Muon Component Research Articles

USE OF COSMIC RAY MEASUREMENTS TO IDENTIFY THE SECTOR POLARITIES OF THE INTERPLANETARY MAGNETIC FIELD

The knowledge of the interplanetary magnetic field sector polarity at the Earth's location is relevant to study many phenomena related to the Space Climatology. We filled the gaps in the daily polarities of the interplanetary magnetic field derived from spacecraft observations by using two sets of ground-based measurements: i) the cosmic ray muon component intensities supplied by the multidirectional Nagoya telescope; ii) the geomagnetic field from the Antarctic Vostok Observatory. We discuss the time variability of the sector polarities inferred from the wavelet technique in the period 1971–1992.

The water Cherenkov detector array for studies of cosmic rays at the University of Puebla

We describe the design and performance of a hybrid extensive air shower detector array built on the Campus of the University of Puebla ( 19 ∘ N , 90 ∘ W , 800 g / cm 2 ) to measure the energy, arrival direction and composition of primary cosmic rays with energies around 1 PeV, i.e., around the knee of the cosmic ray spectrum. The array consists of 3 water Cherenkov detectors of 1.86 m 2 cross-section and 12 liquid scintillator detectors of 1 m 2 distributed in a square grid with a detector spacing of 20 m over an area of 4000 m 2 . We discuss the calibration and stability of the array for both sets of detectors and report on preliminary measurements and reconstruction of the lateral distributions for the electromagnetic (EM) and muonic components of extensive air showers. We also discuss how the hybrid character of the array can be used to measure mass composition of the primary cosmic rays by estimating the relative contents of muons with respect to the EM component of extensive air showers. This facility is also used to train students interested in the field of cosmic rays.

A large area muon tracking detector for ultra-high energy cosmic ray astrophysics—the GRAPES-3 experiment

Certain aspects of ultra-high energy (UHE) cosmic ray astrophysics require correlated studies on the electron and muon components of air showers, namely, the search for cosmic ray sources through γ -ray astronomy and studies on the variation of the nuclear composition of primary cosmic rays with energy. While studies on the electron component provide basic information about the arrival direction and energy, it is the muon component that plays a crucial role in distinguishing primary γ -rays from charged cosmic ray particles and in determining the composition. A large area (560 m 2 ), tracking muon detector of the GRAPES-3 experiment, operating at Ooty in southern India, has been designed for detailed studies on both of these aspects of UHE cosmic ray astrophysics. We present here the details of the muon detector, associated electronics and the data acquisition system. A brief discussion of the potential of the muon detector is presented through simulation studies.

Direct cosmic ray muons and atmospheric neutrinos

A possible contribution of very short living particles (particles with life-time much shorter than that of charmed particles), for example, resonances, into cosmic ray muon and atmospheric neutrino fluxes (direct muons and neutrinos) is estimated. This contribution could become of the same order of magnitude as that from pions and kaons (conventional) already at energies of hundreds TeV and tens TeV for muons and muon neutrinos coming to the sea level in the vertical direction correspondingly. Of course, the estimation has quite a qualitative character and even it is quite arbitrary but it is necessary to keep this contribution in mind when studying EAS, cosmic ray muon component or trying to interpret data of experiments on cosmic neutrino searching at high energies

