Quantum chromodynamics and leptoproduction as a large psub(T) process

As an alternative to the classical moment analyses of structure functions, we discuss tests of QCD in leptoproduction of hadrons associated with the transverse momentum and energy flow of the secondaries. Gluon emission, computed to lowest order in αsub(s), allows a simultaneous description of the rates and spectra of large psub(T) secondaries (typically p2sub(T) > 1 GeV2) in oN, μN and also e+e- interactions. We point out that gluon-quark jet separation might be possible with present leptoproduction data. (orig.)