The paper is devoted to the modeling and analysis of data detected by the TAIGA-IACT installation in the stereo mode. Five Imaging Atmospheric Cherenkov Telescopes (IACT) with a viewing angle of 9.6° are expected to be included in the installation. Today there are three telescopes spaced far apart (from 320 to 500 m) in the installation. The effective area of the installation is as large as 0.6 km2; therefore, it is possible to conduct statistically significant measurements of weak γ-ray sources in the energy range above 10 TeV over a reasonable observation time (300–400 h). The Monte Carlo procedure for simulating the hadrons and γ-rays detected by the telescopes is described as is the procedure for reconstructing the parameters of extensive air showers, such as the arrival direction of an event, the axis position, the depth of the maximum of shower development (Xmax), and the primary-particle energy. In order to solve the problem of γ-hadron separation, the criteria for selecting γ-rays detected in the stereo mode have been optimized and the effective area of the installation has been calculated.

В оз. Байкал продолжается развертывание глубоководного нейтринного телескопа Baikal-GVD. К апрелю 2022 г. было введено в эксплуатацию 10 кластеров телескопа, в состав которых входит 2880 оптических модулей. Одной из актуальных задач Байкальского проекта является исследование возможности увеличения эффективности регистрации детектора на основе опыта его эксплуатации и результатов, полученных на других нейтринных телескопах за последние годы. В данной работе рассматривается вариант оптимизации конфигурации телескопа путем установки дополнительной гирлянды оптических модулей между кластерами детектора (внешней гирлянды). Экспериментальная версия внешней гирлянды была установлена в оз. Байкал в апреле 2022 г. В работе представлены результаты расчетов эффективности регистрации нейтринных событий для новой конфигурации установки, техническая реализация системы регистрации и сбора данных внешней гирлянды и первые результаты ее натурных испытаний в оз. Байкал.

Neutrino telescope Baikal-CVD is a deep-underwater Cherenkov detector of elementary particles of the 1-km3 scale, which has been developed beginning from 2016 in Lake Baikal. The telescope is assembled from separate blocks (clusters of optical modules), which makes it possible to perform scientific research even at early stages of its development. In the 2021 configuration, the detector contains eight clusters with 2304 optical modules in total and is the largest neutrino telescope in the Northern hemisphere. The design and main characteristics of the Baikal-GVD data acquisition system are described, the problems of deep-underwater engineering associated with the development of the detector are considered, and some physical results obtained on the facility are presented

Baikal-GVD is a deep-underwater neutrino detector of cubic-kilometer scale. It is designed to detect astrophysical neutrinos up to multi-PeV energies and beyond. The deployment of this facility began in spring 2015. Since April 2020, the detector includes seven clusters, each consisting of eight strings carrying in total 288 optical modules located at depths of 750 to 1275 m. By the end of the first phase of construction of the detector in 2024, it is planned to deploy 15 clusters, whereby an effective volume of 0.75 km $${}^{3}$$ for detecting high-energy cascades would be reached. The design and status of the Baikal-GVD detector are described in the present article along with selected results of data analysis.

Lake Baikal in Siberia is one of the most interesting lakes in the world. It is the world’s largest reservoir of fresh surface water and home to several hundred endemic species. At the same time it harboured the first underwater neutrino telescope NT200, now followed by its successor Baikal-GVD, a cubic-kilometre scale neutrino telescope. Within the Baikal Neutrino project a number of methods and instruments have been designed to study various processes in the Baikal ecosystem. Hundreds of optical, acoustic and other sensors allow for long-term 3D monitoring of water parameters like temperature, inherent optical properties or the intensity of water luminescence, as well as processes like sedimentation or deep water renewal. Here we present selected results of the interdisciplinary environmental studies.

