Evolution effects in Z0 fragmentation into charmonium

Abstract:
In Z0 decay into prompt charmonium, i.e. charmonium not originating from B-meson decays, the most important contribution is expected to come from colour-octet mechanisms. However, previous fixed-order calculations of the colour-octet contribution contain large logarithms which, in a more complete treatment, should be resummed to all orders. We study this resummation by using a Monte Carlo QCD cascade model and find that the fixed-order colouroctet result is diminished by 15%. We compare the Monte Carlo calculations with results obtained by using analytical evolution equations.