Possible influence of cosmic rays on climate through thunderstorm clouds

With decreasing of cosmic ray (CR) intensity caused by increasing of solar activity (SA) or in some short periods of Forbush-decreases, the intensity of secondary CR relativistic electrons decreases and the probability of formation of thunderstorm clouds and discharges between clouds or between clouds and ground is also expected to decrease. This will influence on weather and climate. In this case is very important to have more detail information on the atmospheric electric field distribution in the atmosphere, additional to information what gave now electric field sensors (EFS) only in about one point near the ground. We show that CR not only influenced on atmospheric electric field phenomenon, but can give practically continuous information on the atmospheric electric field distribution in the atmosphere. We extend our theory of CR atmospheric electric field effect on electron–photon, muon and neutron component including different multiplicities. We take into account that about 0.07 of neutron monitor counting rate caused by negative soft muons captured by lead nucleons and formed mesoatoms with generation of several MeV energy neutrons from lead. In this case the neutron monitor or neutron super-monitor works as analyzer that detects muons of only one, negative sign. It is very important because the atmospheric electric field effect have opposite signs for positive and negative muons that main part of this effect in the muon telescope or in ionization chamber is compensated and we can observe only small part of total effect of one sign muons. On the basis of our general theory of CR atmospheric electric field effects with taking into account of negative soft muon acceleration and deceleration in the Earth atmosphere (in dependence of direction and intensity of electric field) we discuss the possibility of existing this effect in CR neutron monitor counting rate and in different multiplicities and calculate the expected effects in dependence of atmospheric electric field distribution in the atmosphere. We show that the comparison of observed effects with theoretically expected will give important information on the value of atmospheric electric field and its distribution in the atmosphere. We consider also the possible influence of secondary relativistic electrons of CR and relativistic electrons precipitated from the Earth’s radiation belts on thunderstorms and lightnings, and through this – on climate change.

Identification of the primary cosmic ray

The nature of the primary particle giving rise to an atmospheric shower may be, to some extent, inferred from the observable properties: longitudinal profile (especially position of the maximum of the number of charged particles) or shape at ground level (lateral distribution, curvature and thickness of the shower front, muonic component). Distinguishing different nuclei cannot be performed unambiguously on a single shower, because of the random fluctuations in the first steps of the cascade; however, it is possible to study the composition of the incident flux on a statistical basis: showers from heavier nuclei have a faster development, and contain more muons. The uncertainties on the hadronic interactions at the highest energies limit the reliability of the identification. Other primaries, if they exist, could be easier to distinguish. Photons would give a slower development than protons, especially at highest energies, and a very reduced muonic component; neutrinos would be characterized by deep interactions in the atmosphere, or even within the Earth, giving almost horizontal showers with a large electromagnetic component, clearly different from the muonic tail of showers induced in the upper atmosphere by nuclei. Such ‘exotic’ primaries have not yet been observed. To cite this article: P. Billoir, P. Sommers, C. R. Physique 5 (2004).

Observations on muon multiplicity distribution with the GRAPES-2 experiment at Ooty for studies on the mass composition of cosmic rays at PeV energies

Precise knowledge of the mass composition of the primary cosmic ray flux below and above the knee in the primary energy spectrum at $E\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{15}$ eV is essential for understanding the acceleration and propagation of high energy cosmic rays. Simulations have shown that the correlations between the electron and muon components of showers are very sensitive to the mass of the primary nuclei. In particular, different regions of the muon multiplicity distribution observed with a large area muon detector, for well-defined selection on the electron component of showers, have a high sensitivity to different nuclear groups present in the primary flux. The GRAPES-2 experiment at Ooty seeks to exploit this sensitivity using a $200{\mathrm{m}}^{2}$ area muon detector to study the mass composition of the primary flux in the energy range ${10}^{14}--{10}^{16}$ eV. The details of the experiment are presented and early observations are discussed in relation to the expectations from simulations.

Test of interaction models with the KASCADE hadron calorimeter

The interpretation of extensive air shower measurements often requires the comparison with EAS simulations. These calculations rely on hadronic interaction models which have to extrapolate into kinematical and energy regions not covered by present-day collider experiments. The KASCADE experiment with its large hadron calorimeter and its detectors for the electromagnetic and muonic components provides experimental data to check hadronic interaction models. For the EAS simulations the program CORSIKA with several hadronic event generators embedded is used. Different hadronic observables are investigated as well as their correlations with the electromagnetic and muonic components. Comparing the interaction models QGSJET 98, NEXUS II, and DPMJET 11.5, it is found, that QGSJET describes the data best.

