertner
• Andrey Romanov
• Angela Zegarelli
• Ankur Sharma
• Anna Pollmann
• Anna Sinopoulou
• Annarita Margiotta
• Antoine Kouchner
• Antonio Ambrosone
• Antonio Marinelli
• Antonio Palazzo
• Apoorva Bhatt
• Arjen van Vliet
• Bair Shaybonov
• Barbara Caiffi
• Barbara Skrzypek
• Bei Zhou
• Benito García
• Benjamin Smithers
• Benoit GUILLON
• Bhuti Nkosi
• Bianca De Martino
• Bouke Jung
• Brian Clark
• Brían Ó Fearraigh
• Camiel Pieterse
• Carlo Giunti
• Carlo Guidi
• Carlos Perez de los Heros
• Cecilia Lunardini
• Chiara Bellenghi
• Chiara Poirè
• Christian Glaser
• Christian Haack
• Christian Spiering
• Christian Spiering
• Christoph Andreas Ternes
• Christoph Tönnis
• Christos Markou
• Chun Fai Tung
• Chung Hei Leung
• Clara Gatius Oliver
• Cristiano Bozza
• Cristina Fernandez
• Damien Dornic
• Daniel Guderian
• Daniel Lopez-Coto
• David Guevel
• Davide Meloni
• Deesha Divecha
• Delia Tosi
• Dhavalkumar Ajana
• Dimitris Stavropoulos
• Dmitrii Petukhov
• Dmitry Chirkin
• Dmitry Zaborov
• Doğa Veske
• Dídac Diego-Tortosa
• Eduardo Ros
• Efstratios (Stratos) Anassontzis
• Ek Narayan Paudel
• Ekaterini Tzamariudaki
• Eligio Lisi
• Elisa Lohfink
• Elisa Resconi
• Eliška Eckerová
• Els de Wolf
• Emanuele Leonora
• Emma Kun
• Erin O'Sullivan
• Evgenii Ryabov
• Feifei Huang
• Felix Henningsen
• Fernando García
• Francesco Filippini
• Francisco Martínez López
• Francisco Salesa Greus
• Frank Schroeder
• Fuyudi Zhang
• Gabriela Emilia Pavalas
• George Privon
• Gilles Quéméner
• Giorgi Kistauri
• giorgio riccobene
• Giovanni Renzi
• Giovanni Renzi
• Gogita Papalashvili
• Grant Parker
• Grigory domogatsky
• Grigory Safronov
• Guillermo Lara Martinez
• Gwenhaël de Wasseige
• Hannah Erpenbeck
• Harold Yepes Ramirez
• Hugo Chancay
• Hyeonja Jhang
• Igor Belolaptikov
• Iván Navarro Arrebola
• Jannis Necker
• Jean Pierre Twagirayezu
• Jerzy Manczak
• Jessie Micallef
• Jeyson Alomoto
• Jhilik Majumdar
• Joao Coelho
• Johannes Schumann
• John Kelley
• Jordan Seneca
• Joshua Peterson
• Joshua Villarreal
• Juan Antonio Martínez-Mora
• Juan Macharé
• Juan Palacios González
• Juan zuniga
• Juan-Jose Hernandez-Rey
• Juan-Pablo Yanez
• Juande Zornoza
• Juergen Brunner
• Julia Tena Vidal
• Julien Aublin
• Jutta Schnabel
• Kay Graf
• Kayla Leonard DeHolton
• Ke Fang
• Kimy Agudelo Jaramillo
• Kohta Murase
• Kwok Lung Fan
• Lakshita Bageja
• Lali Kharkhelauri
• Leander Fischer
• Lishuang MA
• Luigi Antonio Fusco
• Lukáš Fajt
• Maitha Alshamsi
• Maksim Sorokovikov
• Manuel Bou-Cabo
• Manuel Silva
• Marc Labalme
• marco Anghinolfi
• Marco Chianese
• Marco Circella
• Mariam Tórtola
• Mariel Marceau
• Mariel Maurice
• Mark Shelepov
• Markus Ahlers
• Markus Dittmer
• Marta Colomer Molla
• Martin Rongen
• Massimiliano Lincetto
• Mateusz Wiśniewski
• Mathieu Lamoureux
• Mathieu Perrin-Terrin
• Matteo Sanguineti
• Mauricio Bustamante
• maurizio spurio
• MAURO TAIUTI
• Meriem Bendahman
• Merlin Varghese
• Michael Larson
• Miguel Ardid
• Miguel Gutiérrez
• Mohamed Lamine Abdelali
• Mohammed Bouta
• Mohan Khubchandani
• Munera Alrashed
• Nafis Rezwan Khan Chowdhury
• Nectaria Gizani
• Newton Nath
• Nhan Chau
• Nicole Geißelbrecht
• Nikolay Budnev
• Ningqiang Song
• Nora Valtonen-Mattila
• Noureddine Mebarki
• Oleg Kalekin
• Olga Botner
• Olga Suvorova
• Omar Gabella
• Paolo Fermani
• Paschal Coyle
• Pavlo Plotko
• Paweł Malecki
• Percy Cáceres
• Piotr Kalaczyński
• Pratik Kafle
• Qinrui Liu
• Rahmat Rahmat
• Rasa Muller
• Ravinder Dhayal
• Reda Attallah
• Rezo Shanidze
• Robert Lahmann
• Rogan Clark
• Rosa Coniglione
• Rémy Le Breton
• Sabya Sachi Chatterjee
• Salva Ardid
• Sandra Zavatarelli
• Santiago Pena Martinez
• Sara Rebecca Gozzini
• Sarah Mancina
• Sarah Mechbal
• Semyun Khokhlov
• Sen QIAN
• Sergey Troitsky
• Sergio Alves Garre
• Sergio Navas
• Sergio Palomares-Ruiz
• Sewta Sanjay
• Shabeeb Alalawi
• Shiqi Yu
• Siham Kalli
• Silvia Celli
• Simone Biagi
• Sohan Roy
• Sotiris Loucatos
• Sreetama Goswami
• Stefan Reck
• Steffen Hallmann
• stephane colonges
• Suman Kumar
• Summer Blot
• Surender Surender
• Sébastien Le Stum
• Tetiana Kozynets
• Thijs van Eeden
• Thomas Eberl
• Timur Elzhov
• Tommaso Chiarusi
• Tyce DeYoung
• Uli Katz
• Vahab Nazari
• Valentin Pestel
• Vedant Basu
• Victor Carretero
• Victor Muñoz
• Victor Valera
• Viktoriya Dik
• Vincent van Beveren
• Vivian ODell
• Viviana Niro
• Véronique Van Elewyck
• Wing Yan Ma
• Winnie Wang
• Wojciech Noga
• yahya Tayalati
• Yong Du
• Yuliya Yablokova
• Zhan-Arys Dzhilkibaev
• zineb aly
• Zuzana Bardačová
Contact
• Tuesday, 18 May
• 14:50 16:00
Plenary: Plenary talks

Plenary talks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

• 14:50
Welcome 10m
Speaker: Juande Zornoza (IFIC)
• 15:00
Status and plans for the KM3NeT detector 30m
Speaker: Dr. Rosa Coniglione (INFN - LNS)
• 15:30
Present status of the Baikal-GVD neutrino telescope 30m

Baikal-GVD is a cubic-kilometer scale deep-underwater neutrino detector being constructed in Lake Baikal. Since April 2020 the detector includes seven 8-string clusters carrying in total 2016 optical modules located at depths from 750 m to 1275 m. The progress in the construction and operation of the Baikal-GVD is reported. We review the scientific case for Baikal-GVD, the construction plan, and selected results from the partially built array which provides an effective volume of 0.35 km3 for cascades with energy above 100 TeV.

Speaker: Dr. Vladimir Aynutdinov (INR RAS)
• 16:00 16:40
Discussion: Neutrino astrophysics and multi-messenger astronomy

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

Convener: Ke Fang (University of Wisconsin-Madison)
• 16:40 17:00
Break 20m
• 17:00 19:20
Dark matter and exotics: Dark matter

VLVnT 2021 | Parallel Session Room C
https://cern.zoom.us/j/69737018748

• 17:00
Decaying Dark Matter at IceCube and its Signature in High-Energy Gamma-Ray Experiments 20m

Observations of high-energy astrophysical neutrinos in IceCube have opened the door to multi-messenger astronomy, by way of which questions in particle physics could be explored collaboratively between IceCube and optical experiments such as Fermi-LAT. However, the origin of these astrophysical neutrinos is still largely unknown. Among the tensions that still need to be resolved, for example, is the excess of neutrinos in the High Energy Starting Event (HESE) sample in the energy range of 40-200 TeV, a contribution that could come from dark matter decay. The dark matter decay hypothesis can be tested through comparisons with Fermi-LAT gamma-ray data. In particular, HESE predicts a soft neutrino spectrum that extends below around 50 TeV, but such a spectrum is incompatible with current gamma ray measurements and suggests that gamma-rays become heavily suppressed for sources dominating in this lower-energy range. A reason for this is that properties of the traversed medium, which consists of extragalactic background light (EBL), the cosmic microwave background (CMB), and the intergalactic magnetic field, significantly alter the final gamma ray spectrum that reaches telescopes on Earth. The existence of competing EBL models, moreover, complicates estimates of dark matter constraints. In this presentation, we address these questions by studying the impact that the EBL has on indirect measurements of dark matter decay. I present my predictions for galactic, inverse-Compton, and extragalactic gamma-ray spectra undergoing attenuation by different EBL models.

Speaker: Barbara Skrzypek (Harvard University)
• 17:40
Indirect search for dark matter in the Galactic Centre with IceCube 20m

Neutrino telescopes, such as IceCube, can be used to conduct indirect dark matter searches. A common assumption is that dark matter consists of Weakly Interacting Massive Particles (WIMPs), which are expected to produce standard model particles when they annihilate or decay. IceCube could then detect the neutrinos generated by these standard model particles. Since the Milky Way is expected to be immersed in a dark matter halo whose density increases towards its centre, the Galactic Centre is a designated target for indirect searches. In this contribution, we present the sensitivities of the search for dark matter in the Galactic Centre based on IceCube data, probing annihilation through $\nu\bar{\nu}$, $\mu^{+}\mu^-$, $\tau^{+}\tau^-$, $W^{+}W^-$ and $b\bar{b}$. The sensitivities presented here show considerable improvements when compared to results from previous IceCube searches and other neutrino telescopes in the energy range considered.

Speaker: Nadège Iovine (Université Libre de Bruxelles)
• 18:00
Solar WIMP Search with 10 Years of IceCube Data 20m

The existence of dark matter (DM) has been well-established by repeated observations probing many length scales. Although DM is expected to comprise the majority of the current matter content of the Universe, its nature remains unknown. Weakly interacting massive particles (WIMPs) are a class of DM that arise naturally from Standard Model (SM) extensions. Generically WIMPs have a non-zero cross-section with SM nuclei, which allows them to scatter off nuclei in large celestial bodies such as the Sun, losing energy and becoming gravitationally bound in the process. After repeated scatterings, WIMPs will eventually sink to the solar center, leading to an excess of WIMPs there. For sufficiently high densities, WIMPS will annihilate to stable SM particles, either directly or through a decay chain of unstable SM particles. Among stable SM particles, only neutrinos can escape the dense solar core. Thus, one may look for an excess of neutrinos from the direction of the Sun as evidence of WIMPs. The IceCube Neutrino Observatory, which detects Cherenkov radiation of charged particles produced in neutrino interactions, is especially well-suited to such searches since it is sensitive to WIMPs with mass in the preferred region for super symmetric extensions of the SM. In this contribution, I will present the status of IceCube's most recent solar WIMP search, which covers the WIMP mass range from 10 GeV to 1 TeV.

Speaker: Jeffrey Lazar
• 18:20
Search for secluded dark matter with 6 years of IceCube data 20m

The IceCube neutrino observatory consists of 5160 photomultiplier-tubes spread among 86 vertical strings making a total
detector volume of more than a cubic kilometer. It detects neutrinos via Cherenkov light of
charged relativistic particles from neutrino interactions with the detector volume. In this
analysis we search for secluded dark matter which annihilates into metastable mediator particles that subsequently
decay into neutrinos. Regular signals from dark matter annihilations in
the Sun are strongly attenuated at higher energies due
to absorption in the solar plasma. Secluded dark matter models allow the mediator to escape
the Sun before producing any neutrinos, thereby avoiding attenuation and yielding an enhanced neutrino signal. IceCube is ideal to search
for this enhanced high-energy neutrino signal due to its good sensitivity to high energy neutrinos. We present the sensitivities of an analysis of six
years of IceCube data looking for dark matter in the Sun. Mediator lifetimes between
1 ms to 10 s and dark matter masses between 100 GeV and 75 TeV are considered in this analysis.

