The Universe has many unsolved problems. Part of these are gradually finding an explanation, while others remain mysteries for science. One such unsolved mystery of the Universe is the abundance of muons. The measurements found that more muons are observed at the Earth’s surface than standard physics models predict.
These elementary particles are byproducts of high-energy cosmic rays interacting with the atmosphere. In a new study, a team of scientists offers an explanation for this phenomenon through what is known as “gluon condensation.”
How are muons formed?
Cosmic rays traveling through time-space at nearly the speed of light collide with the nuclei of atoms in the upper atmosphere, causing a cascade of particles. The resulting pions, kaons, and baryons decay rapidly, giving rise to muons, the heavy analogs of electrons. About 90% of muons arise from the decay of pions and kaons. These particles are able to penetrate through the atmosphere almost without loss of energy and reach the surface of the Earth, which is explained by the principles of the special theory of relativity.
According to calculations, one muon passes each minute through every square centimeter of the Earth’s surface, but observations indicate that their number exceeds the expected by 30-60% in the range of energies from 6 to 16 EEV.
Gluon condensation
The researchers suggest that the main reason for the discrepancy between theory and observations lies in the first collision of cosmic rays with colliding atomic nuclei in the atmosphere. Under such conditions, when the cosmic ray particle has extremely high energy, gluon condensates can form in the nuclei.
Gluons are particles that carry strong interactions between the quarks that make up hadrons (e.g., protons, neutrons, pions, and kaons). Under normal conditions, gluons behave complexly because of their “colored” charge, which makes them difficult to analyze. However, at ultrahigh energies they can form states where a significant fraction of their energy is concentrated at one level, forming a gluon condensate.
Influence of gluon condensates
Gluon condensates can significantly influence the formation of hadrons during collisions. For example, they increase the appearance of pions and strange quarks, which are part of kaons. These processes lead to the formation of more muons than the standard model suggests.
Calculations have shown that the number of strange quark pairs can be 2-10 times larger in the presence of a gluon condensate than in an ordinary quark-gluon plasma. This, in turn, explains the excess of muons on the Earth’s surface.
The authors of the study in the article The Astrophysical Journal emphasize that the standard models, that take into account only the influence of quark-gluon plasma, can not fully explain the excess of muons. But their gluon condensate theory offers a more precise explanation. They believe that these states can form at extreme collision energies, favoring the formation of strange quarks and consequently more muons.
Earlier we reported on how to check your watch using cosmic rays.
Provided by phys.org
