== Gamma/Z interference in e+e- -> mu+ mu- ==

   * Calculate analytically the cross section for  %$e^+ e^- \to \mu^+ \mu^-$% as function of the CMS energy, including
    both exchange of a photon and a Z boson. Neglect masses of the external fermions. Compare your result with 
    Software.MadGraph.
   * The Forward-Backward asymmetry is 
    %$A_{FB}(\theta)=\frac{ d\sigma (\theta) - d\sigma(\pi-\theta)}{ d\sigma (\theta) + d\sigma(\pi-\theta)}$%.
    Plot it as a function of the CMS energy.

-- Main.FabioMaltoni - 30 Aug 2007