Atmospheric Muons Research Articles

Muon tomography with Micromegas: Archaeology, nuclear safety and new developments for Geotechnics.

Muon tomography, or muography, stands out as a non-invasive technique for the scanning of big objects’ internal structure. It relies on the measurement of the direction changes or absorption of atmospheric muons when crossing the studied object. Proposed several decades ago, the performance achieved in particle detectors in the last years, specially in terms of stability, robustness and precision, has enlarged the possible applications of this technique. Bulk Micromegas represent a well-known technology suitable for the construction of muon telescopes based on these detectors. Thus autonomous and portable instruments have been conceived and constructed at Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA), being able to perform muography measurements in-situ, next to the studied objects. At present, a new muon telescope concept is being developed at CEA, combining a Time Projection Chamber (TPC) readout by a 2D multiplexed bulk Micromegas. This new generation of detectors will enlarge the possible application fields of muography, being specially interesting for geotechnics.

Determining the muon charge ratio using an experimental measurements and the CORSIKA simulation code

Abstract The muon charge ratio contains important information about the flux of atmospheric neutrinos and the hadronic interactions. Using a cosmic ray telescope, the atmospheric muon charge ratio has been studied. The result of this experiment is compared with simulation results using the CORSIKA code.

Using a portable muon detector for radioactive source measurements and identification

We have re-purposed portable plastic scintillator muon detectors, designed by the CosmicWatch project, for the measurement of electrons emitted by the decay of radioactive sources. For the latter purpose we have first calibrated the detectors using the local atmospheric muon flux, performing angular distribution and attenuation measurements. In addition, we have simulated the detector using Geant4 in a detailed fashion for a cross-check and better understanding of the device. Then, we have developed a method to evaluate the activity of $\beta$-sources and to discriminate different $\beta$-sources by looking into their respective voltage spectrum output.

Examination of Calculations of the Atmospheric Muon and Neutrino Spectra Using New Measurements

The atmospheric muon and neutrino fluxes at energies from 10 GeV to 10 PeV are calculated with the Kimel–Mokhov (KM), SIBYLL 2.1, EPOS LHC, and QGSJET-II hadronic models for known parameterizations of the cosmic ray spectra by Zatsepin--Sokolskaya and Hillas–Gaisser. The calculations with the KM, EPOS LHC, and SIBYLL 2.1 models are agree well with the measurements of the atmospheric muon spectra in IceCube and IceTop experiments. The measurement of high-energy muon spectra indicates the presence of the prompt muon component at energies above 500 TeV, which is well reproduced in calculations with the quark-gluon string model. The calculations of the atmospheric muon neutrino spectrum performed for the KM, EPOS LHC, and SIBYLL 2.1 models give good fit with the measurement data of IceCube, ANTARES, and Super-Kamiokande experiments.

New Estimates of the Energy of Inclined Showers, According to the EPOS LHC and QGSJETII-04 Models

It is proposed that the energy of inclined extensive air showers be estimated using signals from the surface scintillation detectors of the Yakutsk array, located at a distance of 600 m from the shower axis and the zenith angle of shower arrival. Estimates of the energy of inclined showers are calculated using new formulas obtained from simulations using different models of hadron interaction. These models of hadron interaction are validated by comparing calculated and experimental spectra of atmospheric muons. It is found that the muon spectrum calculated with the EPOS LHC and QGSJETII-04 models differs little from the experimental spectrum. It is shown for the first time that the energy spectrum of primary cosmic radiation is in good agreement with the literature data.

Measurement of delayed fluorescence in plastic scintillator from 1 to 10 μs

The time dependence of the relative light emission of Eljen Technology EJ-200 polyvinyltoluene-based plastic scintillator was measured between 1 and 10 μ s after the passage of a particle shower, a singly charged particle (atmospheric muon), and with a UV LED exciting the fluor. This was compared in magnitude to the integrated response for the prompt light (within 500 ns of excitation). A model with a time-dependent yield consisting of three exponentially decaying components (fast, medium, and slow) was developed to fit the data. Note that the exact time structure of early (< 1 μ s ) light emission was not measured for individual components, only for all three components together This model assumes all three components share the same rise time. The decay time constants of the fast, medium and slow components are, respectively, 7.8 ns, 490 ns, and 2370 ns. The relative total normalized yields for each component are: fast 95.8%, medium 2.2%, and slow 2.0%.

