Frame Dependence of the Pair Contribution to the Pion Electromagnetic   Form Factor in a Light-Front Approach
  The frame dependence of the pair-term contribution to the electromagnetic form factor of the pion is studied within the Light Front approach. A symmetric ansatz for the pion Bethe-Salpeter amplitude with a pseudo scalar coupling of the constituent to the pion field is used.   In this model, the pair term vanishes for the Drell-Yan condition, while it is dominant for momentum transfer along the light-front direction. 
J. P. B. C. de Melo (1), T. Frederico (2), E. Pace (3) and G. Salme   (4) ((1) Instituto de Fisica Teorica, UNESP, Sao Paulo...