Calculable observables in quantum chromodynamics I

A simple heuristic proof of infrared finiteness to all orders of perturbation theory is given for a class of observables in massless field theories including quantum chromodynamics. This class includes the average energy E( Omega ) carried into a given solid angular region Omega by final-state particles in e/sup +/e/sup -/ annihilation and its positive integral powers; it also includes energy correlations between different angular regions: E( Omega /sub 1/)E( Omega /sub 2/) ... E( Omega /sub N/). It is argued that appropriately defined inclusive jet cross sections are infrared finite, even for vanishing fractional energy resolutions. Extensions to lepton-hadron and hadron- hadron collisions are described. (8 refs).