Speaker: Dr. Christoph Tönnis (Sungkyunkwan University)
• 18:40
Search for dark matter from the center of the Earth with 8 years of IceCube data 20m

Neutrinos have been proved to be unique messengers in the understanding of fundamental physics processes, particularly in the astrophysics field. Also, they are thought to be able to provide hints of physics beyond the Standard Model, like Dark Matter models, among which those based on Weakly Interacting Massive Particles (WIMPs) physics. This kind of Dark Matter can scatter off Standard Matter nuclei in the vicinity of massive bodies such as the Sun or the Earth, lose velocity, and be gravitationally trapped in the center of the body. Self-annihilation of dark matter into Standard Model particles results in a flux of which the final products include neutrinos. For the case of the Earth, an excess of neutrinos coming from the center of the planet could indicate that the process described is taking place. The IceCube Neutrino Observatory, located at the geographical South Pole, can detect the neutrino flux described. A search has been conducted on 8 years of IceCube data, probing multiple dark matter channels and masses. The latest sensitivities of this analysis are competitive, world-leading in a part of the phase space, in comparison with previous analyses performed in the field.

Speaker: Giovanni Renzi (Université Libre de Bruxelles)
• 19:00
Progress in Solar Atmospheric Neutrino Searches with 9 Years of IceCube Data 20m

Cosmic rays interact with nucleons in the solar atmosphere to create pions, kaons, and other particles which decay to produce a flux of high-energy neutrinos. Although this flux is predicted in the literature, it has yet to be observed experimentally. This flux is an irreducible background for current solar WIMP searches. The detection of these neutrinos would improve the sensitivity floor for these searches, and would allow neutrino telescopes to measure neutrinos in yet-unprobed oscillation regimes, characterized by a ratio of baseline to the energy of L/E~1e5km/GeV. In this contribution, we will present recent progress in a new IceCube analysis optimized to detect solar atmospheric neutrinos.

Speaker: Joshua Villarreal (Harvard University)
• 17:00 19:00
Detector R&D and construction: Electronics

Hardware, calibration, measurement of medium properties, DOMs, photon detectors, deployment/installation

VLVnT 2021 | Parallel Session Room B
https://cern.zoom.us/j/68306216278

• 17:00
Evolution of the IceCube Data Acquisition System for IceCube-Gen2 20m

IceCube-Gen2 is a future large-scale extension to the IceCube Neutrino Observatory, a kilometer-scale neutrino detector at the geographic South Pole. The IceCube data acquisition system (DAQ) architecture, while running stably with over 99% uptime, will be re-optimized for IceCube-Gen2 to solve design challenges with power consumption, communications bandwidth, and cable specifications, while also integrating new types of instrumentation such as the cosmic ray and radio neutrino detection components. In particular, we describe how distribution of the photomultiplier tube signal digitization and pre-trigger storage can reduce power and bandwidth requirements. Changes to IceCube's custom communications protocol can also relax crosstalk requirements on the copper cabling. We report on the status of these optimizations in the prototype Gen2 digital optical module design for the upcoming IceCube Upgrade.

Speaker: John Kelley (Univ. of Wisconsin – Madison)
• 17:20
Status of the DOM electronics 20m

The KM3NeT Collaboration has already produced electronics to produce more than one thousand Digital Optical Modules, which have started to be deployed at the bottom of the Mediterranean Sea. An upgrade of the electronics is currently underway, expecting to have a revision of it by mid-2021 Here we describe the main improvements added to the DOM electronics, including the new high reliability transceiver in the Central Logic Board and the increased efficiency in the Power board.

Speaker: Diego Real Mañez (IFIC)
• 17:40
Underwater autonomous voltage supply systems 20m

The KM3NeT project aims to build a neutrino telescope in the depth of the Mediterranean Sea. The detector consists of a Kilometer-cube grid of Optical Modules, photosensors encapsulated into transparent pressure resistant glass spheres. A crucial component is the acoustic positioning system, which provides the position of photodetectors and structures in the deep sea with an accuracy of about 10 cm. The system is based on measurements of acoustic signals between fixed seabed emitters and receiving hydrophones. A subset of the required acoustic beacons is powered by an autonomous voltage supply system, based on a battery pack.
The talk will describe the innovative design used to build the battery packs, deriving from the expertise of the Catania KM3NeT group in the construction of underwater detectors encapsulated in glass vessels. The battery pack uses a pressure resistant 17-inch glass sphere as housing, identical to those used for optical modules. It contains a cluster of 96 batteries connected to supply an output voltage of 12 Volt with a total capacity of 410 Ah. With a dimension of 44 cm and a weight of 42 kg, the final result has then a very high energy density, especially for deep underwater application. The cluster of batteries is surrounded by silicone glue, the same technology used in the optical modules, that stacks all the part together and ensures mechanical strength and a stable link with the vessel. In order to increase the operating time of the beacon, a custom designed wake-up board implements a duty cycle operating mode, where an electronic switch controlled by an ARDUINO microprocessor connects the battery pack to the beacon only for a defined time. So far, 6 supply systems have worked among the Italian and the France sea site of the KM3NeT project. The system, designed for beacons, could be easily used to supply voltage for also other kinds of detectors in underwater high-pressure environments.

Speaker: Emanuele Leonora (INFN, sezione di Catania)
• 18:00
Proposal for fiber optic data acquisition system for Baikal-GVD 20m

The first stage of the construction of the deep underwater neutrino telescope Baikal-GVD is planned to be completed in 2024. The second stage of the detector deployment is planned to be carried out using a data acquisition system based on fiber optic technologies, which will allow for increased data throughput and more flexible trigger conditions. A dedicated test facility has been built and deployed at the Baikal-GVD site to test the new technological solutions. We present the principles of operation and the results of tests of the new data acquisition system.

Speaker: Mr. Aleksandr Doroshenko (INR RAS)
• 18:20
Gateware Calibration Unit architecture 20m

The KM3NeT Collaboration is currently deploying the first Detection Units of a neutrino observatory in the Mediterranean Sea, which, once completed, will be equipped with tens of thousand of so-called Digital Optical Modules. In addition to the Detection Units KM3NeT has designed an independent Calibration Unit, housing a set of calibration instruments, including e.g. an acoustic beacon and a laser beacon. The firmware and the embedded software developed to operate the Calibration Unit are presented here.

Speakers: David Calvo (IFIC), Diego Real Mañez (IFIC)
• 18:40
Embedded software developments in KM3NeT Phase I 20m

The KM3NeT Collaboration has already produced more than one thousand acquisition boards, used for building two deep-sea neutrino detectors at the bottom of the Mediterranean Sea, with the intention of instrumenting a volume of several cubic kilometers. The acquisition modules, the so-called Digital Optical Modules, house the PMTs and the acquisition and control electronics of the module, the Central Logic Board, which includes a Xilinx FPGA and embedded soft processor. The present work presents the architecture and functionalities of the software embedded in the soft processor of the Central Logic Board.

Speaker: Vincent Van Beveren (Nikhef)
• 17:00 19:00
Methods and tools: Calibration

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 17:00
Time synchronization system of the Baikal-GVD 20m

The Baikal-GVD neutrino telescope is currently a multi-cluster infrastructure composed by 7 separately operating clusters of more than 2000 photosensitive modules in lake Baikal. Single cluster comprises 8 strings of 288 optical modules by means of 36 OM on each string divided into three groups (sections) of 12-channel control modules with ADCs. Two independent systems of time synchronization are integrated in the GVD. This paper presents the methods of time synchronization between the different GVD components (optical modules, sections, clusters) and estimations of time synchronization accuracy.

Speaker: Mr. Dmitrii Petukhov (INR RAS)
• 17:20
The Calibration Units of KM3NeT 20m

KM3NeT is a deep-sea infrastructure composed of two neutrino telescopes being deployed in the Mediterranean Sea : ARCA, near Sicily in Italy, designed for neutrino astronomy and ORCA, near Toulon in France, designed for the study of atmospheric neutrino oscillations. These two telescopes are 3D arrays of optical modules used to detect the Cherenkov radiation, which is a signature of charged particles created in the neutrino interaction and propagating faster than light in the sea water.

To achieve the best performance for the event reconstruction in the telescopes, the exact location of the optical modules, affected by the sea current, must be known at any time and the timing resolution between optical modules must reach the sub-nanosecond level. Moreover, the properties of the sea environment, such as temperature and salinity, are continuously monitored to allow best modelling of the acoustic signal propagation in the water.

KM3NeT will deploy Calibration Units hosting instruments dedicated to meet these calibration goals. The Calibration Base will host a Laser Beacon for time calibration and a long-baseline acoustic emitter and a hydrophone, which are part of the positioning system for the optical modules. Some of these Calibration Units will also be equipped with an Instrumentation Unit hosting environmental monitoring instruments.

This talk describes all the devices, features and purposes of the Calibration Units, with a special emphasis on the first such unit that will be deployed on the ORCA site in 2021.

Speaker: Rémy Le Breton (APC)
• 17:40
In-situ gain calibration based on single byte PMT signals 20m

Bouke Jung$^1$, Maarten de Jong$^2$, Paolo Fermani$^3$
on behalf of the KM3NeT collaboration

$^1$) University of Amsterdam, Nikhef
bjung@nikhef.nl
$^2$) Leiden University, Nikhef
mjg@nikhef.nl
$^3$) Sapienza Università di Roma
paolo.fermani@roma1.infn.it

Present and foreseen neutrino observatories, such as IceCube, P-ONE, GVD, Antares and KM3NeT have to operate in challenging environments, where high count rates go hand in hand with limited bandwidths.
To keep the data rates in these experiments within the allowed range, rigorous data reduction is essential.
At the same time, sufficient information needs to be recorded to accurately measure the neutrino properties.
The KM3NeT collaboration has developed a novel data acquisition procedure, in which each PMT signal is reduced to a datapacket of 6 Bytes, containing the PMT identifier (1 B), the hit time (4 B) and the duration over which the associated PMT pulse exceeded the threshold (1B).
This talk highlights an analytical pulse-shape model which is used to perform in-situ calibrations of the gain and its spread, using only the time-over-threshold statistics associated with single photon hits.
In addition, a set of tools is presented which allows in-situ monitoring of the PMT gains over time.
Data from the first 6 detector strings deployed at the French KM3NeT site (ORCA),
indicate that PMT high-voltages can be successfully tuned to obtain nominal gain-values,
allowing detector operation with stable PMT gains over the lifetime of the experiment.

Speaker: Mr. Bouke Jung (Nikhef and University of Amsterdam)
• 18:00
A self-monitoring precision calibration light source for large-volume neutrino telescopes 20m

With neutrino astronomy on the rise, calibration aspects of large-volume detectors are becoming one of the key targets to boost detector performance. In the scope of the IceCube Upgrade planned for the South Pole season of 2022/23, we developed a novel isotropic, self-monitoring, precision calibration light source aimed for use in large-volume detectors in order to boost understanding of the detector. We present the device characteristics as well as first studies of calibration impacts for different detection environments.

Speaker: Felix Henningsen (Max Planck Institute for Physics / Technical University Munich)
• 18:20
Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope 20m

The ANTARES neutrino telescope is operating in the Mediterranean Sea in its full configuration since 2008. On their journey to the Earth, cosmic rays (CRs) can be absorbed by celestial objects, like the Sun, leading to a deficit in secondary muons produced by CR interactions from the solid angle region covered by the Sun, the so-called Sun "shadow" effect. This phenomenon can be used to evaluate fundamental telescope characteristics: the detector angular resolution and pointing accuracy. This work describes the study of the Sun "shadow" effect using the ANTARES data collected between 2008 and 2017. The statistical significance of the Sun shadow observation is $3.7\sigma$ and the estimated angular resolution value of the ANTARES telescope for downward-going muons is $0.59^{\circ} \pm 0.10^{\circ}$. This result is consistent with the expectations obtained from the Monte Carlo simulations and also with the estimation from the Moon "shadow" analysis of 2007-2016 years. No evidence of systematic pointing shift is found and the resulting pointing accuracy is in agreement with the expectations.

Speaker: Andrey Romanov (Dipartimento di Fisica dell’Universit`a, Via Dodecaneso 33, Genova 16146, Italy; NFN, Sezione di Genova)
• 18:40
Monitoring of optical properties of the deep water of Lake Baikal 20m

We present the results of a one year monitoring of absorption and scattering lengths of light with wave length 375÷532nm within the effective volume of the
Baikal-GVD deep underwater neutrino telescope. The measurements were
performed using a dedicated device, BAIKAL-5D, which was installed
during the 2020 winter expedition at a depth 1250 m. The device has a shaded point-like isotropic light source with spectral resolution about 3nm. A wide angle light receiver is moved by a stepper motor so that the distance between the receiver and the light source changed between 0.9 and 7,4 m. Absorption and scattering lengths were measured every week in 6 spectral points. Shot-time variation of absorption and scattering length was estimated.

