In November 2020, the IceCube Neutrino Observatory registered a neutrino event with an energy of 150 TeV directed at the Cygnus Cocoon gamma-ray source. In the Carpet-2 experiment, as part of the Baksan Neutrino Observatory (BNO), a sharp increase in the flow of events with an energy above 300 TeV was recorded from the same direction within the angular accuracy of the events. This flux is 4 orders of magnitude higher than the expected intensity of gamma quanta of this energy region according to data in the region of less than 100 TeV. It was expected that such a powerful flare could be registered by the TAIGA-HiSCORE installation of the TAIGA astrophysical complex. We analyzed the events of the EAS recorded by the installation of TAIGA-HiSCORE for 18 h in October–November 2020 from the Cygnus Cocoon source. This article provides the upper limit of the expected excess flow.

A scintillation experiment is a part of the TAIGA astrophysical complex located in the Tunka Valley, 50 km from Lake Baikal. It consists of the Tunka-Grande and TAIGA-Muon arrays. Its scientific program is devoted to the study of cosmic rays (CRs) and search for astrophysical gamma rays by detecting charged particles (electrons and muons) of extensive air showers (EASs). We present the current status of the scintillation experiment, methods of EAS and CR parameters’ reconstruction, the main results obtained by the Tunka-Grande array and our scientific program for the future.

The TAIGA astrophysical complex includes now 3 IACTs at the distance 300-500 m between each other and 1km2 area wide-angle timing array TAIGA-HiSCORE. At energies above 40 TeV, a hybrid approach to the detection of gamma-rays becomes possible - the detection of EAS by both IACTs and the TAIGA-HiSCORE installation. The main advantage of the joint operation of the IACTs and timing is their good gamma/hadron separation, even by only few telescopes on the large area, by image parameters information and EAS another parameter (core position, direction and energy) that can be better reconstructed by the timing array. In this paper the following topics of a hybrid method are discussed: data processing and analysis, a comparison experimental results with Monte-Carlo simulations, selection of the first events with the energy more than 100 TeV from Crab Nebula in 250 hours of observation. The data were taken during the period of installation deployment, with one IACT in operation and half of the area of TAIGA-HiSCORE installation.

This paper is devoted to the analysis of simulation results of TAIGA-IACT in stereo mode of observations and describes the technique of gamma-ray detection with energies higher than several TeV. TAIGA-IACT is part of the TAIGA astrophysics complex. Installation currently consists of three operating telescopes located 300-500 m apart. Two additional telescopes will begin operation in the next two years. We describe a new gamma-hadron separation technique for point-like source observations.

In the era of multi-messenger astronomy it is extremely important to obtain data from many instruments to get the most complete information about transient and short-lasting phenomena. The TAIGA observatory has also started observations in multi-messenger regime. The TAIGA observatory is a hybrid detector complex for high-energy gamma-ray astronomy and cosmic ray physics that combines the detection of extensive air showers with different detector systems: timing array TAIGA-HiSCORE, scintillation array TAIGA-Muon and imaging atmospheric Cherenkov telescopes of the TAIGA-IACT installation. The General Coordinates Network (GCN), that distributes online alerts from different instruments around the world, makes it possible to observe GRBs with TAIGA-IACTs to search for very high energy gamma-quanta. This work presents the current status of the TAIGA-IACT telescope control and alert system for GRB observations as well as its performance.

Experiments on detection of charged particles from EAS in the Tunka Valley are the part of the TAIGA astrophysical complex and consists of two arrays: the operating Tunka-Grande facility and TAIGA-Muon array under construction. In report we present description of arrays, methods of EAS parameters reconstruction, scientific programs and the main results of Tunka-Grande array based on 6 seasons of operation: CR energy spectrum in the energy range 10 PeV - 1000 PeV and limit on the flux of the diffuse gamma rays in the same energy range. In addition, we provide prospects for studying primary cosmic radiation in the energy range 100 TeV - 1000 PeV.

The status of the TAIGA experiment (Tunka Advanced Instrument for cosmic-ray physics and Gamma-ray Astronomy) located in the Tunka Valley is presented. The paper presents mainly the tasks, developed approaches for their solution, and first results on high-energy gamma-ray astronomy (10 TeV and higher) obtained from a two- to three-year exposure. The current tasks of gamma-ray astronomy and plans for development of the installation are discussed.

The concept of the TAIGA experiment is to combine wide-angle timing and imaging Cherenkov telescopes as well as electron and muon detectors. The TAIGA facility aims at gamma-ray astrophysics at energies from a few TeV to several PeV and cosmic-ray physics from 100 TeV to several EeV but also pursues searches for astrophysical nanosecond transients, axion-like particles, Lorentz invariance violation and other unexpected manifestations of New Physics. TAIGA-1, a hybrid detector complex with an area of 1 km2, operating since 2021 in the Tunka valley, 50 km to the West from the southernmost tip of lake Baikal, and the plans for its upgrade are presented.

The Tunka-Grande experiment is a scintillation array with about 0.5 km ^2 2 sensitive area at Tunka Valley, Siberia, for measuring charged particles and muons in extensive air showers (EASs). Tunka-Grande is optimized for cosmic ray studies in the energy range 10 PeV to about 1 EeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. This paper attempts to provide a synopsis of the current results of the experiment. In particular, the reconstruction of the all-particle energy spectrum in the range of 10 PeV to 1 EeV based on experimental data from four observation seasons is presented.

