Muons of very and ultra-high energy cosmic rays. Bulletin of the Russian Academy of Sciences: Physics Volume 77, Issue 11, November 2013, Pages 1322-1325

In many cosmic rays experiments at very and ultra-high energies, an excess of muons (including those of very high energy, >100 TeV) is observed that cannot be explained within existing models of hadron interactions. This excess is usually explained in terms of the heavier mass composition of primary cosmic rays. However, the excess over the predicted values even for extremely heavy compositions, and especially the observed excesses of muons with energies of >100 TeV, requires that we consider other possibilities with respect to the generation of muons, including changes in models of hadron interaction.
Indexed keywords
Mass composition; Ultra high-energy cosmic rays; Ultra-high energies; Very high energies