Speakers: Dr. Evgenii Ryabov (Baikal-collaboration), Boris Tarashchansky (Baikal-collaboration)
• 17:00 19:20
Methods and tools: Simulation and data processing

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 17:00
Recent advances in the low-energy atmospheric neutrino flux modelling with the MCEq code 20m

An accurate atmospheric neutrino flux is crucial for a multitude of physics studies with modern neutrino telescopes; as a signal for neutrino oscillation measurements, and as a background for searches of astrophysical neutrino sources. We seek to advance in the low-energy neutrino flux calculations (up to a few GeV) using the MCEq (Matrix Cascade Equations) code that numerically solves the one-dimensional cascade equations. For precision calculations at energies below a few GeV, which are well within reach of the IceCube Upgrade and KM3NeT-ORCA, the lateral component of hadronic cascades becomes important, requiring three-dimensional calculation schemes. We present a new study on the two-dimensional development of air showers within the MCEq framework as a necessary initial step towards a full 3D calculation. Since the uncertainties of the flux calculations are limited by the physics models, in particular the currently available hadronic interaction models, we will discuss the prospects of moving forward using data-driven models and calibration techniques.

Speaker: Tetiana Kozynets (NBI)
• 17:20
Upgrading gSeaGen: from MeV to PeV neutrinos 20m

The gSeaGen framework has been upgraded to simulate events detectable in neutrino telescopes induced by neutrino or cosmic ray interactions. The new version is well-suited to generate neutrino interactions at energies from a few MeV to EeV, profiting from the latest GENIE extensions to lower and higher energies. In addition, a brand new functionally to propagate leptons from CORSIKA air showers has been developed. Novel features of gSeaGen will be presented, related to simulation of PeV tau neutrinos and charged lepton propagation, using the KM3NeT detectors as physics case.

Speaker: Alfonso Andres Garcia Soto (NIKHEF)
• 17:40
GiBUU based neutrino interaction simulations in KM3NeT 20m

The simulation of the neutrino interaction vertex is a crucial step for the simulation chain of a neutrino experiment. The different processes taking part in the neutrino scattering at a nucleus require several approximations in order to make the simulation possible and to realize reasonable computation times. This can be realised in different ways, e.g. by parametrised models for the different scattering processes and energy regimes as it is implemented in GENIE. The GiBUU neutrino generator utilises the Boltzmann-Ueling-Uhlenbeck equation to simulate the particle flow after the neutrino interactions, i.e. the final state interctions. This talk highlights the KM3BUU project, which is a Python wrapper for GiBUU with additional functionalities related to the KM3NeT data formats. The detector specific results in form of the visible energy in the detector after the light propagation simulation and the KM3NeT event reconstruction are presented. In addition to that, the comparison to the GENIE based simulation environment in KM3NeT (gSeaGen) is drawn.

Speaker: Johannes Schumann (ECAP - Universität Erlangen-Nürnberg)
• 18:00
Automatic data processing for Baikal-GVD neutrino observatory 20m

Baikal-GVD is a gigaton-scale neutrino observatory under construction in Lake Baikal. It currently produces about 100GB of data every day. For their automatic processing, the Baikal Analysis and Reconstruction software (BARS) was developed. At the moment, it includes such stages as a hit extraction from PMT waveforms, assembling events from raw data, assigning timestamps to events, determining the position of the optical modules using an acoustic positioning system, muon track and cascade reconstruction, as well as the alert signal generation. These stages are implemented as C++ programs which are executed sequentially one after another and can be represented as a directed acyclic graph. The most resource-consuming programs run in parallel to speed up processing. A separate Python package based on the luigi package is responsible for program execution control. Additional information like program execution status, run metadata etc are saved into a central database and then displayed on the dashboard. Results can be obtained several hours after the run completion.

Speaker: Bair Shaybonov (JINR)
• 18:20
Developments in Waveform Unfolding of PMT Signals in Future IceCube DOMs 20m

Waveform unfolding, in which photomultiplier tube signals are expressed as a linear combination of single-photoelectron waveforms, is a useful processing method both for analysis and for data compression in the IceCube Neutrino Observatory. This processing is currently only possible with a cluster of computers on the surface, but improvements in embedded technology allow moving this analysis into the digital optical modules for planned extensions of IceCube such as IceCube Gen2. In order to meet power constraints, waveform unfolding is most efficiently implemented with field programable gate arrays (FPGA). A non-negative least squares (NNLS) algorithm developed for use with FPGAs was modified to reproduce the results of the Lawson and Hanson algorithm that is currently used for waveform unfolding in IceCube. High Level Synthesis (HLS) tools were used to synthesize firmware directly from C code and to implement the modified algorithm on hardware. This talk will discuss the structure and performance of the modified NNLS algorithm that was developed, and demonstrate what can be accomplished with new FPGA synthesis tools.

Speaker: J. H. Peterson (University of Wisconsin - Madison)
• 18:40
Data Quality Monitoring system of the Baikal-GVD experiment 20m

The main purpose of the Baikal-GVD Data Quality Monitoring (DQM) system is to verify the detector status and collected data in both on- and off-line modes. Besides the quality estimation of the obtained data and providing the charge calibration using recorded signals the system efficiently performs validation of the trigger thresholds, as well as the monitoring of the environmental noise levels and trigger system quality. The DQM system is integrated within the Baikal-GVD’s unified software framework (“BARS”) and its GUI interface is used for the DQM shifts. This allows us to correct promptly and effectively the telescope conditions.

Speaker: Maksim Sorokovikov (JINR)
• 19:00
Monitoring pipeline for Baikal-GVD 20m

Baikal-GVD is a gigaton volume neutrino telescope currently under construction in Lake Baikal. GVD's detection, calibration and control units are submerged between the depths of 730 and 1275 meters and are equipped with sensors allowing for monitoring the state of individual components. Spatial configuration of the entire detector is obtained using an acoustic positioning system consisting of an array of acoustic modems installed along the strings of the detector. We describe a data pipeline used to collect, store and process the monitoring and positioning data in Baikal-GVD.

Speaker: Mr. Alexander Avrorin (INR RAS)
• 17:00 19:00
Multi-messenger

Gamma rays, gravitational waves, RF, optical follow-up, coincidences among neutrino detectors

VLVnT 2021 | Parallel Session Room D
https://cern.zoom.us/j/63734092003

• 17:00
Search for periodic neutrino emission from X-ray Binaries 20m

X-ray binaries (XRBs) are binary system with an accreting compact object. They have long been suggested to be possible galactic cosmic ray accelerators. In such models, the protons accelerated by the accretion process at the compact object could carry out $pp$ or $p\gamma$ interactions in the accretion disk, in the atmosphere of the companion star, or in the stellar wind. High energy neutrinos may be produced from these interactions and will serve as a smoking-gun evidence for CR acceleration. Furthermore, many models predicted their neutrino emission to be modulated by the orbital periods. In this talk, I will present the result of the latest search for periodic neutrino emission from X-ray binaries performed by IceCube Neutrino Observatory. Using 7.5 years of IceCube's muon track data, this search featured an improved unbinned maximum likelihood ratio method, and was performed on a catalogue of 55 XRBs with declination $\geq -5^o$, greatly expanded over the previous periodic point-source searches. This study found no evidence for neutrino emission, but have placed upper limits on the neutrino flux from each XRB. Comparisons between the results and some phenomenological models, and predictions for observations by IceCube Gen2 will also be presented.

Speaker: Chun Fai Tung (Georgia Institute of Technology)
• 17:20
Multi-messenger searches via IceCube’s high-energy neutrinos and gravitational-wave detections of LIGO/Virgo 20m

Multi-messenger detections of astrophysical events improve our understanding of the underlying sources. In addition to probing different physics, such detections can provide improved localization in low latency, guiding astronomers who perform follow-up observations. We will present the real-time and offline searches for high-energy neutrinos associated with gravitational-wave events via IceCube’s neutrinos and LIGO/Virgo’s public announcements and detections.

Speaker: Doga Veske (Columbia University)
• 17:40

The high-energy neutrino events of the IceCube telescope, which trigger
neutrino alerts in one of two probability ranks of astrophysical origin,
“gold " and "bronze", have been followed up with Baikal-GVD in a fast
quasi-online mode since September 2020. Search for correlations between
alerts and events reconstructed in two modes, track and cascade, for the
time windows \pm 1 hour and \pm 12 hours does not indicate statistically
significant excess of the measured events over the expected number of
background events. Upper limits on the neutrino fluence will be presented

Speaker: Viktoriya Dik (Joint Institute for Nuclear Research)
• 18:00
Multi-messenger studies with the Baikal-GVD telescope 20m

The current activity of the Baikal-GVD neutrino experiment in the multi-messenger program on discovering the astrophysical sources of high energy fluxes of cosmic particles will be presented, with emphasis on results of the follow up of high energy neutrino alerts.

Speaker: Olga Suvorova (Institute for Nuclear Research of the Russian Academy of Sciences)
• 18:20
ANTARES search for neutrino flares 20m

In 2017, a high-energy muon neutrino detected by IceCube was found positionally coincident with the direction of a known blazar, TXS 0506+056, in a state of enhanced $\gamma$-ray emission. Soon after, IceCube reported a compelling evidence for an earlier neutrino flare from the same direction found in the archival data, this time not accompanied by any observed electromagnetic activity. The IceCube findings suggest searching for flaring neutrino emissions from astrophysical sources, not necessarily accompanied by flares detected in $\gamma$-rays. The analysis presented in this contribution scans the events collected by the ANTARES neutrino telescope in 13 years of data taking in a search for clustering in space and time. The analysis method is based on an unbinned maximum likelihood approach. A generic Gaussian profile is assumed for the signal time emission, with both the Gaussian mean (time of the peak of the flare) and sigma (duration of the flare) being free parameters in the likelihood maximization. We plan to apply the time-dependent approach to the catalog of radio-bright blazars for which a promising directional correlation with IceCube muon tracks was recently reported [ApJ 894(2020)101, ApJ 908(2021)157].

Speaker: Giulia Illuminati
• Wednesday, 19 May
• 15:00 16:00
Plenary: Plenary talks

Plenary talks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

• 15:00
The IceCube-Gen2 Neutrino Observatory 30m

The IceCube Neutrino Observatory opened the window on neutrino astronomy by discovering high-energy astrophysical neutrinos in 2013 and identifying the first compelling astrophysical neutrino source, the blazar TXS0506+056, in 2018. In this talk, I will discuss the science reach and ongoing development of the IceCube-Gen2 facility--a planned extension to IceCube. IceCube-Gen2 will increase the rate of observed cosmic neutrinos, be able to detect fainter neutrino sources, and extend the measurement of astrophysical neutrinos to higher energies. I will discuss the envisioned design of the instrument, which will include an enlarged in-ice optical array, a surface array for the study of cosmic-rays, and a shallow radio array to detect ultra-high energy (>100 PeV) neutrinos. I will also highlight ongoing efforts to develop and test new instrumentation for IceCube-Gen2.

Speaker: Brian Clark (MSU)
• 15:30
Status of radio technique for cosmic neutrino detection 30m
Speaker: Abigail Vieregg (KICP - Univ. of Chicago)
• 16:00 16:40
Discussion: Construction, deployment, R&D...

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

Convener: Marco Circella (INFN-Bari)
• 16:40 17:00
Break 20m
• 17:00 19:20
Detector R&D and construction: Electronics - Light detectors

Hardware, calibration, measurement of medium properties, DOMs, photon detectors, deployment/installation

VLVnT 2021 | Parallel Session Room B
https://cern.zoom.us/j/68306216278

• 17:00
The OctoPAES board for the validation of KM3NeT data acquisition system 20m

For testing and optimizing key elements of the KM3NeT data acquisition system, a test-bench has been set up at the INFN Sezione di Bologna. In this setup, a full detection unit is simulated, to test the optical network, time synchronisation, and on-shore computing resources. A fundamental tool in the test-setup is a dedicated electronic board: “the OctoPAES”.
Based on an ALTERA Max10 CPLD, they are designed to deterministically emulate the optical and acoustic signals recorded by the underwater detectors. They allow to stress-test the acquisition system and validate its performance with realistic data. If properly configured, the optical data provided by the OctoPAES can be combined to emulate the signals of a through-going muon or other calibration events. In this contribution we present the OctoPAES boards and some of their use cases at the test-bench.

Speaker: Francesco Filippini (Department of Physics and Astronomy, University of Bologna, INFN-BO)
• 17:20
Electronics Reliability methods for Neutrino Telescopes: The KM3NeT Case 20m

The KM3NeT Collaboration is building a deep-sea neutrino observatory in the Mediterranean Sea equipped with thousands of glass spheres, hosting the so-called Digital Optical Modules, with an instrumented volume of several cubic kilometers. Reliability of the components used in the construction of the detectors is of extreme importance as the deployed Detection Units, each one composed of 18 Digital Optical Modules, will not be accessible for any kind of maintenance and the detector should be functional for a period longer than 10 years. This work presents the different reliability methods used in KM3NeT to assess and improve the reliability of the electronics housed in the Digital Optical Modules of KM3NeT.

