Inclusive Production of $\eta$ and $\eta '$ Mesons in Two- and Three-Jet Events from Hadronic Z Decays

The production rates and the fragmentation functions of the isoscalar mesons eta and eta^prime and of the isovector meson pi^0 as a function of scaled energy x=E_{meson}/E_{beam} in two- and three-jet events from hadronic Z decays have been measured for every jet and compared to Monte Carlo models. The eta and eta^prime production in hadronic events has also been updated. The analysis is based on 2.9 million hadronic events collected with the ALEPH detector at LEP at a center-of-mass energy of sqrt{s}=91.2 GeV. The fragmentation functions and the production rates of all three particles analyzed are in good agreement with the predictions of the JETSET model for each jet of three-jet events. Within errors and taking into account the sensitivity of the analysis, the JETSET modelling of the gluon fragmentation into isoscalar mesons is in agreement with the experimental results for the measured region.