Production of \({\rm K}^0_{\rm S}\) and \(\Lambda\) in quark and gluon jets from \(\mathrm{Z^0}\) decay

The production of \({\rm K}^0_{\rm S}\) mesons and \(\ Lambda\) baryonsin quark and gluonjets has been investigated using two complementary techniques. In the first approach, which provides high statistical accuracy, jets were selected using different jet finding algorithms and ordered according to their energy. Production rates were determined taking into account the dependences of quark and gluoncompositions as a function of jet energy as predicted by Monte Carlo models. Selecting three-jet eventswith the \(k_{\perp}\) (Durham) jet finder (\(y_{\mathrm{cut}} = 0.005\)), the ratios of \({\rm K}^0_{\rm S}\) and \(\Lambda\) production rates in gluonand quark jets relative to the mean charged particle multiplicity were found to be \(1.10 \pm 0.02 \pm 0.02\) and \(1.41 \pm 0.04 \pm 0.04\), respectively, where the first uncertainty is statistical and the second is systematic. In the second approach, a new method of identifying quark jets based on the collimation of energy flow around the jet axis is introduced and was used to anti-tag gluonjets in symmetric (Y-shaped) three-jet events. Using the cone jet finding algorithm with a cone size of 30°, the ratios of relative production rates in gluonand quark jets were determined to be \(0.94 \pm 0.07 \pm 0.07\) for \(\mathrm{K^0_S}\) and \(1.18 \pm 0.10 \pm 0.17\) for \(\Lambda\). The results of both analyses are compared to the predictions of Monte Carlo models.