Speaker: Mr. Stephane Colonges (APC)
• 17:40
The study of the 20 inch Large Area MCP-PMTs 20m

The large scalar neutrino detectors (JUNO, HyperK), need the 20 inch area PMTs as the photo-detection device for their large photocathode coverage and less electronic channels. In 2009, the researchers at IHEP have conceived a new concept of large area PMTs, of which the small MCP units replace the bulky Dynode chain. After several years R&D, the 20 inch MCP-PMT was successfully produced. This type of PMT has large sensitive area, high QE, and large P/V for good single photon detection. The JUNO ordered 15000 pic 20 inch MCP-PMTs in Dec.2015. Then, from 2017 to 2020, all the 20-inch PMTs will be produced and tested one by one in the company for JUNO. This presentation will talk about the R&D, the mass production and batch test result of the 15K pieces of MCP-PMT prototypes for JUNO. Further more, another Flower-liked MCP-PMT will also be introduced. This new type of 20 inch MCP-PMT designed with the TTS less than 5ns, has already evaluated by the PMT group in HyperK, and also be used in the LHAASO project in China.

Speaker: Sen QIAN (IHEP,CAS)
• 18:00
Hybrid optical modules for IceCube Extensions 20m

Novel optical sensor design decouples the photo-sensitive area from the PMT cathode area. Light guides can be shaped in a more favourable geometry for the target detector.
Twelve wavelength shifting optical modules (WOMs) will be deployed in the IceCube Upgrade.
The photo-sensitive area is a long cylinder coated with wavelength shifting paint which exploits the UV part of the Cherenkov spectrum that is read out with two PMTs.
Compared to classic modules the overall noise is significantly decreased which provides various applications for this new device.
The successor of the WOM is the Advanced Cylindrical Optical Module (ACOM) for IceCube Gen2 which comprises of additional PMTs for timing and directional information. Also dichroidic filters are investigated in order to improve the light collection efficiency.
The design and performance of the WOM as well as the concepts for the ACOM will be presented.

Speaker: Anna Pollmann
• 18:20
A long multi-PMT optical sensor for IceCube-Gen2 20m

A new long optical module (LOM) is under development for IceCube-Gen2, the proposed expansion to the IceCube neutrino observatory at the South Pole. The module is housed in an elongated borosilicate-glass pressure vessel, the size of which is constrained by the borehole diameter, which impacts drilling economy. The designs under consideration use either 16 or 18 4-inch PMTs, conditional on future performance tests, mounted so as to guarantee full angular coverage. Modular electronics have been custom-designed to fit into the available space and to minimize cost and power requirements for the ~10000 modules to be installed. We will provide an overview of our approach to these design considerations and summarize the results of our tests and simulations. Prototype modules will be installed in the upcoming IceCube Upgrade.

Speaker: Vedant Basu (Wisconsin IceCube Particle Astrophysics Center)
• 18:40
Testing of the optical module inside the volume of Cherenkov water detector NEVOD 20m

At the last VLVnT-conference in the talk “NEVOD as a test facility for future neutrino telescopes” presented by A.A. Petrukhin the methods for testing of optical modules inside the volume of the Cherenkov water detector NEVOD have been discussed. It was assumed that in 2020 the new optical module mDOM of the IceCube-Upgrade will be calibrated in this way. However, the covid-19 pandemic did not allow to realize this plan.
So, these methods have been tested on quasispherical optical module QSM-6M, in which PMTs FEU-200 were replaced by PMTs of Hamamatsu R877. The spatial lattice of the detector NEVOD and deployed outside of the water tank calibration telescope system and coordinate-tracking detector DECOR allow calibrating the response of OM with respect to the Cherenkov light from single muons, muon bundles and cascades with known trajectories. Technique and results of calibration optical modules QSM-6M are presented at this talk.

Speakers: Semyon Khokhlov (National Research Nuclear University MEPhI), Dr. Victor Kindin (MEPhI)
• 19:00
Surface detectors for IceCube-Gen2 20m

The IceCube-Gen2 Neutrino Observatory will feature an in-ice optical array, a larger in-ice radio detector array, and a surface cosmic ray air shower array.
The surface array will consist of stations based on the experience from the planned IceTop enhancement, each station having 4 pairs of scintillator panels, 3 radio antennas and a central hub hosting electronics for data readout and time digitization.
In the currently proposed implementation, a surface station will be located in the proximity of each of the 120 in-ice optical strings. The designed array will help to test hadronic interaction models, will improve the measurement of cosmic ray anisotropy and will extend IceTop's measurement of the energy spectrum and mass composition to higher energies. The array will also serve as a background veto for down-going candidate neutrino events.  In addition, the surface stations will be fundamental to characterize the atmospheric component of the in-ice spectrum(i.e. atmospheric neutrinos and muons) and may serve as a cross calibration tool for the in-ice radio array.
In this presentation I will review the physics motivations for the surface array, and our proposed implementation plan.

Speaker: Frank Schroeder (Bartol Bartol Research Institute)
• 17:00 19:00
Methods and tools: Reconstruction and classification

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 17:00
Using Convolutional Neural Networks to Reconstruct Energy of GeV Scale IceCube Neutrinos 20m

The IceCube Neutrino Observatory, located under 1.4 km of Antarctic ice,
instruments a cubic kilometer of ice with 5,160 optical modules that detect
Cherenkov radiation originating from neutrino interactions. The more
densely instrumented center, DeepCore, aims to detect atmospheric neutrinos
at 10-GeV scales to improve important measurements of fundamental neutrino
properties such as the oscillation parameters and to search for
non-standard interactions. Sensitivity to oscillation parameters, dependent
on the distance traveled over the neutrino energy (L/E), is limited in
IceCube by the resolution of the arrival angle (which determines L) and
energy (E). Event reconstruction improvements can therefore directly lead
to advancements in oscillation results. This work uses a Convolutional
Neural Network (CNN) to reconstruct the energy of 10-GeV scale neutrino
events in IceCube, providing results with competitive resolutions and
faster runtimes than previous likelihood-based methods.

Speaker: Jessie Micallef (MSU)
• 17:20
Direction Reconstruction using a CNN for GeV Scale Neutrinos in IceCube 20m

The
IceCube Neutrino Observatory is designed to observe neutrinos interacting deep within the South Pole ice. It consists of 5,160 digital optical modules, which are arrayed over a cubic kilometer from 1,450 m to 2,450 m depth. At the lower center of the array is the DeepCore subdetector. It has a denser configuration which lowers the observable energy threshold to about 10 GeV and creates the opportunity to study neutrino oscillations with low energy atmospheric neutrinos. A precise reconstruction of neutrino direction is critical in the measurements of oscillation parameters. In this talk, I will present a method to reconstruct the zenith angle of 10-GeV scale events in IceCube by using a convolutional neural network and compare the result to that of the current likelihood-based reconstruction algorithm.

Speaker: Shiqi Yu (Michigan State University)
• 17:40
An efficient hit selection algorithm for muon reconstruction in Baikal-GVD 20m

The Baikal-GVD is a large scale neutrino telescope being constructed in Lake Baikal. The majority of signal detected by the telescope are noise hits, caused primarily by the luminescence of the Baikal water. Separating noise hits from the hits produced by Cherenkov light emitted from the muon track is a challenging part of the muon event reconstruction. We present an algorithm that utilizes a known directional hit causality criterion to construct a graph of hits and then use a clique-based technique to select the subset of signal hits. The algorithm was tested on realistic detector Monte-Carlo simulation for a wide range of muon energies and has proved to select a pure sample of PMT hits from Cherenkov photons while retaining above 90% of original signal.

Speaker: Mr. Alexander Avrorin (INR RAS)
• 18:00
Muon track reconstruction algorithms for Baikal-GVD 20m

Muon track reconstruction methods developed for Baikal-GVD detector
and their performance are discussed in this talk. This includes
methods for the rejection of noise due to water chemilumenescence and
track parameter reconstruction based on chi^2 minimisation. The
performance of the algorithms is assessed using realistic Monte Carlo
(MC) simulations of the detector. Benchmark results obtained on real
data from Baikal-GVD are compared to MC predictions.

Speaker: Grigory Safronov (INR RAS & JINR)
• 18:20
Deep-learning reconstruction in ANTARES 20m

ANTARES is currently the largest undersea neutrino telescope, located in the Mediterranean Sea and taking data in its full configuration since 2008. It consists of a 3D array of photosensors, instrumenting about 10Mt of seawater to detect Cherenkov light induced by secondary particles from neutrino interactions. The event reconstruction and background discrimination is challenging and machine-learning techniques are explored to improve the performance. In this contribution, two case studies are presented. In the first one, a deep-learning approach is used to improve the direction reconstruction of low-energy single-line events, for which the reconstruction of the azimuth angle of the incoming neutrino is particularly difficult. We observe a promising improvement in resolution over classical reconstruction techniques and expect to at least double our sensitivity in the low-energy range, important for dark matter searches. The second study employs deep convolutional neural networks for neutrino vs background classification and for energy determination. For both studies, performance results will be presented and compared to other techniques used in ANTARES.

Speaker: Salva Ardid (Universitat Politècnica de València)
• 18:40
KM3NeT Detection Unit Line Fit reconstruction using positioning sensors data 20m

KM3NeT is constructing two large neutrino detectors in the Mediterranean Sea: KM3NeT/ARCA, located near Sicily and aiming at neutrino astronomy, and KM3NeT/ORCA, located near Toulon and designed for neutrino oscillation studies. The two detectors, together, will have hundreds of Detection Units (DUs) with 18 Digital Optical Modules (DOMs) maintained vertical by buoyancy, forming a large 3D optical array for detecting the Cherenkov light produced after the neutrino interactions. To properly reconstruct the direction of the incoming neutrino, the position of the DOMs must be known precisely with an accuracy of less than 10 cm, and since the DUs are affected by sea current the position will be measured every 10 minutes. For this purpose, there are acoustic and orientation sensors inside the DOMs. An Attitude Heading Reference System (AHRS) chip provides the components values of the Acceleration and Magnetic field in the DOM, from which it is possible to calculate Yaw, Pitch, and Roll for each floor of the line. A piezo sensor detects the signals from fixed acoustic emitters on the sea floor, so to position it by trilateration. Data from these sensors are used as an input to reconstruct the shape of the entire line based on a DU Line Fit mechanical model. This talk presents an overview of the KM3NeT monitoring system, as well as the line fit model and its results.

Speaker: Dídac Diego-Tortosa (Universitat Politècnica de València (UPV) – Institut d'Investigació per a la Gestió Integrada de Zones Costaneres (IGIC))
• 17:00 18:40
Multi-messenger

Gamma rays, gravitational waves, RF, optical follow-up, coincidences among neutrino detectors

VLVnT 2021 | Parallel Session Room D
https://cern.zoom.us/j/63734092003

• 17:00
KM3NeT/ARCA expectations in view of a novel multimessenger study of starburst galaxies 20m

Starburst galaxies (SBGs) and more in general starforming galaxies represent a class of galaxies with a high star formation rate (up to 100 Mo/year). Despite their low luminosity, they can be considered as guaranteed “factories” of high energy neutrinos, being “reservoirs” of accelerated cosmic rays and hosting a high density target gas in the central region. In this contribution we present a novel multimessenger study of these sources and the possibility of observing their neutrino signals with the KM3NeT/ARCA telescope. The differential sensitivity and discovery potential for different SBG scenarios are reported considering track-like events in the 100 GeV-100 PeV energy range.

Speaker: Antonio Marinelli (INFN Naples)
• 17:20
Constraining the contribution to Gamma-Ray Bursts to the high-energy diffuse neutrino flux with 10 years of ANTARES data 20m

Gamma-Ray Bursts (GRBs) are considered very interesting astrophysical sources to be studied in the context of the neutrino astronomy. Indeed, their jet composition continues to be an open issue. Within the framework of the fireball model, mesons can be produced during photo-hadronic interactions occurring in the internal shocks between shells emitted by the central engine. From their decays, high-energy gamma rays and neutrinos are expected to be generated. Neutrino telescopes are particularly interested in GRBs: being the most powerful explosions observable in the Universe, they are potentially able to achieve the energetics required to reproduce the diffuse astrophysical neutrino flux measured few years ago and, thus, they are expected to give a contribution to such astrophysical neutrino flux. The analysis here presented relies on the search of time and space coincidence between neutrinos and the GRB emission. The undersea neutrino telescope ANTARES, operational in the Northern hemisphere since 2008 in its full configuration, plays an important role in the cosmic neutrino searches. In this contribution, the results of a stacked search for muon astrophysical neutrinos are presented for 784 GRBs in the period 2007-2017 using the ANTARES data. Given the absence of coincidences between a neutrino and a GRB in the considered sample, this analysis has allowed us to constrain the contribution of the detected GRB population to the neutrino diffuse flux to be less than 10% around 100 TeV, within the context of the internal shock model. In addition, for the first time in this kind of analysis, the uncertainties on the not well characterized GRB parameters, needed to compute the neutrino flux expectations, are taken into account for each individual burst and then propagated to the diffuse flux from GRBs and to the stacked limit.

