We have measured the differential production cross sections as a function of scaled momentum $x_p{=2p/E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ of the identified hadron species ${\pi }^{+},$ $K^{+},$ $K^0,$ $K^{*0},$ $\phi ,\hspace{0.5em}p$, ${\Lambda }^0,$ and of the corresponding antihadron species in inclusive hadronic $Z^0$ decays, as well as separately for $Z^0$ decays into light $(u,$ $d,$ $s),$ c and b flavors. Clear flavor dependences are observed, consistent with expectations based upon previously measured production and decay properties of heavy hadrons. These results were used to test the QCD predictions of Gribov and Lipatov, the predictions of QCD in the modified leading logarithm approximation with the ansatz of local parton-hadron duality, and the predictions of three fragmentation models. The ratios of production of different hadron species were also measured as a function of $x_p$ and were used to study the suppression of strange meson, strange and non-strange baryon, and vector meson production in the jet fragmentation process. The light-flavor results provide improved tests of the above predictions, as they remove the contribution of heavy hadron production and decay from that of the rest of the fragmentation process. In addition we have compared hadron and antihadron production as a function of $x_p$ in light quark (as opposed to antiquark) jets. Differences are observed at high $x_p,$ providing direct evidence that higher-momentum hadrons are more likely to contain a primary quark or antiquark. The differences for pseudoscalar and vector kaons provide new measurements of strangeness suppression for high-$x_p$ fragmentation products.

• Received 30 April 1998

DOI:https://doi.org/10.1103/PhysRevD.59.052001