Inclusive production of charged hadrons and ${\rm K}^0_{\rm S}$ mesons in photon–photon collisions

Abstract

The production of charged hadrons and ${\rm K}^0_{\rm S}$ mesons in the collisions of quasi-real photons has been measured using the OPAL detector at LEP. The data were taken at $\mbox{e}^+\mbox{e}^-$ centre-of-mass energies of 161 and 172 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the charged hadrons and ${\rm K}^0_{\rm S}$ mesons have been compared to the leading order Monte Carlo simulations of PHOJET and PYTHIA and to perturbative next-to-leading order (NLO) QCD calculations. The distributions have been measured in the range $10 < W < 125$ GeV of the hadronic invariant mass W. By comparing the transverse momentum distribution of charged hadrons measured in $\gamma\gamma$ interactions with $\gamma$ -proton and meson-proton data we find evidence for hard photon interactions in addition to the purely hadronic photon interactions.