Speaker: Angela Zegarelli (INFN, Sapienza/Tor Vergata Universities, Rome)
• 17:40
Expected arrival-direction correlations between ultra-high-energy cosmic rays and high-energy neutrinos 20m

The discovery of a diffuse flux of astrophysical neutrinos by IceCube has opened up new possibilities for the search of cosmic-ray sources. The sources that accelerate cosmic rays to extreme energies are most-likely also high-energy neutrino emitters. To find such sources one can look for correlations in arrival directions between astrophysical neutrinos and ultra-high-energy cosmic rays (UHECRs). However, UHECRs are deflected by magnetic fields on their way from their sources to Earth, and are subject to energy-loss processes (resulting in a maximum distance from which they can arrive). We investigate how these effects influence the expected probability to find correlations between high-energy neutrinos and UHECRs, taking into account the evolution with redshift of the sources and UHECR spectrum and composition measurements [1]. The possibility to observe correlations between UHECRs and neutrinos is already strongly constrained by the absence of neutrino multiplets in the IceCube measurements. However, if connections between neutrinos and cosmic rays are measured, it would give a precise indication for the local density of the emitters.

[1] A. Palladino, A. van Vliet, W. Winter and A. Franckowiak, Mon. Not. Roy. Astron. Soc. 494 (2020) 3, 4255

Speaker: Arjen van Vliet (DESY Zeuthen)
• 18:00
Real-time Multi-Messenger Analysis Framework of KM3NeT 20m

KM3NeT is a multi-purpose cubic-kilometer neutrino observatory in construction in the Mediterranean Sea. It consists of ORCA and ARCA (for Oscillation and Astroparticle Research with Cosmics in the Abyss, respectively), currently both with a few detection lines in operation. Although having different primary goals, both detectors can be used for neutrino astronomy over a wide energy range, from a few tens of MeVs to a few tens of PeV. In view of the growing field of time-domain astronomy, it is crucial to be able to identify neutrino candidates in real-time. This online neutrino sample will allow trigger neutrino alerts that will be sent to the astronomy community and to look for time/space coincidence around external electromagnetic and multi-messenger triggers. These real-time searches can significantly increase the discovery potential of transient cosmic accelerators and refine the pointing directions in the case of poorly localized triggers, such as gravitational waves. In the field of core-collapse supernovae (CCSN), the detection of the MeV-scale CCSN neutrinos is crucial as an early warning of the electromagnetic follow-up. KM3NeT’s digital optical modules act as good detectors for these supernovae neutrinos. This talk presents the status of KM3NeT's real-time multi-messenger activities, including online event reconstruction, event classification and selection, alert distribution, and supernova monitoring.

Speakers: Damien Dornic (Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France), Feifei Huang (Aix Marseille Univ, CNRS / IN2P3, CPPM, Marseille, France)
• 18:20
Multi-messenger offline follow-up studies with the ANTARES Neutrino Telescope 20m

The ANTARES neutrino telescope has been operating in the Mediterranean sea since 2008 in its full configuration, with the main purpose of searching for high-energy cosmic neutrinos. During the last years, multi-messenger astronomy has become one of the most exciting topics in astroparticles, and a promising strategy to identify astrophysical sources of neutrinos. The ANTARES Collaboration is actively participating to the follow-up of alerts sent by different experiments, covering the full electromagnetic spectrum and gravitational waves detected by interferometers.

ANTARES real-time response to these alerts is complemented with dedicated offline analyses, which are the focus of this talk. These studies allowed to set upper limits that constrain the neutrino emission from various astrophysical processes. The latest results, including Fast Radio Bursts, Gamma Ray Bursts and compact binary mergers, as well as neutrino alerts by others neutrino observatories (IceCube, GVD) will be discussed.

Speaker: Marta Colomer Molla (APC/IFIC)
• 17:00 18:00
Neutrino properties

Neutrino oscillations, NMO, NSI, neutrino decay, others

VLVnT 2021 | Parallel Session Room C
https://cern.zoom.us/j/69737018748

• 17:00
Search for light sterile neutrinos with ANTARES and KM3NeT/ORCA telescopes 20m

The standard model with three flavor neutrino oscillations is supported by the majority of neutrino oscillation data. However, a few experiments have observed anomalies, which are difficult to accommodate within the three flavour framework. One possible explanation of some anomalies is to postulate the existence of light sterile neutrinos.
Neutrino telescopes such as ANTARES and KM3NeT are promising detectors to probe the sterile neutrino hypothesis using atmospheric neutrinos. ANTARES is the largest deep-sea neutrino telescope, located in the Mediterranean Sea, in operation since 2008 in its full configuration. KM3NeT, now under construction in the Mediterranean Sea, is a next-generation network of water Cherenkov detectors. When completed, it will consist of two separate building blocks: ARCA (Astroparticle Research with Cosmics in the Abyss), optimized for high-energy neutrino astronomy, and ORCA (Oscillation Research with Cosmics in the Abyss) designed for neutrino oscillation studies in the GeV energy range. In this contribution, upper limits with 10 years of ANTARES data and ORCA sensitivities to the active-sterile mixing angles (θ14, θ24, θ34) in the (3+1) flavor model are presented.

Speaker: Dr. Alba Domi (University of Genoa - INFN, Genoa, Italy)
• 17:20
Status of IceCube Searches for Sterile Neutrinos 20m

Existing anomalies in experimental results, for neutrino oscillation experiments, may require a fourth, “sterile” neutrino with non-interacting flavor states. Recent sterile neutrino results from the IceCube South Pole Neutrino Observatory, a Cherenkov neutrino experiment using a cubic kilometer of instrumented ice, are presented. Multiple analyses are discussed, including one enabled by a matter-enhanced resonance occurring for a sterile neutrino with eV$^{2}$-scale mass-squared differences. We introduce possible future analyses involving the use of new event topologies as a means of searching for neutrino appearance with non-zero $\theta_{34}$.

Speaker: Benjamin Smithers (University of Texas, Arlington)
• 17:40
Search for eV-scale sterile neutrinos with 8 years of IceCube DeepCore data 20m

Several anomalies in reactor and accelerator neutrino experiments motivate the search for sterile neutrinos at mass splittings in the eV-scale. We present an analysis that probes the elements $U_{\mu4}$ and $U_{\tau4}$ of the extended (3+1) neutrino mixing matrix using an 8 year data sample from IceCube’s DeepCore sub-array containing atmospheric neutrinos between 5 and 300 GeV. The analysis is expected to produce world leading limits on $|U_{\mu4}|$ and $|U_{\tau4}|$ under the assumption of sterile mass splittings between 1 and 100 eV$^{2}$, as well as limits on $|U_{\mu4}|$ for sterile mass splittings below 1 eV$^{2}$. We specifically discuss how we overcame the challenges of efficiently calculating neutrino oscillation probabilities in the presence of very fast sterile oscillations as well as the impact of the additional sterile CP-violating phase $\delta_{24}$

Speaker: Alexander Trettin (DESY)
• 18:00 19:20
Dark matter and exotics: Exotics

VLVnT 2021 | Parallel Session Room C
https://cern.zoom.us/j/69737018748

• 18:00
Search for nuclearites with the KM3NeT detector 20m

Strange quark matter (SQM) is a hypothetical type of matter composed of almost equal quantities of up, down and strange quarks. Massive SQM particles are called nuclearites. Nuclearites with masses greater than $10^{13}$ GeV and velocities of about 250 km/s (typical galactic velocities) could reach the Earth and interact with atoms and molecules of sea water within the sensitive volume of the deep-sea neutrino telescopes. The SQM particles can be detected with the KM3NeT telescope (whose first lines are already installed in the Mediterranean Sea and taking data) through the visible blackbody radiation generated along their path inside or near the instrumented area. In this work the results of a study using Monte Carlo simulations of down-going nuclearites are discussed. Preliminary sensitivities of the KM3NeT experiment for a flux of nuclearites are also presented.

Speaker: Ms. Alice Paun (Institute of Space Science (ISS), Atomistilor 409, Magurele, RO-077125 Romania)
• 18:20
Nuclearite search with ANTARES 20m

ANTARES is a Cherenkov underwater neutrino telescope operating in the Mediterranean Sea since 2008 in its full configuration. Even though optimised for the search of cosmic neutrinos, this telescope is also sensitive to nuclearites of strange matter.

We discuss here the possible detection of non-relativistic down-going nuclearites with the ANTARES telescope and present the first results of an updated analysis using data collected in the period 2009-2017.

Speaker: Mohammed Bouta (LPMR)
• 18:40
Search for Magnetic Monopoles with ten years of ANTARES data 20m

The present study is an updated search for magnetic monopoles using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). In accordance with some grand unification theories, magnetic monopoles could have been created during the phase of symmetry breaking in the early Universe, and accelerated by galactic magnetic fields. As a consequence of their high energy, they could cross the Earth and emit a significant signal in a Cherenkov-based telescope like ANTARES, for appropriate mass and velocity ranges. This analysis uses a run-by-run simulation strategy, as well as a new simulation of magnetic monopoles taking into account the Kasama, Yang and Goldhaber cross section. The results obtained for relativistic magnetic monopoles with velocity v ≥ 0.57c will be presented.

• 19:00
Magnetic monopole searches with IceCube 20m

Magnetic monopoles are hypothetical particles carrying magnetic charge. They are predicted to exist in most extensions of the Standard Model of particle physics. A wide range of masses is allowed for magnetic monopoles, leading to a broad speed range for a hypothetical flux of these relics of the Big Bang. A magnetic monopole passing through IceCube would produce light through several different physical processes depending on its speed.
An overview will be given of the methods and results of current and recently finished searches for magnetic monopoles in IceCube. A focus will be put on the two most recent searches for magnetic monopoles: firstly, a search above the Cherenkov threshold in ice where the dominant background consists of rare, extremely high energy astrophysical neutrinos. Secondly the first search for monopoles inducing luminescence light at low relativistic speeds. New limits were obtained which exceed previous analyses by orders of magnitudes.

Speaker: Anna Pollmann
• Thursday, 20 May
• 15:00 16:00
Plenary: Plenary talks

Plenary talks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

• 15:00
Multi-messenger prospects with next-generation observatories 30m
Speaker: Prof. Markus Ahlers (Niels Bohr Institute)
• 15:30
Models of neutrino production in cosmic sources 30m
Speaker: Prof. Cecilia Lunardini (GWC - Arizona State University Tempe)
• 16:00 16:40
Discussion: Dark matter and exotics

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

Convener: Carlos de los Heros (Uppsala university)
• 16:40 17:00
Break 20m
• 17:00 19:20
High-energy neutrino sources

Diffuse, point-like, extended, galactic plane, others

This session is distributed in multiple rooms along the week:
Thu:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Fri:
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Click on each contribution for details

• 17:00
Neutrinos from galactic sources 20m

The HAWC telescopes has recently revealed new spectra for gamma-ray sources in the Galactic plane. In this talk I will review the possibility of detecting these sources at KM3 detectors. I will consider, with particular emphasis, the 2HWC J1825-134 source. Amongst the HAWC sources, it is indeed the most luminous in the multi-TeV domain and
therefore is one of the first that should be searched for with a neutrino telescope in the northern hemisphere. I will show the prospects to detect this source at the KM3NeT detector and comment on the possibilities for others neutrino telescopes.
I will consider, moreover, the gamma-ray sources eHWC J1907+063, eHWC J2019+368 and 2HWC J1857+027. For these sources, I will show the prediction for neutrinos at the IceCube detector, presenting the calculation of the statistical significance, considering 10 and 20 years of running time, and I will comment on the current results reported by the collaboration.

Speaker: Niro Viviana
• 17:20
Search for an association between neutrinos and radio-selected blazars with ANTARES 20m

Recently, evidence for an association between high energy neutrinos detected by
IceCube and radio-selected blazars has been found by Plavin et al. (2020, 2021). This result was achieved using an all sky complete sample of 3411 blazars selected on their parsec-scale flux density at 8 GHz higher than 150 mJy. We perform an analysis using the same sample of radio-selected blazars and search for a positional correlation with the astrophysical neutrino candidates selected for point source searches from the data collected by the ANTARES detector between January 29, 2007 and February 28, 2020.
First results of this search are presented and discussed.

Speaker: Julien Aublin (APC, Université de Paris)
• 17:40
Search for high-energy neutrino emission from hard X-ray AGN 20m

The IceCube Neutrino Observatory has detected high-energy astrophysical
neutrinos in the TeV-PeV range. These neutrinos have an isotropic
distribution on the sky, and therefore likely originate from extragalactic
sources. Active Galactic Nuclei (AGN) form a class of astronomical objects
which are promising neutrino source candidates given their high
electromagnetic luminosity and potential ability to accelerate cosmic rays
up to energies larger than 1016 eV. Interactions of these cosmic rays
within the AGN environment are expected to produce both neutrinos and
pionic gamma rays. Some hadronic models of AGN emission suggest that such
gamma rays can in turn interact with the dense photon fields of AGN and
cascade down to hard X-rays and MeV gamma rays. We present an update on the
IceCube stacking analysis searching for high-energy neutrinos from hard
X-ray sources sampled from the Swift-BAT AGN Spectroscopic Survey (BASS).

