Gamma gamma rightarrow M^{+}M^{-}(M=pi , K) processes with twist-3 corrections in QCD

Abstract

We study the gamma gamma rightarrow M^{+}M^{-}(M=pi , K) processes with the contributions from the two-particle twist-2 and twist-3 distribution amplitudes of pion and kaon mesons on BHL prescription in the standard hard-scattering approach. The results show that the contributions from twist-3 parts are actually not power suppressed compared with the leading-twist contributions in the low energy region. The cross sections with twist-3 corrections agree well with the experimental data in the two-photon center-of-mass energy W>2.8 GeV and we also predict the cross section ratio sigma _{0}(K^{+}K^{-})/sigma _{0}(pi ^{+}pi ^{-}), which is compatible with the experimental data from TPC and Belle.