Baksan Underground Scintillation Telescope Research Articles

Search for neutrino counterparts of LIGO/Virgo gravitational-wave events

The LIGO/Virgo collaborations have reported the results of their searches for gravitational-waves from the first half of their third observing run. 39 events were combined into the second Gravitational-Wave Transient Catalog (GWTC-2), reaching the total number of 50. In addition to these, two neutron star - black hole merger events were also confirmed. The search for neutrino counterparts of LIGO/Virgo gravitational-wave events was performed on the Baksan Underground Scintillation Telescope. The processing algorithm and the results of the counterpart search are described.

Search for muon neutrinos from the gravitational wave event GW170817 at the Baksan Underground Scintillation Telescope

Using data of the Baksan Underground Scintillation Telescope we have searched for muon neutrinos and antineutrinos with energies above 1 GeV coinciding with the gravitational wave (GW) event GW170817 that was recorded on August 17, 2017, by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo observatories. This is the first detection of the new type of events occurring as a result of a merger of two neutron stars in a binary system. A short gamma-ray burst (GRB) GRB170817A accompanying this event is evidence of particle acceleration in the source whose precise position was determined by detection of the subsequent optical signal. No neutrino signals were found with the Baksan Underground Scintillation Telescope in the interval ±500 s around the moment of the gravitational wave event GW170817, as well as during the next 14 days. The upper limits on integral fluxes of muon neutrino and antineutrino from the source are derived.

38 years of galactic observations in searching for neutrino bursts from core collapse supernovae with the Baksan Underground Scintillation Telescope

The core collapse of a massive star in the Milky Way will produce a neutrino burst, which will be detected by the Baksan Underground Scintillation Telescope (BUST). The stable and enough low background at the BUST is a clear asset for searching for neutrino bursts. Now two parts of the facility (with the total mass of 242 tons) are used as independent coinciding detectors. Such approach allows us to increase dependability detection of the neutrino signal and the radius of sensitivity of the BUST. The facility has the potential to see a supernova in the Galaxy independently from other detectors.No burst candidate for the core collapse has been detected during the observation period of June 30, 1980, to June 30, 2019. The actual observation time is 33.477 years. This is the longest observation time of our Galaxy with neutrinos at the same facility. An upper bound on the mean frequency of gravitational collapses in the Galaxy is 6.88 per century (at 90% C.L.).

Fast-Neutron Background at the Baksan Underground Scintillation Telescope

The search for neutrino signals from gravitational core collapses in the Milky Way is one of the main lines of research at the Baksan Underground Scintillation Telescope (BUST). Neutrons generated by cosmic-ray muons produce a considerable background in such experiments. The contribution from the elastic scattering of fast neutrons off protons to the overall single-event background rate measured in the inner detector planes is estimated via neutron activation analysis. The resulting value of the fast-neutron flux agrees with one based on the results from FLUKA modeling for the depth of the BUST detector. The same technique can be used to estimate the neutron background in similar experiments focused on rare events.

The Search for Neutrino Bursts at the Baksan Underground Scintillation Telescope: 37 Years of Exposure

The search for neutrino bursts at the Baksan Underground Scintillation Telescope began in the middle of 1980. Two parts of the setup with a total mass of 240 t are used as the target. The actual observational time accumulated in the period from June 30, 1980, to December 31, 2017, is 32.1 years. No neutrino burst candidate events were detected, yielding the following upper bound for the mean rate of core-collapse supernovas in the Milky Way: 0.072 yr−1 (90% CL).

Developing a New Data Acquisition System for the Baksan Underground Scintillation Telescope

The Baksan Underground Scintillation Telescope (BUST) is located in the North Caucasus in an underground laboratory at an effective depth of 850 m.w.e. The BUST began working in 1977, and the installation is still in operation. The successful design of the BUST allows it to be used to solve a number of problems in astrophysics and particle physics. The new data acquisition system is designed to record and analyze experimental data with greatly improved measurement characteristics of digital and analog signals. The data acquisition system is based on the VME interface and provides complete compatibility with existing low-level BUST recording electronics. The hodoscope of pulse channels was completely redeveloped and implemented on field-programmed gate array (FPGA) and LVDS chips.

Search for electron neutrinos associated with gravitational-wave events at the Baksan Underground Scintillation Telescope

Results of a search for electron neutrinos from the gravitational wave events GW150914, GW151226, GW170104, GW170608, GW170814, and GW170817 at the Baksan underground scintillation telescope (BUST) are presented. We searched for coincident neutrino candidates in the data recorded by the BUST detector. No neutrino candidates in temporal coincidence with the gravitational wave events were found. Upper bounds on neutrino and antineutrino fluence from astrophysical sources of gravitational bursts have been set.

A search for neutrino bursts in the Galaxy at the Baksan Underground Scintillation Telescope

The experiment on recording neutrino bursts operates since the mid-1980. As the target, we use two parts of the facility with the total mass of 240 tons. Over the period of June 30, 1980 to December 31, 2017, the actual observational time is 32.1 years. No candidate for the stellar core collapse has been detected during the observation period. An upper bound of the mean frequency of core collapse supernovae in our Galaxy is 0.072 year−1 (90% CL).

