Muon Intensity Research Articles

Study of characteristics of Forbush decreases detected in 2006 – 2011 by means of muon hodoscope URAGAN

Results of the study of variations of cosmic ray muon flux at the Earth surface during Forbush decreases (FD) registered in 2006 – 2011 by means of muon hodoscope URAGAN both for the integral counting rate and for different angular intervals are presented. Dependences of the amplitude of the decrease of cosmic ray muon intensity on the energy of primary particles in the energy region above 10 GeV during different phases of the FD were obtained. On the basis of the analysis of spatial-angular distribution of muon flux, values of the horizontal projections of the local anisotropy vector were calculated and their dynamics was studied. Energy, angular and temporal characteristics of Forbush decreases determined from cosmic ray muon data are compared with basic parameters characterizing conditions of near-Earth space before and during FD.

Geant4 Simulation Study of Deep Underground Muons: Vertical Intensity and Angular Distribution

Underground muon intensities up to 10000 m.w.e. and angular distribution up to 6500 m.w.e. in standard rock have been investigated using Geant4 simulation package. Muons with energies above 100 GeV were distributed from the ground level taking into account the muon charge ratio of~1.3 at sea level. The simulated differential muon intensities are in good agreement with the intensities given in the literature. Furthermore, the simulation results for the integrated intensities are consistent with the experimental data, particularly at depths above 4000 m.w.e., where the simulation gives slightly smaller intensities than the experimental ones. In addition, the simulated exponentnat different underground depths agrees well with the experimental points, especially above~2000 m.w.e.

Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector

Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4mrad from the measured profile center. The normalized event rate is measured with 4% precision.

Production target and muon collection studies for an experimental muon source at CSNS

Intense muon beams have very important applications by using μSR techniques and other methods. An experimental muon source (EMuS) as a parasitic facility at China Spallation Neutron Source (CSNS) is proposed. EMuS makes use of a small portion of the high power proton beam from the CSNS accelerator complex. It will provide an excellent platform for muon beam based multidisciplinary research, and will also serve as the development base for a future full-scale muon source at CSNS. The available proton beam power of 4kW at 1.6GeV can produce intense muon flux with a thick production target. The muon yields with different target materials and shapes, and the muon collection efficiency have been simulated by using the FLUKA code. It is found that the graphite target of about 10–12cm in thickness and rectangular in cross-section is a good choice, and that the collection at 90° from the beam direction is the best for surface muons. It is found that 4-D emittance volume instead of two independent 2-D emittances should be used to define the relation between the optimal muon intensity and the muon channel acceptance, due to the asymmetry between the distributions in the two transverse phase planes. The collected muon intensities for both surface muons and cloud muons with different emittances have also been studied, which are important for designing the muon beam transport line. The intensities of positive and negative muons are in the orders of 105μ+/s and 104μ−/s, respectively.

Effect of thunderstorm electric field on intensity of cosmic ray muons

Neutron monitor (NM) in Yangbajing Cosmic Ray Observatory mainly detects nucleus components with energy in a range of 500 MeV20 GeV and a small number of negative muons. On the basis of synchronous data of neutron monitor and atmospheric electric field during 62 thunderstorms from 2008 to 2010, obvious changes of NM counting rate during 27 thunderstorms with significance greater than S5 are found, and among them, 13 cases with significance greater than S10 . A coincident approximate change trend is found between counting rate change percentage and atmospheric electric field amplitude for 13 cases with significance S10 . However no obvious coincident change trend is found for 14 cases with significance 5 S10 . Obvious changes of counting rate do not occur when thunderstorm is just over electric field mill, however obvious changes occur when electric field mill is not exactly below thunderclouds but in the control of bottom positive charge layer. Dorman put forward the theory that NM counting rate changes are correlated with the atmospheric electric field, thus they attributed the former to the acceleration of the electric field to negative muons inside thunderstorms. However, there is found no evident correlation between NM counting rate charge and the atmospheric electric field in this paper, so our experiment does not support Dormanetal's theory.

