In 2023, the journal Physical Review D published an article on the first observation of a diffuse cosmic neutrino flux by the Baikal-GVD neutrino telescope. In the 2018–2021 cascade-event dataset, a significant excess of events over the expected atmospheric background was detected. This excess was consistent with the diffuse high-energy cosmic neutrino flux observed by the IceCube observatory. The hypothesis of a zero cosmic flux is rejected at a confidence level of 3.05σ. Assuming that the astrophysical neutrino flux is described by a single power law with equal contribution from each neutrino flavor, the following best-fit parameter values were obtained: spectral index γastro = 2.58 +0.27−0.33 and flux normalization ϕastro = 3.04+1.52 −1.21 per flavor at an energy of 100 TeV.
V. A. Allakhverdyan et al. (Baikal-GVD Collaboration), Diffuse neutrino flux measurements with the Baikal-GVD neutrino telescope, Phys. Rev. D 107, 042005 (2023) // https://doi.org/10.1103/PhysRevD.107.042005
A 2018–2022 data set of cascade events was analyzed in order to identify possible coincidences between neutrinos detected by Baikal-GVD and the activity of known astrophysical sources. Due to the relatively high angular resolution of the neutrino telescope for cascade events of Baikal-GVD (2–3 degrees), astrophysical point sources can be studied using this type of events. The sensitivity of the telescope in the cascade channel for high-energy astrophysical sources was estimated, and the analysis algorithms were refined. The main focus was on cascades with energy above 100 TeV, which were used to search for correlation with radio-bright blazars. Although the currently limited neutrino sample does not yield statistically significant effects, the analysis points to a number of possible associations with both extragalactic and Galactic sources. In particular, an analysis of an observed triplet of possible neutrino events in the Galactic plane was presented, considering its potential connection with certain Galactic sources, and the coincidence of cascades with several bright blazars was also discussed.
V. A. Allakhverdyan et al. (Baikal-GVD Collaboration), Search for directional associations between baikal gigaton volume detector neutrino-induced cascades and high-energy astrophysical sources, MNRAS 526, 942 (2023) // https://doi.org/10.1093/mnras/stad2641
In December 2023, an article was published on detecting in April 2021 by Baikal-GVD a rare neutrino event with an estimated energy of 224±75 TeV in the direction of the blazar TXS 0506+056 — an active galactic nucleus with a compact radio jet oriented toward Earth. This event was an ultrahigh-energy cascade detected by Baikal-GVD from a direction below the horizon. Thanks to the obtained result, the assumption is confirmed that radio blazars in general, and TXS 0506+056 in particular, are sources of high-energy neutrinos, and the possibility of research in neutrino astronomy using the cascade channel is also affirmed.
Previously, the IceCube Collaboration reported a possible connection of a neutrino with an energy of 290 TeV with a gamma-ray flare of the blazar TXS 0506+056: it was shown that radio-bright blazars with high statistical significance could be sources of neutrino events. However, until December 2023, these conclusions had not been confirmed by data from independent experiments.
V. A. Allakhverdyan et al. (Baikal-GVD Collaboration), High-energy neutrino-induced cascade from the direction of the flaring radio blazar TXS 0506 + 056 observed by Baikal-GVD in 2021, MNRAS 527, 8784–8792 (2024) // https://doi.org/10.1093/mnras/stad3653
Thanks to observations of the Galactic component of the high-energy neutrino flux, as well as to the detection of Galactic diffuse gamma radiation up to sub-petaelectronvolt energies, new opportunities opened for studying acceleration and propagation of cosmic rays in the Milky Way. On the basis of a sample of cascade events with neutrino energies above 200 TeV obtained by Baikal-GVD over 6 years of operation, the Galactic neutrino flux was examined. The distribution of directions of arrival of Baikal-GVD cascades with energy above 200 TeV on the celestial sphere indicates an excess of neutrinos from regions with low Galactic latitudes; the random probability is 1.4 × 10⁻². In the latest open-access IceCube data sets, an excess above 200 TeV was found for both cascades and tracks. The random probability of the excess in the combined analysis of IceCube and Baikal-GVD is 3.4 × 10⁻⁴. The measured flux of Galactic neutrinos above 200 TeV contradicts the commonly used templates for neutrino searches based on cosmic ray modelling.
V. A. Allakhverdyan et al. (Baikal-GVD Collaboration), Probing the Galactic Neutrino Flux at Neutrino Energies above 200 TeV with the Baikal Gigaton Volume Detector, Astrophys. J. 982, 73 (2025) // https://doi.org/10.3847/1538-4357/adb630
In September 2025, the Baikal-GVD Collaboration obtained constraints on the diffuse flux of astrophysical neutrinos with energies of several PeV. The recent detection of a neutrino with an energy of ∼ 10¹⁷ eV in the KM3NeT experiment confirms the fundamental possibility of studying such high-energy particles with modern facilities. Upper limits on the flux of astrophysical neutrinos with energies of 10¹⁵·⁵ − 10²⁰ eV were obtained in the mode of detecting cascade-like events. The astrophysical consequences of these results were considered, and constraints were established on several models of cosmogenic neutrinos using the combined data of Baikal-GVD, KM3NeT, IceCube, and Pierre Auger Observatory.
V. A. Allakhverdyan et al. (Baikal-GVD Collaboration), Constraints on the diffuse flux of multi-PeV astrophysical neutrinos obtained with the Baikal Gigaton Volume Detector, PhysRevD112,083025(2025) // https://doi.org/10.1103/jlz3-26lw
