Angular distribution of particle flows and perturbative QCD predictions

We discuss the predictions of perturbative QCD for angular flows of final state particles in two and three jet events including their $cms$ energy and jet resolution ($y_{cut}$) dependence. The simple analytical formulae for gluon bremsstrahlung from primary partons, modified for gluon cascading, reproduce the main features of the experimental data well. For $y_{cut}$-selected events, the particle flow is derived from a superposition of colour dipoles in much the same way that photon radiation is derived from electric dipoles