  The scaling behavior of large-pT hadron production in hadronic collisions is
investigated. A significant deviation from the NLO QCD predictions is reported,
especially at high values of xT=2pT/sqrt(s). In contrast, the prompt photon and
jet production data prove in agreement with leading-twist expectations. These
results are interpreted as coming from a non-negligible contribution of
higher-twist processes, where the hadron is produced directly in the hard
subprocess. Predictions for scaling exponents at RHIC are successfully compared
to PHENIX preliminary measurements. We suggest to trigger on isolated large-pT
hadron production to enhance higher-twist processes, and point that the use of
isolated hadrons as a signal for new physics at colliders can be affected by
the presence of direct hadron production processes.
