EVOLUTION EFFECTS IN Z(0) FRAGMENTATION INTO CHARMONIUM

In Z(O) decay into prompt charmonium, i.e. charmonium not originating from B-meson decays, the most important contribution is expected to co me from colour-octet mechanisms. However, previous fixed-order calcula tions of the colour-octet contribution contain large logarithms which, in a more complete treatment, should be resummed to all orders. We st udy this resummation by using a Monte Carlo QCD cascade model and find that the fixed-order colour-octet result is diminished by 15%. We com pare the Monte Carlo calculations with results obtained by using analy tical evolution equations.