Photon structure function
![Figure 1. Electron-photon scattering generic Feynman diagram.](/Images/godic/202502/02/Fgamfeyndia1853.png")
![Fig2: Photon structure function versus x for Q2 = 4.3 GeV2 (blue crosses) and 39.7 GeV2 (black crosses) compared to the QCD prediction explained in the text.](/Images/godic/202502/02/F2versusxtwoQ21853.jpg")
![Fig 3: Photon structure function versus log Q2 for 0.3 < x < 0.5 compared to the QCD prediction explained in the text.](/Images/godic/202502/02/F2versusQ21853.jpg")
The quark content of the photon is described in quantum field theory by the photon structure function defined by the process e + γ → e + hadrons. It is uniquely characterized by the linear increase in the logarithm of the electronic momentum transfer log Q and by the approximately linear rise in x , the fraction of the quark momenta within the photon.These characteristics are borne out by the experimental analyses of the photon structure function.