Charge-exchange reactions from the standpoint of the parton model

Using simple arguments, we show that charge-exchange reactions at high energies go through the hard scattering of fast quarks. On this basis we describe ${\pi }^{-}p\to M^{0}n$ and $K^{-}p\to M^0\mathrm{\Lambda }$, $M^0 =\pi^0, \eta, \eta’$, in a combined approach which defines hard contributions in the parton model and soft ones in Regge phenomenology. The disappearance of a dip according to recent GAMS-4$\pi$ data in the differential cross-section $K^- p \to \eta\Lambda$at$|t| \approx$0.4--0.5(GeV$!$\mathrm{/}c)$^2$ at transition to relatively high momenta, is explained as a manifestation of a mode change of summation of hard contributions from coherent to incoherent. Other manifestations of the mentioned mode change are discussed. Constraints on the $\eta$–${\eta }^{\mathrm{\prime }}$ mixing and gluonium admixture in ${\eta }^{\mathrm{\prime }}$ are obtained.