Predicting Neutron Production from Cosmic-ray Muons

Fast neutrons from cosmic-ray muons are an important background to underground low energy experiments. The estimate of such background is often hampered by the difficulty of measuring and calculating neutron production with sufficient accuracy. Indeed substantial disagreement exists between the different analytical calculations performed so far, while data reported by different experiments is not always consistent. We discuss a new unified approach to estimate the neutron yield, the energy spectrum, the multiplicity and the angular distribution from cosmic muons using the Monte Carlo simulation package FLUKA and show that it gives a good description of most of the existing measurements once the appropriate corrections have been applied.Comment: 8 pages, 7 figure

Analysis of Cosmogenic Neutron Characteristics and the Pulses Counting Rate Using ASD, LSD, and LVD Scintillation Detectors

International audienceExperimental 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

Characterization of the varying flux of atmospheric muons measured with the Large Volume Detector for 24 years CHARACTERIZATION of the VARYING FLUX of ATMOSPHERIC ... N. YU. AGAFONOVA et al

The Large Volume Detector, hosted in the INFN Laboratori Nazionali del Gran Sasso, is triggered by atmospheric muons at a rate of 3c0.1 Hz. The data collected over almost a quarter of a century are used to study the muon intensity underground. The 5 7107 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\u3bc0=3.35\ub10.0005stat\ub10.03sys 710-4 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 \u3b1T=0.94\ub10.01stat\ub10.01sys, 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

Characterization of the varying flux of atmospheric muons measured with the Large Volume Detector for 24 years

International audienceThe Large Volume Detector, hosted in the INFN Laboratori Nazionali del Gran Sasso, is triggered by atmospheric muons at a rate of ∼0.1  Hz. The data collected over almost a quarter of a century are used to study the muon intensity underground. The 5×107 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: Iμ0=3.35±0.0005stat±0.03sys×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 αT=0.94±0.01stat±0.01sys, 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

Measurement of muon charge ratio with the Large Volume Detector

The value of ${\mu^+/\mu^-}$ ratio for atmospheric muons has been measured with the Large Volume Detector, (LVD) at the INFN Gran Sasso National Laboratory, Italy (minimal depth is 3000 m w.e.). To reach this depth muons should have an energy at the sea level higher than 1.3 TeV. The muon charge is determined studying the decay of stopping positive muons in the LVD iron structure and the decay of stopping positive and negative muons in scintillator. We obtain a ratio ${R = 1.26 \pm 0.04(stat) \pm 0.11(sys)}$

Exploration of the stratosphere with cosmic-ray muons detected underground

International audienceCosmic 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