Sum rule for photon target

The amplitude of zero angle scattering of an electron on photon in the 3rd QED order of fine structure constant with γ*γ intermediate state converting into quark-antiquark is considered. Utilizing analytic properties of the elastic photon-photon scattering amplitude, an explicit expression for the differential cross section of quark-antiquark pair production at the electron-photon collision in peripheral kinematics is apparently derived. The limiting case of small transferred momenta with an application of the Weizsaecker-Williams like relation gives the sum rule for the photon target, bringing into the relation the sum of ratios of the four powers of the quark charges to squared quark masses with an integral over the total γγ→2 jets cross section