Muon Data Research Articles

The Internal Field in a Ferromagnetic Crystal with Chiral Molecular Packing of Achiral Organic Radicals

The achiral organic radical dinitrophenyl nitronyl nitroxide crystallizes in two enantiomorphs, both being chiral tetragonal space groups that are mirror images of each other. Muon-spin rotation experiments have been performed to study the magnetic properties of these crystals and demonstrate that long-range magnetic order is established below a temperature of 1.10(1) K. Two oscillatory components are detected in the muon data, which show two different temperature dependences.

New cosmic ray observations at Syowa Station in the Antarctic for space weather study

Muon detectors and neutron monitors were recently installed at Syowa Station, in the Antarctic, to observe different types of secondary particles resulting from cosmic ray interactions simultaneously from the same location. Continuing observations will give new insight into the response of muon detectors to atmospheric and geomagnetic effects. Operation began in February, 2018 and the system has been stable with a duty-cycle exceeding 94%. Muon data shows a clear seasonal variation, which is expected from the atmospheric temperature effect. We verified successful operation by showing that the muon and neutron data are consistent with those from other locations by comparing intensity variations during a space weather event. We have established a web page to make real time data available with interactive graphics (http://polaris.nipr.ac.jp/cosmicrays/).

A Method for Estimating the Normalized Instrument Response Function of the URAGAN Muon Hodoscope

This paper offers a method for estimating the normalized instrument response function (IRF) of the URAGAN muon hodoscope (MH). A multiparametric model of the instrument response function is derived from digitally processed time series of MH matrix data and the hypothesis of muon-flux (MF) intensity distribution is formulated. Formulae for estimating the normalized instrument response function are devised and used in an algorithm for estimating normalized variations of functions in MF intensity. The algorithm was tested on simulated and experimental muon observation data.

Feasibility study to measure the muon bremsstrahlung cross section with the energy loss profile using neutrino telescopes

Muons are the dominant event signature for neutrino telescopes like IceCube and they are the main background for neutrino searches. Furthermore, they are used to investigate extended air showers. In both cases, the stochasticity of the muon propagation plays a key role in the data extraction step and an accurate understanding, even of the edge cases, is crucial. The main process driving stochastic losses for TeV scale muons is bremsstrahlung.In this paper, a feasibility study is presented to measure the cross section of stochastic losses using neutrino-induced muons. The simulation study is based on the propagation of muons using the Monte-Carlo library PROPOSAL. For different reconstruction methods and resolutions, the energy loss distribution for different muon energies is used to estimate the sensitivity to measure the bremsstrahlung cross section. Two further systematic parameters, the detection efficiency, which scales the amount of detected light, and the spectral index are also estimated to analyze their correlation to the estimated bremsstrahlung normalization. The statistics of the simulated dataset correspond to 10 years of up-going muon neutrino data in IceCube.

Calibration of the CMS hadron calorimeters using proton-proton collision data at √s = 13 TeV

Methods are presented for calibrating the hadron calorimeter system of the CMS detector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities |η| < 3 and are positioned inside the solenoidal magnet. An outer calorimeter, outside the magnet coil, covers |η| < 1.26, and a steel and quartz-fiber Cherenkov forward calorimeter extends the coverage to |η| < 5.19. The initial calibration of the calorimeters was based on results from test beams, augmented with the use of radioactive sources and lasers. The calibration was improved substantially using proton-proton collision data collected at √s = 7, 8, and 13 TeV, as well as cosmic ray muon data collected during the periods when the LHC beams were not present. The present calibration is performed using the 13 TeV data collected during 2016 corresponding to an integrated luminosity of 35.9 fb−1. The intercalibration of channels exploits the approximate uniformity of energy collection over the azimuthal angle. The absolute energy scale of the central and endcap calorimeters is set using isolated charged hadrons. The energy scale for the electromagnetic portion of the forward calorimeters is set using Z→ ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy.

