Instanton Contribution to the Pion Electro-Magnetic Formfactor at Q2 > 1 GeV2
Abstract
We study the effects of instantons on the charged pion electro-magnetic formfactor at intermediate momenta. In the Single Instanton Approximation (SIA), we predict the pion formfactor in the kinematic region Q2=2-15 GeV2. By developing the calculation in a mixed time-momentum representation, it is possible to maximally reduce the model dependence and to calculate the formfactor directly. We find the intriguing result that the SIA calculation coincides with the vector dominance monopole form, up to surprisingly high momentum transfer Q2~10 GeV2. This suggests that vector dominance for the pion holds beyond low energy nuclear physics.
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