New results on the EAS muon component in the GAMMA experiment at Mt. Aragats

We present analysis of the data connected with study of muon characteristics with 5 GeV energy threshold for EAS with N e ϵ [3 10 5−10 7] obtained with help of the new configuration of the muon underground detector on the GAMMA array. The results are compared with previous GAMMA results as well as with data of the Tien-Shan experiment. Comparison with the simulation data is also carried out.

Determination of primary energy and mass in the PeV region by Bayesian unfolding techniques

The field detector array of the KASCADE experiment measures the electron and muon component of extensive air showers in the knee region with high precision. A baysian unfolding procedure is presented in which the two-dimensional shower size distribution ( N e , N μ tr ) is examined. On the arbitrary assumption that the chemical composition consists of five primary mass groups (hydrogen, helium, carbon, silicon and iron) the size distribution is deconvoluted to reconstruct the energy spectra of these mass groups in the energy range between 10 15 eV and 10 17 eV. The energy spectra of the lighter element groups result in a knee-like bending with a steepening above the knee. The topology of the individual knee positions suggest a rigidity dependence.

Electron and muon densities in cosmic rays measured at L 3+C

The L 3+C experiment at CERN has been extended with an air shower scintillator array. The combination of the measurement of the shower particle density with the precision measurement of cosmic ray muons in the L 3 spectrometer provides a new tool to study the physics of cosmic rays. Correlations between the electron-photon and the muon components of air showers observed with large area detectors are known to provide information about the composition of the primary cosmic ray flux. For this, new observations on the energy spectrum of muons over a large energy range and the multiplicity distribution of high energy muons are needed. We present here the details of the L 3+C experiment relevant for such studies and discuss some preliminary observations.

Muon density spectra as a probe of the muon component predicted by air shower simulations

The KASCADE experiment measures local muon densities of air-showers in the knee region at various core distances for two different muon energy thresholds. Muon density spectra have been reconstructed for the total EAS sample, as well as for particular subsamples with enhanced light and heavy induced EAS, classified on the basis of the shower size ratio N μ/N e . By comparing these spectra for different muon energy detection thresholds and core distances with detailed Monte Carlo simulations each spectrum should result in the same primary energy spectrum. This allows a comprehensive test of the simulation procedures of the muon lateral distribution and the muon energy spectrum by various Monte Carlo codes. Different combinations of high-energy and low-energy interaction models in the frame of the CORSIKA code are used for comparisons.

Measurements of the muon component of extensive air showers at 320 m.w.e. underground

The ALEPH detector at LEP has been supplemented with five scintillator telescopes to measure the muon component of cosmic ray air showers underground. The emphasis of the present analysis of a new data set is to measure coincidences over distances up to about 1 km which are sensitive to the forward production of hadronic interactions and the chemical composition of primary cosmic rays in the energy range around 10 15 eV. First results indicate that the observed decoherence curve of muons is compatible with a light primary composition and the arrival directions of muons show no obvious clustering in galactic coordinates.

Thunderstorms' atmospheric electric field effects in the intensity of cosmic ray muons and in neutron monitor data

Theoretical and experimental results on the influence of thunderstorms' atmospheric electric field on cosmic ray secondary components are presented. On the basis of the approach proposed by Dorman [1987], theoretical models for a correct numerical evaluation of these effects on hard muon, soft muon, and neutron monitor component are developed. For hard and soft muons the validity of the models are checked by their comparison with experimental results of the Baksan muon detector. For the first time, the effect of thunderstorms' atmospheric electric field on cosmic rays is investigated by simultaneous measurements of one‐minute neutron monitor intensity and of atmospheric electric field at the Emilio Segre' Observatory on Mt. Hermon (Israel). A series of large thunderstorms during February 2000 is investigated; for each thunderstorm the maximum atmospheric electric field intensity was ranging from 10 to about 100 kV/m. Clear correlation between field intensity and neutron monitor intensity variations is presented for total intensity and for different detected multiplicity channels. This correlation is quantitatively in agreement with the developed model which takes into account the formation of short‐living meso‐atoms by the capture of slow negative muons in the lead of the monitor. The effect is relevant only for neutron events with detected multiplicity m = 1 and evident for multiplicity m = 2; the other multiplicity channels are not influenced by neutrons from meso‐atoms.