Galactic cosmic ray transport in the heliosphere: Study with muon data

We use the galactic cosmic ray (GCR) solar diurnal anisotropy (SDA) data of Nagoya vertical muon telescope (NagV-MT) to compute the ratio α of GCR free paths normal and parallel to mean interplanetary magnetic field (IMF) B. The values are compared to those computed earlier for the neutron monitors (NMs) of the global network for three sunspot cycles (21–23) and parts of the other two (19, 24). Current GCR modulation theories do not provide any guidance for α, its rigidity and solar cycle dependence. We use a flat heliosphere current sheet and the Master equations derived by Ahluwalia and Dorman [1997] for computing α and study its rigidity dependence and correlation with solar activity for positive (p) and negative (n) polarity intervals of B at 1 AU; B points outward/ inward from the sun during p/n interval in north hemisphere; IMF polarity changes sign near SSN maximum. For NagV-MT (Rm = 60 GV), Rm being the median value of response to GCR differential rigidity spectrum, we find that α is high for p- and low for n-intervals, compared to being nearly flat for NMs; α for NM2 (Rm = 25 GV) is larger than that for NM1 (Rm = 15 GV), implying an increase in α with GCR rigidity. The α values for NagV-MT are low near SSN maximum as is the case for NMs and high near SSN minimum, when effective limiting GCR rigidity (Rc) for SDA is known to be lower than 100 GV. The results challenge the validity of current conceptual understanding of GCR modulation processes in the heliosphere, pointing to a great need to develop an acceptable theory to explain the empirical results reported in this paper.

CdS versus ZnSnO buffer layers for a CIGS solar cell: a depth-resolved analysis using the muon probe

The influence of a buffer layer in the surface of a Cu(In,Ga)Se2 (CIGS) solar cell material is studied using implanted positive muons as a probe. A depth resolved analysis of the muon data suggests that both CdS and ZnSnO reduce the width of a defect layer present at the CIGS surface to about half its original value. Additionaly, CdS is able to reduce the intensity of the distur¬bance in the defected region, possibly due to a surface reconstrution in CIGS.

Analysis of thunderstorms based on the data obtained by MH URAGAN and DMRL-C

Muon snapshots (muonographs) obtained by means of muon hodoscope URAGAN and meteorological maps from the Doppler weather radar DMRL-C during a thunderstorm event occurred in Moscow on August 30, 2018 are compared with each other in detail. Wavelet analysis of obtained muon data is performed. Search for possible predictors of a thunderstorm event is conducted.

Muon-spin relaxation and AC magnetometry study of the ferrimagnet LaSr2Cr2SbO9

AC susceptibility and muon spin relaxation data have been collected from a polycrystalline sample of LaSr2Cr2SbO9, a perovskite-like compound wherein the unequal distribution of Cr3+ and Sb5+ cations over two crystallographically-distinct six-coordinate B sites results in the onset of ferrimagnetism at ~150 K. The data are used to elucidate the dynamics of the ferrimagnetic domain walls, thought to lie in Sb-rich regions, and suggest an energy barrier of ~0.13 eV to their motion. The muon data confirm that the ferrimagnetic order is a true bulk phenomenon. The behaviour of this material is briefly compared to that of Ni2+- based relaxor ferromagnets.

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.

Using Muon Rings for the Calibration of the Cherenkov Telescope Array: A Systematic Review of the Method and Its Potential Accuracy

The analysis of ring images produced by muons in an Imaging Atmospheric Cherenkov Telescope (IACT) provides a powerful and precise method to calibrate the IACT optical throughput and monitor its optical point-spread function (PSF). First proposed by the Whipple collaboration in the early 90's, this method has been refined by the so-called second generation of IACT experiments: H.E.S.S., MAGIC and VERITAS. We review here the progress made with these instruments and investigate the applicability of the method as the primary throughput calibration method for the different telescope types forming the future Cherenkov Telescope Array (CTA). We find several additional systematic effects not yet taken into account by previous authors and propose several new analytical methods to include these in the analysis. Slight modifications in hardware and analysis need to be made to ensure that such a calibration works as accurately as required for the CTA. We derive analytic estimates for the expected muon data rates for optical throughput calibration, camera pixel flat-fielding and monitoring of the optical PSF. The achievable statistical and systematic uncertainties of the method are also assessed.