The physical motivations and performance of the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV and astroparticle physics. The pilot TAIGA-1 complex locates in the Tunka valley, ∼ 50 km West from the southern tip of the lake Baikal. It includes integrated air Cherenkov TAIGA-HiSCORE array with 120 wide-angle optical stations distributed over on area 1.1 square kilometer about and three 4-m class Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array. The latter array has a shape of triangle with side lengths of about 300, 400 and 500 m. The integral sensitivity of the 1-km ^2 TAIGA-1 detector is about 2.5× 10^-13 TeV cm ^-2 s ^-1 for detection of E≥ 100 TeV gamma-rays in 300 hours of source observations. The combination of the wide-angle Cherenkov array and IACTs could offer a cost effective-way to build a large (up to 10 km ^2 ) array for very high energy gamma-ray astronomy. The reconstruction of a given EAS energy, incoming direction, and the core position, based on the TAIGA-HiSCORE data, allows one to increase the distance between the relatively expensive IACTs up to 600–800 m. These, together with the surface and underground electron/Muon detectors, will be used for selection of gamma-ray-induced EAS. Present status of the project, together with the current array description, the first experimental results and plans for the future are reported.

The TAIGA experiment in Tunka Valley is expanding the present scintillation detector array with new TAIGA-Muon detector stations. A simulation model was developed to optimise the layout of the new stations and study the identification performance of the array. The extensive air showers (EASs) were simulated with the CORSIKA simulation tool

The TAIGA gamma observatory is continuing its deployment at the Tunka valley, close to lake Baikal. The new, original detectors, able to work under severe conditions of Siberia, were developed to increase the TAIGA sensitivity for the study of gamma-quanta at energies about 1 PeV and above. The distinguishing feature of the detectors is the use of the wavelength shifting light guides for scintillation light collection on a photodetector. Several designs of the counters have been tested: equipped with PMT or SiPM photo-detectors, acrylic or polystyrene based scintillators with thickness from 1 to 5 cm and detecting area from 0.75 to 1.0 m2. The data on the amplitude of the signal from cosmic muons measured in different points within the counter are presented. The first 48 counters were produced and deployed in 2019 at the TAIGA experiment. They form 3 stations each with 8 surface detectors and 8 underground detectors buried at the depth of 1.7 m. After two winters, all counters are working.

The TAIGA astroparticle observatory is progressing with the deployment of new detector stations. The Tunka-Grande — scintillation counter array of the observatory expands with the new TAIGA-Muon stations. Several simulation studies were conducted for optimisation of the new station positioning and performance. Extensive air showers induced by gamma quanta or a proton in the range from 100 TeV to 1 PeV at a zenith angle of 0° were used for these studies. Based on the developed simulation, the capabilities of identification of high energy extensive air showers were studied. The soil thickness, the detector and station positions, the lowest measurable energy range of the cosmic rays, and different methods of air shower identification were investigated.

The TAIGA experiment in Tunka valley is expanding the present scintillation detector array with new TAIGA-Muon detector stations. A simulation model was developed for optimization of the layout of the new stations and study of the identification performance of the array. The extensive air showers (EASs) were simulated with the CORSIKA simulation tool, and the detector response was simulated with the GEANT4 package. EASs induced by gamma quanta or protons in the energy range from 1 PeV to 10 PeV and the zenith angle range from 0° to 45°, are used for these studies. For the identification of high energy extensive air showers, a method based on a neural network was suggested. With this method, the proton identification efficiency is more than 90%, while the gamma identification efficiency not less than 50%.

The current status of the equipment development for the new wide-angle gamma-ray imaging air Cherenkov telescope for TAIGA hybrid installation is presented. A front-end electronic and data acquisition system board based on the Zynq family Xilinx FPGA chips specially designed for this project have been produced and are being tested. A detailed description if presented for internal structure of the four main subsystems: four 8-channel 100 MHz ADCs, board’s control system, internal clock and synchronization system and the power supply system. Additionally, the current status of a small scale prototype telescope SIT consisting of 49 SiPM is presented. The telescope includes a digital camera for observing the stars and weather condition. The SIT-HiSCORE synchronization systems and the telemetry information collection had been tested.

The Tunka-Grande scintillation array is a part of the TAIGA experimental complex designed for high-energy gamma-ray astronomy and cosmic-ray physics. In this work methods of reconstruction of primary particles parameters are presented, as well as the accuracy of reconstruction of the EAS core position, energy, and arrival direction, obtained by comparing the reconstruction results with the data of the Tunka-133 and TAIGA-HiSCORE Cherenkov arrays. The preliminary all-particle energy spectrum based on 3 operation seasons of the installation is presented.

A corrected energy dependence of the depth of the maximum in the wide range of energies 10 15 to 10 18 eV is obtained using data collected at the Tunka-133 facility over 7 years of operation (2009–2017) and the TAIGA-HiSCORE facility in the 2019–2020 season. At the highest energies, our results match those of the Pierre Auger observatory. The results are converted to parameter ❬ln A ❭, which characterizes the mean EAS composition.

The physics motivations and advantages of the hybrid detector complex TAIGA are presented. TAIGA aims to address gamma-ray astronomy at energies from a few TeV to several PeV units, as well as cosmic-ray physics from 100 TeV to several EeV units and astroparticle physics problems. In 2021 deployment and commissioning of the one square kilometer TAIGA setup in the Tunka valley $$\sim$$ 50 km West from Lake Baikal will be finished. The first experimental results with the TAIGA are presented.