Photon Structure Functions: Target Photon Mass Effects and QCD   Corrections
  We present a systematic analysis of the processes $e^+ ~e^- \rightarrow e^+ ~e^- X$ to study the polarised and unpolarised photon structure functions. The effect of target photon mass, which manifests itself as new singly polarised structure functions is studied. The physical interpretation of these structure functions in terms of hadronic components is given using the free field analysis. Assuming factorisation of the photon structure tensor, the relevant QCD corrections to the various structure functions are evaluated. The effect of the target photon mass and QCD corrections on the unpolarised and polarised cross sections are also studied. 
Prakash Mathews and V. Ravindran