Three-jet events and fragmentation at CDF

We present some analysis results on jet data from proton-antiproton collisions at √s = 1.8 TeV. Preliminary analysis of a sample of 2 pb-1 of three jet events collected in 1988/89 run of CDF shows obvious deviations from phase space behavior. The data are well reproduced by leading order QCD predictions for events with three partons in the final state. Final results on jet fragmentation from the 1987 data sample are also described. This analysis is performed on good quality dijet events in the central rapidity region. Track momenta are measured with a resolution σ(PT)/PT = 0.2%* PT in 1.5 Tesla magnetic field. The charged fragmentation function, defined in terms of z = p//(track)/p(jet), is seen to agree with Herwig Monte Carlo predictions. The dependence of the fragmentation function on the mass of the dijet system shows a scaling violation effect that is consistent with Herwig. The fragmentation function appears to be softer than in e+e- experiments, asexpectable on the basis of the presence of a significant fraction of gluon-initiated jets. The average charged momentum fraction is 0.65±0.02(stat)±0.08(sys)