The aim of this work is to give a pedagogical derivation of polarization observables for the annihilation
reaction $e^+ + e^- \\rightarrow N+ \\bar N$. The reaction mechanism is one photon + two photon
exchange, the last is described by axial parametrization. After deriving the general expressions for the
cross section of a binary process, the matrix element is written in terms of three complex amplitudes.
The method to derive polarization observables is detailed and all expressions are given in terms of
generalized form factors. The strategy for determining physical form factors in annihilation reactions
in presence of two photon exchange is suggested, on the basis of model independent properties of the
relevant observables. |