Statistical properties of variations in cosmic ray muons during thunderstorms

An analysis is made of experimental data on variations in muons with a threshold of 100 MeV, detected by the CARPET air shower array in the Baksan Valley during thunderstorms of 2008. It is shown that with using a special criterion for selecting statistically significant variations (0.2%), muon intensity variations are observed in the majority of cases. Their characteristic duration is ∼8 min. Their amplitudes can have different polarities and do not exceed 1%.

Design and performance of the muon monitor for the T2K neutrino oscillation experiment

This article describes the design and performance of the muon monitor for the T2K (Tokai-to-Kamioka) long baseline neutrino oscillation experiment. The muon monitor consists of two types of detector arrays: ionization chambers and silicon PIN photodiodes. It measures the intensity and profile of muons produced, along with neutrinos, in the decay of pions. The measurement is sensitive to the intensity and direction of the neutrino beam. The linearity and stability of the detectors were measured in beam tests to be within 2.4% and 1.5%, respectively. Based on the test results, the precision of the beam direction measured by the muon monitor is expected to be 0.25mrad.

Seasonal Variation of Atmospheric Leptons as a Probe of Charm

The intensity of TeV atmospheric muons and neutrinos depends on the temperature in the stratosphere. We show that the energy dependence in the 100 TeV range of the correlation with temperature is sensitive to the fraction of muons and neutrinos from decay of charmed hadrons. We discuss the prospects for using the temperature effect as observed in gigaton neutrino detectors to measure the charm contribution.

Observation of muon intensity variations by season with the MINOS far detector

The temperature of the upper atmosphere affects the height of primary cosmic ray interactions and the production of high-energy cosmic ray muons which can be detected deep underground. The MINOS far detector at Soudan MN, USA, has collected over 67 million cosmic ray induced muons. The underground muon rate measured over a period of five years exhibits a 4% peak-to-peak seasonal variation which is highly correlated with the temperature in the upper atmosphere. The coefficient, $\alpha_T$, relating changes in the muon rate to changes in atmospheric temperature was found to be: $\alpha_T = 0.874 \pm 0.009$ (stat.) $\pm 0.010$ (syst.). Pions and kaons in the primary hadronic interactions of cosmic rays in the atmosphere contribute differently to $\alpha_T$ due to the different masses and lifetimes. This allows the measured value of $\alpha_T$ to be interpreted as a measurement of the K/$\pi$ ratio for $E_{p}\gtrsim$\unit[7]{TeV} of $0.13 \pm 0.08$, consistent with the expectation from collider experiments.

Technique to measure the cosmic muon flux at the old Canfranc Underground Laboratory

A technique to measure the cosmic muon flux distribution has been developed in the old Canfranc Underground Laboratory (2450 m.w.e.).This technique can determine the muon direction and it allows to obtain a three-dimensional distribution of the muon intensity which could be correlated to the mountain profile, as well. The experimental set-up, which has been taking data since November 2008, consists of a Time Projection Chamber (TPC) detector and a veto system composed of two plastic scintillators.

Down going muons

Recent measurements observed by different groups indicate that the muon intensities are 10% – 15% lower than observed in earlier measurements. Changing dependencies of these intensities as a function of zenith angle make it difficult to precisely understand these data. Integral muon intensities at different underwater depths are compared with muon intensities on the surface. The observed differences are the subject of this paper.

Potential of the ATLAS detector for studying high-energy solar cosmic rays

The ATLAS detector is intended for testing the Standard Model and for seeking new physics at the Large Hadron Collider (LHC). In addition, it permits detecting cosmic-ray muons. At the same time, unusual bursts of the muon intensity that correlate with powerful solar flares were recorded and investigated earlier at the Baksan underground scintillation telescope in the period spanning 1981 and 2006 (2.5 solar cycles). The nature of these muon bursts and their relation to solar cosmic rays have so far remained not quite clear. The ATLAS detector possesses an excellent muon system that allows searches for similar muon bursts. Within the next few years, when the LHC and ATLAS should start operating, one expects an increase in the solar activity in the new 24th cycle. Owing to this, the probability of observing muon bursts may become higher.

