Hadron Production in Quark, Antiquark, and Gluon Jets from Electron-Positron Interactions at the Z0 Pole

Abstract

We present production measurements of the charged hadrons π ± , K ± and p/p in e + e − interactions at the Z 0 pole. The excellent particle identification capability of the SLC Large Detector (SLD) at the Stanford Linear Collider (SLC) are used. In addition to studies over a wide momentum range in hadronic Z 0 events of all five flavors, we have made the most precise measurements in light (uds), c and b flavor events separately. Unambiguous flavor dependencies have been observed, and the results have been compared with the predictions of several QCD fragmentation models. We have also exploited the unique feature of electron beam polarization in our experiment to compare hadron production separately in quark and antiquark jets. Direct evidence that higher momentum hadrons are more likely to contain the primary quark and antiquark is seen, with precision sufficient to provide new model tests. Finally, we have studied hard gluon jets in detail. We have confirmed that gluon jets have a higher multiplicity of softer particles than light quark jets, and found this enhancement to be the same for π ± , K ± and p/p at the few percent level at all momenta. Any overall difference in the hadron fractions is limited to 0.018 at the 95% confidence level, indicating that there are no differences at the hadronization stage in jet formation between gluons and quarks.