Bayesian joint muographic and gravimetric inversion applied to volcanoes

SUMMARY Gravimetry is a technique widely used to image the structure of the Earth. However, inversions are ill-posed and the imaging power of the technique rapidly decreases with depth. To overcome this limitation, muography, a new imaging technique relying on high energy atmospheric muons, has recently been developed. Because muography only provides integrated densities above the detector from a limited number of observation points, inversions are also ill-posed. Previous studies have shown that joint muographic and gravimetric inversions better reconstruct the 3-D density structure of volcanic edifices than independent density inversions. These studies address the ill-posedness of the joint problem by regularizing the solution with respect to a prior density model. However, the obtained solutions depend on some hyperparameters, which are either determined relative to a single test case or rely on ad-hoc parameters. This can lead to inaccurate retrieved models, sometimes associated with artefacts linked to the muon data acquisition. In this study, we use a synthetic example based on the Puy de Dôme volcano to determine a robust method to obtain the resulting model closest to the synthetic model and devoid of acquisition artefacts. We choose a Bayesian approach to include an a priori density model and a smoothing by a Gaussian spatial correlation function relying on two hyperparameters: an a priori density standard deviation and an isotropic spatial correlation length. This approach has the advantage to provide a posteriori standard deviations on the resulting densities. Using our synthetic volcano, we investigate the most reliable criterion to determine the hyperparameters. Our results suggest that k-fold Cross-Validation Sum of Squares and the Leave One Out methods are more robust criteria than the classically used L-curves. The determined hyperparameters allow to overcome the artefacts linked to the data acquisition geometry, even when only a limited number of muon telescopes is available. We also illustrate the behaviour of the inversion in case of offsets in the a priori density or in the data and show that they lead to recognizable structures that help identify them.

Investigation of acoustic signals correlated with the flow of muons of cosmic rays, in connection with seismic activity of the north Tien Shan

The work is aimed at revealing a possible connection between seismic activity and cosmic-ray muon fluxes capable of penetrating into the Earth’s crust and generating a nuclear electromagnetic cascade in a tense seismically active medium, leading to the formation of microcracks, the opening of which is accompanied by the generation of acoustic and, under certain conditions, seismic energy as predicted by Tsarev and Chechin (Atmospheric muons and high-frequency seismic noise. In: Preprint of the FIAN, vol 179, 1988). The data of the underground installation (in a well at a depth of 52 m) for monitoring geoacoustic signals correlated in time with the flow of high-energy cosmic-ray muons generated in extensive atmospheric showers implemented on the basis of the experimental complex “ATHLET” in the Tien Shan High-Altitude Scientific Station of the Physical Institute of the Russian Academy of Sciences were used. It is found that the daily number of acoustic pulses increases significantly before and during appreciable regional earthquakes. The most pronounced pulsed emissions of acoustic energy, correlated in time with the flow of high-energy cosmic-ray muons generated in extensive atmospheric showers, are followed by an increasing seismic activity in the region, that support idea that penetrating into Earth’s crust the flux of cosmic-ray muons may become a “trigger” of earthquake.

A water tank muon spectrometer for the characterization of low energy atmospheric muons

Abstract In this work, a water tank muon spectrometer was designed, assembled and operated to measure the energy distribution of low energy atmospheric muon flux induced by cosmic-rays at sea level in the energy range 100–500 MeV. The principle of this experiment is to use water as muon moderator inserted between two coincidence detectors to select the cutoff energy below which muons can no longer be detected. The differential and integral muon spectra are then derived from successive measurements by varying the liquid height within the water tank. The instrument was entirely characterized and modeled in terms of detector efficiency, cutoff energy and counting rate. Experimental data are reported for the energy distribution of muon flux at sea level (43 ∘ N of latitude) and finally compared with literature survey.

High-energy atmospheric muon flux calculations in comparison with recent measurements

Recently the atmospheric muon spectra at high energies were reconstructed for two ranges of zenith angles, basing on the events collected with the IceCube detector. These measurements reach high energies at which the contribution to atmospheric muon fluxes from decays of short-lived hadrons is expected. Latest IceCube measurements of the high-energy atmospheric muon spectrum indicate the presence of prompt muon component at energies above 500 TeV.

