Confronting fragmentation function universality with single hadron   inclusive production at HERA and $e^+ e^-$ colliders
  Predictions for light charged hadron production data in the current fragmentation region of deeply inelastic scattering from the H1 and ZEUS experiments are calculated using perturbative Quantum Chromodynamics at next-to-leading order, and using fragmentation functions obtained by fitting to similar data from $e^+ e^-$ reactions. General good agreement is found when the magnitude $Q^2$ of the hard photon's virtuality is sufficiently large. The discrepancy at low $Q$ and small scaled momentum $x_p$ is reduced by incorporating mass effects of the detected hadron. By performing quark tagging, the contributions to the overall fragmentation from the various quark flavours in the $ep$ reactions are studied and compared to the contributions in $e^+ e^-$ reactions. The yields of the various hadron species are also calculated. 
S. Albino, B. A. Kniehl, G. Kramer, C. Sandoval