  The top quark, the heaviest quark and, indeed, the heaviest elementary
particle known today, constitutes a novel probe of the long-lived medium in
quark-gluon phase which, as expected, can be produced even in light nuclei
collisions at ultra-high energies. Some distinctive features are considered for
particle production in the top sector in ultra-high energy domain. The
antitop-top pair production is studied within the quantum chromodynamics and
effective field theory approach used for calculations of total partonic cross
sections. Predictions for all observables are computed at NNLO in quantum
chromodynamics and at LO in effective field theory. These quantitative results
can be important for both the future collider experiments at center-of-mass
energy frontier and the improvement of the phenomenological models for
development of the cosmic ray cascades in ultra-high energy domain. Thus the
study allows the better understanding of heavy particle production and
emphasizes the exciting interrelation between the high-energy physics on
accelerators and ultra-high energy cosmic ray measurements.
