Measurements and correlation analysis of radon and aeroion concentrations in the underground laboratory were carried out. For pairs of variables “pressure — radon” and “pressure — ions”, a delayed pumping effect was found, similar to that previously observed for neutrons and gamma quanta. A simple phenomenological model explaining the results is presented. In this model, the reason for the delay is the gradual accumulation of radon in the room with a decrease in atmospheric pressure. The balance of the radon accumulation rate, the time of its radioactive decay and the characteristic time of pressure variations leads to an effective delay of 2 days between atmospheric pressure variations and radon concentration. Correlation analysis for the variables “pressure — ions” indicates that ions formed in the pores of the soil are already present in the air carrying radon to the laboratory. These ions make up approximately 21% of the total number of ions in the laboratory.

A study is performed of variations in the count rate of detector background pulses in the LVD experiment (Gran Sasso, Italy). Such variations are caused by the injection of radon from the rock into the experimental hall. Dependences are presented for variations in the air pressure on the Earth’s surface and in the experimental hall of the LVD, along with others in the count rate of LVD events associated with changes in the concentration of radon.

We present a study of a directional search for Dark Matter boosted forward when scattered by cosmic-ray nuclei, using a module of the NEWSdm experiment. The boosted Dark Matter flux at the edge of the Earth's atmosphere is expected to be pointing to the Galactic Center, with a flux 15 to 20 times larger than in the transverse direction. The module of the NEWSdm experiment consists of a 10 kg stack of Nano Imaging Trackers, i.e. newly developed nuclear emulsions with AgBr crystal sizes down to a few tens of nanometers. The module is installed on an equatorial telescope. The relatively long recoil tracks induced by boosted Dark Matter, combined with the nanometric granularity of the emulsion, result in an extremely low background. This makes an installation at the INFN Gran Sasso laboratory, both on the surface and underground, viable. A comparison between the two locations is made. The angular distribution of nuclear recoils induced by boosted Dark Matter in the emulsion films at the surface laboratory is expected to show an excess with a factor of 3.5 in the direction of the Galactic Center. This excess allows for a Dark Matter search with directional sensitivity. The surface laboratory configuration prevents the deterioration of the signal in the rock overburden and it emerges as the most powerful approach for a directional observation of boosted Dark Matter with high sensitivity. We show that, with this approach, a 10 kg module of the NEWSdm experiment exposed for one year at the Gran Sasso surface laboratory can probe Dark Matter masses between 1 keV/c^2 and 1 GeV/c^2 and cross-section values down to 10^-30 cm^2 with a directional sensitive search.

According to the Large Volume Detector (LVD), located in the underground laboratory of Gran Sasso, Italy, a modulation of the concentration of the radioactive gas radon from the natural radioactivity of the rock, associated with lunar-monthly cycles, was detected. The rising phase falls on the days of the full moon. The amplitude of variations varies from 0.5 to 0.8 % .

The LVD detector, located in the Gran Sasso Laboratory at a depth of 3600 m w.e., is designed for research in the field of neutrino physics, astrophysics, cosmic ray physics and the search for rare processes predicted by theory. The LVD experiment was built in 1991 to detect neutrinos from collapses of stellar nuclei in our galaxy. The background of the detector is atmospheric muons, neutrons generated by muons in the detector material and natural radioactivity underground. The report presents the latest experimental results obtained at LVD: a limit on the frequency of supernova outbreaks, muon variations with a period of 1, 4, 10 years, and also describes the problems of studying the low-energy background underground.

The LVD experiment, located in a low-background Laboratory of the Gran Sasso, is designed to search for supernovae neutrinos burst and for studying cosmic ray muons. As part of the studies of variations of atmospheric muons underground, we analyzed the obtained energy calibrations of the LVD counters in the energy range of 50−450 MeV. Energy calibration of 840 LVD counters is carried out monthly through muons passing through the detector. The procedure consists in obtaining the muon spectrum average in the form using the ADC linear channels and then in the approximation of the spectrum of each counter to determine the channel number corresponding to the muon peak. We show a seasonal change in the position (channel) of the “muon peak” used for calibration.

Cosmic radiation is a potential additional tool for atmospheric monitoring. High-energy cosmic rays, interacting in the atmosphere, produce secondary particles, the production and propagation of which are ruled by the state of the atmosphere. Atmospheric muons carry information on the stratosphere, as its temperature modulates their intensity. Here, we present a comprehensive investigation of the 24-year series of the muon flux recorded underground with the Large Volume Detector in the Gran Sasso Laboratory in Italy. Using advanced spectral-analysis methods, we reveal, in addition to the well-known annual cycle, two significant variations with periods of about four and ten years. These two multiannual components, however, are not present in the series of the so-called effective temperature---an average parameter commonly used to describe the entire atmospheric profile in relationship to the detected muon flux---but we find them in the series of the raw temperatures in the lower-stratospheric levels. We show that the weaker multiannual cycles emerge in the temperature series thanks to the dampening of the dominant annual radiative cycle at these levels, which are affected by higher-frequency variability related to transport and wave processes. We also show that the multiannual variations are not typical only of the Gran Sasso area but are present at large scales throughout the Northern Hemisphere. The analysis of the series of the muon flux also reveals evidence of daily to monthly scale variations, especially during the highly variable winter period. Although such short-term modulations are also found in the series of the effective temperature, we show that the variations of the two series are brought to better agreement when considering only specific layers of the atmosphere depending on the event. The amplitudes of the multiannual variations are significantly larger than those expected based on the temperature modulations. Such differences may be due to acknowledged difficulties of the adopted temperature reanalysis dataset to thoroughly represent long-term variability scales, so that long-term modulations in the raw temperature series and, consequently, in the effective temperature record would result as artificially attenuated. The muon flux therefore may be envisaged as a high time-resolution integrated proxy of lower-stratospheric temperatures.