The underground muon flux with 24 years of data of the LVD detector

The Large Volume Detector (LVD), in the INFN Gran Sasso National Laboratory (Italy), has been taking data since June 1992. The experiment, 1 kton of liquid scintillator at the equivalent depth of 3600 m w.e., has been mainly designed to observe low energy neutrinos from the core collapse of a supernova but allows also the measure of the atmospheric muon flux underground as well as the induced neutron production.In this work we summarize the results of the analysis of the global LVD data set, 5.6 107 muons in a livetime of 8402 days collected during 24 years of continuos operations since 1994 up to 2017. The present measurement represents an unprecedented collection obtained by a unique experiment in a fixed location. The modulation in time of the flux and its correlation with the the effective temperature in the upper atmosphere are here discussed.

Atmospheric Muons Measured with IceCube

IceCube is a cubic-kilometer Cherenkov detector in the deep ice at the geographic South Pole. The dominant event yield is produced by penetrating atmospheric muons with energies above several 100 GeV. Due to its large detector volume, IceCube provides unique opportunities to study atmospheric muons with large statistics in detail. Measurements of the energy spectrum and the lateral separation distribution of muons offer insights into hadronic interactions during the air shower development and can be used to test hadronic models. We will present an overview of various measurements of atmospheric muons in IceCube, including the energy spectrum of muons between 10 TeV and 1 PeV. This is used to derive an estimate of the prompt contribution of muons, originating from the decay of heavy (mainly charmed) hadrons and unflavored mesons. We will also present measurements of the lateral separation distributions of TeV muons between 150m and 450m for several initial cosmic ray energies between 1 PeV and 16 PeV. Finally, the angular distribution of atmospheric muons in IceCube will be discussed.

Improving the prediction of the Atmospheric neutrino flux using the atmospheric muon flux

It is well known that the correlation of atmospheric neutrinos and muons are simply correlated in the energy region of 1–10 GeV, and used for the test bench of the hadronic interaction model used for the calculation of the atmospheric neutrino flux. However, the correlation becomes unclear for neutrinos in the energy range below 1 GeV, which is important for the study of mass ordering of neutrino and CP phase of the neutrino mass. We extend the study of the correlation to the lower neutrino energies and find that the atmospheric muon flux observed at high altitude shows a good correlation to the atmospheric neutrino flux, and could be used to calibrate the hadronic interaction model.

Measurement of the cosmic ray Moon shadow with the ANTARES detector.

The ANTARES detector is the largest neutrino telescope currently in operation in Mediterranean sea. One of the main goals of the ANTARES telescope is the search for point-like neutrino sources, so both the pointing accuracy and the angular resolution of the detector need a proper direct estimation. One possibility to evaluate the pointing performance of the detector is to analyse the shadow of the Moon, i.e. the deficit in the atmospheric muon flux in the direction of the Moon induced by absorption of cosmic rays. The ANTARES data taken between 2007 and 2016 shows aMoon shadow evidence of 3.5σsignificance. This is the first measurement of the ANTARES angular resolution and absolute pointing for atmospheric muons using a celestial calibration source. The presented results confirm the good pointing performance of the detector as well as the predicted angular resolution.

Moon shadow in ANTARES

The ANTARES neutrino telescope is the largest Cherenkov detector currently in operation in Mediterranean sea. The search for point-like neutrino sources is one of the telescope goals. For this reason, both the detector angular resolution and the pointing accuracy need a proper estimation. Measuring the deficit of the atmospheric muons in the direction of the Moon induced by the absorption of primary cosmic rays, the so called Moon shadow, allows to evaluate the pointing performance of the telescope. In this contribution we show the result of the analysis of the data taken between 2007 and 2016. The Moon shadow is detected with 3.5σ significance. This is the first measurement of the ANTARES angular resolution for atmospheric muons and its absolute pointing using a celestial calibration source. The presented results confirm the good pointing performance of the detector as well as the expected angular resolution.