Speaker: Sreetama Goswami (University of Alabama)
• 18:00
Astrophysical Neutrino Source Searches with IceCube Starting Track Events 20m

Muons and neutrinos created by cosmic rays interacting in the atmosphere create a significant background for IceCube astrophysical neutrinos in the southern sky. However, looking for neutrino events that start in the detector can reduce both the atmospheric muon and atmospheric neutrino background while retaining the astrophysical neutrino signal. The method presented here results in a higher astrophysical neutrino purity for IceCube events at declinations less than -25°. We specifically select for track events, which results in better directional reconstruction due to the long path the muon leaves in the detector than for cascade events. Due to the reduced background and good pointing resolution, we will discuss how this event selection will improve IceCube's sensitivity to southern neutrino sources. We will focus on its impact on searches for galactic plane point sources and diffuse galactic plane neutrino emission. This selection also allows IceCube to send out high astrophysical purity realtime alert events with neutrino energies in the tens of TeV to the multimessenger community.

Speaker: Sarah Mancina
• 18:20
The Baikal-GVD neutrino telescope: search for high-energy cascade 20m

Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently under construction in Lake Baikal. GVD is formed by multi-megaton subarrays (clusters) and is designed for the detection of astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. The design of Baikal-GVD allows one to search for astrophysical neutrinos with flux values measured by IceCube already at early phases of the array construction. We present here preliminary results of the search for high-energy neutrinos via the cascade mode with the Baikal-GVD neutrino telescope.

Speaker: Mark Shelepov
• 18:40
Observations of muon neutrinos with Baikal-GVD 20m

The Baikal-GVD detector currently consists of 2016 optical modules arranged on 56 vertical strings in a water volume of 0.35 km$^3$. The data from the partially complete array have been analyzed using a $\chi^2$-based track reconstruction algorithm. After a zenith angle cut and other background suppression cuts, a sample of upgoing neutrino candidate events is obtained. The analysis is optimized for the detection of muon neutrinos and muon anti-neutrinos in the multi-TeV energy regime. The observed characteristics of the neutrino candidate sample are compared with Monte Carlo predictions for the atmospheric neutrinos.

Speaker: Dmitry Zaborov (INR RAS, Moscow, Russia)
• 19:00
The Future of High-Energy Astrophysical Neutrino Flavor Measurements 20m

The next generation of neutrino telescopes, including Baikal-GVD, KM3NeT, P-ONE, TAMBO, and IceCube-Gen2, will be able to determine the flavor of high-energy astrophysical neutrinos with 10% uncertainties. With the aid of future neutrino oscillation experiments --- in particular JUNO, DUNE, and Hyper-Kamiokande --- the regions of flavor composition at Earth that are allowed by neutrino oscillations will shrink by a factor of ten between 2020 and 2040. We critically examine the ability of future experiments and show how these improvements will help us pin down the source of high-energy astrophysical neutrinos and a sub-dominant neutrino production mechanism with and without unitarity assumed. As an illustration of beyond-the-Standard-Model physics, we also show that the future neutrino measurements will constrain the decay rate of heavy neutrinos to be below $2\times 10^{-5}~$$m$/eV/s assuming they decay into invisible particles.

Speaker: Ningqiang Song (Queen's University)
• 17:00 18:00
Methods and tools: Policies

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 17:00
Baikal GVD data's transfer and organization 20m

Data collected by the Baikal Gigaton Volume Detector (Baikal GVD) needs to be processed in real time at a data centre located in Dubna, Moscow Oblast, approx. 4,300 km away. An infrastructure facilitating data transfer and storage was designed and implemented. In this paper, we discuss the details of the implementation and our approach to ensuring fault tolerance and 24/7 access to the data.

Speaker: Timur Elzhov (Joint Institute for Nuclear Research (JINR))
• 17:20
Meeting the challenge of Open Science in KM3NeT 20m

In the upcoming decades, the KM3NeT detectors will produce valuable data that can be used in various scientific contexts from astro- and particle physics to environmental and Earth and Sea science. Based on the Open Science policy established by the KM3NeT Collaboration, several efforts to offer science-ready data, foster common analysis approaches and publish open source software are currently pursued. In this contribution, ongoing projects focusing on the exchange of high-level data and simulation derivatives, production of particle event simulations and establishment of an integrated computing environment supporting an open-science focused workflow will be discussed.

Speaker: Jutta Schnabel (ECAP - FAU Erlangen-Nürnberg)
• 17:40
The KM3NeT Control Unit: advanced techniques and best practices in data acquisition software development 20m

The Control Unit of the KM3NeT Data Acquisition is the software suite that is responsible for operating all the components of the KM3NeT telescopes in a coordinated and scientifically proficient way. It controls a wide span of parameters and procedures, from the power supplies, to the operating voltages of more than 64000 photomultipliers in each detector block, to the setup of the various trigger algorithms that are applied online. The same software suite is also used in all test and qualification benches, from single Digital Optical Modules to full Detection Units. As the KM3NeT detectors are being incrementally built, the Control Unit is employed in a variety of setups and configurations, and is a dynamic software project, still adapting to shifting needs.

The conflicting requirements of flexibility and stability are reconciled by proper code development policies. The Control Unit is able to cope with dynamically changing scenarios of multiple firmware generations coexisting in the same detector, for various reasons including hardware compatibility as well as testing purposes. The code also allows for static verification and extensive unit tests.

A Central Logic Board Simulator software was also developed to help test the whole architecture. Such a simulator provides properly faked slow control parameters, features a fully specification-compliant state machine and can generate fake data with specific profiles to feed the Trigger and Data Acquisition System. In this way, offline integration tests can be executed at each new software release, ensuring their smooth deployment to production sites and minimising operator chances of mistakes.

Speaker: Cristiano Bozza (University of Salerno and INFN Gruppo Collegato di Salerno)
• 17:00 19:20
Methods and tools: Reconstruction and classification

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 17:00
Suppression techniques for background cascades produced by atmospheric muon bundles 20m

Detection of high energy astrophysical neutrinos is the main aim of Baikal-GVD (Gigaton Volume
Detector) neutrino experiment located in the southern part of Lake Baikal. It is a three dimensional grid of optical modules (OMs), which are attached to the vertical cables, called strings. The whole detector is sub-arranged into functionally independent units, referred to as clusters.

Highly energetic muons created by muon neutrino charged current interactions in the water induce “track-like” events. Charged-current interactions of electron neutrino and neutral-current interactions of all three neutrino flavours create a unique light signature of a single “cascade” in the detector. Nevertheless, muons can also produce cascade-like signatures via discrete stochastic energy losses. For that reason, atmospheric muon bundles represent the most abundant background in the search of astrophysical neutrinos via cascades. Therefore, different kinds of data analysis techniques for the suppression of background events have been developed.

These methods predominantly rely on the timing and charge information of detected signals at the OMs (called hits). While one method tries to find the maximum number of track hits among cascade hits, the other uses the distribution of charges and positions of hit OMs associated with cascade events. All suppression tools were developed and tested on the Monte Carlo simulations of neutrino-induced cascades and atmospheric muon bundles.

Speaker: Zuzana Bardačová (Comenius University in Bratislava)
• 17:20
Characterization of Starting Track Events above 1 TeV in IceCube 20m

The IceCube Neutrino Observatory is a cubic kilometer-sized detector designed to detect neutrinos of astrophysical origin. We discuss a new method using a boosted decision tree to classify and reduce the cosmic ray muon rates from ~billion per year to ~1 per year, the same BDT is also used to select for starting track events (~900 per year). The classification and removal of incoming muons is also efficient at removing atmospheric neutrinos with accompanying muons allowing us to characterize the astrophysical neutrino flux at energies between 1-100 TeV in the southern sky. The high purity starting track dataset has two advantages: excellent energy and angular resolution. The presence of the hadron and muon allow us to directly reconstruct the energy of the neutrino due to the vertex being well contained within the detector volume. A Random Forest is used resulting in a neutrino energy resolution below 30%. The outgoing muon track is then used to reconstruct the neutrino direction with an estimated median angular resolution of 1.4° at 1 TeV improving to 0.7° at 100 TeV. These advantages are particularly useful in this high-statistic starting track dataset where detector and theoretical systematics begin to dominate over statistical uncertainty.

Speaker: Manuel Silva
• 17:40
Low Energy Event Classification in IceCube using Boosted Decision Trees 20m

The DeepCore sub-array within the IceCube Neutrino Observatory is a densely instrumented region of Antarctic ice designed to observe atmospheric neutrino interactions above 5 GeV via Cherenkov radiation. An essential aspect of any neutrino oscillation analysis is the ability to accurately identify the flavor of neutrino events in the detector. This task is particularly difficult at low energies when very little light is deposited in the detector. This talk will discuss the use of machine learning to perform event classification at low energies in IceCube using a boosted decision tree. A BDT is trained using reconstructed quantities to identify track-like events, which result from muon neutrino charged current interactions. This new method improves the accuracy of particle identification compared to traditional classification methods which rely on univariate straight cuts.

Speaker: Kayla Leonard DeHolton (University of Wisconsin-Madison)
• 18:00
Detecting double shower $\nu_{\tau}$ signatures with the KM3NeT detector 20m

The detection of astrophysical $\nu_\tau$ is an important verification of the observed flux of high-energy neutrinos. A flavour ratio of $\nu_{e} : \nu_\mu : \nu_\tau \approx 1 : 1 : 1$ is predicted for astrophysical neutrinos measured at Earth due to neutrino oscillations. On top of this, the $\nu_\tau$ offers a unique channel for neutrino astronomy due to absence of an atmospheric $\nu_\tau$ background contribution. When a $\nu_\tau$ interacts it produces a particle shower and often a $\tau$ lepton which in turn decays mainly into another shower. This results in a double shower signature. An excellent angular resolution can be achieved when both shower vertices are reconstructed. The main challenge lies in identifying two showers when the $\tau$ energy and travelling length are small. The KM3NeT/ARCA detector, which is under construction in the Mediterranean sea, will be able to detect this signature due to its timing and spatial resolution for showers. We will discuss the reconstruction algorithms under development and the first performance estimates for detecting double showers using KM3NeT.

Speaker: Thijs van Eeden (Nikhef)
• 18:20
Graph Neural Networks for reconstruction and classification in KM3NeT 20m

KM3NeT, a neutrino telescope currently under construction in the Mediterranean Sea, consists of a network of large-volume Cherenkov detectors. Its two different sites, ORCA and ARCA, are optimised for few GeV and TeV-PeV neutrino energies, respectively. This allows for studying a wide range of physics topics spanning from the determination of the neutrino mass hierarchy to the detection of neutrinos from astrophysical sources.

Deep Learning techniques provide promising methods to analyse the signatures induced by charged particles traversing the detector. This talk will cover a Deep Learning based approach using Graph Convolutional Networks to classify and reconstruct events in both the ORCA and ARCA detector. Performance studies on simulations as well as applications to real data will be presented, together with comparisons to classical approaches.

Speaker: Stefan Reck (ECAP - University of Erlangen)
• 18:40
A new and improved IceCube point-source analysis 20m

The IceCube Neutrino Observatory investigates high-energy astrophysical phenomena by studying the corresponding high-energy neutrino signal. Its successful discovery of a diffuse flux of astrophysical neutrinos with energies up to the PeV scale in 2013 has triggered a vast effort to identify this signal's sources, which recently resulted in an improved analysis method. Here, we present a new IceCube point-source search that improves the accuracy of the statistical analysis, especially at energies of a few TeV and below. The new approach includes multidimensional kernel density estimation based probability density functions, angular error estimates using a boosted decision tree, and a new deep neural network energy estimator.

Speaker: Chiara Bellenghi (Physics Department - Technical University Munich)
• 19:00
Neutrino direction resolution of the ARIANNA detector, with Implications for future ultra-high energy neutrino astronomy 20m

High-energy neutrinos with energies above a few $10^{16}~$eV can be measured efficiently with in-ice radio detectors which is explored successfully in the ARIANNA test-bed detector, an array of shallow radio detector stations. Here, we demonstrate the neutrino pointing capabilities of a shallow radio station. Using the residual hole from the South Pole Ice Core Project, radio pulses were emitted from a transmitter located up to 1.7 km below the snow surface. By measuring these signals with an ARIANNA surface station, the angular and polarization reconstruction abilities are quantiﬁed, which are required to measure the direction of the neutrino. The direction to the transmitted radio pulse was measured with an angular resolution of $0.37^\circ$. For polarization, the statistical error of the polarization vector was measured to $1^\circ$ with a slow systematic variation as a function of depth of $2.7^\circ$. We also report on the results of a simulation study using NuRadioMC to determine the statistical uncertainty at low signal strengths. Using a global fit to the recorded voltage traces of the 5 antennas of a shallow station, we find a neutrino space angle resolution of below $3^\circ$ of all triggered events.