Joint inversion of gravity with cosmic ray muon data at a well-characterized site for shallow subsurface density prediction

SUMMARYEstimating subsurface density is important for imaging various geologic structures such as volcanic edifices, reservoirs and aquifers. Muon tomography has recently been used to complement traditional gravity measurements as a powerful method for probing shallow subsurface density structure beneath volcanoes. Gravity and muon data have markedly different spatial sensitivities and, as a result, the combination is useful for imaging structures on spatial scales that are larger than the area encompassed by crossing muon trajectories. Here we explore and test a joint inversion of gravity and muon data in a study area where there is an independently characterized target anomaly: a regionally extensive, high-density layer beneath Los Alamos, New Mexico, USA. We resolve the nearly flat-lying structure using a unique experimental set-up wherein surface and subsurface gravity and muon measurements are obtained above and below the target volume. Our results show that with minimal geologic (prior) constraints, the joint inversion correctly recovers salient features of the expected density structure. The results of our study illustrate the potential of combining surface and subsurface (e.g. borehole) gravity and muon measurements to invert for shallow geologic structures.

A novel method for atmospheric correction of cosmic-ray data based on principal component analysis

A new method for atmospheric correction of cosmic ray data is designed. It’s fully empirical, based on the principal component analysis. The method requires knowledge of the pressure and the temperature profile of the atmosphere. It’s applicable to all muon detectors. The method is tested on muon data from two detectors in Belgrade cosmic ray station, one located on the ground level and the other at the depth of 25 mwe. Correction reduces variance by 64.5% in ground level detector data and 38.1% in underground data. At the same time, the amplitude of the annual variation is reduced by 86.0% at ground level and 54.9% underground. With the same data sets the presented method performs better than the integral correction method.

Temperature Effect Observed for the Muon Component in the Yakutsk Cosmic-Ray Spectrograph

The temperature effect is studied for the muon detectors of the Yakutsk cosmic-ray spectrograph, which consists of an ionization chamber and ground-level and undergroundmuon counter telescope deployed at depths of 0, 7, 20, 40, and 60 mwe. This array makes it possible to study muon fluxes over a wide energy range (from 2 to 200 GeV). The dependence of the temperature effect for muon component on the depth and on the zenith angle (that is, on the energy of detected particles, as well as on the solar-activity cycle) is studied. A brief description of the muon detector database (mddb) created at IZMIRAN is given. This database includes observational data from muon detectors and data on the atmospheric pressure and vertical profiles of the atmospheric temperature at standard isobaric levels.

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.

Muon Tomography Applied to a Dense Uranium Deposit at the McArthur River Mine

AbstractThis article reports on the first application of muon tomography (a novel method for imaging density contrasts underground using cosmic rays) for imaging dense uranium deposits within the Athabasca Basin in Canada. We present a qualitative assessment of the radiographic imaging and 3‐D density inversion of a uranium deposit using muon tomography. The muon tomography survey summarized in this article was performed at the McArthur River mine. We demonstrate the validity of muon tomographic imaging with data acquired at a depth of about 600 m underground. The statistical significance of the uranium deposit signature in the muon data was larger than 5 standard deviations, and the corresponding 3‐D density inversion compared well with drill assay data from the deposit.

