INVARIANT AMPLITUDES FOR ELECTROMAGNETIC PION PRODUCTION FROM THE NUCLEON AND ITS IMPLICATION FOR SEPARATED STRUCTURE FUNCTIONS

摘要

The electromagnetic production of pions on the nucleon, including photoproduction and electroproduction, is the main source of information about the nucleon structure and the nature of the strong interaction. As such, it has been a subject of comprehensive experimental and theoretical studies for the past several decades - see recent work in references [1-5], where references to earlier research can also be found. The most prominent example is the A(1232)-resonance, which decays almost exclusively into pion-nucleon channel.