Speaker: Christian Glaser (Uppsala University)
• 17:00 19:20
Neutrino properties

Neutrino oscillations, NMO, NSI, neutrino decay, others

VLVnT 2021 | Parallel Session Room C
https://cern.zoom.us/j/69737018748

• 17:00
Current status of neutrino masses and mixing 20m

In this talk I present the results from our global fit to neutrino oscillation data. Neutrino oscillation experiments have reached a very good level in precision. Due to correlations among parameters a global fit combining many different datasets can give more precise results than a single experiment on its own. I will present the results of the latest global fit performed by our group and focus on the remaining unknowns in the standard picture: Atmospheric octant, CP violation and neutrino mass ordering.

Speaker: Dr. Christoph Andreas Ternes (INFN Torino)
• 17:20
Recent neutrino oscillation results from IceCube/DeepCore 20m

The IceCube neutrino observatory, along with its DeepCore in-fill array, detects a large amount of atmospheric and astrophysical neutrinos across a wide range of energies from GeV to PeV. DeepCore is sensitive in measuring neutrino oscillation parameters using events in GeV-TeV range. This talk will present an update of muon neutrino disappearance analysis using 8 years of DeepCore data, using a fast and robust reconstruction tool to select a sample of high quality events. An outlook for upcoming results from both a higher statistics data sample from DeepCore and the future IceCube Upgrade will also be presented.

Speaker: Wing Yan Ma (DESY)
• 17:40
Neutrino mass ordering determination through combined analysis with JUNO and KM3NeT/ORCA 20m

The determination of neutrino mass ordering (NMO) is one of the prime goals of several neutrino experiments. KM3NeT/ORCA and JUNO are two next-generation neutrino oscillation experiments both aiming at addressing this question. ORCA can determine the NMO by probing Earth matter effects on the oscillation of atmospheric neutrinos in the GeV energy range. JUNO, on the other hand, is sensitive to the NMO by investigating the interference effects of fast oscillations in the reactor electron antineutrino spectrum at medium baseline.

This talk presents the potential of determining the NMO through a combined analysis of JUNO and ORCA data. When measuring the $\Delta m^2_{31}$ with a wrong ordering assumption, the best-fit values are different between the two experiments. This tension, together with good constraints on the $\Delta m^2_{31}$ measurement by both experiments, enhances the combined NMO sensitivity beyond the simple sum of their sensitivities. The analysis shows that $5\sigma$ significance is reachable in less than 2 years of data taking with both experiments for true normal neutrino mass ordering assuming current global best-fit values of the oscillation parameters, while 6 years will be needed for any other parameter set.

Speaker: Nhan Chau (APC)
• 18:00
Update on the IceCube High Energy Non-Standard Interactions Analysis 20m

The existence of neutrino masses and tensions between measurements of neutrino mixing parameters indicates there is new physics yet to be discovered. A viable explanation for these discrepancies are non-standard interactions (NSI)— subdominant neutrino-quark interactions not described by the Standard Model (SM). A portion of neutrinos detected by IceCube travel through distances of Earth’s matter near the oscillation length, making IceCube particularly sensitive to flavor-changing, neutral current NSI. Here we report progress on an IceCube NSI search employing a sample of high energy (>100GeV), upgoing muon tracks to constrain NSI that alter muon-tau neutrino oscillations.

Speaker: Grant Parker (University of Texas at Arlington)
• 18:20
Search for non-standard neutrino interactions with ANTARES and KM3NeT/ORCA 20m

Non-standard interactions (NSIs) in the propagation of neutrinos in matter can lead to significant deviations in neutrino oscillations expected within the standard neutrino oscillation framework. These additional interactions would result into an anomalous flux of neutrinos discernible at neutrino telescopes. The ANTARES detector and its next-generation successor, KM3NeT, located in the Mediterranean Sea, have the potential to measure sub-dominant effects in neutrino oscillations, coming from non-standard neutrino interactions.

In this presentation, a likelihood-based search for NSIs with 10 years of atmospheric muon-neutrino data recorded with ANTARES will be reported and sensitivity projections for KM3NeT/ORCA (ORCA being the low energy sub-array of KM3NeT), based on up-to-date simulations, will be shown. The phenomenological consequence of NSIs on the neutrino mass ordering (NMO) measurement at ORCA will be addressed as well. Remarkably, the bounds obtained with ANTARES in the NSI $\mu - \tau$ sector constitute the most stringent limits up to date.

Speaker: Nafis Rezwan Khan Chowdhury (IFIC, Valencia)
• 18:40
New Physics in the Lepton sector from future Neutrino experiments 20m

The phenomenon of Neutrino Oscillation has been very well confirmed by a plethora of data; we are now entering a precision era in which the mixing angles and mass differences are going to be measured with unprecedented precision by ongoing and planned experiments. However, the new measurements could reveal that the standard three flavor scenario is not enough for a complete description of oscillations and a new paradigm beyond the standard physics in the lepton sector must be invoked. In this talk I will review the current experimental situation on neutrino masses and mixing and discuss some example of physics beyond the Standard Model that could show up in the next years.

Speaker: Davide Meloni (Dipartimento Matematica e Fisica, Universita' di RomaTre)
• 19:00
Search for a Astrophysical Neutrino Suppression due to Dark Matter Neutrino Scattering with IceCube 20m

Numerous astrophysical and cosmological experiments have observed the effects of dark matter, however, its properties have yet to be discovered. Simultaneously, the nature of high-energy astrophysical neutrinos detected by IceCube remains unresolved. If dark matter and neutrinos are coupled to each other, they may exhibit a non-zero elastic scattering cross section. Such an interaction between an isotropic extragalactic neutrino flux and dark matter would be concentrated in the Galactic Centre, where the dark matter column density is greatest. This scattering would attenuate the flux of high-energy neutrinos, which could be observed in IceCube. Using the seven-year Medium Energy Starting Events (MESE) sample, we perform an unbinned likelihood analysis, searching for a signal based on four possible DM-neutrino interaction scenarios. We search for a suppression of the high-energy astrophysical neutrino flux in the direction of the Galactic Centre, and compare these constraints to complementary low-energy information from large scale structure surveys and the cosmic microwave background.

• 18:00 19:20
Detector R&D and construction: Optical properties

Hardware, calibration, measurement of medium properties, DOMs, photon detectors, deployment/installation

VLVnT 2021 | Parallel Session Room B
https://cern.zoom.us/j/68306216278

• 18:00
The Pacific Ocean Neutrino Explorer (P-ONE) and its pathfinder missions 20m

In the search for astrophysical neutrinos, neutrino telescopes instrument large volumes of clear natural water. Photomultiplier tubes placed along mooring lines detect the Cherenkov light of secondary particles produced in neutrino interactions, and allow us to search for possible neutrino sources in the sky. The P-ONE experiment proposes a new neutrino telescope off the shore of British Columbia, where it will complement the sky coverage of other neutrino telescopes.
To overcome the challenges of a deep-sea installation, we have developed prototype mooring lines in collaboration with Ocean Networks Canada, an initiative of the University of Victoria, which provides the infrastructure for many Oceanographic instruments. The STRAW and STRAW-b mooring lines, deployed in 2018 and 2020, provide continuous monitoring of optical water properties at a new possible detector site in the Pacific.
We present the measurements of the pathfinder missions, and the plans for the future deployment of P-ONE.

Speaker: Andreas Gaertner (University of Alberta)
• 18:20
Laser events analysis in Baikal-GVD 20m

In order to accurately reconstruct track and cascade events in a neutrino telescope, it is necessary to have information about the optical properties of the medium. The main purpose of the laser event analysis is to evaluate the light absorption length and the light scattering length in the deep Baikal water. Currently, the Baikal-GVD detector is equipped with 5 lasers with a wavelength of 532 nm, located on vertical strings at various depths. The lasers emit powerful flashes of light which are recorded by the Baikal-GVD optical modules. The positions of the lasers are reconstructed from the optical module data using a chi^2 fit, taking into account the anisotropic light emission pattern of the lasers. The optical parameters of the medium are estimated using the likelihood minimization method assisted with Monte-Carlo simulations.

Speaker: Ms. Yuliya Yablokova (JINR)
• 18:40
Advances in IceCube ice modelling and what to expect from the Upgrade 20m

The IceCube Neutrino Observatory instruments about 1 km^3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light from relativistic, charged particles. Most IceCube science goals rely on precise understanding and modelling of the optical properties of the instrumented ice. A peculiar light propagation effect observed by IceCube is an anisotropic attenuation, which is aligned with the local flow of the ice. Recent efforts have shown this effect is most likely due to curved photon trajectories resulting from the asymmetric light diffusion in the birefringent polycrystalline microstructure of the ice. This new model can be optimized by adjusting the average orientation, size and shape of the ice crystals. We present the parametrization of the birefringence effect in our photon propagation simulation, the fitting procedures and results. The anticipated potential of calibration instrumentation the upcoming IceCube Upgrade to improve on known shortcoming of the current ice modelling are also discussed.

Speaker: Martin Rongen (JGU Mainz)
• 19:00
Method and portable bench for tests of the laser optical calibration system components for the Baikal-GVD underwater neutrino Cherenkov telescope 20m

The large-scale deep underwater Cherenkov neutrino telescopes like Baikal-GVD, ANTARES or KM3NeT, require calibration and testing methods of their optical modules. These methods usually include laser-based systems which allow to check the telescope responses to the light and for real-time monitoring of the optical parameters of water such as absorption and scattering lengths, which show seasonal changes in natural reservoirs of water. We will present a testing method of a laser calibration system and a set of dedicated tools developed for Baikal- GVD, which includes a specially designed and built, compact, portable, and reconfigurable scanning station. This station is adapted to perform fast quality tests of the underwater laser sets just before their deployment in the telescope structure, even on ice, without darkroom. The testing procedure includes the energy stability test of the laser device, 3D scan of the light
emission from the diffuser and attenuation test of the optical elements of the laser calibration system. The test bench consists primarily of an automatic mechanical scanner with a movable Si detector, beam splitter with a reference Si detector and, optionally, Q-switched diode-pumped solid-state laser used for laboratory scans of the diffusers. The presented test bench enables a three-dimensional scan of the light emission from diffusers, which are designed to obtain the isotropic distribution of photons around the point of emission. The results of the measurement can be easily shown on a 3D plot immediately after the test and may be also implemented to a dedicated program simulating photons propagation in water, which allows to check the quality of the diffuser in the scale of the Baikal-GVD telescope geometry.

Speaker: Konrad Kopański (H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences)
• Friday, 21 May
• 15:00 15:30
Plenary: Plenary talk

Plenary talks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

• 15:00
Long-baseline tagged neutrino experiments with very large volume neutrino telescopes 30m

Long-baseline neutrino experiments using very large volume neutrino telescopes
as far detectors can collect sizeable neutrino samples - $\mathcal{O}(10^3) \nu_e/year$ - even with moderate beam intensities - $\mathcal{O}(100) kW$. The presentation will show that at these intensities it is possible to instrument the beam with charged particle silicon pixel trackers to reconstruct precisely the energy, direction, initial flavour and chirality of the neutrino produced in each $\pi^\pm \to \mu^\pm \nu$ decay.

With proper synchronisation between these trackers and the far detector, the interacting neutrinos can be associated with the one reconstructed from the $\pi^\pm \to \mu^\pm \nu$ decay kinematics. The far detector is then only left with the identification of the oscillated neutrino flavour. This task is greatly simplified by the prior knowledge of the other neutrino properties.

In such a tagged long-baseline neutrino experiment, the individual tracking of each neutrino of the beam from production to detection greatly reduces systematic uncertainties. Added to that, the sub-percent energy resolution and the large neutrino sample size will allow to reach unprecedented precision on neutrino oscillation parameters. For instance the $\delta_{CP}$ phase could be determined with a few degree precision across the whole $\delta_{CP}$ range with 10 years of data of a long-baseline tagged neutrino experiment from U70 in Protvino, Russia, to a KM3NeT-ORCA like detector offshore Toulon, France.

Speaker: Mathieu Perrin-Terrin (Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France)
• 15:30 16:30
Earth and Sea sciences

VLVnT 2021 | Parallel Session Room A
https://cern.zoom.us/j/62997581748

• 15:30
Luminescence of Baikal Water as a Dynamic Background of the Baikal-GVD Neutrino Telescope 20m

Baikal-GVD is a neutrino telescope situated in the deepest freshwater lake in the world – Lake Baikal. It is a three-dimensional array of photo-multiplier tubes, that are arranged in independently working units called clusters. The main purpose of this telescope is to detect neutrinos via detecting the Cherenkov radiation of the secondary charged particles that are created in the interactions of neutrinos.

The design of the Baikal-GVD trigger system allows also to study the ambient light. The analysis of the optical noise, particularly, time and spatial variations of the noise frequency collected by various clusters will be presented.