Baikal-GVD is a cubic kilometer-scale neutrino telescope currently under construction in Lake Baikal. The detector’s components are mobile and may drift from their initial coordinates or change their spatial orientation. This introduces a reconstruction error, particularly a timing error for PMT hits. This problem is mitigated by a combination of a hydroacoustic positioning system and per-component acceleration and orientation sensors. Under regular conditions, the average positioning accuracy for a GVD component is estimated to be less than 13 cm.

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 obtained in 2015 and 2016.

The 1-cubic km deep Baikal-GVD underwater Cherenkov detector, a new-generation neutrino telescope, is now being deployed in Lake Baikal. The telescope’s status is described and the first physical results from its operation are presented.

Baikal-GVD is a next generation, kilometer-scale neutrino telescope under construction in Lake Baikal. It is designed to detect astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. GVD is formed by multi-megaton subarrays (clusters). The array construction started in 2015 by deployment of a reduced-size demonstration cluster named "Dubna" . The first cluster in it’s baseline configuration was deployed in 2016, the second in 2017 and the third in 2018. The full-scale GVD will be an array of ~10.000 light sensors with an instrumented volume about of 2 cubic km. The first phase (GVD-1) is planned to be completed by 2020-2021. It will comprise 8 clusters with 2304 light sensors in total. We describe the design of Baikal-GVD and present selected results obtained in 2015 - 2017.

The Advanced Laser Interferometer Gravitational-Wave Observatory and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst that followed the merger of this binary was also recorded by Fermi gamma-ray burst monitor and International Gamma-Ray Astrophysics Laboratory, indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the energy range of 1 TeV–100 PeV using the Baikal Gigaton Volume Detector. No neutrinos directionally coincident with the source were detected within ±500 s around the merger time, as well as during a 14-day period after the gravitational wave detection. We derived 90% C.L. upper limits on the neutrino fluence from GW170817 during a ±500 s window centered on the gravitational wave trigger time, and a 14-day window following the gravitational wave signal under the assumption of an E −2 neutrino energy spectrum.

В настоящее время сотрудничеством “Байкал” ведутся работы по созданию глубоководного нейтринного телескопа НТ1000 с эффективным объемом 2 км3 на оз. Байкал. Телескоп будет состоять из функционально независимых установок – кластеров гирлянд оптических модулей на основе фотоэлектронных умножителей (по 8 гирлянд в каждом кластере). Начиная с 2011 г. на оз. Байкал ведутся натурные испытания базовых элементов и систем будущего телескопа в составе автономных измерительных комплексов – прототипов кластера НТ1000. В статье описаны базовые элементы и принципиальная схема функционирования одного из рассматриваемых в настоящее время вариантов акустической системы позиционирования телескопа НТ1000 и приводятся результаты испытаний прототипа этой системы в составе экспериментального кластера 2012 года.

В настоящее время сотрудничеством “Байкал” ведутся работы по созданию глубоководного нейтринного телескопа НТ1000 с эффективным объемом 2 км3 на оз. Байкал. Телескоп будет состоять из функционально независимых установок – кластеров гирлянд оптических модулей на основе фотоэлектронных умножителей (по 8 гирлянд в каждом кластере). Начиная с 2011 г. на оз. Байкал ведутся натурные испытания базовых элементов и систем будущего телескопа в составе автономных измерительных комплексов – прототипов кластера НТ1000. В статье описаны базовые элементы и принципиальная схема функционирования одного из рассматриваемых в настоящее время вариантов акустической системы позиционирования телескопа НТ1000 и приводятся результаты испытаний прототипа этой системы в составе экспериментального кластера 2012 года.

A new analysis of the data from the NT200 neutrino telescope based on the reconstruction of parameters for high-energy showers generated in neutrino interactions has yielded new upper limits on the diffuse neutrino fluxes predicted by a number of theoreticalmodels. The upper limit on the all-flavor neutrino flux with an energy spectrum E −2 is E 2Φ ν < 2.9 × 10−7 GeV cm−2 s−1 sr−1.