  In these proceedings we discuss next-to-leading order (NLO) perturbative-QCD
calculations of the cross section for the process $\ell N\to h X$. We briefly
present the main features of the calculation and in particular analyze the role
of quasi-real photons that enter the processes because the scattered lepton is
not observed. We find that the NLO corrections are sizable for the
spin-averaged cross section. In order to quantify this statement we present the
K-factors of the cross sections for fixed target experiments HERMES, JLab12 and
COMPASS.
