In summary, we have shown that one can describe the experimental data of the HERMES Collaboration for hadron attenuation on nuclei without invoking any changes in the fragmentation function due to gluon radiation. In our dynamical studies, that include the most relevant FSI, we employ only the ‘free’ fragmentation function on a nucleon and attribute the hadron attenuation to the deceleration of the produced (pre-)hadrons due to FSI in the surrounding medium. We find that in particular the z-dependence of RMh is very sensitive to the interaction cross section of leading prehadrons and can be used to determine σlead. The interaction of the leading prehadrons during the formation time could be interpreted as an in-medium change of the fragmentation function, which however could not be given in a closed form. The extracted average hadron formation times of τf≳0.3 fm/c are compatible with the analysis of antiproton attenuation in p+A reactions at AGS energies [17]. In an upcoming work we will investigate in detail the spectra for different particle species (π±,K±,p,p̄) to examine, if the formation times of mesons and antibaryons are about equal. In addition we will improve our model to describe the primary photon–nucleon reaction below the PYTHIA threshold of W⩾4 GeV.
