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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The possibility of large geo-antineutrino fluxes from K decays and the presence of an excess of positive electric charge in the Earth's crust are predicted by the Hydridic Earth model. The data of the Borexino experiment do not contradict the proportion of potassium equal to several percent of the Earth's mass and predicted by this model. The detection of an excess of positively charged air ions in underground laboratories can be explained by the presence of an excess of positive electric charge in the Earth's crust. Further studies are needed to confirm the existence of both of these effects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The authors consider results from analyzing the energy spectrum of single events obtained in Phase III of the Borexino experiment. The experimental spectrum is fitted by a set of standard sources of single events with the addition of events from potassium geo-antineutrino (40K-geo-ν) scattering on electrons. The adding of 40K-geo-ν events improves the agreement between the experimental and fitted spectra. Experimental results indicate considerable amounts of potassium in the Earth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 1017 and 1018 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 FROM AUTHOR]

A model is proposed in which the electrical voltage measured between the electrodes in Lake Baikal is a consequence of two effects: electrochemical processes near the electrodes and a positive charge current flowing through the lake. The electrochemical component of the voltage in the case of lead electrodes arises due to the difference in concentrations of carbonate anion— at different depths. In the case of the use of chlorine-silver electrodes, only the effect of the positive charge current flowing through the lake is measured. We proposed an interpretation of an increase of electrical voltage registered in Lake Baikal during an earthquake in August 2008. The reason for the increase in voltage is the release of positively charged hydrogen-containing gases from the Earth's interior. [ABSTRACT FROM AUTHOR]

Carpet-2 is an air-shower array at Baksan Valley, Russia, equipped with a large-area (175 m2) 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 Eγ > 1 PeV, directionally associated with IceCube high-energy neutrino events, in the data obtained in 3080 days of Carpet-2 live time. [ABSTRACT FROM AUTHOR]

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 40K decay. Possibly, this flux has already been observed at the Borexino detector. [ABSTRACT FROM AUTHOR]

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 40K 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. [ABSTRACT FROM AUTHOR]

The Carpet-3 array at the Baksan Neutrino Observatory is designed to detect extensive air showers generated by primary cosmic rays of more than 100 TeV in energy. The main aim is to search for cosmic extrahigh-energy gamma rays. In this work, we describe the current state of the facility and the results from searching for extrahigh-energy photons from regions of the localization of candidates for gravitational-wave events detected by LIGO/Virgo during the third observational period. [ABSTRACT FROM AUTHOR]

In the framework of model with Lorentz violation (LV) we discuss a physical observables for qq¯ pair production at lepton-lepton colliders and describe the experimental signal to be detected. We obtain a conservative limits on Lorentz-violating dimensionless coupling for quark sector from LEP data. We also make a phenomenological prediction for LV model at the future lepton collider. [ABSTRACT FROM AUTHOR]

In the present work we report on the observation of an excess of gamma-ray candidate events in temporal and spatial coincidence with the IceCube high-energy neutrino alert consistent with the origin in the Cygnus Cocoon region. The observations have been performed with Carpet-2, a surface air-shower detector equipped with a large-area muon detector at the Baksan Neutrino Observatory in the Northern Caucasus. As well as we report about the current state of the Carpet-3 facility, which includes a muon detector with an increased area and an expanded surface array. The main aim of the Carpet-3 facility is the registration of cosmic gamma-rays with energy larger than 100 TeV. Moreover, it gives a possibility to carry out research on the composition of primary cosmic rays around the knee. It is planned that the Carpet-3 EAS array will be operation by the end of 2021. [ABSTRACT FROM AUTHOR]

We have studied the phase composition of the overlayer of scale which forms on TiFe at 700°C and 900°C (τ=5 h) by x-ray and metallographic analysis. The upper layers of the scale were shown to consist of TiO and FeO after heat treatment at 700°C, but the lower layers contain mainly TiO, FeO, and Fe. The underlayer on the boundary with the scale contains TiFeO (η-phase). The inert marker is covered with rutile at 900°C, and FeTiO + TiO is below the marker. But the next (relatively thick) internal layer consists of FeTiO, TiO, and Fe. Large pores associated with intensive growth of the FeO phase are detected in the scale formed at 700°C. As a result, the scale cracks. At 900°C, the scale is denser because the pores and cracks are covered by rutile. We have shown that FeO (p-type semiconductor) is nonstoichiometric in the upper layers of the scale, and TiO (n-type semiconductor) is nonstoichiometric close to the boundary with the alloy. The results obtained correlate with the results for the oxidation kinetics previously studied for FeTi, and support a change in the oxidation mechanism when the temperature increases from 700°C to 900°C. Such a change occurs because of the influence of diffusion of the metal ion on oxygen diffusion through the boundary between the scale and the alloy: diffusion of iron through the vacancies in the FeO lattice at 700°C, and interstitial diffusion of titanium ions in the TiO lattice at 900°C. [ABSTRACT FROM AUTHOR]

Comparative tests of the electroerosion resistance and rate of removal of tungsten-copper composites in different structural conditions were made on a standard production Model 4720 electroerosion profile broaching machine equipped with an ShGI-16-880B wide-range pulse generator. The relatively low resistance of the El'konait composition in machining VK20 sintered carbide may be explained by the strong nonuniformity of its structure and the presence in it of coarse (on the order of 30 μm) grains of tungsten. Composites characterized by high dispersion of the constituent components and a significant degree of uniformity of their distribution possess the highest erosion resistance. The relative wear of these alloys is the lowest (10-15%) of all of those known until now. [ABSTRACT FROM AUTHOR]

The elastic recovery of volume of compacts from titanium nickelide powder, which possesses the property of superelasticity, is linked with rupture of interparticle contacts in the compacts and is determined by their strength (which depends on their porosity and contact binding forces). Additions of fine powders, which weaken the binding forces in a titanium nickelide compact, substantially increase the elastic effect, the composition dependence of the elastic aftereffect being nonmonotonic. Generally speaking, titanium nickelide with a nonsingle-phase structure is characterized by a smaller overall elastic recovery of volume, although at room temperature the structural factor may actually result in an increased elastic effect. [ABSTRACT FROM AUTHOR]

With a cryochemical charge, an aluminum-magnesium spinel is formed at a temperature which is lower than that in conventional solid-phase synthesis. Cryochemical synthesis processes ensure that MgAlO powders retain high activity in subsequent processing operations. [ABSTRACT FROM AUTHOR]