Strong variations of cosmic ray muons during thunderstorms

Experimental data about a strong decrease of the intensity of cosmic ray muons are presented. The event occurred during a thunderstorm on September 24, 2007 in Baksan Valley (North Caucasus). The threshold energy of muons is 100 MeV. In comparison with other events of this type detected previously, this event is remarkable by a longer duration (more than an hour and a half) and by the fact that well-pronounced correlations with lightning strokes are observed for the first time.

Performance of the first ANTARES detector line

In this paper we report on the data recorded with the first Antares detector line. The line was deployed on the 14th of February 2006 and was connected to the readout 2 weeks later. Environmental data for one and a half years of running are shown. Measurements of atmospheric muons from data taken from selected runs during the first 6 months of operation are presented. Performance figures in terms of time residuals and angular resolution are given. Finally the angular distribution of atmospheric muons is presented and from this the depth profile of the muon intensity is derived.

Integral energy spectrum of muons deep underground

Latest measurements of the muon intensities on the ground surface in atmosphere, taken by different groups indicate that the muon intensities are 10%–15% lower than taken in old experiments. Changing dependencies of these intensities in function of zenithal angles are making it difficult to precise understanding those data. Independent group of measurement integral muon intensities on different levels underground are compared with muon intensities measured on the surface. The differences are the subject of this paper.

The use of cosmic muons in detecting heterogeneities in large volumes

The muon intensity attenuation method to detect heterogeneities in large matter volumes is analyzed. Approximate analytical expressions to estimate the collection time and the signal to noise ratio, are proposed and validated by Monte Carlo simulations. Important parameters, including point spread function and coordinate reconstruction uncertainty are also estimated using Monte Carlo simulations.

Density Enhancement of Muon Beams with Tapered Glass Tubes

We have demonstrated that the beam density of 54 MeV/c muons can be increased almost by a factor of two when a tapered glass tube is inserted coaxially along the muon beam. The observations are compared with a multiple Coulomb scattering calculation, which reproduces the observation reasonably. This technique opens a new and simple way to increase the muon intensity effectively.

Atmospheric variations in muon intensity for different zenith angles

The barometric and temperature coefficients of muon intensity for a layer of variable mass and the temperature coefficients for mass-weighted mean atmospheric temperature are found by regressions analysis from the results of continuous measurements of muon intensity at different zenith angles and atmospheric parameters. The temperature coefficients of muon intensity are determined for different atmospheric layers. Using the characteristics obtained, the changes in temperature are found for different atmospheric layers from the data on variations in muon intensity. The results obtained are compared with the observed temperature changes.

Measurements of the integrated muon intensity at large zenith angles

Precision measurements of the zenith-angle distributions of muons in the range 61°–89° are performed using the DECOR coordinate detector. The total number of selected events is more than 20 million. The dependence of the integrated muon intensity on the zenith angle is determined for several threshold energies in the range from 1.7 to 7.2. GeV. The experimental results in these ranges of zenith angles and threshold energies are obtained for the first time. It is demonstrated that the dependence of the integrated muon intensity on the zenith angle is adequately described by a simple analytical relationship.

Measurements of integrated muon intensity at large zenith angles

Data from the DECOR coordinate detector on the integrated intensity of muons that have a threshold energy of 1.2 to 2 GeV are analyzed over the zenith-angle interval 60°–90°. Experimental results in these intervals of zenith angles and threshold energies were obtained for the first time. In the interval θ ≤ 80°, the integrated intensity at E min = 1.5 GeV as a function of the cosine of the zenith angle is described by a power-law function characterized by an exponent value of n = 1.884 ± 0.005, which is close to the value obtained in earlier experiments.