Speaker: Ms. Eliška Eckerová (Comenius University in Bratislava)
• 15:50
Passive Acoustic Monitoring of Cetaceans with KM3NeT acoustic receivers 20m

The KM3NeT infrastructure comprises a network of underwater neutrino telescopes in the Mediterranean Sea. Secondary particles, produced when neutrinos interact, emit Cherenkov photons which are measured by the KM3NeT detectors.
In order to precisely reconstruct muon tracks and showers, it is necessary to know the position of the photomultipliers with an accuracy of about 10 cm.
For this purpose, an acoustic system consisting of hydrophones and piezoelectric sensors is set up and three acoustic emitters are placed around the detector.
Using underwater acoustic sensors as a passive acoustic monitoring system opens the possibility to study several aspects related to underwater noise present in the marine environment. Of special relevance are the bio-acoustic signals produced by marine mammals present in the Mediterranean Sea. The Gulf of Lion area has particular importance due to the presence of many cetacean’s species such as sperm whales and various types of dolphins. Depending on the detected bio acoustic signals (echolocation clicks or whistles) it is possible to infer, from absence/presence of marine mammals, the circadian and seasonal patterns of activity. Moreover, considering the click intervals, the identification of different cetacean species is possible.
The purpose of this talk is to illustrate the potential of the KM3NeT acoustic system to perform long term monitoring regarding bio-acoustic signal detection.
Simulations and applications to real data of marine mammal click detection and consequent reconstruction of the position of the acoustic sources have been performed, together with studies on dolphin whistle activity and the statistics related with the frequency band estimation, revealing that KM3NeT infrastructure is a relevant system for underwater passive acoustic monitoring.

Speaker: Mr. Carlo Guidi (INFN - Genova)
• 16:10
Perspectives for probing the Earth core composition with atmospheric neutrino detectors 20m

Our knowledge about the Earth's interior is mainly based on seismic measurements, cosmochemical and petrological constraints, and theories of Earth formation. Whereas the matter density profile is determined with a high precision, the chemical composition of the deep Earth can only be estimated indirectly. In particular the amount and nature of light elements in the Core remain controversial.

A new approach comes from the field of particle physics. The oscillation probabilities of neutrinos traversing the Earth are affected by the electron density along their trajectory. In combination with a known matter density profile, their measurement leads to a direct constrain of the proton-to-nucleon (Z/A) ratio along the neutrino path. Since this parameter varies among chemical elements this technique has the potential to provide insights into the chemical composition of the core. From the current knowledge of the Earth’s interior, oscillation resonance effects are expected at ~GeV energies, making atmospheric neutrinos excellent candidates for oscillation tomography research

In our study we find that the atmospheric neutrino telescope KM3NeT/ORCA will be able to resolve the Z/A ratio of the Earth’s outer core with an uncertainty of <10% at 1σ. We further show that, in order reach resolutions sufficient to constrain the Earth core composition, bigger and denser versions of currently existing detector types are needed.

Speaker: Lukas Maderer (APC, Université de Paris)
• 15:30 16:30
High-energy neutrino sources

Diffuse, point-like, extended, galactic plane, others

This session is distributed in multiple rooms along the week:
Thu:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Fri:
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Click on each contribution for details

• 15:30
Detection of a neutrino event at the Glashow resonance with IceCube 20m

The Glashow resonance describes the resonant production of a W− boson during
the interaction of an electron antineutrino with an electron.
The cross-section of this process peaks at an antineutrino energy of 6.3 petaelectronvolts (PeV) in the rest frame of the electron.
In this talk, I will report on the observation by the IceCube Neutrino Observatory of a neutrino-induced particle shower with a deposited energy of ~6 PeV. A detailed study of the event revealed features in the PMT waveforms, which are consistent with the production of secondary muons in the particle shower. While these muons confirm the hadronic nature of the particle shower - as expected from the decay of a W- boson -,they also enable an independent verification of the directional reconstruction of the primary neutrino.
This evidence for the Glashow resonance demonstrates the presence of electron antineutrinos in the astrophysical flux.
While currently limited by statistics, this work demonstrates the feasibility of measuring the astrophysical anti-electron neutrino flux in future neutrino telescopes. By disentangling neutrinos from antineutrinos, it becomes possible to distinguish astronomical accelerators that produce neutrinos via hadronuclear or photohadronic interactions with or without strong magnetic fields.

Speaker: Dr. Christian Haack
• 15:50
All-flavour search for a diffuse cosmic neutrino flux with ANTARES 20m

The ANTARES neutrino telescope, located in the Mediterranean Sea, is the longest-operated under-sea neutrino detector, having collected data for more than 14 years and since 2008 in its full configuration. These data have been used to search for a diffuse flux of cosmic neutrinos, upgrading previously published results both in terms of livetime and in search method. In particular, a new event selection strategy, developed for the study of the atmospheric neutrino flux, allows a further rejection of atmospheric foregrounds, thus enabling a considerable reduction of previous systematic uncertainties connected with the background estimation . The results of this new analysis are reported in this contribution.

Speaker: Luigi Antonio Fusco (CPPM, Marseille)
• 16:10
Sensitivity estimates for diffuse, point-like and extended neutrino sources with KM3NeT/ARCA 20m

The identification of cosmic objects emitting high energy neutrinos could provide new insights about the Universe and its active sources. The existence of these cosmic neutrinos has been proven by the IceCube collaboration, but the big question of which sources these neutrinos originate from, remains unanswered. The KM3NeT detector for Astroparticle Research with Cosmics in the Abyss (ARCA), with a cubic kilometer instrumented volume, is currently being built in the Mediterranean Sea. It will excel at identifying cosmic neutrino sources due to its unprecedented angular resolution for muon neutrinos (< 0.2 degree for E > 10 TeV events). KM3NeT has a view of the sky complementary to IceCube, and is sensitive to neutrinos across a wide range of energies. In order to identify the signature of cosmic neutrino sources in the background of atmospheric neutrinos and muons, statistical methods are being developed and tested with Monte-Carlo pseudo-experiments. This contribution presents the most recent sensitivity estimates for diffuse, point-like and extended neutrino sources with KM3NeT/ARCA.

Speaker: Rasa Muller (PhD, Nikhef)
• 15:30 16:30
Low energy neutrino sources

VLVnT 2021 | Parallel Session Room C
https://cern.zoom.us/j/69737018748

• 15:30
KM3NeT Core Collapse Supernovae observation program in standalone and multi-messenger modes 20m

The KM3NeT research infrastructure in the Mediterranean is a multi-purpose cubic-kilometer neutrino observatory consisting of two detectors optimized to study cosmic and atmospheric neutrinos between GeV to PeV energies. Additionally, KM3NeT multi-photomultiplier optical modules allow the detection of nearby MeV interaction products by selecting nanosecond coincidences within the photomultipliers of the same module. Distribution of the number of photomultipliers forming a coincidence (multiplicity) for the whole supernova emission behaves as a proxy of the average neutrino energy. An optimised coincidence selection allows the KM3NeT detectors to be sensitive to Galactic supernovae and beyond. The large KM3NeT effective volume allows a high number of detected events for a core collapse supernovae explosion and the measurement of the neutrino light curve properties, such as the light curve start time and the presence of the standing accretion shock instability oscillations. Sub-millisecond time synchronization between KM3NeT detectors allows common observation. Such a scheme can be also a viable solution to synchronize the KM3NeT telescopes with other detectors aiming to observe neutrino emission from core collapse supernovae through the SNEWS network.

Speaker: Dr. Massimiliano Lincetto (Aix Marseille Univ, CNRS/IN2P3, CPPM)
• 15:50
Multi-detector approach to enhance the sensitivity of neutrino telescopes to low-energy astrophysical sources 20m

While large neutrino telescopes have so far mainly focused on the detection of TeV-PeV astrophysical neutrinos, several efforts are ongoing to extend the sensitivity down to the GeV level for transient sources. Only a handful of searches have been carried out at the moment leaving the signature of astrophysical transients poorly known in this energy range.
In this contribution, we discuss the motivations for high-energy neutrino telescopes to explore the GeV energy range and summarize the current limitations of detectors, such as IceCube and KM3NeT. We then present and compare different approaches for multi-detector analyses that may enhance the sensitivity to a transient GeV neutrino flux.

Speaker: Gwenhaël de Wasseige (APC, Université de Paris)
• 16:10
KM3NeT sensitivity to low energy astrophysical neutrinos 20m

KM3NeT, a new generation of neutrino telescope, is currently being deployed in the Mediterranean Sea. While its two sites, ORCA and ARCA, were respectively designed for the determination of neutrino mass hierarchy and high-energy neutrino astronomy, this contribution presents a study of the detection potential of KM3NeT in the MeV-GeV energy range. At these low energies, the data rate is dominated by low-energy atmospheric muons and environmental noise due to bioluminescence and K40 decay. The goal of this study is to characterize the environmental noise in order to optimize the selection of low-energy neutrino interactions and increase the sensitivity of KM3NeT to transient astrophysical phenomena, such as close-by core-collapse Supernovae, solar flares, and extragalactic transients. In this contribution, we will study how using data science tools might improve the sensitivity of KM3NeT in these low-energy neutrino searches. We will first introduce the data sets and the different variables used to characterize KM3NeT sensor response to the environmental noise. We will then compare the efficiency of various tools in identifying different components in the environmental noise and in disentangling low-energy neutrino interactions from the background sources. We will conclude with the implication for future astrophysical transient neutrino searches.

Speaker: Gwenhaël de Wasseige (APC, Université de Paris)
• 15:30 16:30
Methods and tools

Simulation, reconstruction techniques, machine learning/NNs/BDTs, likelihoods, strategies, computing, software, data formats, virtual observatories

This session is distributed in multiple rooms along the week:
Tue:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room E: https://cern.zoom.us/j/68700031104
Wed:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
Thu:
- VLVnT 2021 | Parallel Session Room A: https://cern.zoom.us/j/62997581748
- VLVnT 2021 | Parallel Session Room B: https://cern.zoom.us/j/68306216278
Fri:
- VLVnT 2021 | Parallel Session Room D: https://cern.zoom.us/j/63734092003
Click on each contribution for details

• 15:30
Atmospheric neutrinos with the first detection units of KM3NeT-ARCA 20m

The KM3NeT Collaboration is constructing two deep-sea Cherenkov detectors in the Mediterranean Sea. The ARCA detector aims at TeV-PeV neutrino astronomy, while the ORCA detector is optimized for atmospheric neutrino oscillation studies at energies of a few GeV. In this contribution, an analysis of the data collected with the first deployed detection units of the ARCA detector is presented. A high-purity sample of atmospheric neutrinos is selected demonstrating the capability of the ARCA detector.

Speaker: Anna Sinopoulou
• 15:50
Comparison of the measured atmospheric muon rate with Monte Carlo simulations and sensitivity study for detection of prompt atmospheric muons with KM3NeT 20m

The KM3NeT Collaboration has successfully deployed the first detection units of the next generation undersea neutrino telescopes in the Mediterranean Sea at the two sites in Italy and in France. The data sample collected between December 2016 and January 2020 has been used to measure the atmospheric muon rate at two different depths under the sea level: 3.5 km with KM3NeT/ARCA and 2.5 km with KM3NeT/ORCA . Atmospheric muons represent an abundant signal in a neutrino telescope and can be used to test the reliability of the Monte Carlo simulation chain and to study the physics of extensive air showers caused by highly-energetic primary nuclei impinging the Earth’s atmosphere. At energies above PeV the contribution from prompt muons, created right after the first interaction in the shower, is expected to become dominant, however its existence was not yet experimentally confirmed. In this contribution data collected with the first detection units of KM3NeT are compared to Monte Carlo simulations based on MUPAGE and CORSIKA codes. The main features of the simulation and reconstruction chains are discussed and presented. Additionally, sensitivities of both KM3NeT/ARCA and KM3NeT/ORCA to the prompt muon component are derived using CORSIKA code.

Speaker: Piotr Kalaczyński (NCBJ Warsaw)
• 16:10
Analysis of the first KM3NeT-ORCA data 20m

ORCA, Oscillation Research with Cosmics in the Abyss, is the low energy KM3NeT neutrino underwater detector, located in the French Mediterranean sea. It comprises a dense array of optical modules designed to detect the emitted Cherenkov light emitted from charged particles resulting from neutrino interactions in the vicinity of the detector. Its main physics goal is the determination of the neutrino mass hierarchy by quantifying the matter-induced effect on the oscillation probabilities of atmospheric neutrinos in the energy range, 3-50 GeV, where the effects of neutrino oscillation phenomena are dominant.

In 2019, four detection units were operational. Two more had been added in early 2020. This work presents an overview of the detector performance in 2019 and 2020 as well as its sensitivity to neutrino oscillations.

Speakers: Valentin Pestel (Nikhef, NWO), zineb aly (Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France)
• 16:40 17:10
Discussion: Final remarks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895

Convener: Uli Katz (ECAP / Univ. Erlangen)
• 16:40
Final remarks 30m
Speaker: Uli Katz (ECAP / Univ. Erlangen)
• 17:10 17:20
Plenary: Farewell

Plenary talks

VLVnT 2021 | Main Room
https://cern.zoom.us/j/67801176895