Charge-exchange reactions from the standpoint of the parton model

Abstract

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 $K^{-}p\to M^0\Lambda$, $M^0={\pi }^0,\eta ,{\eta }^{\prime }$, 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/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 $\eta$--${\eta }^{\prime }$ mixing and gluonium admixture in ${\eta }^{\prime }$ are obtained.

Comments: 18 pages, 8 figures; version to appear in EPJA