Search

Local sources of muon neutrinos are searched for with the Baksan underground scintillation telescope. In the period from December 1978 through May 2017 (live-time 31.05 yr), 1635 neutrino events with zenith angles between 95° and 180° have been detected. No local sources of muon neutrinos with energies over 1 GeV have been found. Upper limits on the fluxes of muon neutrinos emitted by known astrophysical objects are established.

Matrices of silicon photomultipliers (SiPM) are promising multichannel photosensors for scintillation detectors. They can be used to construct tracks of relativistic particles inside detectors. The first detectors based on the direct contact of the SiPM matrices with the surface of the scintillation detector and with the application of Fresnel lenses are developed; promising variants of large detectors for neutrino astrophysics and geophysics are proposed.

In this work, modernized data acquisition systems of the Andyrchi and Carpet-3 shower facilities with automated data preprocessing and data transmission systems to the observatory of the Terskol Branch of the Institute of Astronomy are described. To solve joint problems on searching transient sources, data from the Andyrchi and Carpet facilities are processed and transmitted to the observatory of the Terskol Branch of the Institute of Astronomy in the form of astronomic coordinates for observations with an optical telescope.

The Baksan Underground Scintillation Telescope has been operating under the program of searching for neutrino bursts since the middle of 1980. The target is two parts of the facility with the total mass of 240 t. The actual observation time over the period from June 30, 1980, to December 31, 2016, is 31.27 years. No candidate for the stellar core collapse has been detected during the observation period. The upper bound for the mean rate of the supernova core collapse in our Galaxy is 0.074 y $$^{{ - 1}}$$ (90% CL).

A prototype scintillation detector with photosensors based on silicon photomultiplier (SiPM) arrays is described. Such a method of data-taking will make it possible to obtain an image (snapshot) of the event and, thereby, to separate different types of events (particle interactions) in the detector. For this purpose, the characteristics of SiPMs have been studied and a calibration measurement technique developed.

An experiment for measuring the flux of cosmic gamma rays with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. For this purpose, based on the Carpet-2 shower array which has been operating for many years, the Carpet-3 multipurpose shower array is being constructed. In particular, the preparation of the experiment supposes an increase in the area of the muon detector (MD) and ground part of the array. For ground modules of the Carpet-3 array, a scintillation detector with a liquid scintillator in a plastic package has been elaborated. In this work, descriptions of the Carpet-3 array and working characteristics of the new scintillation detector are presented.

An experiment for measuring the flux of diffuse cosmic gamma rays with energies above 100 TeV (the Carpet-3 experiment) is now being prepared at the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. The preparation of the experiment entails an increase in the area both of the muon detector and of the surface part of the air shower array. This work presents an estimate of the experiment sensitivity to showers generated by primary gamma quanta for different configurations of the array. According to experimental data of the Carpet-2 array for 9.2 years of pure data acquisition time, preliminary estimates for the upper limit of the diffuse cosmic gamma ray flux with energies above 930 PeV have been obtained.

The characteristics of fast neutrons produced by cosmic-ray muons at the Baksan Underground Scintillation Telescope (BUST) are investigated. A novel approach to the problem consists in estimating the neutron flux by the production rate of the unstable radioactive nuclide 12B in the (n, p) reaction on carbon nuclei of the BUST organic scintillator. The processing of the data collected in 2002–2015 yielded $${N_{{{12}_B}}} = 337 \pm 2.5$$ events consistent with those of the reaction 12C(n, p)12B. For the BUST internal planes, the background of fast neutrons with E > 28.6 MeV is experimentally estimated as Φ ∝ 10−11cm–2 s–1. This is lower than the theoretically predicted total neutron flux by nearly two orders of magnitude. The disagreement with predictions is attributed to the suppression of neutron flux in the external scintillator planes of the detector.

Preliminary results of a neutron background measurement at the Baksan underground scintillation telescope (BUST) are presented. The external planes of the BUST are fully covered with standard scintillation detectors shielding the internal planes and suppressing thus background events due to cosmogenic and local radioactivity. The shielded internal planes were used as target for the neutron flux registration. The experimental method is based on the delayed coincidences between signals from any of the BUST counters. It is assumed that the first signal is due to inelastic interaction of a neutron with the organic scintillator, while the second signal comes from the decay of an unstable radioactive isotope formed when the fast neutron interacts with the 12C nuclei. Using the Monte-Carlo method (GEANT4) we also simulated propagation of neutrons through a layer of scintillator. The experimentally found muon induced neutron flux is j =1.3-0.3+0.7 ×10-10cm-2s-1 for neutron energies E ≥ 22MeV, which is in a qualitative agreement with similar measurements of other underground laboratories as well as with predictions of the GEANT4.

The current status of the experiment on recording neutrino bursts from core collapse stars is presented. The actual observational time is 29.76 years. An upper bound of the mean frequency of core collapse supernovae in our Galaxy is f col < 0.077 year–1 (90% CL).

The search for muon neutrinos with energy ≥1 GeV correlated with Gamma-Ray Bursts (GRBs) has been carried out at the Baksan Underground Scintillation Telescope (BUST). Between 1978 December and 2013 December more than 1500 localized gamma-ray bursts occurred in the field of view of the BUST were coincided with the BUST operation periods. No neutrino signal from GRBs was detected. Upper limits on associated gamma-ray burst neutrino production are presented.

The origin of gamma-ray bursts is still one of the unresolved problems in physics. They are short, intense, and non-repeating flashes of MeV gamma-rays with a wide range of spectral and temporal properties. Also these bursts are perhaps sources of neutrino emission. Unlike the photons, which may scatter or be absorbed, the neutrinos, due to their small interaction cross section, arrive at the Earth unaffected. This paper describes experimental methods for detection of low energy neutrinos in the range from 20 MeV to 100MeV at the Baksan Underground Scintillation Telescope. In the analysis we search neutrinos in time coincidence with a gamma-ray burst. We use filtered data collected at the Telescope during 2012. We also use the catalogue of gamma-ray bursts of the SWIFT satellite experiment.

The results of a characterization study of the scintillation detector with SiPM matrices as multichannel photosensors are presented. The SiPM matrix attached to a plastic scintillator gives a snapshot of the glowing track of a charged particle traversing the scintillator.