Creation of the FIAN Neutrino Laboratory and underground laboratories

We describe the history of how the FIAN Neutrino Laboratory was created and how the main methods, later to underlie the construction of the BUST (Baksan Underground Scintillation Telescope), ASD (Artyomovsk Scintillation Detector), LSD (Liquid Scintillation Detector), and LVD (Large Volume Detector) underground facilities, were developed and first implemented. This work, initiated by G T Zatsepin, was crucial for the development of underground physics and gave the Institute for Nuclear Research, RAS, a leading role in experiments to study stellar-collapse neutrinos. We discuss underground physics as an effective method for studying a wide class of rare processes related to cosmic rays, neutrino physics, neutrino astrophysics, and elementary particles. The latest LVD and LSD results on the search for stellar-collapse neutrinos are discussed, and research on cosmic ray muon characteristics and on muon interaction products at various depths underground is reviewed.

Search for Local Neutrino Sources with the Baksan Underground Scintillation Telescope

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.

Search for Neutrino Bursts at the Baksan Underground Scintillation 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).

Astroparticle Physics Experiments in the Baksan Neutrino Observatory

The Baksan Neutrino Observatory (BNO) of the Institute for Nuclear Research of the Russian Academy of Sciences is one of the first-rate scientific centers where the experimental research in the field of astroparticle physics is performed. In this paper, a brief overview of research at the unique complex of surface and underground experimental facilities, consisting of the Baksan Underground Scintillation Telescope (BUST) and EAS arrays Carpet-2 and Andyrchy, is presented.

Search for Electron Neutrinos from Gravitational Wave Events at the Baksan Underground Scintillation Telescope

In the data obtained at the Baksan underground scintillation telescope (BUST), electron neutrinos and antineutrinos with energies above 21 MeV have been sought in coincidence with the GW150914, GW151226, GW170104, GW170608, GW170814, and GW170817 gravitational wave events. No neutrino signals from gravitational wave events have been detected in the interval of ±500 s at the Baksan underground scintillation telescope. Bounds on the fluxes of low-energy electron neutrinos and antineutrinos from astrophysical sources of gravitational bursts have been obtained.

Neutron flux measurement at the Baksan Underground Scintillation Telescope

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.

Problems of Neutrino Radiation from SN 1987A: 30 Years Later

Experimental data obtained by means of underground detectors during the explosion of the SN 1987A supernova on February 23, 1987, are discussed. At that time, such data were being collected by two scintillation detectors—the Soviet–Italian liquid scintillation detector (LSD) in a Mont Blanc tunnel and the Baksan underground scintillation telescope (BUST) of the Institute forNuclear Research (Russian Academy of Sciences)—and two Cherenkov detectors—Kamiokande II (Japan) and the Irvine–Michigan–Brookhaven (IMB) detector (USA). Two key instants in SN 1987A evolution that were accompanied by neutrino signals are highlighted. These were 2:52 UT in LSD and 7:35 UT in the other detectors. A group of studies in which correlations between pulses in the different detectors between 1:45 and 3:45 UT and double pulses in LSD between 5:40 and 10:15 UT were observed are also discussed.

Searching for neutrino bursts in the galaxy: 36 years of exposure

The Baksan Underground Scintillation Telescope has operated within the program of searching for neutrino bursts since the mid-1980s. We present the current status of the experiment and some results related to the investigation of background events and the stability of facility operation. Over the period from June 30, 1980, to December 31, 2016, the pure observation time was 31.27 years. No neutrino burst candidate event from the explosion of a core-collapse supernova in the Galaxy was recorded in this time. This sets an upper bound of 0.074 yr–1 on the mean frequency of gravitational stellar collapses in the Galaxy at a 90% confidence level.

The neutron flux at a depth of 850 m.w.e., according to BUST data

A way of estimating a muon-enduced neutron flux has been proposed. The technique is used to estimate the neutron background at the Baksan Underground Scintillation Telescope (BUST). A two-pulse signature (unstable 12B production and its subsequent decay) is used to identify neutron events. The integrated average neutron flux on the external planes of detector is an order of magnitude higher than the one on the internal planes. Within the limits of statistical error, the resulting neutron flux agrees with predictions from simulations for the depth at which the BUST lies using the FLUKA program.

Measuring Muon-Induced Fast Neutrons at the Baksan Underground Scintillation Telescope

A technique to estimation low intensity muon-induced fast neutrons has been developed. The procedure for data analysis and interpretation of the results are discussed. The technique has been applied to estimate the neutron background from rock at the Baksan Underground Scintillation Telescope (BUST). A neutron background measurement relies on the production of a cosmogenic nuclide 12B by fast neutrons in an organic scintillator. The method exploited the delayed coincidences between the 12B production signals and electrons from 12B β−-decay. The total flux of muon-induced neutrons from rock was determined to be Φn = (21.5 ± 5) · 10−9 cm−2s−1. The estimated full fluxes of neutrons agree with results of Monte-Carlo simulations.

Neutron flux measurement using activated radioactive isotopes at the Baksan underground scintillation telescope

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 search for neutrino bursts from supernovae with Baksan underground scintillation telescope

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 fcol < 0.077 year–1 (90% CL).