The influence of several atmospheric variables on cosmic ray muons observed by KACST detector

In this study, the effects of atmospheric pressure and temperature on cosmic ray muons have been investigated using data recorded by the KACST detector (Riyadh, Saudi Arabia; Rc = 14.4 GV) for the beginning of the quiet periods of the 24th solar cycle. The muon data were, initially, correlated with the atmospheric pressure, and the desired coefficient was obtained and used to eliminate the pressure effect from the muon measurements. The pressure-corrected data are then analysed to study the effect of the atmospheric temperature on cosmic ray muons, using five methods. Four methods investigate the effect of the ground temperature, the atmospheric temperatures and atmospheric heights at several atmospheric levels, on the measured muon rate. In the fifth method, the muon data were correlated with the atmospheric weighted temperatures integrated up to different atmospheric heights. For all cases, the desired correction coefficients were obtained, and their variations at several atmospheric levels were studied. The obtained coefficients were then used to correct the cosmic ray data. We found that the atmospheric pressure effect shows the greatest differences between the corrected and uncorrected rate (up to 1%). Instead, corrections made to the muon data using the remainder of the considered parameters modify the muon rate by a small amount (less than 0.5%) compared to the uncorrected rate.

Predicting Muon-Induced SEU Rates for a 28-nm SRAM Using Protons and Heavy Ions to Calibrate the Sensitive Volume Model

Muon-induced single-event upset cross sections are estimated for a 28-nm static random access memory (SRAM) using Monte Carlo simulations informed by ion test results. As an exercise in modeling with limited information, details of the 28-nm SRAM’s cell structure were not used (and not available) to inform choices of device model parameters such as sensitive volume dimensions and efficiencies. Instead, inferences were made based on heavy-ion and proton single event upset data. Volume dimensions were sufficiently small to resolve the charge collection profile resulting from highly localized low linear energy transfer particle strikes. Results are compared to muon experimental data taken at TRIUMF for validation. Rate predictions are made for the 28-nm SRAM using the calibrated model and compared to expected neutron rates. Muon-induced upset rates at sea level for both marginally reduced and significantly reduced electrical biases, as well as rates at 39 000 feet, are predicted to be significantly less than neutron rates in all these environments. This result is consistent with other authors’ efforts in similarly scaled bulk CMOS SRAMs, indicating that the modeling method used is reliable.

Inherent Differences between Bound and Radiation Fields

The purpose of the paper is to use fundamental theoretical and experimental elements of electrodynamics for deriving properties of radiation fields and of bound fields. A wide variety of examples prove that radiation fields and bound fields do not represent the same physical object. This conclusion is new. Some examples belong to the classical domain and others belong to the quantum domain. Consequences of this outcome affect several physical issues. In particular, these fields should be treated separately. For this reason, changes must be introduced to the present form of the fields’ Lagrangian density of quantum electrodynamics, where the fields tensor Fuv is a sum of bound and radiation fields. Since the Lagrangian density is a key element of the theory, its revision may entail changes of other specific issues. The recent failure of quantum electrodynamics to explain the electron and the muon data of the proton charge radius supports this conclusion.

Constraints on Galactic Neutrino Emission with Seven Years of IceCube Data

Abstract The origins of high-energy astrophysical neutrinos remain a mystery despite extensive searches for their sources. We present constraints from seven years of IceCube Neutrino Observatory muon data on the neutrino flux coming from the Galactic plane. This flux is expected from cosmic-ray interactions with the interstellar medium or near localized sources. Two methods were developed to test for a spatially extended flux from the entire plane, both of which are maximum likelihood fits but with different signal and background modeling techniques. We consider three templates for Galactic neutrino emission based primarily on gamma-ray observations and models that cover a wide range of possibilities. Based on these templates and in the benchmark case of an unbroken E − 2.5 power-law energy spectrum, we set 90% confidence level upper limits, constraining the possible Galactic contribution to the diffuse neutrino flux to be relatively small, less than 14% of the flux reported in Aartsen et al. above 1 TeV. A stacking method is also used to test catalogs of known high-energy Galactic gamma-ray sources.