Investigations of a recombination chamber as a mixed field dosimeter in comparison with a tissue-equivalent proportional counter at CERF

A comparison of two types of dose equivalent meters, a recombination chamber REM-2 and a tissue-equivalent proportional counter (TEPC) Homburg Area Neutron DosImeter (HANDI), were carried out at the CERN-EC high-energy reference field facility, CERF, in October 2001. Here, the mixed high-energy radiation field in commercial flight altitudes can be simulated with dose rates up to 2 orders of magnitude higher. The total absorbed dose and the dose equivalent have been measured at different radiation field intensities. Of particular interest for measuring in the CERF field is the assessment of the low LET-component, i.e. the γ and muon components of the field, which are not taken into account by existing Monte Carlo simulations modeling the radiation field. The new results for the estimation of the low LET-component are compared with previous ones delivered by REM-2 at CERF. The results show good agreement between the REM-2 chamber and the HANDI.

Preparation of enriched cosmic ray mass groups with KASCADE

The KASCADE experiment measures a high number of EAS observables with a large degree of sampling of the electron–photon, muon, and hadron components. It provides accurate data for an event-by-event analysis of the primary cosmic ray flux in the energy range around the knee. The possibility of selecting samples of enriched proton and iron induced extensive air showers by applying the statistical techniques of multivariate analyses is scrutinized using detailed Monte Carlo simulations of three different primaries. The purity and efficiency of the proton and iron classification probability is investigated. After obtaining enriched samples from the measured data by application of the procedures the reconstructed number of hadrons, hadronic energy and other parameters are investigated in the primary energy range 10 15–10 16 eV. By comparing these shower parameters for purified proton and iron events, respectively, with simulated distributions an attempt is made to check the validity of strong interaction models at high energies.

Observation of the Moon Shadow in Cosmic Ray Muons

The effect of cosmic ray shadowing by the Moon is observed by recording the single muon component with the Baksan underground scintillation telescope (BUST). A statistically significant (three standard deviations) deficit of muon intensity in the Moon's direction is discovered. A comparison of the experimental results with the simulation of the shadowing effect for the BUST observations is made. An estimate of the angular resolution of the BUST for the single muon component is derived experimentally for the first time. The results and the technique developed are planned to be used for observations of the Sun's shadow.

A non-parametric approach to infer the energy spectrum and the mass composition of cosmic rays

The experiment KASCADE observes simultaneously the electron–photon, muon, and hadron components of high-energy extensive air showers (EAS). The analysis of EAS observables for an estimate of energy and mass of the primary particle invokes extensive Monte Carlo simulations of the EAS development for preparing reference patterns. The present studies utilize the air shower simulation code corsika with the hadronic interaction models VENUS, QGSJet and Sibyll, including simulations of the detector response and efficiency. By applying non-parametric techniques the measured data have been analyzed in an event-by-event mode and the mass and energy of the EAS inducing particles are reconstructed. Special emphasis is given to methodical limitations and the dependence of the results on the hadronic interaction model used. The results obtained from KASCADE data reproduce the knee in the primary spectrum, but reveal a strong model dependence. Owing to the systematic uncertainties introduced by the hadronic interaction models no strong change of chemical composition can be claimed in the energy range around the knee.

Primary cosmic ray and muon measurements with CAPRICE

The WiZard Collaboration has performed several investigations of the cosmic ray muon component in the atmosphere. In this paper, we review the most recent results from the balloon-borne CAPRICE experiment and discuss their relevance in the context of the atmospheric neutrino observations.

Behaviour of the EAS electron-photon and muon component characteristics in the knee region at mountain altitudes

The characteristics of the EAS electron-photon and muon components in showers with given sizes 10 5 ≤ Ne ≤ 10 7 are obtained by the GAMMA installation at the Mt. Aragats (Armenia, 700 g/cm 2. The analysis of data was carried out having in mind the different explanations about the nature of the knee.