The Muon’s Particle & Detectors

Due to the interaction of cosmic rays with the Earth’s atmosphere, a shower of subatomic particles called “Muons” occurs.

This rain is nearly constant, with an approximate flux (at sea level) of one muon per square centimeter per minute, with no preference in its direction of arrival. In addition, a muon of high energy (> 100 GeV) can travel several hundred feet through solid matter before losing all its energy. For example, it is able to pass through meters of rock with an attenuation related to the amount of matter along its trajectory (Marteau 2012; Nagamine 1995). In general, it will lose energy at a rate of 2MeV/cm medium density (Stefaan 2010). These muons have proved to be useful for prospective studies in monumental structures. Tanaka and colleagues (Tanaka 2003, 2005, 2007) have demonstrated the possibility of using an X-ray muon type technique using quasi-horizontal muons to study the internal structure of volcanoes. Developing this technology in countries like Mexico is important, because contain with large mountain chains, and volcanoes that have different forms of activity and are relatively close to urban centers.

When subatomic particles pass through a material, their flux is reduced by the interactions with the atoms of the medium. This attenuation is directly related to the density and composition of the material. Measuring the absorption of particles passing through a volcano, a density distribution of the interior can be derived, e.g., allowing to know the internal channels of the structure (Tanaka 2003,2005, 2007).

In an experiment à la Luis Alvarez, who in the late 1960s concluded that there are no tombs in Egypt’s Chephren pyramid. Then some physicists and archaeologists hoped to glean answers to these questions by monitoring the passage of muons through the Pyramid of the Sun in Teotihuacan too, 50 kilometers northeast of Mexico City. In the Teotihuacan experiment, muons were tracked in three dimensions with a traditional multiwire chamber, in which passing muons generate electrical signals by ionizing gas. The one meter cubed chamber was sandwiched between scintillators to identify muons by coincidence signals (Physics Today, May 2003, page 19).

This kind of detector could be inspired by the work of Tanaka et. (2003), in which the internal structure of Mt. Asama volcano, located on the island of Honshu Japan, was studied.

It is relevant to note that the study of energy resulting from muons and their attenuation is related to the amount of matter traversed.
The muons that reach the earth’s surface are capable of penetrating it to a depth of several thousand meters. The earth’s surface is constantly bathed by muons, a roughly flow of one muon per square centimeter per minute that is independent of the hour and little dependent on the direction in which we look. Experimental physicists are familiar with this value when using horizontal detectors (Olive et al., 2014).

In general, the muons lose 2 MeV / cm, depending on the density of the medium they pass through (Stefaan 2010).

In the picture we can see one cosmic ray shower simulation. Some red lines represent the muon’s particles passing trough the atmosphere.

On the other hand, there are some huge muon’s detector around the the world. Example given…


IceCube is a particle detector with an instrumented volume of about one cubic kilometer, located at the geographic South Pole.

Muons produced in atmospheric cosmic ray showers account for the by far dominant part of the event yield in large-volume underground particle detectors. The IceCube detector, with an instrumented volume of about a cubic kilometer, has the potential to conduct unique investigations on atmospheric muons by exploiting the large collection area and the possibility to track particles over a long distance. Through detailed reconstruction of energy deposition along the tracks, the characteristics of muon bundles can be quantified, and individual particles of exceptionally high energy identified. The data can then be used to constrain the cosmic ray primary flux and the contribution to atmospheric lepton fluxes from prompt decays of short-lived hadrons.


“Compact Muon Solenoid”

The Large Hadron Collider (LHC) at CERN smashes protons together at close to the speed of light with seven times the energy of the most powerful accelerators built up to now.

Some of the collision energy is turned into mass, creating new particles which are observed in the Compact Muon Solenoid (CMS) particle detector. CMS data is analyzed by scientists around the world to build up a picture of what happened at the heart of the collision.

Because muons can penetrate several metres of iron without interacting, unlike most particles they are not stopped by any of CMS’s calorimeters. Therefore, chambers to detect muons are placed at the very edge of the experiment where they are the only particles likely to register a signal.

CMS detection of muons is an important task, because they expect them to be produced in the decay of a number of potential new particles; for instance, one of the clearest “signatures” of the Higgs Boson is its decay into four muons.

At CMS scientists are looking into the unknown and trying to answer the most fundamental questions about our Universe

At the INFN National Laboratory of Legnaro (Padova, Italy) an apparatus for the study of muon radiography has been assembled using two spare Muon Chambers Detectors, produced for CMS (CERN experiment at LHC). Some application is a muon tomography for the detection of hidden nuclear substances in containers.

A portable cosmic muon detector has been developed for environmental, geophysical, or industrial applications.

So, the information on the number of muons incidents in the detector can then be associated with the ability to capture, analyze and display it in a form suitable for experts in various fields (astrophysics, geophysics, high energy physics, etc.), so that they can obtain the introspection necessary for structures using cosmic rays; information that is not only interesting in the field of science but also in social areas, as previously it has been possible to reconstruct images of the internal structure of mountains and volcanoes, which has helped to monitor and assess risks of a possible explosive eruption.

T. Oceguera-Becerra


T. Oceguera-Becerra, Eduardo de la Fuente, Ruben Alfaro. (2014). Information Acquisition System and sensitive position detector for atmospheric muon prospecting. Proceeeding Book. ISSN: 2146–7382

Marteau J. et al., (2012). Muons tomography applied to geosciences and volcanology. Nuclear Instruments and Methods in Physics Research Section A. 695, 23–28.

Nagamine K, Iwasaki M, Shimomura K, Ishida K. Method of probing inner-structure of geophysical substance with the horizontal cosmic-ray muons and possible application to volcanic eruption prediction. Nuc. Instrum. Methods Phy. Res. Sect. A. 356, 585–595.

Stefaan, T., (2010). Experimental techniques in nuclear and particle physics. (pp. 23–53). Springer Berlin Heidelberg.

Tanaka, H., Nagamine, K., Kawamura, N., Nakamura, S. N., Ishida, K., & Shimomura, K. (2003). Development of a two fold segmented detection system for near horizontally cosmic ray muons to probe ‐ ‐ the internal structure of a volcano. Nucl. Instrum. Methods A. 507, 657–669.

Tanaka, H. K. M., Nagamine, K., Nakamura, S. N., & Ishida, K. (2005). Radiographic measurement of the internal structure of Mt. West Iwate with near-horizontal cosmic-ray muons and future developments. Nucl. Instrum. Methods Phys. Res., Sect. A. 555, 164– 172.

Tanaka, H. K. M., Nakano, T., Takahashi, S., & Niwa, K. (2007a). Development of an emulsion imaging system for cosmic-ray muon radiography to explore the internal structure of a volcano, Mt. Asama. Nucl. Instrum. Methods. Phys. Res., Sect. A. 575, 489–497.

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