Investigations aimed at searching for possible existence of quark–antiquark pairs in a nucleon with a distribution similar to the distribution of valence quarks at large fractions of the quark momentum were reviewed.
Upper limits of the probability for observing this charm–anticharm quark pair were presented, which were estimated from the experimental data recently obtained by the ATLAS collaborations in hard proton–proton collisions with production of direct photons accompanied by c-jets at the LHC. Calculations of distributions of nonperturbative gluons in a proton that are initial functions in QCD evolution equations were also considered. Their decisive role both in soft processes at low transverse momenta of produced hadrons and in hard production of heavy mesons, jets, and even Higgs bosons was shown. Quite satisfactory agreement of the calculated transverse-momentum spectra of these particles with numerous experimental data obtained at the LHC was demonstrated.