Testing of almost all the hadronic interaction models by comparing calculated muon energy spectrum with data

Uncertainties of the model energy spectra of the most energetic secondary charged mesons are discussed. Computer simulations of the partial energy spectra of the atmospheric vertical muons induced by primary cosmic particles with various fixed energies in terms of hadronic interactions models had been carried out with the help of the CORSIKA package. These partial spectra have been convolved with the contemporary spectra of the primary cosmic particles in the energy range 0.1-10 000 TeV. Results of simulations are compared with the contemporary data of the atmospheric vertical muon flux. Comparison shows that all models underestimate the production of secondary charged π±-mesons (and K±-mesons) by a factor of ~ 1.4 ÷ 2 at the highest energies. This underestimation induces a more rapid development of extensive air showers in the atmosphere and results in uncertainties in estimates of energy and composition of the primary cosmic particles.

The cosmic ray shadow of the Moon observed with the ANTARES neutrino telescope

One of the main objectives of the ANTARES telescope is the search for point-like neutrino sources. Both the pointing accuracy and the angular resolution of the detector are important in this context and a reliable way to evaluate this performance is needed. In order to measure the pointing accuracy of the detector, one possibility is to study the shadow of the Moon, i.e. the deficit of the atmospheric muon flux from the direction of the Moon induced by the absorption of cosmic rays. Analysing the data taken between 2007 and 2016, the Moon shadow is observed with 3.5sigma statistical significance. The detector angular resolution for downward-going muons is 0.73^{circ }pm 0.14^{circ }. The resulting pointing performance is consistent with the expectations. An independent check of the telescope pointing accuracy is realised with the data collected by a shower array detector onboard of a ship temporarily moving around the ANTARES location.

Identification of Geoeffective Disturbances of Solar Wind in the Flux of Cosmic-Ray Muons

The method of flicker-noise spectroscopy is used for remote identification of geoeffective disturbances of the solar wind. The method is based on the study of short-term variations in the cosmic-ray flux that arise when it crosses the perturbed regions in the inner heliosphere. The magnitude of the effect is usually small and it is hidden in statistical noise. The analysis uses data from a continuous flux of secondary atmospheric muons. Bumps of the “nonstationarity” parameter of time series of muons indicate the emergence of advanced signals (predictors) 1–3 days before the disturbances enter the Earth’s magnetosphere. Geoeffective events with a low threshold (Ap > 30 nT) for various types of solar wind are analyzed. The results are obtained using a ground-based muon hodoscope URAGAN (Moscow). The technique can be used for continuous monitoring of space weather.

A method for determining the angular distribution of atmospheric muons using a cosmic ray telescope

A cosmic ray telescope consisting of two scintillators (each one with a surface area of 0.14 m2, spaced 283 cm top of each other) was constructed to study the angular distribution of atmospheric muons. Using the CORSIKA code, the muons energy spectrum is parameterized in different energy regions at Tehran’s altitude (1200 m above sea level ≡897gcm−2), and by using a Monte Carlo program, the minimum energy recorded by the telescope is calculated. Due to the geomagnetic field, in the azimuth angle distribution of atmospheric muons, an anisotropy is observed in the East–West direction. The zenith angle distribution of the atmospheric muons follows the function cosnθ. Due to the relatively large field of view of the telescope, the iteration method is used to obtain the effective angle of orientation of the telescope. With this method, the value n=2.33±0.11 is calculated. The simulation data also provides the mean value n̄=2.30±0.10, which has a good match with the experimental result.

Energy and angular distributions of atmospheric muons at the Earth

A fair knowledge of the atmospheric muon distributions at Earth is a prerequisite for the simulations of cosmic ray setups and rare event search detectors. A modified power law is proposed for atmospheric muon energy distribution which gives a good description of the cosmic muon data in low as well as high energy regime. Using this distribution, analytical forms for zenith angle [Formula: see text] distribution are obtained. Assuming a flat Earth, it leads to the [Formula: see text] form where it is shown that the parameter [Formula: see text] is nothing but the power of the energy distribution. Exact analytical function is obtained for inclined trajectory of muon. A new closed form for zenith angle distribution is obtained without assuming a flat Earth and which gives an improved description of the data at all angles even above [Formula: see text]. These distributions are tested with the available atmospheric muon data of energy and angular distributions. The parameters of these distributions can be used to characterize the cosmic muon data as a function of energy, angle and altitude.