Experimental data obtained using three scintillation detectors are analyzed. The characteristics of cosmogenic neutrons in underground experiments their analytic dependences are considered. The behavior of background counting rate for the LVD detector for two measuring thresholds (0.5 and 5 MeV) are discussed.

An analysis is performed for muons passing through the Large Volume Detector (LVD) horizontally over 15 years of operation. Horizontal muons pass through the ground at around 5 km w.e. with a threshold energy of 4.7 TeV. The energy characteristics of the LVD allow the detection of neutrons produced by muons in the detector’s material. The great volume of statistics ensures high accuracy in determining seasonal variations in the number of neutrons. The temporal distributions of pulses with energy releases of 1 to 12 MeV are used in a time interval of 150–650 μs after a muon crosses the setup to find the specific number of neutrons.

The main sources of the background at the low threshold of the underground Large Volume Detector (LVD; Gran Sasso National Laboratory, Italy) are the natural radioactivity of the ground and radon, which escapes from groundwater into the atmosphere of the underground chamber through multiple microcracks in the rock. The LVD registers gamma quanta from decays of radon daughter nuclei. Deformations of the Earth’s crust produce stress and increase the number of microcracks, leading to enhanced concentration of radon. The detector’s count rate during the powerful earthquakes in central Italy in 2019 is analyzed.

The analysis of atmospheric muons detected in the LVD underground experiment (Gran Sasso, Italy) has been completed. Atmospheric muons and the low-energy background that the LVD detects undergo annual (seasonal) variations. The background is created by gamma quanta from decays of $${}^{\mathrm{222}}$$ Rn daughter nuclei. Variations are due to seasonal fluctuations in radon concentration and additional injection of radon from groundwater associated with tectonic activity. At the LVD, research is underway to identify the relationship between the behavior of radon fields and seismic activity. The paper will discuss various sources of variations associated with geophysical aspects (the influence of the moon’s motion; changes in pressure, humidity and temperature; seismic activity).

The Large Volume Detector, hosted in the INFN Laboratori Nazionali del Gran Sasso, is triggered by atmospheric muons at a rate of similar to 0.1 Hz. The data collected over almost a quarter of a century are used to study the muon intensity underground. The 5 x 10(7) muon series, the longest ever exploited by an underground instrument, allows for the accurate long-term monitoring of the muon intensity underground. This is relevant as a study of the background in the Gran Sasso Laboratory, which hosts a variety of long-duration, low-background detectors. We describe the procedure to select muon-like events as well as the method used to compute the exposure. We report the value of the average muon flux measured from 1994 to 2017: I-mu(0) = 13.35 +/- 0.0005(stat) +/- 0.03(sys) x 10(-4) m(-2) S-1. We show that the intensity is modulated around this average value due to temperature variations in the stratosphere. We quantify such a correlation by using temperature data from the European Center for Medium-range Weather Forecasts: we find an effective temperature coefficient alpha(T) = 0.94 +/- 0.01(stat) +/- 0.01(sys), in agreement with other measurements at the same depth. We scrutinize the spectral content of the time series of the muon intensity by means of the Lomb-Scargle analysis. This yields the evidence of a 1-year periodicity, as well as the indication of others, both shorter and longer, suggesting that the series is not a pure sinusoidal wave. Consequently, and for the first time, we characterize the observed modulation in terms of amplitude and position of the maximum and minimum on a year-by-year basis.

The results of the searching for rare events in the Large Volume Detector (LVD) are presented. The rare events could be caused by neutrino interactions in the experimental setup. In the work, the experimental data for 2006-2017 are analyzed. A stability of LVD background counting rate during the specified period is shown. Candidates on neutrino bursts from collapsing stars in the sequence of the LVD events are not found.

The underground Large Volume Detector (LVD) has been in operation at the Gran Sasso National Laboratory since 1992. The research program includes a search for neutrino bursts from stellar core colapses, studies of the cosmic ray penetrating component, and investigations of background sources at detecting rare events. In this work, the low-energy background (E > 0.5 MeV) in the LVD experiment is analyzed.

The current status of the ASD (Artemovsk scintillation detector) experiment aimed at search for a neutrino flux from gravitational collapses of stellar cores is presented. Experimental data obtained for 40 years of operation of the detector situated in a salt mine at a depth of 570 mwe are processed. The results obtained by calculating the expected signal in the detector on the basis of two models of supernova explosion are described. No candidates for neutrino bursts from gravitational star collapses have been revealed: the limit on the frequency of gravitational collapses was found to be less than one event per 17.15 yr at a 90% confidence level ( f col < 0.058 yr −1 ).

The current status of the LVD (large volume detector) experiment aimed at search for neutrinos from the gravitational collapse of stellar cores is described. Within the period of observations from June 1992 to February 2017, no gravitational collapse was found in the Milky Way Galaxy and Magellanic Clouds, including hidden ones (not ejecting the envelope). The LVD collects data for 99% of the live time. A limit on the frequency of supernova bursts within a distance of 25 kpc was set at a level of 0.1 event/yr. The most recent results obtained by studying the muon component of cosmic rays are presented.

Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution.