Some unexpected sporadic increases of an environmental radioactive background have been recorded at mountain level at Baksan Neutrino Observatory (BNO, 1700 m above sea level) using electron-neutron ...detectors (en-detectors), which could be explained by radioactive aerosol enhancements. The large area inorganic scintillator en-detectors developed for cosmic ray study are continuously monitoring environmental thermal neutron fluxes at various geophysical conditions. Application of the pulse shape discrimination method allows us to select and separately measure both thermal neutrons and radioactive beta-decay nuclides being products of radon decays in air (mostly Rn-222 and Rn-220). There are two en-detector setups running now at BNO, one deep underground while another one at surface. Both installations had recorded some strange sporadic increases of radioactive nuclides in air. In this paper, we present results and the most probable explanation of the significant increases joint by radioactive aerosols production but caused by different reasons: Baksan river floods or nearby underground experiment with powerful Cr-51 radioactive source.
•High mountain river flow level, flood and waterfall can increase nearby charged aerosol concentration.•Radon and its progenies above mountain rivers attracting by charged aerosols make them radioactive.•Intensive radioactive source can be a reason of radioactive aerosol concentration enhancement in underground laboratories.
Abstract
Galactic sites of acceleration of cosmic rays to energies of order 10
15
eV and higher, dubbed PeVatrons, reveal themselves by recently discovered gamma radiation of energies above 100 TeV. ...However, joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. In 2020 November, the IceCube neutrino observatory reported an ∼150 TeV neutrino event from the direction of one of the most promising Galactic PeVatrons, the Cygnus Cocoon. Here we report on the observation of a 3.1
σ
(post-trial) excess of atmospheric air showers from the same direction, observed by the Carpet–2 experiment and consistent with a few months flare in photons above 300 TeV, in temporal coincidence with the neutrino event. The fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. This is the first evidence for the joint production of high-energy neutrinos and gamma-rays in a Galactic source.
The Carpet-3 experiment for investigation of gamma radiation with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian ...Academy of Science. At present the plastic scintillation counters with a total continuous area of 410 m
are installed in the muon detector (MD) underground tunnel, and they are totally equipped with electronics. The counters’ gains and thresholds have been adjusted. Fifteen modules of shower detectors are placed on the surface of the MD absorber. Ten of them contain 9 standard plastic counters with an area of 1 m
each. Also 24 modules without counters are arranged on the territory of the array. These modules will accomplish a surface part of the Carpet-3 array. The preliminary estimates show that the new array will have the best sensitivity to the flux of primary gamma rays with energy in region 100 TeV
1 PeV. The increased area of the surface part of the array gives a possibility to increase the area of location of the shower axis, thereby increasing the statistics of detected events and decreasing the energy threshold for primary cosmic radiation. The Carpet-3 experiment will start data taking at the end of 2021.
The Baksan Neutrino Observatory setups are currently performing search for neutrino and ultra-high-energy gamma-ray counterparts of the events on the Gamma-ray Coordinates Network. The Gamma-ray ...Coordinates Network is a system for distributing alerts from gamma-ray bursts, transients. Muon neutrinos and antineutrinos with energies above 1 GeV are registered with the Baksan Underground Scintillation Telescope. Ultra-high-energy gamma rays are registered with the ‘‘Carpet-2’’ setup. Registration of events and analysis of alerts occurs in near-real time. Alerts from Swift BAT, Fermi-GBM, Fermi-LAT, INTEGRAL, IceCube, HAWC are used. This work presents the description of the alert processing program and preliminary results.
Abtract
—Over the last several years, an increase in the amplitude of a seasonal pressure wave and the concentration of heavy radionuclides in the near-surface layer of the atmosphere has been ...observed in the area of the Baksan Neutrino Observatory of Institute for Nuclear Research in the North Caucasus. This trend is being investigated along with accompanying anomalies in readings recorded by detectors in the fall and winter of 2017, and the winter and spring of 2021. Hypotheses regarding possible causes of these anomalies are considered.
We report on the search of astrophysical gamma rays with energies in the 100 TeV to several PeV range arriving in directional and temporal coincidence with public alerts from HAWC (TeV gamma rays) ...and IceCube (neutrinos above ∼ 100TeV). The observations have been performed with the Carpet-2 air-shower detector at the Baksan Neutrino Observatory, working in the “photon-friendly” mode since 2018. Photon candidate showers are selected by their low muon content. No significant excess of the photon candidates have been observed, and upper limits on gamma-ray fluences associated with the alerts are obtained. For events with good viewing conditions, the Carpet-2 effective area for photons is of the order of the IceCube effective area for neutrinos of the same energy, so the constraints start to probe the production of neutrinos in fast flares of Galactic sources.
Isotropic diffuse gamma-ray flux in the PeV energy band is an important tool for multimessenger tests of models of the origin of high-energy astrophysical neutrinos and for new-physics searches. So ...far, this flux has not yet been observed. Carpet-2 is an air-shower experiment capable of detecting astrophysical gamma rays with energies above 0.1 PeV. Here we report the upper limits on the isotropic gamma-ray flux from Carpet-2 data obtained in 1999–2011 and 2018–2022. These results, obtained with the new statistical method based on the shape of the muon-number distribution, summarize Carpet-2 observations as the upgraded installation, Carpet-3, starts its operation.
Carpet-2
is an air-shower array at Baksan Valley, Russia, equipped with a large-area (175 m
2
) muon detector, which makes it possible to separate primary photons from hadrons. We report the first ...results of the search for primary photons with energies
E
γ
> 1 PeV, directionally associated with IceCube high-energy neutrino events, in the data obtained in 3080 days of
Carpet-2
live time.
Early results of the search for E
γ
> 1 PeV cosmic photons from point sources with the data of
Carpet–2
, an air-shower array equipped with a 175 m
2
muon detector, are presented. They include 95% CL ...upper limits on PeV photon fluxes from stacked directions of high-energy IceCube neutrino events and from four predefined sources, Crab, Cyg X-3, Mrk 421 and Mrk 501. An insignificant excess of events from Mrk 421 will be further monitored. Prospects of the use of the upgraded installation,
Carpet–3
(410 m
2
muon detector), scheduled to start data taking in 2019, for searches of E
γ
> 100 TeV photons, are briefly discussed.
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