Radiative Corrections in the Framework of Quantumelectrodynamics
Calculations in quantumelectrodynamics usually employ the methods of perturbation theory and since the expansion parameter is small the results of lowest order are in general sufficiently exact. In the following we shall therefore consider a simple scattering process with just one additional photon and get acquainted with the occurrence of infrared divergences and the method of how to master their difficulties. These divergences exactly cancel (in any order) if one considers elastic and inelastic events together. Although higher order approximations in QED are connected with seemingly unsurmountable mathematical complications it is, however, possible to sum over the contributions of soft photons in closed form. We then describe in more detail a formalism which can be applied to scattering processes in general. Some special examples will be discussed in chapter IV.
KeywordsMatrix Element Pure Spin Virtual Photon High Order Approximation External Line
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