2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49489We discuss observables in multiparticle production for three kinds of limits of decreasing kinematical scales: 1. the transition jet \to hadron (limit y_{cut}\to 0 of the resolution parameter y_{cut}); 2. single particle inclusive distributions normalized at threshold \sqrt s\to 0 and 3. particle densities in the limit of low momentum p,p_T\to 0. The observables show a smooth behaviour in these limits and follow the perturbative QCD predictions, originally designed for large scales, whereby a simple prescription is supplemented to take into account mass effects. A corresponding physical picture is described.talk at Ringberg workshop "New trends in HERA physics 1999", Tegernsee, May 1999; LaTeX, 13 pages, 6 FigsHigh Energy Physics - Phenomenologytext