SCALING AND SCALE BREAKING PHENOMENA IN QCD JETS

The perturbative QCD approach to multiparticle production assuming Loc al Parton Hadron Duality (LPHD) and some recent results are discussed. Finite asymptotic scaring limits are obtained for various observables , after an appropriate rescaling, in the Double Logarithmic Approximat ion (DLA). Non-asymptotic corrections are also known in some cases. Th e DLA applies also to very soft particle production where energy conse rvation constraints can be neglected. In this region the particle dens ity follows rather well a scaling behaviour over the full energy range explored so far in e(+)e(-) annihilation.