Reconstructed tracks of muons produced in neutrino interactions provide the precise probe for the neutrino direction. Therefore, track-like events are a powerful tool to search for neutrino point ...sources. Recently, Baikal-GVD has demonstrated the first sample of low-energy neutrino candidate events extracted from the data of the season 2019 in a so-called single-cluster analysis - treating each cluster as an independent detector. In this paper, the extension of the track-like event analysis to a wider data set is discussed and the first high-energy track-like events are demonstrated. The status of multi-cluster track reconstruction and that of the event analysis are also discussed.
We present the results of the two-year (2021-2022) monitoring of absorption and scattering lengths of light with wavelength 400-620 nm within the effective volume of the deep underwater neutrino ...telescope Baikal-GVD, which were measured by a device Baikal-5D No.2. The Baikal-5D No.2. was installed during the 2021 winter expedition at a depth of 1180 m. The absorption and scattering lengths were measured every week in 9 spectral points. The device Baikal-5D No.2 also has the ability to measure detailed scattering and absorption spectra. The data obtained make it possible to estimate the range of changes in the absorption and scattering lengths over a sufficiently long period of time and to investigate the relationship between the processes of changes in absorption and scattering. An analysis was made of changes in absorption and scattering spectra for the period 2021-2022.
The Baikal-GVD is a deep-underwater neutrino telescope being constructed in Lake Baikal. After the winter 2023 deployment campaign the detector consists of 3456 optical modules installed on 96 ...vertical strings. The status of the detector and progress in data analysis are discussed in present report. The Baikal-GVD data collected in 2018-2022 indicate the presence of cosmic neutrino flux in high-energy cascade events consistent with observations by the IceCube neutrino telescope. Analysis of track-like events results in identification of first high-energy muon neutrino candidates. These and other results from 2018-2022 data samples are reviewed in this report.
The Baikal-GVD neutrino detector is a deep-underwater neutrino telescope under construction and recently after the winter 2023 deployment it consists of 3456 optical modules attached on 96 vertical ...strings. This 3-dimensional array of photo-sensors allows to observe ambient light in the vicinity of the Baikal-GVD telescope that is associated mostly with water luminescence. Results on time and space variations of the luminescent activity are reviewed based on data collected in 2018-2022.
We present a new procedure for time calibration of the Baikal-GVD neutrino telescope. The track reconstruction quality depends on accurate measurements of arrival times of Cherenkov photons. ...Therefore, it is crucial to achieve a high precision in time calibration. For that purpose, in addition to other calibration methods, we employ a new procedure using atmospheric muons reconstructed in a single-cluster mode. The method is based on iterative determination of effective time offsets for each optical module. This paper focuses on the results of the iterative reconstruction procedure with time offsets from the previous iteration and the verification of the method developed. The theoretical muon calibration precision is estimated to be around 1.5-1.6ns.
Baikal-GVD has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. We further explore the Baikal-GVD cascade dataset ...collected in 2018-2022, with the aim to identify possible associations between the Baikal-GVD neutrinos and known astrophysical sources. We leverage the relatively high angular resolution of the Baikal-GVD neutrino telescope (2-3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. We estimate the telescope's sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using Monte-Carlo simulations. We primarily focus on cascades with energies exceeding 100 TeV, which we employ to search for correlation with radio-bright blazars. Although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and Galactic sources. Specifically, we present an analysis of an observed triplet of neutrino candidate events in the Galactic plane, focusing on its potential connection with certain Galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars.
We report on the observation of a rare neutrino event detected by Baikal-GVD
in April 2021. The event GVD210418CA is the highest-energy cascade observed by
Baikal-GVD so far from the direction below ...the horizon. The estimated cascade
energy is $224\pm75$~TeV. The evaluated signalness parameter of GVD210418CA is
97.1\% using an assumption of the E$^{-2.46}$ spectrum of astrophysical
neutrinos. The arrival direction of GVD210418CA is near the position of the
well-known radio blazar TXS~0506+056, with the angular distance being within a
90\% directional uncertainty region of the Baikal-GVD measurement. The event
was followed by a radio flare observed by the RATAN-600 radio telescope,
further strengthening the case for the neutrino-blazar association.
Baikal-GVD (Gigaton Volume Detector) is a neutrino telescope installed at a
depth of 1366 m in Lake Baikal. The expedition of 2023 brought the number of
optical modules in the array up to 3492 ...(including experimental strings). These
optical modules detect the Cherenkov radiation from secondary charged particles
coming from the neutrino interactions. Neutrinos produce different kinds of
topologically distinct light signatures. Charged current muon neutrino
interactions create an elongated track in the water. Charged and neutral
current interactions of other neutrino flavors yield hadronic and
electromagnetic cascades. The background in the neutrino cascade channel arises
mainly due to discrete stochastic energy losses produced along atmospheric muon
tracks. In this paper, a developed algorithm for the cascade event selection is
presented.
The deployment of the Baikal-GVD deep underwater neutrino telescope is in
progress now. About 3500 deep underwater photodetectors (optical modules)
arranged into 12 clusters are operating in Lake ...Baikal. For increasing the
efficiency of cascade-like neutrino event detection, the telescope deployment
scheme was slightly changed. Namely, the inter-cluster distance was reduced for
the newly deployed clusters and additional string of optical modules are added
between the clusters. The first inter-cluster string was installed in 2022 and
two such strings were installed in 2023. This paper presents a Monte Carlo
estimate of the impact of these configuration changes on the cascade detection
efficiency as well as technical implementation and results of in-situ tests of
the inter-cluster strings.
Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently
under construction in Lake Baikal. GVD consists of 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 large detector volume and modular
design of Baikal-GVD allows for the measurements of the astrophysical diffuse
neutrino flux to be performed already at early phases of the array
construction. We present here recent results of the measurements on the diffuse
cosmic neutrino flux obtained with the Baikal-GVD neutrino telescope using
cascade-like events.
