NLO K-factors for Single-Inclusive Leptoproduction of Hadrons

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.