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.
We present the results of measurements of the air ion densities of both signs in the unventilated underground laboratory of the Moscow State University. We used the stationary station based on a ...Sapfir-3M modified air ion counter. We solved the problems of accuracy of relative measurements of air ion densities and stability of measurements in conditions of high humidity of underground cavities. We investigated the spatial distribution of air ion densities and their variability over time. An excess of positively charged air ions was found everywhere in the laboratory. The obtained data indicate the presence of a weak electric field directed downward in the underground laboratory. We observed the dependence of the air ion densities of both signs on the atmospheric pressure. We found the correlation of air ion densities with radon activity in the laboratory air and show that the ionization of air by alpha particles from the decay of radon and its daughter elements is the main source of air ions in closed underground cavities. A variant for explaining the presence of an excess of positive charge in underground cavities is proposed.
The results of correlation analysis of radon and air ion concentrations based on measurement data in an underground laboratory are presented. For pairs of pressure–radon and pressure–ion variables, a ...delayed pumping effect was revealed, similar to that previously observed for neutrons and gamma rays. A simple phenomenological model is presented to explain the results obtained. Within this model, the delay is caused by the gradual accumulation of radon in the room as atmospheric pressure decreases. The balance of the accumulation rate of radon, the time of its radioactive decay, and the characteristic time of pressure variations leads to an effective delay of 2 days between variations in atmospheric pressure and radon concentration. Correlation analysis for pressure–ion variables indicates that the air carrying radon into the laboratory already contains ions formed in soil pores. These ions make up approximately 21% of the total ions in the laboratory.
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.
The Sydney University Giant Air-shower Recorder(SUGAR) measured the energy spectrum of ultra-high-energy cosmic rays reconstructed from muon detector reading. Comparison of their spectra SUGAR and ...Pierre Auger Observatory allows us to reconstruct the empirical dependence of the number of muons in a vertical shower on the primary energy for energies between 10
17
and 10
18
eV. We compared this dependence with the predictions of hadronic interaction models QGSJET-II-04, EPOS-LHC and SIBYLL-2.3c. In addition, we analyzed the response of the array of muon detectors in order to determine the slope of the muon lateral distribution function. It is important to understand how much the number of muons differs from the predictions of modeling at different distances from the shower axis.
Abstract
The mechanisms of origin of ultrahigh-energy gamma radiation are poorly studied. One way to find out is to search for temporal and directional coincidences of high-energy galactic neutrinos ...with photons of similar energies. The results of such a search could provide indications of the hadronic origin of this radiation. In this paper, we report on the search for photons with energies above 300 TeV in coincidence with high–energy neutrinos. The searches of ultrahigh–energy gammas were carried out at the Carpet–2 EAS array, using three years of data taking.
The Borexino collaboration observed an excess of the counting rate over the expected counting rate of events from CNO-ν. This result is consistent with the prediction of the Hydridic Earth Model on ...the contribution of
40
K geo-antineutrino scattering on electrons to single Borexino events. The proportion of potassium in the Earth 1.5 ± 1.0% of the Earth’s mass is the most likely value that provides the observed excess of the counting rate.
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.
The heat flux from the Earth’s interior and its connection with the number of neutrinos recorded by detectors at the Earth’s surface are discussed. The values predicted for the geoneutrino fluxes may ...be matched with experimental data, but the observed flux of the Earth’s internal heat requires the presence of a larger amount of radioactive elements. The amount of uranium and thorium within the Earth is constrained by measurements performed with the aid of modern geoneutrino detectors. This makes it possible to explain completely a flux of 50 TW. There are indications that the flux from the Earth’s interior is 200 to 250 TW. Such a flux could be explained only by the presence of a substantially larger amount of potassium in the Earth. In order to determine precisely the heat flux from the Earth’s interior, it is necessary to measure completely the flux of antineutrinos from all heat-releasing isotopes, including the flux of neutrinos from
40
K decay. Possibly, this flux has already been observed at the Borexino detector.
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