Search

The Sydney University Giant Air-shower Recorder (SUGAR) measured the muon component of extensive air showers with a unique array of muon detectors. The SUGAR data allow us to reconstruct the empirical dependence of muon density on the distance from the axis of the shower, the lateral distribution function (LDF). We compare the shape of this function with the predictions of hadronic-interaction models, QGSJET-II-04 and EPOS-LHC, in the energy range 10^17.6 - 10^18.6 eV. We find a difference between the observed data and the simulation: the observed muon density falls faster with the increased core distance than it is predicted in simulations. This observation may be important for interpretation of the energy-dependent discrepancies in the simulated and observed numbers of muons in air showers, known as the "muon excess"., 7 pages revtex, 4 figures (7 panels). V2: discussion of systematic uncertainties added, results unchanged. Version accepted by Phys. Rev. D

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— $${\text{CO}}_{3}^{{2 - }}$$ 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.

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.

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.