Treatment of the infrared contribution: NLO QED evolution as a pedagogic example
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We show that the conventional prescription used for DGLAP parton evolution at NLO has an inconsistent treatment of the contribution from the infrared (IR) region. We illustrate the problem by studying the simple example of QED evolution, treating the electron and photon as partons. The deficiency is not present in a physical approach which removes the IR divergency and allows calculation in the normal 4-dimensional space.
KeywordsSplitting Function Soft Photon Ladder Diagram Infrared Singularity Exact Cancellation
E.G.d.O. and M.G.R. thank the IPPP at the University of Durham for hospitality. This work was supported by the grant RFBR 11-02-00120-a and by the Federal Program of the Russian State RSGSS-4801.2012.2; and by FAPESP (Brazil) under contract 2012/05469-4.