REPORT OF THE WORKING GROUP ON RADIATIVE-CORRECTIONS AT HERA

In inclusive deep-inelastic lepton-nucleon scattering, the radiative ' tails' originating from processes at Q2 values from the interval Q(mea s)2 greater-than-or-equal-to Q2 > 0 contribute to measurements at Q2 = Q(meas)2 and a knowledge of the structure functions in this Q2 interv al is necessary, We review and compare existing parametrizations of st ructure functions and their extrapolations into the as-yet unexplored very low-Q2 regions and discuss the resulting uncertainties for lepton ic radiative corrections. The unfolding procedures to determine struct ure functions from observed cross sections by the experiments NMC, ZEU S and H1 are compared with each other.